1994 Honda XR250L Rebuild
Well, the project is under way. It all sort of started with this thread... --> http://www.advrider.com/forums/showthread.php?t=690344 ... and turned into something quite a bit uglier. Below is a copy/paste from another forum I post on. I figured I'd at least get you guys up to speed before continuing with the updates. This all took place back in June of this summer.
Presenting... the beast.
I had been having some issues lately in regards to performance. First there were some electrical issues, and then I found an exhaust header crack.. Furthermore, what was a 'puff' of smoke was slowly turning into a constant puff of smoke. And.. when the girlfriend, who is not entirely mechanically inclined, noticed the smoke, I decided it was time to perhaps tear this thing apart. As I will be commuting almost solely on the bike come September, which leaves me about two months to get this thing sorted out. There are many outstanding issues on the bike that I have wanted to address since the initial purchase. My plan is to use this downtime to do just that. Shame that it came in the middle of prime riding season, but I'll be busy with summer research in T-minus one week, which is likely going to suck up all of my attention and time. I figured I'd tear the bike apart and at least give myself an idea of what I was in for.
The increased smoking of the bike unfortunately assisted me in discovered some exhaust leaks that I was previously unaware of. I threw a mirror up to the exhaust headers, still attached, and saw this...
As well as this, at the junction.. Tell-tale soot pattern...
The bike had been seemingly lean, with a popping that I just couldn't get rid of. These exhaust leaks were likely the cause of that. I was aware of the header / pipe junction, where the gasket had gone bad... But I wasn't aware of the cracking on the header.
Tear down resumed. Off came the side panels and gas tank.
Something else I planned to address was the battery box. Recently, my battery went bad and started leaking acid. I yanked it out and replaced it with a small capacitor. Pain in the ass, given that I have to yank the headlight fuse in order to start the bike, otherwise the lights steal the energy for the spark. Little bit of corrosion around the box; I plan to clean all of this up, repaint it, and replace it with the appropriate battery. Another option is to install a switch, but that would require cutting the wiring harness in a couple of places, and I'd rather give myself the ability to run the lights with a battery, given that this is *primarily* a commuting vehicle.
Yanked the battery box off. The lower bolt was frozen. PB Blaster combined with a propane torch was enough to free it without sheering it off. I'll clean up the threads and bolt before reinstallation. Notice the turn signals. :facepalm I'm not a fan of wire nuts - solder it and do the job correctly. The PO didn't even go that far. I will be pulling those off, and reinstalling some flexible signals from a Buell Ulysses. Great dual sport mod that gives near unbreakable blinkers. If I break those off, I may go with something flush-mounted.
Buell signals, and another riders' writeup. http://www.vstrom.info/Smf/index.php/topic,3719.0.html
Onward with the tearing apart...
Leaky gasket between the cylinder head & cylinder. I'll be replacing that.
Off comes the exhaust header... The gasket was indeed in terrible shape, with about the last 1/5th of it more or less missing.
Upon further examination, I found the crack. And what a crack it was.... Definitely helps toward explaining the slightly lean condition & backfiring upon decel.
The metal around the entire cracked area was weakened. I'm not sure if this can be repaired or not. I've got a great condition XR250R pipe on order that should arrive any day now. 3mm larger diameter than the L unit. It should wake the bike up pretty damned well. I just need to find a matching XR250R exhaust for it at this point in time. Reports from Rick Ramsey's XR250L mod page note that I should indeed be able to keep mileage about 60mpg, even with these mods... Sounds like a plan to me.
Continued in next post...
At this point, I resumed my work and began removing the parts necessary to yank the valve cover off. I found one of the front bolts had actually been stripped out, with a slight chunk of metal missing on the front of the cylinder... :facepalm I'll throw up a photo of that later, perhaps. I'm not sure if it is worth spending the time and effort to fix; it wasn't leaking, and isn't really in a critical area.
The rear three valve cover bolts, as well as the center bolt, seemed fairly stuck. Stripped one of these out was the last thing I wanted to do. Cue torch. Ideally, I'd prefer MAPP gas, but propane comes fairly close in temperature, and I was able to find a bottle locally for about $15.
Throw on some PB Blaster and let it soak for a few minutes... Heat the bolt, wack with a hammer, and try to remove... Cycle more heat if necessary. The head acts as a heatsink, and bleeds that heat than the bolt itself can. If the surfaces are stuck together, they'll expand at different rates. This heated expansion of the bolt tends to break it free, and voila - out they come. A torch is a thing of beauty, and anybody working in a garage should have one handy for situations like this.
With that out of the way, off came the valve cover. There was a steel gasket in place that looked like it was in pretty darn good condition, as well as some poorly applied RTV in a few places. This valve cover has no doubt been off before. Note the cam chain tensioner... Chain is likely stretched, and probably needs replaced.
Out came the cam. The photo doesn't entirely show it, but the center cam journal is in remarkably good condition. I had a low oil scare (which was how I first found out about the oil burning issue), and was hoping that there wasn't any valvetrain damage. Cam and associated parts were all in good condition.
Next, I pulled off the oil lines on the back of the cylinder head. After that, it was time to pull all of the bolts for the cylinder head out. These came out without any sort of problem whatever, with one small exception... There was only one or two washers present, when I *think* that all four inner bolts are supposed to have them. Furthermore, when I pulled the cylinder head off, I heard something drop. It might have been a washer, and it might have dropped down into the crankcase :facepalm I'm not entirely sure, and am going to have to find a way to check without tearing this thing apart. Please tell me I don't need to crack the cases and there's an easier way....
Valves, and a bit of carbon build up.
And there was the piston, in all of her glory. Quite a bit of carbon buildup on top of the piston. Pushed it down, and ... ahhh, ****. Suddenly it was quite apparent why the bike had been smoking...
Rust pitting that I could feel with my finger. Not terrible - it can't be more than a fraction of a milimeter. I'm *thinking* that this sleeve might just need a bore to clean it up, and an oversize piston to match.
There was a little bit of vertical scoring present in the cylinder sleeve.
At this point, I figured what the hell.. It's only four more bolts to pull the whole cylinder head off. It was late at this point, but curiosity had gotten the best of me and I wanted the full truth before bedtime.
And off she came... The piston had serious scoring on both sides. It was trashed.
And here was my stopping place for the night. I've torn apart transmissions and engines with my father on various projects, but this was my first solo effort. The heart of the beast...
And this is where the bit currently stands.
At this point, it looks like I'm going to, at the minimum, need to bore out the sleeve and find a matching piston. Given that the valves are off, I may also take them to the local machine shop and let them take care of that. Such machining is beyond my capabilities at this point. Between the top end kit, machine shop work, and valve nonsense... I'm probably going to be looking at around $400 at this point for all of the parts & machining. Budget is a concern; I'm a poor grad student trying to get by at this point. This meltdown was unexpected, but I'm hoping that the work will allow me another 15k or so out of the bike. At that point, I'll be pursuing further grad work which should allow me a little more funding. I'll probably buy a DR650 or similar at that point, and turn the XR into more of a trail worthy dual sport.
To Do List...
-Very probable purchase of XR250R oil cooler, side cover, and oil lines.. Should allow for much more longevity and reliability from the engine.
-Purchase a rear rack to allow for installation of my 35L Givi box.
-Spoon on some more street worthy tires for commuting. Probably a set of Distanzias or Shinko 705s.
And that brings us to current. Needless to say, I didn't get nearly as much done as I'd initially planned over the summer, and I'm most definitely not commuting on this bike yet. Further updates to come! Quite a few parts have arrived in the mail, and there's more on the way. Busy as hell, but hopefully I can get this thing on the road by mid to late October.
My valve spring compressor came in the mail along with a few other goodies today. Pulled off the springs, and yanked the valves out. They're a little worn, but still right at Honda spec numbers. What worries me is the combustion side of the head...
Photos, of course...
Serious carbon buildup, which isn't too much of an issue to clean out... Given the abysmal jetting of the previous owner, I'm not surprised. What DOES worry me, however, are the cavities that seem to have developed. The two valve seats on the right side of the last two photos illustrate this quite well. There is quite literally a little hole in the metal itself, and in that general area, it almost looks as if the leaking has made the surrounding area worse.. or eaten away at *that* metal. Perhaps this was partially responsible for the scoring in the cylinder? I don't know.
I am fairly positive that this is not a typical result. Is this simply going to get worse and worse? I believe the bike was run lean in the past due to an exhaust leak; would that cause this?
Please advise. Not sure where to go from here. Onward with the rebuild, clearly... but not entirely sure if I need to start digging for a head or not. Thanks!
A good engine rebuilder should be able to fix the head. The head looks like the damage was caused by spark knock, pinging or detonation(probably due to running lean). They will also be able to replace the valve seats and guides as needed.
As for the cylinder I would use a 77mm big bore kit since you already need it bored out. The price difference is small to none. You need to rejet already anyway from the looks of it.
I have an old 87 XR250R I'm building for next year. I found that parts swapping between my X600R with XR600R suspension and my XR650L is quite interesting.
Mine will have parts from both the 600R and 650L used in my build.
Here's a picture
Thats a XR650L seat and 4.7gal Clarke tank. It now has XR650L forks and rear shock. The spring rate is right on the money for my size.:D
I also found the rear rack from my XR650L will fit. The SuperTrapp exhaust is from my XL600R.
With the 4.7gal Clarke 650L gas tank leaves enough room for USD forks without any clearance issues.:evil
I also used the clutch lever and perch. I'm using the choke lever as my decompression lever. It was simple to make work and it allowed me to use 29" wide bars.
Other parts will be swapped. The XR650L and my 87 XR250R have almost identical frames in many ways. The 650 frame also has reinforcements that are needed to stiffen the XR250R's frame. The seat fits like it was meant to, other then 1 bolt hole requires a new tab for it. It now has a 37.5" seat height. :wink:
The XR650L side panels fit perfect wit the XR650L's seat on the right side, the left side fits a XR600R side panel fits perfect also.
Here's a picture with the 250 side covers(cut for shock adjustment on the left side and a hand hold on the right side).
It makes carb access and rear shock adjustment easy.
I'd get a new piston and rings (OEM Honda, next size up), piston pin and circlips, camshaft bearings, cam chain (new tensioner depending on how yours looks), head gasket and cylinder base gasket. OEM parts are the best, just make sure you order everything at once to save on shipping.
Do that and your bike will be good as new, assuming the bottom end is ok. I wouldn't bother with putting an oil cooler on this bike. If you keep the oil fresh, and the air filter clean, this bike will run forever! Check the oil level frequently and keep it where it should be, no more, no less.
Oh yeah, and new valves and valve seats if needed... Take the head and cylinder to a good machine shop and they'll tell you what the best options are for what you've got.
It looks like high humidity moisture got to the bore and the valve seats. The valve seats might be salvageable with a valve job. I wonder if a hone might just be able to clean up the cylinder.
Appreciate the advice. It seems that the head might very well be repairable, but local estimates have come into the $100-$160 dollar range for seats, and recutting to match the valves. Seems somewhat pricy! Given that my valves are also worn to the service limit (2mm, according to the Honda manual), I may very well look for a low hour/mile head to replace this unit. That will probably put me ahead from a monetary perspective, as I will not have to purchase new valves either. PO didn't do such a great job with the maintenance; who knows how frequent the valve adjustment intervals were done. Will keep you all updated on that matter.
In other news... RE: piston.. that's already been taken care of. I had a machine shop measure the bore for me. Stock is 73, and the current bore is at 74mm. There is some minor rust related pitting to be taken care of, and as such, it'll require a minor overbore. Given the sizes available, I found a Wiseco 75.5mm piston kit w/ gaskets for a fairly reasonable price. Rather than jump straight to the 77mm bore, this should allow me to give myself one more bore (77mm) further down the road, before having to worry about changing the sleeve and all of that.
Couple of items arrived in the mail over the past week...
From left to right, we've got... A new pair of fork boots, gasket kit for the piston, 75.5mm piston, rings & hardware, valve spring compressor, valve stem seals, a pretty much brand new brake caliper, a size 128 main jet, and a new cam chain.
I don't think the bike has ever had a fluid change in the forks. I've got another package that should be arriving Monday-ish with a crate stand, fork oil, and some misc hardware and seals. One of the things I wanted to do was a complete brake and fork rebuild. While trying to change the front tire, I began to remove the caliper only to find that the piston inside of it was falling apart! The pads were badly worn and the top of the brake piston was falling off. While trying to remove the pads, I realized that the brake pins themselves were frozen and semi-stripped. Fantastic :huh Turned into a nightmare of trying to get the front wheel back on with pistons that didn't want to retract!
After that fiasco, I was looking at replacing the caliper. Sadly, XR250L calipers were listed as a different part number than all of the R calipers. Would they fit? Would they not? I had no idea at the time. To further complicate issues, somebody stripped the two screws on the master cylinder, so I was left unable to flush the fluid. Awesome. :huh
Did some detective work and realized that indeed, Honda used the same mounting bracket for the brake caliper. I was able to find a pretty much brand new early/mid 2000s XR250R caliper that bolted right up. The mounting bracket was the same, and the basic architecture of the caliper was identical, but gave me the added bonus of all of the minor changes and improvements that were made over time. To boot, the caliper still had the OEM sintered pads in pretty much brand new condition! $40 was a great price to pay for all of that. Nearly the cost of pads alone, and here I ended up with a better caliper in new condition to boot! FWIW, that caliper seems to be common across MANY bikes... Nearly all of the entire XR lineup, along with some Yamaha WRs and so on. For any of you trying to repair/replace an old caliper on an XR250L or R, definitely look for one of the newer calipers off an XR250/400 - it'll bolt right up.
With that in mind, I'll be doing a fork refresh. Seals are in good condition, but I'll be giving it a fresh change of 10W oil. Brakes will finally be refreshed, too, as I've got replacement hardware for the master cylinder cover. As for the other items... Currently running a 40/125 jetting setup, and I'll be switching to 40/128 for the final product. That should be correct for the bigger exhaust & slight overbore. Cam chain was stretched to the limits before, and that'll be replaced with the chain above. Pro-X / K&L etc both use the same chain. It is a Borg Warner unit, made in Japan.
Lastly.. we had the exhaust issue to deal with.
Stock 'L' setup on the bottom. Top is an XR250R header, from the 86/87ish to 1995 year. It is very possible that an even newer header might bolt up, as well. I'm amazed at how much is the same across these bikes. I snagged a 2008ish CRF250X exhaust, which perfectly fits the older & slightly larger R header. L header will likely go in the trash, and the exhaust will probably go up for sale.
More updates as they come. Extremely busy, but I'll get this thing finished eventually. I haven't been able to actively ride since late June, and it's beginning to bother me :cry
A few more goodies arrived over the past week. I've had a Pitbull rear stand for quite some time now, but it doesn't quite cut it for dirtbike style work. The most simplistic and inexpensive option is of course ye olde crate stand. Along with that, a clutch tool for XRs, a new clutch lever, some 10W fork fluid and a few oil filters.
And a few other items.. New drain plug / washer, spark plug, brake lever, timing hole seals, brake master cover screws, and a clutch cable. Also, the rather useful impact driver.
The brakes were far from perfect when I first purchased the bike. I had planned to do a brake fluid flush, only to find the problems with the caliper, as well as two stripped brake master cover screws. Hence, the need for the impact driver. I'd always been meaning to pick up one of these, and it had the two terribly stripped screws out in quite literally seconds. I expected to find the master full of disgusting looking brake fluid. Instead, it was nearly empty. Awesome.
Amazingly enough, even with the trashed stock caliper and completely worn and falling apart pads, the brakes were actually not too terrible. That said, the new fluid, pads, and caliper should make quite a difference in stopping power. I strongly considered throwing on a stainless brake line, but the budget sadly isn't allowing for that right now. I'm sure I'll chuck one on eventually.
New brake lever!
Clutch lever also replaced at that time... Sadly, it was about 2/3 the length of the brake lever. I also chucked the old worn clutch cable and installed the new unit. I'm happy to report that the clutch pull is significantly easier than it was before. Stripped off the grips, too. I've got a set of Pro-Grip Rally style grips to throw on... Still debating whether or not I want to install a used set of grip-warmers that I once had on another bike. We'll see.
At this point, I yanked the forks off of the bike and drained the fluid.
And off came her legs...
Real pretty stuff, eh? Extremely thin, too. That said, while the old oil was disgusting, it wasn't extremely vile. I'm guessing that somebody has been in these forks before and changed the fluid. It smelled more like semi-recent aftermarket fluid than typical original OE stuff. I filled the forks with ATF fluid, cycled them through a few times, and let them sit for a bit. ATF has some detergents that are actually pretty decent to use as a fork rinse. While those were sitting, I went to work on the battery support bar.
Lots of surface rust.. That particular side of the bar was frozen and was a pain in the ass to remove from the bike. Thankfully, with a bit of torch use, it came off and didn't strip. All of the rust was surface rust and it came right off with a nice combination of scotch-brite pads, a wire brush, and some mild dremel work with an abrasive attachment. Threw on a few layers of spray paint here and there while I was working on the other parts of the bike.
At this point, I went back to work on the forks and reassembled the front end. ATF was drained from the forks, and I filled them with 10W oil, 130mm from the top as per the suggestions for this bike on Racetech's website. After a little cleanup, I installed the replacement fork boots, reinstalled the forks, cleaned and installed the replacement brake caliper, connected the lines, and installed the wheel. The brake disc had a little bit of runout in it, but I was able to actually straighten that out to near perfect. I don't anticipate it'll give me any problems.
And here she is...
The damping on the forks was *terrible* before. Not nearly enough fluid, and it was fairly thin stuff. The new 10W was a marked improvement over the old junk. I'll probably throw some Racetech emulators in this thing sometime next year, but the fluid refresh should hold me over for the time being. As for the rest of the front end, the fender is in pretty darn good condition, but I figured I'd remove and clean it up while I was in that area. All that's really left to do is pour in some fluid, bleed the brakes, install those grips, and reinstall the cleaned and polished fender.
In regards to the head.. I actually found a VERY low hour XR250R head on ebay for not that much money. I figured that repairing my head would cost nearly the same as what I paid for a low hour head, plus I'd likely need new valves at that point as mine were showing some wear. It should arrive within a day or two. I'll be taking it apart and installing some new valve stem seals as I've already got them on hand and might as well put 'em to good use.
As for the cylinder, I'm hoping to drop it and the piston off this week to get them bored out & matched. Thankfully I've got next Monday and Tuesday off, and with a bit of luck, I should be able to have much of the bike reassembled after this next long weekend of mine.
Looks like fun.
I am worried about your connecting rod, it looked like it had bluing on it, like it got red hot.
Having a rod come apart is not nice.
I have worked on some bikes that had bad scoring on the pistons, and ones that melted holes through the top, and never have I seen a rod that looked as cooked as yours.
Hard to tell from the pix about the head, needs to be cleaned up and a light valve lap done to see how the seats are.
When I first tore this thing down, I was pretty worried about that as well. Posted a topic over at ThumperTalk, and was told that because of the way Honda heats and assembles these con rods, all of them have a blue tinge to them. Apparently it is normal.
Examples from other XRs...
I was pretty paranoid about this until it was brought to my attention that nearly all the XR con rods look just like this. I will say the the photograph makes it a little more blue than it actually appears in person, but it seems like it is fairly par for normal as far as XR rods are concerned.
The new /barely used head (hopefully arriving tomorrow) should be in MUCH better shape than what I've got. I plan to change the stem seals, bolt it on, and continue. I may take my old head and have the valve seats re-machined, and then stick it back up on Ebay. Cam slots and everything else is absolutely fine.. It was just those valve seats that were trashed.
As near as I can tell, I'm guessing that... Bike was lean from factory, and jetting was never changed. PO installed Unifilter air filter and removed exhaust baffle without rejetting, making the bike even more lean. Exhaust header cracked, further contributing to lean condition. Bike started to ping/detonate, and pieces of the head & valves were blown off & fell on top of the piston... where they scratched the sides of the cylinder up, leading to oil consumption, and finally to my discovery that the bike was using oil. That's my best guess, anyway.
Thanks for the great pics! I have recently been paying some attention to my XR250L that has been playing village bicycle since I got the 600R. Just bumped up the jetting and it is a bit friskier. Should have done it years ago!
Glad your rod is not toast.
That piston sure got hot though, looks like some old Triumphs I had.
On those bikes, if you broke them in easy, the rings did not seal well the they ran very hot and looked like your piston.
In your case, its likely from lean running?
The replacement cylinder head arrived in great condition, with one little exception... Whoever was disassembling that particular XR had sheered off one of the carb boot bolts. A quick message to the seller, and I was refunded twenty bucks which went towards the purchase of a Heli-coil kit. I'm not a huge fan of Heli-coils in high stress situations, but this is just the intake boot which has around 7-8 ft/lbs of torque on it. No problem. Removed the valves, and all of the seats & valves were in fantastic condition.
My first method of attack was to apply a little bit of heat and try to twist out the remaining edge of the stud with a pair of Vise-grips. No dice. Second attack was via Ez-out, which promptly started to sheer off. I stopped before it broke and abandoned removal, instead opting to simply drill it out and install the aforementioned Heli-coil. Worked like a charm.
Fast forward another week or so... At this point, I finally dug into the rest of the engine and removed the clutch side cover from the engine case. I'd need to remove the clutch basket in order to replace the cam chain. Via another ADV member's XR650L rebuild thread, I constructed a tool from flat aluminum in order to hold the clutch posts in place while I removed the center clutch nut with a breaker bar. I don't own an impact wrench, and it seemed like it would do the trick...
The other 'tip' to help in this case is to hold the rear brake down with the bike in the highest gear possible, and THEN twist on the center nut. I spent a day cleaning up the rear of the bike, but when I tried to bleed the rear caliper, discovered that the damned thing had seized. Ugh! Couldn't get the damned piston out of the caliper for the life of me. I began scouting ebay for another caliper, and meanwhile gave the clutch nut a go with my newly made tool. I figured it would still do the trick.
It didn't :ddog
Sheered off one of the posts... and then two more in rapid succession. Not good! Honda's tool is a little different from the one I constructed, but the general idea is the same. Holding those clutch spring 'posts' further away from the actual clutch plate simply put too much torque on then, and that was that. I was pissed at that point with my $40 dollar mistake, and walked away from the bike for another week and a half, or so. In the meantime, I placed an order for a few more parts..
Clutch side cover gasket, brake seals, swingarm slider, pressure plate, clutch nut, exhaust crush gaskets, and clutch springs.
In regards to that rear caliper... Checking on Ebay and other various sources, it appears that there are a slew of bikes which share the same rear caliper as the XR250L. Older XRs, CR500s, XR600Rs and so on. Couple Suzukis and Yamaha's too. Apparently that particular caliper was used by many Japanese manufacturers throughout the 90s. The mounting bracket for the XR-L is L specific, but the caliper 'plugs' into that bracket, which then slides on to the bike and retains the rear axle.
I was about to pull the trigger on an ebay caliper when I caught wind of a trick to 'unstick' a frozen caliper. Using a grease gun, you can apply grease via the brake bleeder valve, and it should push the piston right out. The PSI output from a grease gun is rather astounding, and it worked more beautifully than I could have imagined! The piston and caliper was filled with grease, which took some cleaning to get rid of, but was definitely salvageable at that point with a set of new seals, as the old ones were absolutely trashed. After some wet sanding with 2000 grit paper, the caliper and piston were once more in great shape. I installed the seals, cleaned out the rear master, and had the rear brakes working good as new.
At this point, I reinstalled and rebled the rear brakes. Given that three out of the four posts were sheered off, that method of removal was no longer viable for me. Family rumor mill had it that my uncle was passing through town, and it turned out he had a few electric impact guns, and would be more than willing to loan one to me. Score! :1drink
He swung by the house a week later, and while holding down the rear brake, I stuck my Motion Pro clutch nut socket on the end of the impact... and.. clickclickzip, off came the clutch nut, followed by the clutch hub. I used a couple of pennies to jam the gears, and had the cam chain removed a few minutes later. Called it a night at that point and exited the garage feeling much more positive about the progress I'd made. Entirely too much had been going wrong with this project, as one crappy discovery led to another, but from this point on, it was fairly smooth sailing.
After a few days of real life, I managed to find a little time and headed back into the garage. First, however.. Valve stem seals replaced and valves reinstalled with a little moly lube on the shaft, as per the Honda manual.
The final steps of reassembly took place over a couple of days. I was close, but a couple of small issues sprung up that slowed progress. The piston wrist pin did not want to come out very easily, but after a quick trip to Ace Hardware, I had constructed a wrist pin puller using a long bolt, two washers, one nut, and a couple of choice length sockets from the toolbox. Five minutes later the wrist pin was out and the piston was free.
After careful inspection of the old piston, I realized the piston I pulled was NOT the stock cast Honda OEM piston, but rather a Wiseco, identical to the replacement I'd be installing! Odds are that whoever installed this piston before went through a ton of work, but still never rejetted the bike to take care of the lean running issue, and thus it ended up eating that replacement piston too. Amazing that such a large bit of work could be done, but they never bothered to fix the actual root issue!
At that point, I checked the ring end gap in the freshly bored cylinder (All were within spec!) and after installing the rings on the piston, applied assembly lube to the piston/wrist pin area, as well as the end of the connecting rod. Another circlip later and the piston was on there for good.
At this point, I called it a night again. Swung by the local Yamaha dealer the next day for some Yamabond 4 / Threebond 1194 / Hondabond etc etc. (It's all the same stuff..) to use in sealing the cylinder head cover. I hadn't realized it at the time, but the giant o-ring on the bottom of the cylinder jug was missing! Oddly, I don't think it was ever really on there to begin with! Previous owners must have removed without replacing it during the original rebuild. I opted against waiting another week and a half for a simple o-ring to arrive, and used the aforementioned Yamabond to seal the base of the cylinder. Common practice on many other bikes, and it worked like a charm. After installing the base gasket and dowel pins, the cylinder head was slipped over the piston with the rings aligned in proper position, and secured into place.
After a little oil on the cylinder stud bolts, as per the manual, I torqued them all to spec (29 ft/lbs) and prepared to install the cylinder head.
And it was here that I ran into another brick wall :huh
I thought I had perfectly cleaned the cylinder before.. but apparently not. The threads had superfine grit in them from sandblasting, and the cylinder head would not have gone on without a fight, and possibly stripped threads. Not a chance in hell that was going to happen... I wasn't about to throw away all of my progress by trying to rush to through to the finish...
The bad news? It was Thanksgiving... My goal had been to get this thing finished by the end of the holidays, no matter the circumstances. I tried to clean the threads but to no avail, the damned studs wouldn't screw in. I desperately tried to look around to find a M10x1.25 tap, but no stores were open who actually carried the damned thing.
Pretty damned near defeated at that point, I started to think about ways that I could clean those threads out. The threads were in good condition, and it was simply the grit that needed removed. A tap and some oil would have done that without a problem, but I didn't have that on hand.. and all of the q-tips and paper towels seemed to be doing nothing. I cut the tip of an old toothbrush in half, and it removed a significant portion of the grit, but not enough... Think think think.. What else could I use? What would be open on Thanksgiving that might have it?
And then it hit me. Braces brushes! God knows I remember those from my days in braces as a kid... I removed the cylinder once more, and made a quick trip down the street to Walgreens. After a couple of passes with hot soapy water and the tiny brushes, I had clean threads! Game on!
From there, it went like clockwork... Back on went the cylinder, and then the cylinder head & gasket. Installing the cam chain and cam on the XR is extremely easy compare to other multicylinder bikes I've had.. Simply put the piston at TDC, and stick the cam in with lobes facing downward, line up the two lines on the cam gear at 9 & 3 o'clock, and screw it all together. Dab of assembly lube on the middle came journal before starting, of course... and with the cam chain in place, I pulled the pin from the tensioner and voila! We were in business, with plenty of travel left in the tensioner courtesy of the new chain.
(Note: When I first purchased the replacement chain and held it up to the old chain, the lengths were near identical... However, under stress, the new chain had significantly less stretching, whereas the other chain had the tensioner piece below and inside the tensioner, completely worn and making it impossible for me to grab with a set of pliers. New chain totally took care of the issue!)
At this point, I sealed my cylinder head gasket with some Yamabond, and installed it.
Next would come the clutch... Plates appeared to be in good condition, and I reinstalled them along with the new springs and new clutch nut. While holding the rear brake, I installed the nut with the impact and tapped down the stake on the nut in order to keep it from rotating out of place.
With everything torqued to spec, I then cleaned up all of the clutch cover bolts by running them through a die, and double checked to make sure all of the engine case clutch cover threads were in good condition, running a tap through those that were not to ensure cleanliness. With the new gasket in place, the clutch cover was reinstalled, along with a new oil filter and new oil pan bolt/washer, as the older bolt had been badly stripped. Rear brake lever and kickstart were reinstalled, and we were good to go.
The last step was to install the new exhaust, which I am unhappy to report did NOT fit. It had been reported that the CRF250X exhaust was plug and play, but it makes contact with the subframe and will not fit without an extension. I am pleased to report that the R header does in fact fit the L exhaust, though I had to construct a makeshift gasket of sorts. I'm still deciding whether to stick with the L exhaust, or trying in the future to make the nicer CRF unit work. We shall see.
I'm sorry to report that I'm a little short on pictures after this point... At this point, it hit me that the bike would be ready to start up soon. I was a bit nervous; I'd been working on the damned thing on and off since June, and this was the big moment.. Would it work? Would it not work? I've worked on cars for a lot of my life, and also assisted my father on a couple of engine & transmission rebuilds, but I had never done a complete rebuild completely by myself.. and here we were, moments from startup...
I took 15 minutes to readjust the valves, threw in some Rotella for break in, grabbed my gear, and gave a salute to the moto gods...
Kicked over once... Kicked over twice... and on the third kick, she fired up!
I think I sat there at that point sort of in shock, thinking... 'Wow, it actually worked...'
At that point, I threw on my gear as quickly as possible, and began the process of constant acceleration / deceleration and varying the RPMs for break in. I rode for about 12 miles over the next 30 minutes, and immediately dumped the oil and changed the filter. Tiny little microscopic sized glitter made for some pretty cool swirls in the oil pan... Almost like the swirls in a nice cup of espresso! During the short time I rode it, I could definitely feel the engine loosening up. But even during those first few miles, the bike was already stronger than it had ever been in the past. :clap
Today, I took the bike out for another 50 miles of countryside twisties and mild gravel road exploration. She's feeling stronger than ever, and easily pulls up the front wheel in first on throttle alone, and also in 2nd with a little effort. The exhaust note sounds deeper and significantly more 'solid' than it ever did pre-rebuild. A little fuel screw adjustment had it running near perfectly, and I'm pleased to report that everything is working fantastically at this point. I replaced many of the rear fender bolts with some more appropriate fitting hardware, and plan to install the Buell turn signals in the near future as well.
As far as I'm concerned, mission accomplished! :freaky This bike was much more of a project than I had ever wanted, but I learned a *lot* in the process and am looking forward to a lot of dual sport fun in the near future. :clap
Nice job. I remember when these were new in the dealer. I wanted one soooo bad. Somewhere around $3,000 new. The hot trick back then was to do a 280 big bore kit.
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