|09-17-2011, 05:39 PM||#1|
Gear Driven Cams!!
Joined: Apr 2008
Location: North Carolina
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.
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