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Old 12-03-2009, 04:27 PM   #811
InfiniteMiles
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I made some progress today, after much work, a few beers and lots of bad words I was able to remove all but one of the stripped fasteners. I don't understand them at all the heads strip down easier than a $2 whore on pay day but everything past the top must be made out of some alien alloy, that is impervious to any material know to man. I broke so many bits trying to get the damn things out.

With the bolts out I was able to take my top end off. The sleeve is not bad looking upon first inspection and luckily I'll be able to hone it out. The piston is alright below the rings but is trashed at the rings and above, it's all marked up and the rings them selves are worthless.

I took some measurements and found that the cylinder has a /\ shape going on, it's only a 5 thou piston to wall clearance at the top and just over 40 thou at the bottom! Look's like a new Wiseco, and a hone and I'll have my oil problem sorted out.

The bottom end from what I can tell is not faring much better. The rod rocks side to side a little bit but that's to be expected, but the left hand crank has a couple of small chips on the bottom side, which match the rest of the crank color wise but are definitely noticeable, also the right hand bearing is blueing a little bit on the top. Sadly I'm going to have to pull the whole bottom end and see what going on.

In the process of taking the carb off the right hand the secondary intake manifold ripped apart like a piece of paper, this surprised me because I had checked these just the other day by running the bike and spraying carb cleaner by the manifolds listening for a jump in rpms and got nothing.

I attribute all these problems at a mere 15k Miles, on a so called bulletproof engine to dangerously lean conditions from the factory coupled with a new less restrictive pipe. The guy who tossed on the piped didn't even cut away the air box to at least feed it some more air, and he only used the bike on trails... So the whole bike cooked in the summer, running lean in first and second with a dirty restrictive air cleaner,and not enough gas and was then put away dirty for the winter to do it all again.

The carb is a funny story, from the outside it was looking rather gnarly, after a good scrubbing and some soaking I got most of the junk off. I then stripped it down and was shocked at how pristine the inside was, despite buying the bike with a dirty air cleaner, and seeing the obvious affects of the dirt making it's way through the carb and into the cylinder, there was none to be found in the carb it self, this is a mystery to me.





Any one know if a TT cylinder will bolt on an XT? I can't find anything that suggests it wont.

InfiniteMiles screwed with this post 12-03-2009 at 06:54 PM
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Old 12-04-2009, 06:45 AM   #812
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Quote:
Originally Posted by InfiniteMiles
I made some progress today, after much work, a few beers and lots of bad words I was able to remove all but one of the stripped fasteners. I don't understand them at all the heads strip down easier than a $2 whore on pay day but everything past the top must be made out of some alien alloy, that is impervious to any material know to man. I broke so many bits trying to get the damn things out.

With the bolts out I was able to take my top end off. The sleeve is not bad looking upon first inspection and luckily I'll be able to hone it out. The piston is alright below the rings but is trashed at the rings and above, it's all marked up and the rings them selves are worthless.

I took some measurements and found that the cylinder has a /\ shape going on, it's only a 5 thou piston to wall clearance at the top and just over 40 thou at the bottom! Look's like a new Wiseco, and a hone and I'll have my oil problem sorted out.

The bottom end from what I can tell is not faring much better. The rod rocks side to side a little bit but that's to be expected, but the left hand crank has a couple of small chips on the bottom side, which match the rest of the crank color wise but are definitely noticeable, also the right hand bearing is blueing a little bit on the top. Sadly I'm going to have to pull the whole bottom end and see what going on.

In the process of taking the carb off the right hand the secondary intake manifold ripped apart like a piece of paper, this surprised me because I had checked these just the other day by running the bike and spraying carb cleaner by the manifolds listening for a jump in rpms and got nothing.

I attribute all these problems at a mere 15k Miles, on a so called bulletproof engine to dangerously lean conditions from the factory coupled with a new less restrictive pipe. The guy who tossed on the piped didn't even cut away the air box to at least feed it some more air, and he only used the bike on trails... So the whole bike cooked in the summer, running lean in first and second with a dirty restrictive air cleaner,and not enough gas and was then put away dirty for the winter to do it all again.

The carb is a funny story, from the outside it was looking rather gnarly, after a good scrubbing and some soaking I got most of the junk off. I then stripped it down and was shocked at how pristine the inside was, despite buying the bike with a dirty air cleaner, and seeing the obvious affects of the dirt making it's way through the carb and into the cylinder, there was none to be found in the carb it self, this is a mystery to me.

Any one know if a TT cylinder will bolt on an XT? I can't find anything that suggests it wont.
Keep an eye on ebay for the crank/rod. The cranks on these things don't usually go out unless they get starved for oil so it's a pretty safe buy. I got one for a fraction of the cost of rebuilding mine.

Also, since you will have the cases split, it's a good idea to put in a new Oil pump gear. It's plastic and will have some wear. good time to change it out.
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Old 12-04-2009, 11:37 AM   #813
InfiniteMiles
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Quote:
Originally Posted by SkidMarx
Keep an eye on ebay for the crank/rod. The cranks on these things don't usually go out unless they get starved for oil so it's a pretty safe buy. I got one for a fraction of the cost of rebuilding mine.

Also, since you will have the cases split, it's a good idea to put in a new Oil pump gear. It's plastic and will have some wear. good time to change it out.
Alright, I'll be sure to change it, I'm trying to get a list together of parts I'll need for sure. I'm worried about having the cases split for to long while I figure out what bearing's I need and search for a crank. I think I'll leave it in the frame for now and go through all the sub systems one by one.

I just have to stay positive and know I'll have a bike I can ride with out fear of breaking down, hopefully we can tear up some trails next summer.
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Old 12-07-2009, 11:55 AM   #814
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Save up your egg cartons.
When you do take it apart, put the bits in the cartons in the order you take them out. Mine sat for months in pieces and this made a huge differance in reassembly.
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Old 12-07-2009, 09:20 PM   #815
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Carb Jetting

AKASY, I'm excited to hear you did the TT fork swap, all I can say is give us more! How'd ya do it? How's it work? Plans for the rear spring/shock assemby? Good job!

Progress in jetting....
I ended up pulling the original jet (that the Yammie shop reamed open quite large), put in the 140 main jet with shim. Runs much better overall. When I turned the pilot scew from 2 1/2 out to 2 turns out it runs better yet, BUT the idle did increase and I still feel some "hesitation" when on the throttle.

I need some direction now if you guys don't mind.

InfiniteMiles, you posted "..to get your idle exact turn your air pilot screw out to 2 and 1/2 turns, then screw it in slowly, and listen to the idle. If it increases you need a richer jet"

Just ream out the main a little and try again?


Here's the plug with the 140 shimmed jet, pilot at 2 1/2 out.

Is it ok to check plug color with a fairly new plug or does it need to be really broken in before checking color??

Miles... bummer to hear you've got some work ahead of you, she'll be ready for even more miles when you done. You story scares me since I have the new pipe, makes me realize how right I need to get my jetting... thanks for all the help.
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Old 12-08-2009, 12:04 AM   #816
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Quote:
Originally Posted by J-Ball

InfiniteMiles, you posted "..to get your idle exact turn your air pilot screw out to 2 and 1/2 turns, then screw it in slowly, and listen to the idle. If it increases you need a richer jet"

Just ream out the main a little and try again?
No, you don't have to mess with the main jet yet, the idle mixture is all controlled by the air fuel mixture screw, and the pilot jet(Part 6 here http://www.bikebandit.com/houseofmotorcycles/1989-yamaha-motorcycle-xt350w/o/m8355). Your idle speed is controlled by the throttle stop screw. To adjust your idle mixture you need to turn your air fuel mixture screw to 2 and 1/2 turns then out a little then in a little. You need to figure out which way raises your engines rpms. Backing the screw out lets more air in and leans out the mixture, which would mean you need a smaller pilot jet. If you turn the screw in and the rpms go up you need a larger jet.

You want to find a jet size were any change to the air fuel mixture screw going in or out from 2/12 turns makes the rpms decrease. Once you have the perfect pilot jet you can set your engines idle speed by adjusting the throttle stop screw on the carb.

After your idle is set you move up to the main jet which controls your wide open throttle, but also has an affect on your mid range, which is way you tune this before your mid range. To get this right, you have to do a few spark plug reads, all you have to do is warm the engine to operating temperatures, then ride in full throttle for in any gear for a distance, then hit the kill switch, pull in your clutch and coast to a stop. Then when you check your plug it will tell you if your to lean or rich at WOT.

After you have you idle set which affects everything, and your WOT throttle set via your main jet which also affects your mid range, you can tune your mid range. You do this by shimming the needle up for a richer mixture and down for a leaner mixture, this is why many people place tiny washers under there needle, to hold it up higher for any given throttle positions, creating a richer condition.

This is all very easy to do with one carb, but is complicated on the XT because of it's dual carb design. The secondary carb is a constant velocity carb which works, a bit different from the primary in which the opening of the throttle directly opens the needle, when the throttle is opened a trap door in the secondary carb called a butter fly opens allowing air to flow through and this air is what pulls up the needle, this is designed so you don't hit a bump and snap the throttle open and lose control of the bike, while at the same time having two small carbs as apposed to one large carb reduces the bog felt when going from low to mid throttle to WOT. As far as tuning goes the secondary carb has a main jet and needle set up, as well as a spring which controls how much tension is on the needle and how much air is required to lift it.

When your tuning for WOT and mid range it's important to make some changes to the secondary carb as well, but be careful as the needle is held by a thin rubber diaphragm, which can be pricey. One thing you can do that is different from shimming the needle or selecting different main jets is snip the spring holding the needle down bit by bit until you have gone to far, then replace it with another spring cut just right.

As far as exhaust goes, if you let more air out you have to let more air in(open your air box a little) and if you let in more air you have to let in more gas(richen the jet's shim up the needles)

Performanceis all about how much you can flow in a perfect balance.

The bike I'm working on came to me this way, I would never let a new bike go this far, but I don't have the cash for a new thumper.
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Old 12-08-2009, 09:31 AM   #817
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InfiniteMiles, I must respectfully disagree. The main jet affects everything, including idle settings. I don't think the idle circuit has much affect on WOT. I think WOT should be gotten right first.

J-Ball, look at all the earlier posts about this. Skidmark (I think) posted another site which had a great method for jetting these Teikei carbs. I don't have time to find it now, but if I remember correctly you basically step up both mains until you get the top end right, then back off the primary main until you get the midrange right. Then fuss with pilots and idle screws. You might also look at TTKlause's recommendations (adjust for altitude -- he's at 6500 ft and should be about 6% lean at sea level).
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Old 12-08-2009, 12:10 PM   #818
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I kind of went about this the opposite way by using a Supertrapp and fine tuning the jetting by way of the exhaust. I went up one size jet on both mains and the pilot, shimmed both needles the equivalent of one notch, made the air screw richer by 1/2 to 3/4 turn and adjusted the linkage so both sides of the carb started to open at once. Then i opened up the airbox. Then I used the Supertrapp to dial in the jetting the rest of the way. I just added plates until it was too lean again and then subtracted one. Mine idled and ran perfectly at all rpm's.

I can tell you from experimenting with mine that the mains and needles didn't have much effect at low rpm. We did those first and it was still pretty weak off idle into the midrange. Once we finally found a source for pilot jets and drilled out the plug for the airscrew so we could go richer on those, it idled better and had nice power right off idle into a pretty solid midrange. That was actually a bigger improvement in how it was to ride the bike than we got by larger mains. It was a major hassle to get right. But it is a really sweet running engine once you do.
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Old 12-08-2009, 05:09 PM   #819
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[quote=J-Ball]AKASY, I'm excited to hear you did the TT fork swap, all I can say is give us more! How'd ya do it? How's it work? Plans for the rear spring/shock assemby? Good job! Quote

Have not had much chance to ride due to weather, I'm hoping to get away from the fork flex and resulting steering deviations that can be seen in this video clip

http://www.newmexicorider.com/video/monticello-2009-3

The swap was not difficult, made a bracket to keep the instruments, got an entire TT front end--key to making it easy--no fork lock, different front rotor and master, drill and tap on screw hole, fret with cable routing, but not difficult in my opinion. I will take it out and bang the crap out of it when the weather is a bit more cooperative and see how it does--so far no issues but it is a total specialize remake of the steering and suspension--no plan to do the rearr.

Here are a couple more pics


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Old 12-10-2009, 01:58 PM   #820
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Quote:
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You want a front sprocket for an 84-89 XT600 or 82-83XT550 or 87-87 TT350 or 83-86 TT600, for the rear 80-84 Xt250, 80-82 TT250 and a couple others fit.
Hi just hijacking this post.

Thanks for the useful info

Can you tell me what length chain links on the 520 conversion?

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Old 12-10-2009, 03:18 PM   #821
missadventure
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luggage rack?

does anyone here know where one can find a luggage rack for an xt350?

i'm sorry if it's been posted before. i tried the search function, but failed to find anything.
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Old 12-11-2009, 08:47 AM   #822
johned206
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xt350 rack

I bought my rack from Cycleracks. Very satisfied with it and the service I got from the guy who makes them. Google them.
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Old 12-11-2009, 10:15 AM   #823
InfiniteMiles
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UUUUHHHGGGG

So if I resleeve my cylinder to the final Wiseco 37.5 mm piston my sleeve will be dangerously thin, and I'm not using a time bomb of a sleeve on a freshly rebuilt engine, so chalk up another $200 in parts and probably the only labor I'll farm out. looks like this will truly be a total rebuild.

On the plus I've taken about a mm of oil build up of the head and have lapped the valves, and I never though I would say this but there is a lot of winter left.

InfiniteMiles screwed with this post 12-11-2009 at 12:47 PM
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Old 12-11-2009, 08:09 PM   #824
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thanks johned206!
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Old 12-11-2009, 08:55 PM   #825
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Anybody know which 55 tooth or bigger 520 rear sprocket fits an XT350B?
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