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Old 20 Jun 2011
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Originally Posted by pursang View Post
While looking for a part number I found this hairline crack on the piston skirt, I don't feel so bad now she didn't fire up this spring.
I'm sure you understand the piston MUST be replaced now !!

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Old 20 Jun 2011
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gixxer.rob: That's exactly what's happening, I'll clean it up and seal it with silicone, about a third of the rubber on the round barrel section has come loose and I can feel it's gritty inside.

*Touring Ted*: Absolutely Ted, I'm just glad I didn't get it running or it might have been a really expensive repair !

oothef: The valves do have some play but I don't have the tools to check if there in or out of spec, I'll have to wait and see what the machinists find. thats the first I've heard of "guide liners" I'll look into those.
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Old 21 Jun 2011
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I can't say for sure if the condition of these carbs is after 60.000km or less, I was told the bike went in for carb work but the extent of it may have only been to pop the float bowl off.
Cylinder head side of the carbs.

Loads of carbon and cylinder sludge has been splashing into the carbs due to the tight intake valves not sealing, this shot is the diaphragm carb.

Same cylinder side of the carbs but this shot is the throttle valve on the regular carb.

One of reasons to do your own repairs, I was told when I bought the bike in 2008 it had recently gone to a shop for carb work, instead of replacing the float bowl seal they used some kind of glop that hardened like cement and ruined the rubber seal.

Top of diaphragm was pretty much spotless.

The underside of the diaphragm is only filtered by a course inline foam filter that works great for keeping the humming birds out, not so much the gritty fine stuff.

Lots of crud found in the regular carb top chamber, I'm sure some of this stuff finds it's way down the throttle valve and into the intake tract.

None of my manuals list this as anything more than a "Diaphragm Set" this is the top spring side, not sure if thats fuel or cleaning solvent.

And where the diaphragm sits, would really like to know the proper name for this valve.

And the underside of the diaphragm that pushes on the brass pin.
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Old 30 Jun 2011
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info please

hi did you get your bore and piston measured? ( i dont know if you could with the split in the piston ) im interested in knowing if this is a bore / piston or valve problem or both thanks steve
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Old 7 Jul 2011
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No Steve the piston/bore was never properly measured since I didn't have a 4" micrometer on hand, the piston did move back and forth in the cylinder, the rings were much worse than the piston, they were excessively worn and sticking, since we discovered the piston was cracked the machinist didn't bother taking measurments, he pretty much just looked at it and said "1st over" I'd say it was a combination of the rings and the valves, the valves were tight and later when I did a solvent seal test all four leaked, also the exhaust valve guides are shot.
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Old 7 Jul 2011
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Well, I've just found out today that if you the crankcase breather tube is wrongly routed and causing the tube to be kinked the bike will smoke like hell lol

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Old 15 Feb 2012
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She's finished and running like a champ ! Thanks to all my fellow XT'ers who helped with this build.

Motorsports Forum. - Top end rebuild
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oil consumption. smoking.

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