Xr650l Vaccum Piston Question.

4 replies to this topic

Posted September 16, 2006 - 08:27 PM


Just Bought A '93 Xr650l With 5 Thou Miles. I Am In The Process Of Doing Dave's Mods In The Stock Carb. I Was Putting Back The Carbs Together, When I Checked For Slide Travel Manually, I Notice That The Slide Does Not Raise Up All The Way Except For About 1/4th Of The Way. Isn't It Supposed To Raise Up All The Way When You Go Full Throttle Or Pull Up On The Cable Guide Housing. I Have Checked Everyhting At Least 10 X Already And Everything Is According To The Manual. Thanks In Advance!

  • LotsOfBikes

Posted September 17, 2006 - 04:18 PM


It will rise up all the way when the bike is running.

It will mechanically rise only a little when the throttle is pinned with the engine not running.

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Posted September 17, 2006 - 06:17 PM


Thanks for the quick reply! I thought i goofed up somewhere. The slider then must only go all the way up when the engine is running close to full throttle and creates the vacuum. I do have another question. I noticed that the 2 drilled holes on the slider are partially covered about 50% by the plastic thing that secures the needle! Would this affect the mod? Do i need to drill a smaller hole that can not be obstructed by the plastic? I cant find a shim that fits snug and has the same circuference head as the needle. Would it be fine if i just put a shim that is slightly bigger O.D. AND I.D? THANKS!

  • LotsOfBikes

Posted September 17, 2006 - 08:52 PM


The plastic thing question is a question for XR650L_Dave. You can PM him, he knows everything about the L -- No joke, I MEAN everything!

I have done no carburetor modifications on my 1995 XR650L, except removing the restrictor tongue on the air screw back in June of 1996. Not even a rejet, nope!

....over 60,000 miles os harsh abuse :thumbsup:

  • XR650L_Dave

Posted September 18, 2006 - 07:53 AM


Mmmm, lemme see.

1) When the carb is assembled you should be easily able to push the slide up all the way with your finger. The throttle manually cracks it open a tiny bit, much less than 1/4.

2) On mine, I don't recall the relationship between the slide holes and the plastic thing, if it was an obstruction I'd hope I'd notice it. Then again... . Anyway, I don't think its an issue. Now the clearance between the seat and the top of the airbox, THAT's an issue.

3) The problem with using a larger shim is that the jet needle has to sit in a little recess on the top of the slide, and if you use a shim larger than the recess, you end up raising the needle waaaay too much. As long as the shim fits in the recess, all is good.


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