Post deleted by Steve_Claus

I can see where valves out of adjustment would make it miss at low rpms, it could be bleeding off compression by the exhaust valves.

What year is the bike? How many hours are on it? What did he mean by "new top end?" Do you have the manual?

Find the manual. Checking / adjusting the valve clearances is very well explained in there.

Im not sure on this, But did you get the work done and this is the result ?

If so then bring it back and get them to fix it...

They may have not adjusted the Vavles correctly.

Need more info! Maniac

What I think you are describing is the off idle bog. This is a know problem with the yzf's, and is easily fixed. Two trains of thought actually three

1: BKMod

2: Jetting

3: Both

The Bkmod allows adjustments to the Accelerator pump down to duration of .3 sec. You can find this mod at http://motoman393.forreal.net/tech.html

Jetting is focused mainly on the pilot and needle.

Raising the pilot to #45 from stock #42 and adjusting the air mixture out 1 1/2 turns will help with the hesitation

The Needle clip can be dropped down effectively raising the needle up one notch.

But remind you each change is distinct and should not be done unless you are aware of and understand jetting dynamics.

I would bet if you do the BKmod it will take care of the issue....

Originally posted by E.G.O.****:

Jetting is focused mainly on the pilot and needle.

Raising the pilot to #45 from stock #42 and adjusting the air mixture out 1 1/2 turns will help with the hesitation

The Needle clip can be dropped down effectively raising the needle up one notch.

EGO - you are telling the poor guy to richen up his jetting. I'm sorry to disagree but on my 2001 that will only WORSEN the bog. I would agree to possibly do this after the BK mod, but not before.

Danny2623 - If in fact you have a "hesitation" or a slight bog off-idle, then you need to LEAN the jetting a little. The first step is to turn in the fuel screw at the bottom of the carb. It may be that's all you need. In is leaner. If you get to a point where you run out of adjustment. Or if the idle starts "hanging" but you still have a hestitation, you need a smaller pilot (not a bigger one).

Here in Texas I am running my stock 2001 with a 40 pilot and needle clip at 3rd position from the top. Everything else is stock. It is hot here now - about 93-96 degrees. This jetting is still a little rich but at least there is no off-idle bog.

Let me restat then.

Depending on you region of the country, teh fact is if the bkmod is done then jetting will need to follow.

Depending on Sea level, air temp and others as posted would depend on jetting.

Again if you read my post real carefully I specificly stated

But remind you each change is distinct and should not be done unless you are aware of and understand jetting dynamics
Indicating one must understand first dynamics...

And this piece of filter material actually passed through the backfire screen? Something stinks in Smellsville.

It is peculiar that something that large would get by the foam..

If you're near sea level then the '01 should run pretty good on stock jetting. It wouldn't hurt to double check the valves and clean the carb, especialy if you know that something dirty has passed through there. A dirty carb can cause a lot of problems, and you'll want to clean it before you mess with the jetting anyway. Be sure to shoot carb cleaner through all of the little holes, just be sure you're wearing safety glasses or something because it will often come back at you. Hope this helps!

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