Rayjay,

What you are describing is definitely way out of the ordinary. All R* have an engineered-in shake that's almost to the point of annoying, but should remain on the side of endearing.

Yours sounds uneven and feels different every few ignition pulses. That would seem to differentiate yours from the norm. The swapping of the coils made no difference, which would suggest something mechanical rather than electrical.

What kind of gas mileage are you getting? If compression is good and it isn't electrical... think about it, it's related to carburetion and the excess fuel you're finding in the manifold.

There's no way you should be finding raw gas in the manifold.

I think the raw gas builds up, flows into the back cylinder and suppresses it, and then builds up again. If that is so, the problem would be the carb. That's my best guess.

Start with float bowl level.

However... if your gas mileage is good, my suggestion really wouldn't make sense, as your mileage should be poor if the carb is to blame.

rayjay, a burnt,bent, or sticking valve and the cylinder will not fire at all, no compression...as far as valve timeing being off, that could only happen if someone has been in there and changed it, those cams are gear driven and cannot jump a tooth. a bent valve could destroy the cam lobe or a lifter tho..
spray some water out of a windex bottle at the joint of the head and mani while running if the sound changes, you have an air leak..hope this helps..

Thanks guys for the input. It helps me think beyond where I'm at. I have sprayed the cylinder joints to see if there were any leaks. There had been a manifold leak when I got the scoot about three weeks ago. I repaired that and the bike ran great for a few miles until it heated up on the way to work. It was a pleasure to ride for those 20 or so minutes.

Questcap, (I'm glad you agree that it is not ordinary vibes) what you are saying sounds like it may be the carb. It kinda makes sense. But...why doesn't it affect BOTH cylinders and not just the rear. I will get a carb rebuild kit (gaskets) and give it a goin' over soon (by the book).

I've been told to take it to a shop, which I don't want to do. I can solve this and I know this bike is capable of an enjoyable ride and I'm determined to get to it!

Thanks,
Rayjay

Are you positive you don't have an manifold leak.

They can sometimes be hard to detect.

Doc

Questcap said:
I think the raw gas builds up, flows into the back cylinder and suppresses it, and then builds up again. If that is so, the problem would be the carb. That's my best guess.

Start with float bowl level.

I went into the cave as soon as I got home from work and set up a clear poly tube to check float/fuel level. It took a while to find all the stuff I needed to do the check. Put the scoot up on blocks to level her. Anyway, I found that the fuel level was at least 1/4" or 3/8" HIGHER than the carb joint. I pulled the carb and adjusted the tang by eye
I re-installed the carb and re-checked the fuel level and it was good to go!!!
Of course I had to go on a test drive . Very humid evening but cool on the ride. My scoot rode like she should and how I expected - even though I think I can tune her a little more to smooth her out a little more. The REAL test will come when I run for a distance and get her hot. But for now, I am confident that Questcap pointed me in the right direction.

Thank you! Thank you!

Rayjay

Now on to tuning that front end....

I didn't want to get my hopes up last post, but I did. And all too soon! The bike ran pretty good for a while but reverted to v-v-v-v-v-i-i-i-i-i-b-b-b-b-bration. It was very bad riding I-195. Between the vibes and wind buffeting, it was so overwhelming I almost lost it. Forced myself to keep going, since there was no where to go but off at the right exit. Thank God it was newly paved so no potholes distracted me on top of it.

Sprayed the *carb joint* when I got home and found that another bad leak developed (no surprise). Today I bought new next-size-larger *O* rings from NAPA for .85 each (that's $7 in Yamaha dealer language )

Had to remove most of the retainer indent to get them in. The bike runs much better, but still vibrates over 55 or 60 MPH. I sprayed the manifold (er...excuse me...carb joint) again and still had leaks near the top of both sides at the flange/head area. I think my manifold went bad. There's no way I can get that thing on any better or tighter. (There were cracks around the flange areas which I silicone'd shut previously.)

Have stock manifolds gone bad on anyone???

I will order a new ported one from Phat Performance

http://www.phatperformanceparts.com/ProductDetails.asp?ProductCode=BA-5524-00

unless you guys have any ideas. I was also thinking of getting a Nemesis manifold, but I have to look, price and see if it will fit the stock carb.

I'm sick of disassembling rather than riding.

Rayjay

Nemesis manifold for 1600 and stock carb ...

Doug Montgomery

DK Powder Coating

PowdercoatKA@aol.com

417-742-4533

Doc

Doc,

Do the stock manifolds go bad and leak???

Do you know how much the Nemesis manifolds run?

Rayjay

Maybe I can get a package deal on the Nemesis manifold and coil set...

Rayjay

I've been following this thread with great interest, Ray. I'm sorry you're having a hell of a time, but it sounds like you're chasing down the problem and you'll have it fixed soon. I just wanted to drop you some encouragement. Hang in there, bro.