Bucking and high idle

[DanielR]

I have an 82 that I bought about 4 months ago
It never ran well, the previous owner left it sit in his garage for almost 3 years with gas in the tank and in the carbs (DUH!)
I cleaned out the tank and put fresh 100 octane in it and rebuilt the carbs, but it STILL runs like crap.
It idles at about 3k but if you back up the idle adjuster 1/100 th of a hair, it will die.
When you rev it in neutral it revs up just fine, but if you goose it in ANY gear at any speed, it stumbles and stalls.
When you hold the throttle perfectly still in any gear at any speed the bike surges and bucks HARD (lifts the front wheel in 1st or 2nd)
Any idea what it might be?
Thanks in advance
-Daniel Ryba

[swat1]

hi have you sync  your carbs?? got  new  spark plugs ??or checked them ,check your vacuum lines also

[h2olawyer]

Carbs may still be clogged - mine took a couple dips in Berryman's to get clean.

YICS may be leaking.  Plug the hoses or cap the fittings on the head, then go about tuning the carbs.

Sync is another possibility.  Often the erratic running is a combination of things - normally dirty carbs & YICS.

Also, get new plugs & wires.  May not cure the problem, but at least you will know they are in good shape for many years to come.

H₂O

[YellowJacket!]

There is a silver triangular box on the right side of the bike with YICS on it.  It can sometimes leak and cause lots of problems.  It connects to two ports on each cylinder base.  Cap the ports off tightly and see how the bike runs.

Take the YICS off the bike and hook a rubber hose up to it and dunk it in some water.  Blow through the hose and if air bubbles leak out from it, its leaking and causing the problems.

The carbs are a pain to clean and sometines need to be cleaned several times.  You MUST make sure that you remove all the jets when you dunk it in the carb cleaner.  If not, it could actually run worse because of gunk trapped in one of the passages or the o ring getting eat up by carb cleaner.

Start there.

David

[DanielR]

When I rebuilt the carbs they went into a vat of berrymans chem-dip with an agitator (with the lid closed on top of the clothes dryer ;) ) for about 3 hours each so i don't think that the carbs could be the problem.
I synced the carbs whan i mounted them, but im gonna do it again just to be sure...
The YICS box has a leak, so im fixing that up with some HOBBYPOXY (2 part epoxy that is fuel, oil, and everything proof) and a gasket.
hopefully that fixes it.
Thanks!
-Daniel Ryba

[Rick G]

Daniel , NEVER , NEVER  leave Vision carbs in the dip longer than 1/2 hour. The butterfly shaft has a seal on each end that can be destroyed by extended exposure to any carb dip. The seals can't be gotten from yamaha, but Polaris ATVs used a Mikuni  carb in the past and the seals can be gotten from them The drawback is, that the butterfly shaft must be removed to change the seals and the screws that hold the butterfly  valve in place are staked and difficult to remove. They are also not reusable  and  not available from Yamaha. You will have to match them from very complete hardware store or industrial hardware supplier. Also, it's  tricky , getting the throttle plate (butterfly valve) back in place for proper operation.
What I'm saying is, don't dip Vision carbs so long  (in one sitting) as to damage the seals . You may have already done so, when the seals are damaged the mixture can be leaned out, especially at low rpm  and an eratic idle will result.
When dipping a set of carbs, after rinsing them off with water, I use an air nozzle to clear all passage ways , then I  use a can of carb spray  to blast through all passageways as a visual aid, to be sure that there totally cleared.
I have a set of XS400 carbs that would not come clean  and after  4 ,1/2 hour dips , the shaft seals are toast  and I picked up a set on eBay to replace them.

[inanecathode]

Try to blow air through all the passages in the carb when you take them off again (you are taking them off again arent you?). Berrymans is righteous stuff, but it doesnt dissolve hard deposits well, especially if they're in jets.
What you describe is a clogged idle circuit. Just take the carbs out and unclog them, easy as that :)