after rebuilt the carbs idle at 5k rpm

[mason79]

pilot jets are 42.5 and has holes in them

thanks topcat for the your version of the bench sync, i thought about that; i checked visual gap after the bread tie anyways and i was thinking i could get it closer.

since the bowl vent led to the airbox i thought it got some vacuum from in front of the velocity stacks thru venturi action, but thanks for letting me know it's just venting fumes.

wierdly; although i dripped motor oil through the cables, when installed, even with no binding, the return action seems dampened,

and it is not hung up on anything, so that's not it, the butterflies are shut, i make sure of this, by counter rotating the grip and it still revs, the only way i can control it is flicking the kill switch on the off.


can it be i set the floats too lean?

mro:

yes no load,

i don't dare to get on it and go for a ride i can't control, it's all about control in this game right?

you say lean, what do you mean by pilot needles, do you mean the needle on the slide?

and what o rings, do you mean the seal on the diaphram 's edge, it's a 79 with washer on the seat for the valve needle, no o rings for this model.

when you say gaskets do you mean carb mount gaskets?

thanks again,

so my new question is , is it rich or lean?


it almost seems as if the enricher/choke circuit is feeding fuel and causing the slides to go up, i just don't understand with the butterfles shut how there can be enough air to go 1/2 way to redline?

[mason79]

thanks ken, the 1st line was refering to the idle speed knob and the second line: the air fuel mixture screw was the one i was giving calibrated turns and counts

i was under the impression once the mikuni's saw met wonderbread, i could, by backing the idle screw, go to zero, and your saying with wonderbread there is a big enough gap always and i could never shut the butterflies completely?

if this is true then, i would like to bench sync it as per topcat as this is the cheap fix without spring for needles or who know what dynojet?.

i hope this is the problem, if wonderbread and mikuni is not the problem, then is it rich or lean?

[excess11]

Carb trouble

Are the butterfly shafts leaking air? Dry cracks in the carb boots or vacuum lines? Is the Vacuum advance stuck,causing engine timing to increase the idle speed? Take some carb cleaner and spray around the carb boots, butterfly shafts and other possible areas for leaks while the engine is running and listen to engine speed. If engine speed spikes up or down while spraying in a certain area check that area for leaks. Just remember that some carb cleaners are not paint friendly.

[TopCatGr58]

Originally posted by mason79
pilot jets are 42.5 and has holes in them

thanks topcat for the your version of the bench sync, i thought about that; i checked visual gap after the bread tie anyways and i was thinking i could get it closer.

wierdly; although i dripped motor oil through the cables, when installed, even with no binding, the return action seems dampened,

and it is not hung up on anything, so that's not it, the butterflies are shut, i make sure of this, by counter rotating the grip and it still revs, the only way i can control it is flicking the kill switch on the off.

can it be i set the floats too lean?

you say lean, what do you mean by pilot needles, do you mean the needle on the slide?


when you say gaskets do you mean carb mount gaskets?

thanks again,

so my new question is , is it rich or lean?

it almost seems as if the enricher/choke circuit is feeding fuel and causing the slides to go up, i just don't understand with the butterfles shut how there can be enough air to go 1/2 way to redline?

Mason,

Our throttle cable system is NOT a push/pull system, so countertwisting the grip is NO guarantee that the cable is getting fully released. The breadstick method works, but what Ken said was that AFTER the initial tie synch, the butterflies are set too far open, and that you then need to turn the MAIN idle screw back which closes ALL of the butterflies at the same time.

You mentioned about the slides moving up!? IF they are moving up, then your butterflies are most likely NOT fully closing! You might try pulling the cable OFF of the carb actuator, and starting the bike, and then flick the throttle with a long screwdriver, and see IF the throttle plate fully closes, and that the idle returns to normal. IF so, then the throttle cable is almost definitely keeping the butterflies from fully closing, either more thoroughly clean and lube it, or replace it!

The Pilot Needles are the needle tips of the Pilot screws on the front top of the carbs. Turning them out will richen it up. Rising idle often is too lean, but out of synch is also common cause. Usually bench synching will get you pretty close!? You can try turning the Pilot screws out 1/2 turns and retesting idle, and repeat as needed. But need to be sure the butterflies are truly closing completely!

T.C.

[mason79]

right topcat, i really meant fully extending the throttle cable by way of counterotaton, or helping the spring do their work.

i closed down the throttle plates after wonderbread, but i just finished your bench sync and i think i am closer now.

i am biased to thinking the plates were open a little more than should have been; contributed from: la ack of slack of the cable as per ken talbot, so i will put the carbs back in the morning and may leave the cable off as per your suggestion.

the revving is gradual, giving the impression of somone or something changing the conditions from point a to point b.

not a condition of wot when starting the motor.

you see, one is 1000-5000rpms

the other is 5000 from the begining

my problem is the former, so i'm afraid it might be leaking air from the shaft, in that case, it would be pretty ugly.

i have the carbs buttoned up andi 'll find out in the morningand thanks a million gents.

the bike already has a fork brace, air caps, s and w rear shocks, so when i get it running i'll work on the cosmetics, bring her back from the brink to glory.

thanks again

[pathfinder]

in the prepurchase state, it would want to stall from the flooding, the only thing i can think i did different is the float levels maybe 3/32" lower/leaner.

Since the carbs were upside down then you actually set the floats richer. Whichever, up or down, your float level is either 1.1057 or .9183 and should be 25.7mm = 1.012 +-0.039
On my 78 you can't do the bread tie sink without removing the idle screw and spring at the rear of carb bank in the middle pointing up. Then reinstall without the spring, do the bread tie sink and reinstall the spring. Set at loose for a slow idle, it may not want to start, tighten slowly to get started.
Slides must go up and down at about the same speed. Try putting some WD40 on your finger tips and rubbing around the piston part of the slide. Check the needles for any burrs.
I didn't see in previous threads, but did you check the rubbers at the top of the slides for pin holes?

[pathfinder]

Forgot to ask how you fixed the leaking float. Are you sure that it is not leaking. I tried my damnedest to fix one and no matter what I did it kept getting worse. Holding the floats under water will not work as water is thicker than gas. I sank all my floats in gas by holding down with something. Get a pencil type soldering gun hot, then remove one at a time then hold the hot soldering tip againt the center part of the floats side. As the gas heats up inside the float it will come out in a stream if there is a leak.

[mason79]

good morning pathfinder

i ponied up for a float $26.00 believe me the good old soldering iron meagerly melted a noncooperating ball of solder, and when i pinched the float to test (dumb) for pressure it gave; permanantly enough for me to call yamaha.

what i meant by lower the floats, it's futher away from the "gasket surface" and the tang doing it's work sooner with less content in the bowls. leaner

insofar as the bread tie, i copped a good feel, for #3 rightway, without losing the spring.

i put the diaphrams up the a light souce, looks good, except for the sealing round looks a little cracked, but they seal nontheless(judgement call)my eyes just aren't good for this criticle work anymore...

i tested the return rate on the slides and miraculously they are about the same, so one one them has to be a good baseline, meaning all of them are good right?

okay thanks for your comments now i go reread the article on vacuum advances, but went i checked the wires connected, they
were pliable and rotation return smooth, we'll see

[remccool]

Sorry if I'm repeating myself, it sounds like what I had on my 78E when I did the same adjustment.
The main adjustment for #3 is located on the back side of the carborators toward the airbox between #2 & #3. I was able to tighten it down far enough to set # 3 withoput removing the spring to set with the bread tie. After setting all of the others following the proceedure, I re-installed the carbs, BUT I forgot to loosen back up the main adjustment (the one on the back side, it is only used in this proceedure to set a reference point for all of the others, once they are all set to the bread tie, I didn't back the main adjuster back out, which left the butterfly valve open the widht of the bread tie. I had the same symptoms you are describing, After I adjusted the main adjuster back out, it idled good. Again, the first adjustment is only to allow a synch of all carbs (a reference point only), it must be returned to the backed out position or it will idle way too high.
If you have done this, I appologize for repeating it, I must have missed when you posted it.

[trbig]

Mason.

I had the same problem with mine. It would start and run fine when it was cold, but after a few minutes of riding and warming up, the rpms would slowly climb at idle until they reached a little over 4 grand. My idle adjust screw wouldn't even be touching anything. It was embarrassing to stop at a light and your engine sitting there screaming.
Anyway... I did TC's bench version of synching to get close, then actually synched the carbs with a vaccum gauge. Even getting them as close as I could on the bench... all the floats lined up perfect... my vaccum readings were way off each other.
After synching the carbs with a gauge, the rev problem went away. I just had my number 4 carb dragging all of them up with it. Good luck.

Tod

[mason79]

thanks everyone, the bench sync worked,