Adjust butterfly laterally? (with pics)

[Anonymous]

Got a GS450T that idles quite high once warmed up. I have replaced the boots and o-rings, had some carb work done, but the idle was still high.

The problem turns out to be that the butterfly in carb#2 is apparently off-center, laterally. Just when the butterfly closes, the right hand side makes contact with the throttle body. Note the polishing of the body right next to the red line.



The result of this contact is that the nylon bushing on the linkage gets pulled inward as the butterfly closes, thus creating friction that the return spring can't overcome. In order to get the butterfly to completely close, it requires a lot of pressure on the linkage. Compare the gap in the following pics; note that the gap of about 0.5mm disappears when the butterfly is closed.




My question is whether the butterfly is adjustable laterally by losening the two brass screws?

The problem is that one of the screws is really tight and I'm afraid of stripping it. If that happens, what are my options?

Suggestions?
Thanks!

[RacingJake]

I would just loosen the two screws with the plate still closed then tighten again

[earlfor]

Those two screws holding the butterfly as set at the factory are not removable. Well, they are not meant to be removed, but they can be. The problem is if they are removed they butcher the threads badly enough that you will probably not be able to reinstall them. I would consider taking a strip of #600 grit emory cloth and pulling it through with the edge of the butterfly held against the cloth's grit by finger pressure. You probably will not need to remove more than a couple thousandths from the butterfly edge to get it to seat all the way closed.

There is no adjustment slot on the butterfly, so no sideways movement is possible.

Earl

[Anonymous]

Earl comes through yet again!

Thanks for this tip and the previous tip on my GS650 starting problems a couple of days ago. Looks like the battery is low (12.25V OFF and 11.3V with ignition ON), so I'm going to charge it for a couple of days , then test the stator.

Chris

[Anonymous]

binding

If the shaft is sloppy them removing material wont do much cause the piggy tail spring tends to push the shaft up in that direction and pull inward and as you remove materal it will just keep binding, you need to hold it up to the light and look thought at the point where it binds an see if the light going thru looks even all the way around, if not then you have a wear problem, if is then cleaning it up as earl sugguest will work,

[bgmart450]

Those two screws holding the butterfly as set at the factory are not removable. Well, they are not meant to be removed, but they can be. The problem is if they are removed they butcher the threads badly enough that you will probably not be able to reinstall them. I would consider taking a strip of #600 grit emory cloth and pulling it through with the edge of the butterfly held against the cloth's grit by finger pressure. You probably will not need to remove more than a couple thousandths from the butterfly edge to get it to seat all the way closed.

There is no adjustment slot on the butterfly, so no sideways movement is possible.

Earl

8O 8O 8O What???? I pulled mine off when I dipped my carbs... I did notice they were hard to remove, but I guess I got lucky and they went back no issues... yet. Those darn things will burr cut you to no end trying to shove them back in the slots....

[Anonymous]

bgmart450,

do you remember if the butterfly could be moved side to side when removed, i.e. are the holes in it just the size of the brass screw, or are they oval or larger?

If they can't be moved side to side, then I think Gee-s-is may be right. There is some play in the shaft and the return spring just pulls the butterfly over and up towards the side where the wear is located.

If I push the shaft the opposite direction while closing, the butterfly closes smoothly.

I'm going to try and add a bit more tension to the return spring and see if that will keep it closed at idle if I can't end up adjusting it laterally.


If I strip one of those brass screws, what are the prospects for replacing it?

Chris

[bgmart450]

I think there MAY have been a very small amount of play.... I don't remember 100% but I think would move just a small amount. I need to dip my other 450's carbs and I'd know better after doing them.

Those screws are very soft, use the right sized screwdriver or you'll be boned for sure.

As for removing a stripped screw, I luckily (for me anyways) have no advice for ya there.

[earlfor]

The holes are exactly the size of the screws, so nothing can be moved. You might try adding a shim on the shaft on the opposite side of the carb to restrict sideways movement in the wrong direction. Possibly something made from a plastic butter lid and cut like a washer with a split in on side so you can fit it over the shaft.

Earl



[quote="Espumoso"]
do you remember if the butterfly could be moved side to side when removed, i.e. are the holes in it just the size of the brass screw, or are they oval or larger?

[Anonymous]

EARL IS RIGHT AGAIN!!!- re butterfly sticking...

AS USUAL - EARLFOR IS RIGHT AGAIN. LISTEN TO EVERYTHING HE HAS WRITTEN.

BUTTERFLYS ARE NOT MEANT TO BE REMOVED USUALLY.

BUTTERFLYS DO HAVE A LITTLE PLAY IN THEM FROM SIDE TO SIDE WHEN THEY ARE OPEN. THEY ARE MEANT TO...JUST A LITTLE.

WHEN BUTTERFLIES CLOSE, THEY "SELF CENTER" THIS IS BECAUSE THE ROUND BUTTERFLY IS PUSHED TOWARDS CENTER AS IT CLOSES BY THE CURVATURE OF THE THROTTLE BODY THROAT OR BORE.

USUALLY THE SCREWS THAT HOLD THE BUTTERFLY TO ITS SHAFT ARE "PEENED" TO AVOID THE SCREW FROM BACKING OUT AND GETTING SUCKED INTO YOUR ENGINE. BAD NEWS.

I SUSPECT THE FOLLOWING POTENTIAL PROBLEMS

CORROSION IN THE CARBURATOR BODY WHERE THE SHAFT MOVES CAUSES THE SHAFT TO BIND.

A BROKEN RETURN SPRING.

A STICKING THROTTLE CABLE - IF STILL CONNECTED.

MISADJUSTED CARBURATOR ON (#2?) CHECK THIS CAREFULLY.

SOMETHING GOT BENT.

GAS LUBRICATES THE CARBURATORS AND LINKAGES NORMALLY.

GOOD LUCK. - DIETER

[isaac]

That last post reeked of insanity FOR SOME REASON.

Anyhoo, I say try to pull the plate. It's not like it wouldn't be incredibly easy to just drill the plate's screwholes a little bigger so that you'd have some adjustment room. That'd take like a minute.

Soak the screw in PB blaster for a couple days before trying to remove it if possible.

[earlfor]

I'm going to say this one more time. Leave the plate IN PLACE. The plate is not the problem. The problem is in the linkage. Adjust the linkage.

The butterfly screws are PEENED over on the ends, soaking them until we all die of old age will accomplish nothing.

Earl

That last post reeked of insanity FOR SOME REASON.

Anyhoo, I say try to pull the plate. It's not like it wouldn't be incredibly easy to just drill the plate's screwholes a little bigger so that you'd have some adjustment room. That'd take like a minute.

Soak the screw in PB blaster for a couple days before trying to remove it if possible.

[Anonymous]

carb

Ok dont listen to earl, but figure this, if there is a lot of play and I don't just mean side to side like some suggest but up and down also, then makeing the holes bigger will only cause a bind in another place in the carb, cause the bushings are shot or the shaft or buttery fly plate is bent, go ahead and do your thing then go to ebay for another carb set, the advice here from evey one is solid

[Anonymous]

Not sure who's talking to whom anymore, but I did take Earl's advice and didn't mess with the butterfly. I did try and do some sanding with 600 grit emory cloth, but that didn't do much at all as it just keeps binding.

After closer inspection, I thought that the reason it was sticking was because the bushing under the return spring was binding against the carb body just as it finished closing. So I removed a few thousands from the bushing so that now it can be rotated when the butterfly is completely closed, but it still binds. This makes me think that it is just the butterfly binding against the body as it closes completely.

I should also note that when I say 'bind' it is just that it takes a little extra pressure to get the butterfly to close the last 0.5mm. However, the return spring can't overcome the binding force and it remains open just a tiny bit, but that's enough to keep the idle at 3000+. The instant you apply any pressure to the linkage the idle drops to normal. I should also note that this just started happening out of the blue. The cable is clean and smooth and does not drag at all. The linkage had never been touched until the idle started sticking so it is as straight as it has ever been. As Dieter said, the butterflies "self-center"... this one just sticks when it does.... I guess this carb is just worn out.

THE SOLUTION: I ended up adding some tension to the return spring and that seems to have solved the problem for now.

If it were a 2-stroke I'd just add a little extra oil to the gas to keep it lubed up :P

Thanks everyone's help!
Chris

[earlfor]

Chris, my comment wasnt directed towards you as you were not even in the conversation the last few replies. :-) :-)

In further head scratching about your predicament, :-) I have a set of CV carbs that the #3 carb (control carb) is as yours. It doesnt quite close.
I have worked around it by doing a carb synch and then fine tuning the mixture screws to the rich side so the idle will drop lower when the butterfy plates are closed. This will probably only work if the gap is very slight. After synching, I would richen the mixture screws 1/4 turn at a time to see if the idle will come down to normal.

Also, one carb not quite closing should not be enough to raise the idle from 1000-1200 to 3000 rpm. I suspect your vacuum levels on your non control carbs are lower than your control carb and need to be increased to match the control carb. After that, richen the mixture screws in small increments and it should help. Also, check you timing. A couple degrees too much advance will make getting a smooth, consistant idle transition hell in a handbasket. :-)

Earl


[quote="Espumoso"]
Not sure who's talking to whom anymore, but I did take Earl's advice and didn't mess with the butterfly. I did try and do some sanding with 600 grit emory cloth, but that didn't do much at all as it just keeps binding.