rebuilt the carbs, quick question on tuning

[beachbum3478]

ok, i finally got around to adjusting the pilot fuel screw on the top of the carbs. i did the thing were to turn it till it idles higher and then adjust the throttle adjuster back down to about 1000 rpm. it def smoothed the revs out, it wont hesitate in the low rpm to rev anymore. but when i took it for a drive it still jumps around and is hesitent in the lower rpm. but once i gently get it up 3 or 4 grand, the thing takes off like a rocket. any ideas whats wrong? thanks.

[chef1366]

You might have an airbox or intake boot leak after reinstalling the carbs and the needle jet isn't rising properly. Fix the leak and fix the problem.

[beachbum3478]

actually, i noticed when i had the airbox off, that the filter is kind of loose in there. the two rails at the end that are supposed to hold one side of the filter down, dont really keep it tight agaisnt the filters mating surface. would that have anything to do with it?

one more thing, i noticed when i was doing the pilot fuel screw adjustment, that the idle didnt change really at all when i turned the screw on one of the carbs. does that mean the hole is gunked up?

[chef1366]

Yes on the loose fitting filter. Could be a number of things on the idle mixture screw. Dirty carbs and air leaks are two of them.

[beachbum3478]

im still stumped. i fixed the loose air filter issue, but no change. i sprayed carb cleaner all around the carb inlet boots on the engine side and air box side, and no change in idle speed. the throttle blades are all aligned evenly, i guess that means their synced? im afraid to have a mechanic do it and then him have troulbe too and cost me a fortune.

[TheCafeKid]

You ever vaccum synch them? You can have them bench synched and it will run, but all you do there is assure that idle and WOT throttle possition relative to the slides is the same, vaccum syncing will fine tune them to eachother, and to each cylinder. I would suggest doing this before you break down and take it to a mech. If you dont have the tools or dont want to buy them, then mayhaps it would be just as cheap to take it to the mech this once if you are concerned about getting it done soon. But i would invest in a set of manometer gauges, maybe even a colour tune plug down the road to help later on. I know i am.

[beachbum3478]

well once its above 4000 rpm, it runs like a bat out of hell. could they need to be synced but still run good in the higher rpms? its just if i give it to much gas when i start to get going is when it bogs and gets all rough. but if i slowly get up to the right speed in the each rpm range for any gear, then it runs pretty good. i also just want to rule out everything else to make sure its just a synch that it needs, before i take it to the mechanic.

[Steve]

... could they need to be synced but still run good in the higher rpms?

Actually, synching the carbs does more good at idle and low speeds. :shock:

What you are doing is synchronizing the opening of all four throttle blades. Imagine that they are just a bit off. Let's say that #1 and #3 are open 1% at idle, #2 is open 3% and #4 is open 5%. #4 would be providing most of the energy to run at idle, and the others would be contributing some, but less, causing a definite imbalance. Now let's open the throttle as wide as possible. #4 would be 100%, #2 would be 98%, and #1 and #3 would be 96%. Still imbalanced, but not nearly as noticeable.

To sync your carbs, you need a set of gauges connected to the intake runners. #3 is the 'master' carb, all the others are synced to it. The adjusters are between the carbs, on the engine side.

To adjust the float level, the carbs have to be drained and removed, turned upside down and the bowls removed. Measure from the bowl gasket surface to the top of the rounded part of the float, not the very top where the mount is. Measure both sides of each pair of floats, make sure all eight measurements are within spec. Keep in mind that a smaller measurement means the floats will sit higher when turned back right-side up, and vice versa.


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[beachbum3478]

ok cool. that makes more sense now. anyone know off hand what the float height is for an 1982 gs1100L? i think i read 24mm somewhere, but im not taking any chances.

[TheCafeKid]

Being that it probably uses the BS type constant velocity carbs, its more likely a range within a few mm's rather than a set number like you'd find on the mechanical type carbs. Its going to be based on your set up, elevation and whatnot. I would find out that range, then perhaps set it in the middle of the range, and see how she runs. Others may have better advice for you than that.

[beachbum3478]

anyone know what the general float height range would be for a bike that will spend its life between sea level and 600 ft above sea level? i really dont have any idea how i would figure this one out haha. and also, are these mesaurments taken when the carbs are upside down resting on the needle valve, or when the carbs are right side up and hanging down? thanks for the replys guys, i really appreicate all the help.

[TheCafeKid]

I dont have the levels for that carbset or bike, but to measure, you'll measure upside down..tang RESTING on the needle..not pressuring it. measure from the gasket mating surface, minus the gasket, to the step inthe float. ALL of them need to be THE SAME. no wavering...as for the float level...check the carb sticky's..hard to believe someone hasnt posted that up in there considering how many guys have 1100's here.

[beachbum3478]

k thanks. i found the float height. its 22.4mm +/- 1mm. one last thing, you say to measure from the gasket mating surface to the "step" in the float. im not really sure what that is, and the carbs are still on the bike. so basically what is the "step" in the float lol. thanks.

[TheCafeKid]

SOME of the BS type carbs have oblong or kinda rectangular shaped floats..tho the BS;s on my yammie have round brass floats, yours may be that way. The rectangular ones have a step down in the float when you flip em upside down, measure from above that (i think) if thats the way yours are, if they are just round floats, measure from the very top of the float. Make sure when using whatever you use ( i suggest some digi calipers picked up on the cheap from your local auto parts store for best results without spending a fortune, trust me, i was dumb and tried using a ruler...yeah...dumb) that you arent compressing the floats at all..just touching the top of it. I have some pics of the proceedure if you need more info.

TCK

[Steve]

k thanks. i found the float height. its 22.4mm +/- 1mm. one last thing, you say to measure from the gasket mating surface to the "step" in the float. im not really sure what that is, and the carbs are still on the bike. so basically what is the "step" in the float lol. thanks.

Look up a few posts to what I said there:

To adjust the float level, the carbs have to be drained and removed, turned upside down and the bowls removed. Measure from the bowl gasket surface to the top of the rounded part of the float, not the very top where the mount is. Measure both sides of each pair of floats, make sure all eight measurements are within spec. Keep in mind that a smaller measurement means the floats will sit higher when turned back right-side up, and vice versa.

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