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rebuilt the carbs, quick question on tuning

  • Thread starter Thread starter beachbum3478
  • Start date Start date
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beachbum3478

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i just got an 82 gs1100L that needed the carbs cleaned and rebuilt in order to run. i did that and it fired right up, but im having some drivabiltiy issues. when i rebuilt the carbs, i didnt know where to initially set the pilot air screws or pilot fuel screws, so i just put them all at one turn from bottom. the bike idles good and revs up fine, but when i get going in first gear and open the throttle, it will hesitate and stumble. but if i slowly bring it to about 2500 or 3000 rpm, and then crack the throttle, it will take off no problem. i just dont really know where to begin. thanks.
 
Open the screws another turn and try again -- most people end up at about 2 to 3 turns out.

Also, make absolutely sure your float height is set correctly and precisely (a lot of people are apparently very confused about this -- peruse a few of the recent carb threads), along with all the other usual things to check when fine-tuning -- airbox/filter sealing, valve clearances, airbox boots, intake boots, intake o-rings, etc.
 
when you say "open the screws" do you mean both the pilot air screws and the pilot fuel screws. and i completly forgot about asking about the float heights. i was so eager to get the carbs back on the bike to see if it would run that i didnt even check the heights. i read somewhere that they are supposed to 24mm or something. but i have no idea between what two parts i measure that distance. thanks.
 
Wrong carbs BeachBum. It's an '82, so there's only the one mixture (air) screw on top.

VM's have 2, BS/CV carbs have only 1
 
gotcha. ok bare with me on this one. what about the four "pilot air jets" that screw in on the airbox side of the carb openings? they are pretty stubby, and i think they are the ones that people commonly strip the heads on when they try to remove them. do they just screw in all the way, or do they have an adjustment? sorry if its a stupid question, but iv never tuned carbs like this before. thanks for the replys.
 
All jets should be fully seated except for the pilot screws.
 
The ones that you are calling "pilot air jets" (and I think that is the correct name) should be fully seated. No gorilla torque involved, but they should not move on their own. Likewise, all the jets found in the float bowl should be fully seated. The only one that is adjustable is the one that is on the top of the outlet throat of the carb, between the carb and the head. Turn them clockwise gently until they seat lightly, counting the turn as you go. Record the number for each one so you can set them back where they are now, if you need to. Start with them all at 2 turns out from lightly seated. When the bike is fully-warmed up, adjust each one slowly, listening for an increase in engine speed. When the speed is the highest you can get with that screw, adjust the master idle adjuster to get the idle back where it should be, then do the next carb. Repeat until all are done. If you want to be anal about it, go through them again, just to be sure.

You also need to sync the carbs for proper operation. Do you have access to a set of gauges?


.
 
There are very small ports that flow gas for the pilot circuit. Because of these and other small ports the carbs should be dipped and blown out with air or I use carb cleaner. Make sure all ports are clear.
Also sounds like you are lean on the idle mixture screws.
 
yea as i have it right now, i turned the pilot fuel screws 1 turn out from lightly seated. im just going to take them somewhat apart again and use compressed air through the holes, which i didnt the first time. does it matter which way i turn the pilot fuel screw as long as it gets to the highest rpm possible. and last question, how would i go about synching these type of carbs, im used to having to take a cap off and turning a synch adjustment screw. but iv never delt with these vaccum operated slides and such. thanks for all the replys so far, they are helping me alot.

ps. the carb rebuild kit came with two sizes of each jet. the carb had all the bigger of the two sizes in it except for the pilot jet in the float bowl, which was a 40. would it help if replaced it with the 45 that came in the rebuild kit, or make it worse. thanks.
 
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in my case i probably should use the new jets because someone prior to me must off used a tiny flat head to get every brass jet out. the jets are mangled up from it. it def runs better with the rebuild kit in it.
 
I think they have been known to wear quicker. Perhaps you should order a set of mikuni's as well just in case. I think they are $5 from flatout or somewhere...

Dan :)
 
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.
 
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.
 
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?
 
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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.
 
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.
 
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