Bogs on accell

[swifty]

I have a 82 GS750T that I need some help with. It has some idle problems and it won't accell. It will bog down like its not getting gas. First the idle issue. It will idle at about 1000 rpm and after I goose the throttle it will be idling at 2000 rpm. Then slowly it will idle down to 1000 rpm. Idle doesn't seem smooth. Now the accell problem. With the bike setting on the center stand and warmed up, when I goose the throttle it revs up but bogs alittle as it climbs. When I get on and ride it, in first gear I goose it and it will bog down and hesitate. The farther I open the throttle the harder it bogs. If I open the choke when I try ro accell, its better but still will bog. If I don't goose it and try to keep it at 30mph steady speed, It will surge.

It has 40k on the bike. The guy I bought it from rejetted the carbs and put on a cheap set of individual air filters on it. When I got it, it ran alot better, but it would surge at any steady speed. It would accell without bogging, but the air filters would be wet with gas if I rode the bike hard.

I did a few thing to the bike.
Complete carbs overhaul. Oil change, replace spark plugs, chain and sprokets. The jets he had in the carbs were 138's. I installed the original 112.5's that came with the carb kits. The jets that he installed had rubber orings under them which from all the research I could find, they should have had brass washers. I test drove the bike with the 112.5 jets in and it wouldn't accell at all even when I goosed it on the center stand. I removed the carbs again and installed 122.5's I got from a friend and it still wouldn't idle right and would bog on accell. Maybe alittle better, but I couldn't ride it. I sprayed the carbs with WD40 and found that the intake boots were leaking. I repaced the boots and carb synced the carbs with the 122.5 jets in place and it ran better at idle but still would bog when I would try to ride the bike. I sprayed the carbs again with WD40 and found the throttle shaft seals were leaking. I ordered orings and jet washers from Motorcyclecarbs.com, and replaced the orings and installed the brass washers under the main jets, and left the 122.5 jets in the carbs. I synced the carbs and the idle is alot better, it still will hang at 2000 rpms sometimes but smoother. I goosed it standing still and it accells better, but when I go to ride it, It will bog down and hesitate.

Somethings I wonder about. The engine isn't noisy so is it safe to say the valves are adjusted ok? I haven't checked the timing, because I don't have a timing light for a motorcycle. I haven't checked the points, if it has points. According to my manual it does. The needle is the factory needle according to my manual. It is not adjustable with shims. When I rebuilt the carbs, they weren't real dirty. I just wanted to find out what jet was installed in the carbs. I haven't pulled the plugs out since I done alot of carb changes. Should I install a new set of plugs and go try to drive it to see what the mixture is on the cylinders? I am about to pull my hair out. Please help!!!!!

Just alittle background about my mechanical ability.
Master certified Chevrolet Technician 13yrs
Master certified Chevrolet Corvette training 10yrs
ASE Master certified 16yrs
Chevrolet Master certified Transmission/Transaxle training 10yrs
Chevrolet Master certified driveability/electrical 13yrs
I worked for two Chevrolet dealerships for a total of 15yrs.
I currently have my own Automotive repair business for the past 9 yrs.
I been through many car and truck carbs, but these were my first mororcycle carbs.

Thanks in advance, ant help is greatly appreciated.
Swifty.......................

[Don Lobacz]

These are CV carbs, have you ever worked with them? They rely on vacuum behind the carb to raise the slides. Since the PO removed the airbox, the vacuum balance has been changed (not just the available air). The jet kit should have come with softer springs to allow the slides to rise sooner. Did you check the needle (in the slide) to see if it is adjustable? The 138 main is a dynojet number and does not compare directly with the mikuni numbers. It is like a 125 mikuni, I think, but may have a different opening to match up with the dynojet needle.

Rejetting these carbs can be a long and tedious task, and some people swear it may never turn out right. If done right, it may add some top end power but often sacrifices rideability. The stock setup with the airbox is viewed by many here as the best way to go.

[Anonymous]

For what it's worth, I removed my airbox, and after some struggles, my bike is running absolutely perfectly, and performs better throughout the rpm range. I think it can be done. Funny thing, though, it absolutely would not run right until I took off the carb vent lines. Wierd, but fact.

[swifty]

I have never had one of these carbs apart before till now. The needles aren't adjustable, but they are the factory needle according to the number on the needle. Its been a frustrating experience to say the least. I wonder if I put a spacer under the needle by the e-clip if that would help? How thick of a spacer should I use?

[Anonymous]

That's the right approach. You can get assorted small washers at Radio Shack that vary in thickness, and are the right diameter. As far as how much, I don't know, but from looking at the spacing on the needles that have multiple grooves, I would guess it's not a tiny amount.

[Anonymous]

I have the same bike and had similar problems. I had the carbs professionally rebuilt and went from velocity stacks (po) to the factory set up airbox and filter. Everything perfect right, nope as soon as I gave it gas bog, stall. Took the petcock out completly rotted mesh and rusty tubes allowed rust from tank to block gas line. The gas line was gravity fed if original so it would get enough to idle eractically but open it up and it starved for fuel quickly most times. Had tank treated new vacuum petcock and the problem was gone. I found out the idle problem was separate though, it was from a too tight throttle cable and worn clutch cable and friction plates had to change those and the idle then set fine. But it was just as you describe your idle problem could not set to the right rpm and then it would rise after I would set and if you gave it gas it would lug down and stall.

[swifty]

I will take it apart tonite and see what I have. Thanks for the info........

[swifty]

Well I took the petcock out and it and the screen was clean. The inside of the tank as alittle surface rust, but not bad. Should I disassemble the petcock and inspect the inside of it? With the tank off, I can turn it to pri. and fuel will flow from it.
The other question I have is when I pull off the carbs again to install the 135 jets, should I go ahead and install a spacer on the needles since I have them apart? These 135 jets are not Mukini jets, and I read somewhere on the forum that they are equivilent to 122.5 Mukuni jets. Is just replacing the jets enough or should I shim the needle?

[Anonymous]

I have a 750 ex with pods on my jetting is 127 on the main jet. It works great. You also might want to consider your coils. I thought I had acarb problem last year only to find out my coils were breaking down. A new set of Dyna's fixed the problem and she pulls to redline. Hope that helps Andy

[swifty]

Well I installed the 135 jets and took it out for a spin, and it runs 100 percent better. I still have the idle problem but at least I can drive it. The 135 jets I installed have the letters RD stamped by the number. Does anyone know who makes this jet and how does it compare to a Mukuni jet? Also how can the clutch adjustment and friction plate wear affect the idle?