83 GL1100 dead spot in throttle

[g0sammo]

Newly registered to the forum but ive read a lot of articles and appreciate the info everyone has shared on here over the years!

Picked up an 83gl1100 Interstate a while back that sat for a couple years. Bike actually came woth a kit from Raddak to rebuild the carbs along with instruction maunal and sync guages. I removed cleaned and rebuilt the carbs and synced per the instructions.

Now the bike idles great. And the first 1/4 throttle is smooth but i get to a section of the throttle where it just starts spitting and stumbling. Giving the bike 3/4 to full throttle it clears up and runs great, its just that small area where it runs terrible and is about where you would normally cruise when riding. Ive checked it all over for vacuum leaks, had the carbs off and on several times to check them over, polished the slides and made sure they are smooth and working.

Just not sure of this is a carb issue that i cant seem to get straightened out or something else going on. Thanks for any advice you could give to help me get this sorted!

[WingAdmin]

Is it different if you open the throttle quickly, or open it very slowly?

[g0sammo]

Its the same either way.

[LAB3]

I'd be thinking it has something to do with the accelerator pump either putting too much or too little gas into the throat.

[g0sammo]

That was my original thought as well, even checked over the diaphram and passages and they were all good. But if it was accelerator pump wouldnt that clear out or equalize fairly quickly? I can actually hold the throttle in that area and it will continue to stumble and pop. Wont get any better untill i give it more throttle, or less.

[WingAdmin]

I'd be thinking it has something to do with the accelerator pump either putting too much or too little gas into the throat.

That's why I asked him if it happens if he opens the throttle quickly or slowly. The accelerator pump only operates if you open the throttle quickly. So if it's still happening when the throttle is opened slowly, then it's not the accelerator pump.

[DenverWinger]

Sticky throttle slides maybe?

[g0sammo]

An issue with the slides would make the most sense to me. Im def not a carb expert but from my reading it seems like it may be when the slides should start to open is when it may be having problems, but then when giving it more throttle it is eventually able to overcome the problem and open the slides. I have removed my slides again and polished them and made sure they are moving up and down very smoothly. Blew through the 4 holes i could see in the top of each carb to make sure its not something blocked causing them not open correctly. Is there something else that controls the slides that i may be missing?

[LAB3]

If the slides and bores are clean the only other thing that comes to mind is the diaphragms. You could remove the slides and hold them up to a light and see if there's any light showing though the diaphragms in order to rule out a vacuum leak. To tell you the truth this one has me stumped, if it where RPM related as opposed to throttle position then it would make more sense (to me)

[g0sammo]

If the slides and bores are clean the only other thing that comes to mind is the diaphragms. You could remove the slides and hold them up to a light and see if there's any light showing though the diaphragms in order to rule out a vacuum leak. To tell you the truth this one has me stumped, if it where RPM related as opposed to throttle position then it would make more sense (to me)

Thanks for your thoughts on this LAB3. My application doesnt have an actual diaphragm on the slides themselves, but i know there are some orings inside the chamber where the needles go i can double check. The rings that seal the caps are a little hardened as well so i might try to source some replacements to make sure im not leaking anywhere there.

[LAB3]

Hmmm, looked over the parts Fischer and I guess they don't have them! Swapped mine out for a single VW carb right after I bought mine rather than trying to fiddle with four carbs. Been commented based on my former projects over the years, I'll stay out of the way...

[Sig45227]

Needles or needle height issue? Sounds like transition from idle to mid throttle is the issue. Maybe a slight lean condition?

[PhotoDoctor]

my money is on the emulsion tubes - that is the jet with the tiny hole that only the smallest guitar wire will go through.

If you don't know the part I'm talking about then you missed it. (Years ago I missed this jet on my first Honda GL500 which is very similar and had to go back and redo the job - this jet clogs super easy on the GL500, GL650, and GL1100 )

Also, if you did clean them yet have rust in your tank they will clog up right away.

If you don't know the jet I'm talking about send me a pm and I'll send you a photo.

[g0sammo]

Just incase anyone checks on this thread chasing the same issue, i eventually found the issue was with the needles. The rebuild kit this bike came with had the instruction manual and guage sync kit from Radakk cycle shack so i assumed the whole kit was. When inspecting my stock needles they did have some grooves in them so i replaced them with the ones in the kit. Looking over the Radakk master kit they do not come with new needles let alone jets like this one did. Since the bike seemed to be starving for fuel at the off idle area, i measured the needles and found they were a different diameter, bigger, which starved it for fuel for too long. Put in the factory needles and bike now runs like a champ.

[MattMcCoy]

Good info — thank you.