1981 GS850 not going above 4000rpm

[XXWoodmanXX]

Ok, so I received a set of carbs from a fellow member, and slapped them on the bike. I bench-sync'd them, but didn't do a complete tear-down of them for cleanliness. Was told they were slap-on-'n'-go ready.

Here's what I have:

1981 GS850L
BS32SS carbs w/ #125 mains and stock pilots
K&N pod filters
Stock 4-to-2 exhaust
Pilot screws currently @ 3 1/2 turns out


Now for my symtoms:
- barely need to choke it. Only initially, then I can start letting it out almost immediately.
- RPMs will hold @ idle, around 1200rpm(preferred setting) , however after about 2-3 minutes, she'll sloooowly start to ramp up, upwards of around 3500 rpm. I give it throttle, and it comes back down to idle again.
- I let it warm up, and still it will not go beyond 4000rpm
- LOTS of popping in the exhaust (sounds like a bag of popcorn in a microwave!)
- It WAS backfiring out the carbs a little, but richening up the A/F fixed that.
- Did a vacuum leak test on the boots, and no idle change what-so-ever. No leaks to be found at the boots, carb-side, or head-side.


What do I need to do? Pull/clean the carbs? Shim the needles? Check/adjust float height?

[Steve]

Have you changed the o-rings on the intake boots?

.

[almarconi]

What do I need to do? Pull/clean the carbs? Shim the needles? Check/adjust float height?

That about covers it. May want to invest in a stage 3 dynojet kit.

[gustovh]

You need to do a lean best idle. Start turning your pilot screws in one at a time slowly. Listen to the idle, it should start ramping up, keep turning in until idle starts to drop off the back off 1/8 turn. Reset the idle and repeat the process for each carb. Once that is done stick the sticks to them and sync em. That should end your problem.
V

[XXWoodmanXX]

I got the link on Basscliff's site for highest-rpm method. But I think I need to pull the carbs and go thru them first. That way, I know exactly what I am working with.

[XXWoodmanXX]

Have you changed the o-rings on the intake boots?

.

I got new o-rings last summer. I removed the boots, and they still look great. Not too terribly flattened, and plenty of cushion left.

[Steve]

You need to do a lean best idle. Start turning your pilot screws in one at a time slowly. Listen to the idle, it should start ramping up, keep turning in until idle starts to drop off the back off 1/8 turn. Reset the idle and repeat the process for each carb. Once that is done stick the sticks to them and sync em. That should end your problem.
V

Personally, I would rather sync them first, that way you know they are all working somewhat equally.

By the way, if you leave the gauges connected after the sync, looking for the highest idle speed is easy.
Just look for the vacuum level to go up on all cylinders as the engine speeds up.
Repeat on all carbs until you have the highest vacuum levels and you are done.

.

[gustovh]

I will remember that Steve, it makes sence.
V

[XXWoodmanXX]

Hmmmmmm, Just looked over my carbs and noticed that I never plugged my vacuum port on Carb #2 when I took my tank off and hooked up my aux. fuel bottle. Would that be a culprit? If so, talk about embarassing

[spchips]

Hmmmmmm, Just looked over my carbs and noticed that I never plugged my vacuum port on Carb #2 when I took my tank off and hooked up my aux. fuel bottle. Would that be a culprit? If so, talk about embarassing

definitely could be it. also, if you pull the carbs be sure the pilot JETS (inside the bowl) are not plugged. they can plug up even just from sitting and will give you a headache.

also, make sure the float needles are not hanging up closed. especially if someone cleaned the carbs and then sent them to you or put them on a shelf. carb cleaner often makes them stick shut or open. always wash carbs outthoroughly with gasoline after dipping to prevent this.

[XXWoodmanXX]

Ugh. STILL not wanting to go over 4000rpm, and I have no idea why. ARGH! I'll keep my spirits up and keep trying however. Just getting frustrated.

[cowboyup3371]

Argghh, if you weren't as far away as you are I'd offer to drive up and help. It's only a 90 minute drive but kinda hard with my schedule right now.

[XXWoodmanXX]

Appreciate the thought. Thx

Anywho. I replaced the vacuum slides with a set that had better rubber on them. It now wants to TRY and turn over, but it just huffs and puffs. So long as I have the idle adjust turned all the way down and the choke all the way out.

My BS32's have 125 main jets(stock = 115) and stock pilot jets with K&N pods on them.

oh yeah,....and it only wants to try and start if I have the A/V screws out 5-6 turns. But I just don't get why it doesn't want to turn over @ 2-3 turns.

[XXWoodmanXX]

Think I will re-inspect my float heighth on my carbs again. Think I might also look into changing my oil. Think I have quite a bit of gas in it by now.