1981 gs850l

[Nhiett1127]

Got this bike a few months ago as a winter project and its coming along nicely. A problem i am having is getting the carbs dialed in. it has the BS carbs and i have gone through them multiple times cleaning with soaking in carb cleaner and clearing all the passages. i have gotten the bike to the point where it will start and idle great. the main issue i am having is getting it to rev up smoothly. if the bike is at idle and i rip the throttle open, revs up great. if i have the throttle at 1/8 to 1/4 open as if i was cruising down the road, it bogs and really struggles to rev up. any ideas or help would be much appreciated.
additonal info on the bike-
-new NGK plugs and all charging system components tested to be working
-OE airbox with new seals
-intake boots new
-new fuel petcock
-no obvious vacuum leaks around the boots(tested with carb cleaner)
- all carbs rebuilt and cleaned multiple times
- upped the pilot jet from stock 40 to a 45
- air screws seem to be best around 2 1/2 turns out
- still has OE size main jets at 115 (new)

I am curious if i bump up the main jet a size or two, would this help my issue? new to these bikes and never encountered an issue like this.

 

[Nhiett1127]

also forgot to add that i have checked the float heights and all are right at 23mm. checked the float bowl seat without gasket to the step on the curved part of the float itself as indicated in the service manual

 

[Steve]

Two questions. :-k
1. Why did you bump the pilot jets, and two sizes at that?
2. Where in oHIo?

.

 

[Nhiett1127]

With the stock pilot's. I had to go more than 4 turns out with the air screws to get it to run somewhat correctly. I did a some research and found that going up one size jet is equal to half a turn less on the air screws. Dayton ohio

 

[Steve]

With the stock pilot's. I had to go more than 4 turns out with the air screws to get it to run somewhat correctly. I did a some research and found that going up one size jet is equal to half a turn less on the air screws.

Not so sure about the "half turn equals one jet size", but the concept is correct. It also depends on other things, like proper float height and CLEAN internal passages in the carbs.

Dayton ohio

Howdy, neighbor. Stop by some time. PM sent with contact info.

.

 

[Nhiett1127]

The float heights are right 23mm if I remember right. Just checked them the other day. That was my initial thinking was the float heights. But according to the manual, 23mm is within tolerance. I am curious to see if a little more tweaking with the air screws would do the trick

 

[Steve]

Yes, 23 is within tolerance, but it is on the leaner side.

You don't have air screws. Many of us call them "mixture" screws, but Suzuki calls them "pilot" screws.

They are "mixture" screws because they control a mixture, not just air. Turning them OUT will richen the overall mixture that goes to the cylinder.

.

 

[Big T]

The main jet has zero effect at those throttle openings
The needles are controlling the mixture at that point

 

[LAB3]

Howdy, neighbor. Stop by some time. PM sent with contact info.

.

A wise man would accept that offer in a heartbeat!

 

[Rich82GS750TZ]

I wish Steve was my neighbor.

 

[Nhiett1127]

Update. I finally got some time to play around the carbs some more. I decided to see if bringing the floats up to 22mm would make a difference. It seemed to help some on the revving issue I was having. It still seems like it is hesitating before it revs up though. Should I bring the floats up more or leave it at that. Any thoughts?

 

[Nhiett1127]

got the bike to a perfect idle and zero problems up to about 1/2ish throttle. it still seems to struggle to rev past that. it acts like it has to gather the fuel it needs and then it will rev. double checked the floats and they are all 21.5-22mm. i also found a set of 117.5 mains to put in it. they seemed to help some with how quickly it reacts at higher RPM. trying to avoid throwing bigger jets at it but if thats what i need to do, i will. something strange i noticed is that the mixture screw for carb 2 seems to do nothing. i can turn it all the way in and that has no effect on the bike at all. is this normal?

 

[Big T]

Is the vacuum port on #2 hooked up to the petcock, plugged, or open?

 

[Nhiett1127]

the vacuum is hooked up to the petcock. it doesnt seem to be misfiring or anything along those lines. i dont think that is related to my high rpm issue since that screw only affects the pilot. just thought it was strange.

 

[gustovh]

Two things come to my mind, a valve adjust, stock jets and a proper carb sync. All other things equal, you now have a starting point to make evaluations. Does your airbox have a snorkel?

V