Not sure if this is a natural occurrence but there is like no acceleration past about 1/2 throttle. If I keep it around 1/2 throttle Everything seems to be fine. Also having issues going up hills unless I play with the clutch. Also i don't know if it was the cold weather but the bike died about 3 times during a 24 mile drive. But started right back up and everything was seemingly fine.

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I haven't had any problems going up hills, provided I'm in a lower gear. What issues are you having, specifically?

As for the acceleration past 1/2 throttle, when you give the bike more throttle, do the Engine RPMs continue to rise, but you just don't seem to be going faster? If that's the case, maybe your clutch is not adjusted properly and is slipping at high RPMs?

Acceleration is perfect at half throttle and less. Any more than that there is literally no more acceleration in higher gears at highway speeds. I have to down shift to lower gears. Does just fine downhill perfect even but when i wanna go full throttle i cant. Its like the bike wants to but cant so it coughs kinda or light backfires. Clutch operates and responds perfectly it seems to be throttle response itself. Maybe mixture screws need to be adjusted or throttle cable needs to be adjusted because the throttle has a bit of freeplay

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Throttle should have a bit of freeplay and the mixture screws only handle idle speed, not open throttle.


Throttle half open is about where the main jets come in.  Either these are clogged or your slides aren't working.
You can visually check this with the airbox off and revving the engine.

If the slides aren't moving you likely have a puncture in the membrane.

Main jet is the bigger of the 2 correct? And by membrane you mean the diaphragm? I submerged both diaphragms in water and saw no bubbles. Thats what I'll check. A little more information though. The bike wants to go. At anymore than 1/2 throttle it kinda surges with acceleration. Its like no power and then a lot of power and the back to nothing. And back and forth until i back off the throttle and then its back to normal.

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Sorry you're having such a hard time with the carbs.  I have to admit to these carbs being particularly finicky.

It sounds like you have a starvation issue now either with air or fuel.  Either the plastic slides aren't lifting enough when you open the throttle (vacuum problem) or you're not getting enough fuel into the mixture, i.e. the needle isn't placed in the slide properly so could perhaps be not rising high enough.   Just to be sure, I'd double/triple check you've put the needles back in the correct way, not missing any of the parts, etc.

The carbs are definitely an acquired taste.

Sounds to me like float level is low, float needle valve getting stuck closed, etc. I would just replace the o-rings and clean the carbs thoroughly, make sure you have the vacuum port caps on and the o-ring under the vacuum ports on the tops is there and in good shape, then as long as the float needle valves work and the float level is right then you should have a running bike.

The thing about these carbs is there really is not a lot of tuning. They kind of do what they do. Put stock or +1 sized jets in and as long as everything is clean and all rubber parts are intact then the ONLY thing to tune is the idle mixture and speed. Get the idle mixture screw at 2.5 turns out and the bike should start and run fine and you might be able to dial it in a tiny bit better but overall basically that's all there is to it. Anything causing it to not run right is not because of carbs being out of tune, it's because of degraded parts in the carbs somewhere causing either a vacuum leak, a fuel leak (bad o-rings), or something is clogged (tiny little orifices).

Quote from: mr72 on February 24, 2017, 09:27:47 AM
The carbs are definitely an acquired taste.

Sounds to me like float level is low, float needle valve getting stuck closed, etc. I would just replace the o-rings and clean the carbs thoroughly, make sure you have the vacuum port caps on and the o-ring under the vacuum ports on the tops is there and in good shape, then as long as the float needle valves work and the float level is right then you should have a running bike.

The thing about these carbs is there really is not a lot of tuning. They kind of do what they do. Put stock or +1 sized jets in and as long as everything is clean and all rubber parts are intact then the ONLY thing to tune is the idle mixture and speed. Get the idle mixture screw at 2.5 turns out and the bike should start and run fine and you might be able to dial it in a tiny bit better but overall basically that's all there is to it. Anything causing it to not run right is not because of carbs being out of tune, it's because of degraded parts in the carbs somewhere causing either a vacuum leak, a fuel leak (bad o-rings), or something is clogged (tiny little orifices).

You guys are awesome. My right side carb float level is low. I figured i would have with running a little lean than a lot rich. I didnt know it would take my throttle away from me. Now i know. The level is about 4-5mm below where the carb bowl meets the carb body.

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I think you've done well to keep troubleshooting and working at it. I'm sure a lot of people would have just cut their losses and outsourced the job. Good for you 

Chris

I went and reset the right carb now its about 2-4mm above where it should be. The issue is a little better but still having problems with surges in power. Downhill I've got no issues which i expected. But uphill and sometimes on level planes its hard to maintain speed or even gain. Would a little rust from the tank cause this or possibly make this issue worse? I noticed a little rust when i drained the float bowl to reset the float height.

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Also the float height is about 2mm below where it should be after rechecking heights.

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downhill/uphill differences probably either float height or o-ring leak in the carb.

O-ring leak where though? And my height on the left is perfect. On the right its about 2mm below where it should be. I dont lose speed uphill i just dont gain any unless i already have a good bit of speed in which case i continue to gain speed.

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Quote from: newbie1993 on March 02, 2017, 03:39:20 PM
O-ring leak where though?

Who cares? On an '89-00 GS (IDK what year yours is) there are four o-rings on each carb that warrant replacing: float, float needle seat, idle mixture needle o-ring and the "little o-ring" on the vacuum port under the top of the carb. Add to that the intake boot o-rings and that makes a round 10 o-rings total that you should replace. Just replace them all and then quit worrying about o-rings. It's almost exactly the same amount of work to replace all of them as it is to replace one and then you don't have to try and figure out which of the dried-up worn-out o-rings is the one that's leaking the most.

While you have that apart replacing the o-rings you can examine the diaphragm under the top and make sure it has not been destroyed by carb cleaner or age. While the carbs are on the bench it's easy to lift the slides and make sure they return smoothly. You can make sure the main needle is not misaligned with the main jet so it hangs up and prevents the slide from closing (it happened to me!). And you can properly set the float level once and for all. Win-win. Takes two hours or less even for a beginner to do all of this with $10 worth of parts.

"there are four o-rings on each carb that warrant replacing: float, float needle seat, idle mixture needle o-ring and the "little o-ring" on the vacuum port under the top of the carb."

Im ordering parts and im not sure which one is the idle mixture needle oring.



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