Carb problem on '81 GS 850

[Anonymous]

Bike: '81 GS 850G, recently put together from a pile of parts.

I hope this hasn't been covered already, but I'm having problems that I just can't figure out. After about a year of finding parts to make this bike complete, I finally got everything put back together, all wiring made right, everything good electrically as far as I can tell. Then to the carbs, at first I just put them on to see if they would work without much work (they had been drained before the bike sat up) but strange things quickly started to happen. I've disassembled and dipped all the carbs, put them all back together, and the bike starts up no problem, idles just fine. But when I try to give it throttle, it will rev up to about 4-6k and then bog until the rev's get back to around 1k and will pick up and rev and bog again. I've checked the float level and it's good, the piston boots are good, and all the jets are clean and clear. I've also rebuilt the petcock and it's working properly. The spark plugs are carbon fouled, which led me to think that it was running rich, and I can generally smell gas when it's running. Any idea what would be keeping it from revving correctly?

Thanks

[Anonymous]

If they're CV carbs (I take it they are) you might want to make sure none of the rubber diaphragms are punctured or torn. Also, that all seals in the carbs are good, no air leaks to the motor, no vents clogged, and that the jet needles are moving freely up and down.

[Anonymous]

I think you just have to balance them.

Sounds like they need to be ballanced. Check / Replace the O-rings between the manifold boots first, and make sure you have a good clean filter on it.

[Anonymous]

Update: Yes they are CV carbs, the rubber diaphrams are in good shape, and unless I'm missing something, all the vents are open and free. Jet needles move freely. I feel like it's running rich, since the plugs are coated in carbon, and I can smell excess gas in the exhaust. However, unlike the SU CV carbs that I'm used to working on, these have no way to adjust the main needle jet. as far as I can tell, the only things that can be adjusted is the float level (it's good), the sync (haven't touched that, should be good), and the fuel/air ratio screw which should affect idle and not open throttle conditions. Is there something else that I'm missing?

oh yeah, it's sans air filter right now, until I get it running right. The maifolds have not been off.
Thanks.

[SqDancerLynn1]

The problem is that you will never get it to run properly with out the air box installed

[Anonymous]

I agree. Install the airbox, use a clean filter, then see how it runs. Trying to tune those carbs without some air restriction is a waste of time. They are very sensitive to air velocity.

[KrazyKarl02]

Main needle jet adhustments

The main needle jet on CV carbs can be adjusted by shimming the needle up or down, if you take the diaphram, slider, needle assembly out you can take the needle off and place shims to move it up or down. These shims can be bought from the suzuki dealer or you can try just using washers.

Before you do this though install that air box!! and synch the carbs, carbs should be synched every time they are dissassembled!

Good Luck

[Anonymous]

Thanks for all the help! I'm actually still wrestling with getting the air box back on, it turns out that the rubber rams are pretty well hardened and shrunk up, it doesn't even look like they are the right size. So now I either have to find replacements, or figure out how to get those stretched some. I did, however, notice that the air box has GS 1000G stamped on the bottom of it, but I would have thought that if anything, the 1000 would have larger carbs than the 850?

Thanks again for all the help and suggestions.

[Anonymous]

Well, I can tell you this, make sure you have those little rubber plugs that fit over the pilot jets. they'll run you about........$12-15 a set and you have to have them........... It should run and stop your over -rich