Bewildered I am tonight.

[JimRobert]

I have my 1985 Suzuki GS700ES running and took it out yesterday for a spin. The bike runs great off idle. It will not idle at 1200 rpm's. When it is cold it is the most cold blooded motorcycle I have ever seen or owned. I've pulled the carbs twice off of this bike to check and recheck everything inside. The floats are all set at the same height. The carbs do not overflow. However it is very easy to flood this bike. I pulled the carbs again tonight and reset the floats a little bit lower. I've freed up the idle screws and have them set at 2 turns out. Once it warms up to around 180 degrees it seems to run better. But it will not keep a constant idle. Sometimes just when you think you have it all set the motor will race up to 2K and stay there. You back off the idle screw and the motor dies. The intake manifolds are not ripped or cracked. I did use silicon sealer on the O rings when I installed them on the new motor. This has me really puzzled as I have never had this much trouble setting up a set of carbs. I never seperated the carbs. The inside of the carbs sparkle and there is not buildup of anykind in th bowl. The jets and idle ports are all open and appear to be working properly. I squirted carb cleaner through every hole that I could find and it came out the other end. I am really stumped on this one. All four of the carbs had closed vanes when I had the cabrs off and appear to be set properly. The valves have been set properly and the motor will easily rev up to 9K in gear.

[earlfor]

You said, ..........................."I did use silicon sealer on the O rings when I installed them on the new motor."

That is a glaring NEVER DO. :-) Never use silicone to seal carb "O" rings or anything that comes in contact with gasoline and preferably never with anything that comes in contact with oil. Certainly not on any internal gasket surfaces or in any place a piece of it could dislodge and clog an oil passageway, etc. Actually, there is no place on a motorcycle engine that silicone is a suitable sealant for. I would expect the "O" rings are leaking.

E.

I have my 1985 Suzuki GS700ES running and took it out yesterday for a spin. The bike runs great off idle. It will not idle at 1200 rpm's. When it is cold it is the most cold blooded motorcycle I have ever seen or owned. I've pulled the carbs twice off of this bike to check and recheck everything inside. The floats are all set at the same height. The carbs do not overflow. However it is very easy to flood this bike. I pulled the carbs again tonight and reset the floats a little bit lower. I've freed up the idle screws and have them set at 2 turns out. Once it warms up to around 180 degrees it seems to run better. But it will not keep a constant idle. Sometimes just when you think you have it all set the motor will race up to 2K and stay there. You back off the idle screw and the motor dies. The intake manifolds are not ripped or cracked. I did use silicon sealer on the O rings when I installed them on the new motor. This has me really puzzled as I have never had this much trouble setting up a set of carbs. I never seperated the carbs. The inside of the carbs sparkle and there is not buildup of anykind in th bowl. The jets and idle ports are all open and appear to be working properly. I squirted carb cleaner through every hole that I could find and it came out the other end. I am really stumped on this one. All four of the carbs had closed vanes when I had the cabrs off and appear to be set properly. The valves have been set properly and the motor will easily rev up to 9K in gear.

[nabrams]

Assuming compression and valve clearances are all OK:
Sounds like the classic air leak to me too. It could also be in the airbox/filter itself, or the boots that connect the airbox to the carbs, or a mild exhaust leak at the point where the exhaust pipes seal to the head. People tend to discount these areas. Been discussed a million times.
In short: Minor jump in idle speed and/or erratic ide = minor air leak somewhere.

[chuckycheese]

Synch

Some people always seem to suggest synching the carbs......but, based on what you've reported, I really think you should try that. You mentioned that you didn't separate them so I'm guessing that you didn't synch them.

I had very similar symptoms before synching mine and the difference was like 'night and day'. Even if they look to be really close....they could be way, way off. Let us know!

[DimitriT]

First check valve clearance and carb balance.

Note: If the RPMs increase when the bike warms up its lean. If the RPMs drop when the bike warms up its rich. Check the plugs to find out which cylinder is the problem and adjust the idle mixture in 1/4 or 1/2 turn increments to get good color on the plugs.

Don't forget to plug the vacuum nozzle on the #2 carb if you are running without a tank.

I wouldn't count on silicone to seal up the boots. Get new o-rings and clean out the sealer.

[JimRobert]

Lo and behold I figured it out. I sprayed some either at the carbs boots and the motor did not change in rpm's. That ruled out the O rings. What I found is that the motor would idle at 2200 rpm's. Any lower than that and the motor would gradually stall out. The idle mixture screws were set at two turns. I lifted up the gas tank and started to mess with the idle mixture screws while holding the throttle at 1250 rpm's. I ended up turning out each mixture screw another 1 1/2 turns. After setting the first carb I was able to release the throttle and the bike was idleing high. I had to turn down the idle screw after setting each one as the motor gained another 200-300 rpm's. The carbs were running so lean that the motor could not run on the idle side of the carbs with the idle mixture screws set at two turns. I just came back from a ride and pulled in my driveway. The motor was purring at 1200 rpm's. I have never seen carbs that had to be set that rich. I wonder if the Vance and Hines exhaust has something to do with it? I guess I should have never touched them to begin with. I'm the one that turned them in and backed them out two turns when I changed the motor and pulled the carbs apart to make sure they were clean. What a frustrating afternoon that was. At least it is fixed now. And thanks for the info on the silicone sealant. I know not to use it any where near the oil as it will plug the oil passages as mentioned above.

First check valve clearance and carb balance.

Note: If the RPMs increase when the bike warms up its lean. If the RPMs drop when the bike warms up its rich. Check the plugs to find out which cylinder is the problem and adjust the idle mixture in 1/4 or 1/2 turn increments to get good color on the plugs.

Don't forget to plug the vacuum nozzle on the #2 carb if you are running without a tank.

I wouldn't count on silicone to seal up the boots. Get new o-rings and clean out the sealer.