Carb 3 and 4 not working

[skchurch]

Well I am new to this forum but have been spending alot of time reading all of the other great posts. We purchased our first motorcycle about 2 months ago and it was a 79 GS750. I had read alot of good things about these bikes and how they were very well built. The bike started when we purchased it but it would not stay running off of choke. So after reading quite a few different posts and watching the videos from BassCliffs site I dis-assembled all 4 of the carbs then dipped them in Berryman Chem Dip. I also ordered all new O rings from Mr Bar which worked out very well. After re-assembling everything the bike still would not run off of choke. So I re dipped the carbs again. I also checked the valve clearances and they are all with in tolerance. I then replaced the spark plugs. I was able to get it running well enough to check the timing and it seems to be right on now after a little adjusting. So now it will run off of choke but it appears that Carbs 3 and 4 are not working. I base this on the exhause pipes off of these 2 cyclinders are not getting warm like 1 and 2 are. I pulled the new plugs and 3 and 4 seem to have some gas on them but not much. I am looking for some advice where to go from here. Again I am far from an expert so any help on this would be great. The weather is geting really nice and my wife and I are very much looking forward to taking the bike out.

Thanks
Scott

[oneliterbeater]

Have you checked for spark on those two cylinders?

[skchurch]

Have you checked for spark on those two cylinders?

Yes, I have spark on all 4 cylinders. I even tried switching the wires for 1 and 4 to see if I had a bad wire. If I let it run for quite a while the exhausts for 3 and 4 do get a little warm but not much.

Scott

[allojohn]

If spark is not the problem then it's gas. Did you set the float height at 24mm? When you dipped the carbs did you also dip all the brass bits?

The float needles could be stuck - try tapping the bowl with a wooden dowl.

[MisterCinders]

Did you synch the carbs? If 3 and 4 are out of whack, they could be too tight to fire. At least do a good bench synch to get the slides close.

Also, put a fan on the engine and try increasing the idle speed to 2500 for a minute. Then see if that brings those cylinders online. That would signal badly synched carbs.

[Crage]

I had the same thing on one of my cylinders are a carb cleaning. I wasnt getting any gas to the cylinder. I took the bowl off of that carb and removed the pilot jet. Sure nuff, I couldnt see through the pin hole.... It had a bit of sand in it, I'm guessing from my garage, so I blew it out with my mouth. Put her back together and she fired right up just fine.