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I have a 1980 900 SS with newer style 40 mm dellorto's with cable operated chokes. I've just tuned them and the engine starts everytime and idles beautifully. The problem is that on acceleration the front cylinder seems to bog down and spit back. On inspection the front seems to be running quite a bit hotter than the rear. The header right at the head is quite blue and yellow in color. Both mixture screws are turned out 1-3/4 which sounds at idle correct. Maybe not. New floats, 155 mains, and 60 idlers. Needles set at mid point. Any thoughts out there?

The Jets are about right. The needle position is too. I would recheck the float level and fuel supply.If that is ok look at the ignition. Check the timing advances when revs come up. Could be the wiring from the pickups has deteriorated.

Thanks for the reply. I'll have to check out the wiring. Just out of curiosity, when replacing the wire do the pick ups have to be removed from the case or can they be rewired in place. If one cylinder appears to be running hotter this means to lean right?

jsey wrote:when replacing the wire do the pick ups have to be removed from the case or can they be rewired in place. If one cylinder appears to be running hotter this means to lean right?

no - do NOT remove the pickups or you will be in trouble as they must be set back up exactly as they were - they are factory set and it takes a special tool to set them. Rewire them in place.

a hot cylinder means either too lean or bad ignition.

Since you have a 1980 BOSCH ignition bike, and you are asking about the pickup wires, I can only assume you have the original wires in place. This tell me that you must replace those wires immediately. Then try things again. You may also need to replace the intake manifold insulators - the thick rubber pieces between manifold and head and/or exhaust gaskets too. I would just out of principal...

Thanks Steve