cylinder #4 problem

[Guest]

Help!!!! I have no hair left from pulling it out and my head is sore from beating it against the wall!!! Ok here we go.... My step father gave me this beautiful bike. 1983 Suzuki GS750E. My step father has done a ton of stuff to this bike. He had problem with the charging system which is now fixed along with many other things. The last problem that he had was the fuel problem so he fixed that problem with a 2012 GSX1250FA. LOL. He was going to sell the 83 but I got back just in time. He also replaced the carbs, new needle and seats. The bike starts and runs great, Garage kept but once the bike warms up cylinder #4 cuts out. I have great spark (pulled the wire off when running) I found the o-ring on the boots from the carb to the head were leaking so I replaced all of them, found that a stone hit the top of the carb and put a pin hole in the plastic cover so I replaced that all on cylinder #4 This is the only cylinder giving me a problem. I've also checked the diapham for a hole and couldn't find anything. I've been over and over the expensive service manual. I don't have the fancy vacuum gauge that they have but I do have a vacuum gauge if I only knew what the spec for that was. I'm thinking Vacuum or fuel delivery problem. Any help would be great I really want to ride, it's been over 15 years since I've had a bike. Big time withdrawal. Thank you in advance for the help.

[tom203]

".....once the bike warms up cylinder #4 cuts out. I have great spark "

Will it stay cut out, if you drop back to idle or shut off and restart? Have you tried switching spark plugs ? plug caps?
After it warms up and behaves like this, remove #4 spark plug and see if it's wet or dry.

[hjfisk]

Try adjusting the valves, when it warms up the valves tighten up and possibly holding open on #4