cool cyl's

I now have my 750 put all back together, but I am having some issues.

the 1 and 3 pipes i can hold while its running, until you get the rpms up. 2 and 4 i would not want to touch....hehe they are good and hot.

while im riding you can hear and feel like a cyl or two is trying to work. Ive metered the coils as per the book and they check ok, as well as the pickups. the plugs and wires are new and if i unplug number 1 while its runnings...it dies. so im lost. all the fuel bowls are getting gas and the floats work smoothly. The pistons in the top of the carbs move free and smooth. It idles ok, but does seem to miss a bit. its more noticable while riding, cause it trys to cut out when you take off...i have to throttle up more than i should so it doesnt die.

anyone have an idea. im new to working on bike's so im not sure what all to check for. The engine is completely rebuilt valves, rings, and all.

Post edited by: Meekrat, at: 2006/04/21 18:29

Well, I would have to say that it sounds like you may want to check the voltage going to the coils first. Also check the contacts of the wires going to the coils. recheck your plugs/wires, make sure you have good spark in every cyl, and that the wires aren't plugged into the wrong cyl. For example 1 and 4 are on one coil while 2 and 3 are on the other.
What color are your plugs in the "cool" cyl's?
If you've ruled out the ignition system, then I would lean to the carbs.
If it's running cool you may not be getting any fuel from the two carbs at all, but not likely. In this case I would check to see that the jets are not clogged in them. Then check the intake boots by spraying some carb cleaner on them. If you spray them and the idle speeds up, then there is a crack/leak that is causing the cyls to run lean. You didn't say anything about the air filter system, Pods or stock? any mods to the exahaust?
Have the carbs been rebuilt as well? are they jetted properly for your application? have you vaccum checked your carbs? If they aren't adjusted you could starve some cyls.

Sorry to ask so many questions, but these are things that make big changes in the performance of the engine.
Hope that helps :whistle: (if not, George can correct my mistakes )
Take care and ride safe

:blink: :blush: WOW! my first double post... do I get a prize? or should I just pretend that it never happened?

sorry about that :whistle:

Post edited by: NOS, at: 2006/04/21 19:33

It has the stock air cleaner system on it. New MAC 4-2 exhaust, not the stock but kept it 4-2. The carbs have not been rebuilt. Ive kept them together on the rails, and have only cleaned out the float bowls, and the diaphram slides. the secondary jet has *90 stamped on it.

I swaped the wires for 1 and 4. but 1 stayed cool, 4 ran good like it was before i swaped them. Plugs are off-white/light tan. they only have a few miles on them. I check the boots during the rebuild for signs of crack, replaced as needed.

with all that i have tried, im really starting to believe it is a carb issue because 2 and 4 are fireing good.1 and 3 are the cool ones. at idle i can hold the header for as long as i want, bring it up to 3k rpm and it warms up real fast.

If i run the mixture screw all the way in on the number 1 and nothing changes...what would that tell me. Would it be the primary jet gumed up? the pipe only gets hot if i rev up to at least 2k.

These carbs did sit for a couple of months during the rebuild.

btw they are the Keilin CV34, stock as far as i know.

Did you check the diaphrams in the CV carbs for cuts/cracks? you may just need to replace or patch them if they are. That could cause the two cylinders to be starved until the vaccum was strong enough to open up the sliders, but I am no expert on this
I had to get rid of my Keihin CV's because they are hard to find parts for and they are even harder to tune.
I would check out Wiredgeorge on his website ( www.wgcarbs.com )and ask in his forums. I think there you will find your answer.

Hope that helps. It seems a shame to be having probs with a fresh rebuilt engine. Hope you get it worked out soon.
Take care and ride safe

Post edited by: NOS, at: 2006/04/22 19:33

Check your carb sync - a couple of carbs may not be open at idle, or opening at all. I had a dead cylinder because a linkage nut had backed off and the slide wasn't moving.