help me out

my dad and I have been up and down on this problem trying to figure it out. Were stuck. After finishing my bike, we decided to start her up. started up fine but blew smoke. we rebuilt the carbes recently and synced them and they are like brand new. the gage shows the same across with the vacume and fuel. But for some reason the number one chamber is missing!! we lean it out... nothing, we richen it... nothing. We pull the plug and the spark plug is fouled. it happeneds to all the pulges we replace it with. we even checked the spark and its good. we checked the wireing and its all green. could the timing have anything to do with it? I dought it because all other 3 sparkplugs are fine. the normal white tip showes up on the plug telling me its fireing fine and its not lean or rich. Magneto? float? someting wrong with the #1 carb? I'm just confused because when you have a good spark, proper air/fuel mix and the timming is fairly good (It might need some work) you shouldn't have a miss right? I took it out for a ride and it misses for a while but when it hit a certain RPM it kickes in and damn near thows me off my bike. no more miss. which leads me to thinking that it could be a stuck valve maybe? any help please. thanks :blink:

Post edited by: badboie, at: 2007/07/10 02:06

bad valve seal leaking too much oil out of an intake valve?

do your secondaries move freely?

Do a compression check.If good, swap #1 and #4 plug wires.If no change check the carb over real good,borrow
another set of carbs if possible for a comparison.

badboie wrote:

...float?....

Easy (no disassembly required) to check service fuel level and compare with other carbs using clear plastic tube method method.

Too high fuel level can cause over-rich mixture even with an otherwise perfect carb.

ok progress report... The compression is great all across. the spark is hitting right. we rebuilt that #1 carb twice now. the valves are working fine. but there is still NO fire for some reason? if it was a timeing problem, wouldn't it show with the other plugs as well, at lease one other?? like I said befor, at idle and up til about 2100 rpm the engine misses in the #1 cylender after 25-3000 rpm it kicks in and runs fine. has anyone had this problem befor and knows or has any idea whats going on?? I'm lost. :huh:

Did you switch the spark plug wires as tjettim suggested? If you do and the problem persists, it's probably not electrical, it's unique to the cylinder. If it runs fine at higher RPM, that suggests the pilot circuit.

When you went through the carbs, did you confirm that air would flow through the pilot jet orifaces? A clogged or partially clogged air oriface would cause a too rich problem at low speeds. Also, inspect the choke. If fuel is leaking past the choke, that will make it run rich.

ohm test your spark plug caps
if they are not between 5K~8K ohms there is the problem higher than 8.5K represents a bad cap

when you remove the caps trim .25 of a inch off of big plug wire to get fresh connection into the cap.

a plug will fire out in the open atmosphere but inside the combustion chamber under pressure the excessive resistance through the plug cap will not allow it to jump the spark:
hence when you rev it up and increase the voltage pressure coming from the stator the threshold is surpassed and bang combustion!!

that is after carb issues are addressed and eliminated.

I just had what sounds to be the same problem with my KZ750. It turns out that the coil was bad and not firing unitl after ~3000rpm. I replaced the coils, WG coil relay mod, trimmed the spark plug wires and the spark plugs. Now it runs great. Idles and pulls great.
Here is a link to my post:
Bad Engine? -- Now with video -- Update
~500 miles later and everything is still working great.

Post edited by: cafekz750, at: 2007/07/13 16:05