backfiring kz750 twin

so I went for as ride today, and everything was fine untill about two miles out when i felt my bike start to jerk, like a cylinder was cuting out. I pulled in the clutch, and let off the gas and it died, i let the speed of the bike start it agin then when I got to a stop sign it died. I finally got it kick started again but with a lot of tries ending in backfires. the kick starter would litterally throw my leg off of it and I could see some small amounts of smoke coming from the carbs. I have ordinaly 10w 40 in it right now. Could this be from the summer heat and heat of the engine making the oil too thin? or is it more likely something more serious?

How long since u have replaced plugs,wires, and looked at the timing advancer? Any issues with leaks at the fuel petcock?Tank clean? Have the carbs been cleaned or rejetted?If the bike is "kicking back" as u describe,I would suspect timing is off.Just some items to start thinking about.bj

It almost sounds like you lost a spring off of your timing advancer during your ride, or your advancer stuck with the arms out.

Sorry but, LOL, can these old twins kick back or what eh! :woohoo:

Garbage in a main jet will do that. Guess how I learned that.... could also be timing advancer, coil, plug wires, etc.

Malfunctioning charging system will do that also

While at it, might as well also assure valve clearances are adjusted to spec, especially the intake valves.

A too tight intake valve clearance can cause backfire through the carb.

Good Fortune!

steell wrote:

Malfunctioning charging system will do that also

this is true...

BWAH!?! Where the hell have you been man!... :laugh:



My guess... timing issue, there you have it!

:silly:

I thought timing too. I just installed a dyn s system, timed it with a timing light, and rejetted the carbs for a k&n air filter. the timing is dead on, but the peice of the dyna system that goes into the advancer didn't fit right so i put an o-ring in the gap. tightened it up enough that it doesn't wobble anymore but it does seem a bit tight. it moves fine and returns but there is a bit of space were the advancer doesn't return the peice all the way back. Could new springs fix this?

That doesn't sound right?
But a stuck advancer? How does it make a bike quit? Hard to start, kick back on kicker, sure. Maybe you need to look farther, possible fuel problem, as suggested check the valves, and cam timing, compression test, to make sure its not mechanical. Do you use a in-line filter? Could you have a electrical/ voltage problem? AS already suggested.

Check compression and spark, could be valves, carbs, timing, anything. If you check the obvious and they're good then you can check them off the list and you'll have a better idea of what the problem could be.

Anything hu? that sux lol. I guess I'l just start with the simple stuff.