Poping while excelerating...help!

Hello all,

Im a noob to the forums and a proud owner of a 1977 KZ650. I just got it running with a friend and it may have had some bad gas while sitting, but when I accelerarte it pops like crazy and I have very minimal exceleration. Just wondering if this is a carb or timing issue? Any feedback would be greatly appreciated.
Thanks,
Dino

Can you define the popping noise better?

Which of these do you think it is - or could be?
DETONATION
BACKFIRE THROUGH CARBURETOR
ROD OR MAIN BEARING KNOCK
VALVE CLATTER

Could be one thing or a whole pile of things.
How long was it sitting ?
Was it running well before it was left sitting ?

First thing I would do is drain the carbs and gastank and fill up with fresh. Then start with the ignition.
Minimal acceleration would make me wonder if it is running on all cylinders - spray water on the exhaust pipes. If it sizzles right off then it's running on that cylinder.

Do you have a manual ?
The bike probably just needs a good service - timing, valves etc.

Welcome to KZr DinOwnSu.


Like suggested, drain all of the old fuel and use new fuel.
From the your description it sounds like one of the points is sticking and/or corroded, so that would be the next area after adding new fuel that I'd recommend checking into.

Welcome! New bike? Bet you want to jump on and ride. Before doing so, I suggest you either get the bike tuned professionally with an emphasis on a full check of all safety items such as brakes, fluids, cables, etc. If you want to give it a shot, purchase either a Clymers manual or a Kaw Factory Service Manual and go through the full tune up and maintenance schedule. It isn't really common for a bike to backfire/pop when accelerating. This indicates that air is getting into the combustion chamber so I would strongly suggest that on top of the tune up and maintenance, buy new exhaust crush gaskets, new carb holders and check the caps on the carb holders as well. Your popping/backfiring suggests the possibility of engine damage otherwise as cold air focused on your piston crowns can hole the pistons.

Sounds like it's poping from the carb and the exhaust. If I had to guess Iwould think it's a carb issue. I have a buddy that is a motorcycle mechanic and he says he thinks the carbs may be sucking in air. If so it's minimal air it's sucking in.

You can test to see if the carbs are sucking in air. You can spray some WD-40 or starter fluid onto the carb boots, intake boots and vaccum ports. Just do one carb at a time. If the idle jumps up then you have an air leak. Make sure to spray the undersideof the boots as well. Be very carefull witht he starter fluid. You should have a water hose with you for two reasons. Mainly because the starter fluid is very flamable and also because it can eat through paint if left on for too long. Spray the carbs a little and if then rinse with water, then repeat. If you keep a nice puddle of water on the engine cases then it shouldn't hurt the paint too bad.

Might weant to check and make sure your ignition advance weights aren't frozen too while you're at it.

I appreciate everyones feedback and I will start with changing the carb holders and exhaust gasgets here soon. I really appreciate the help and hope to get on the road soon.

Thanks again,
Dino