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What the heck?

3488 Views 36 Replies 8 Participants Last post by  zx12ryder
Okay, let me begin by reminding you guys that I'm new to tuning bikes. So many variables for a new guy. Anyway, I got the bike running pretty good, but it is still backfiring on the right side and idles all over the place and then just dies. It will be idling at 1100rpms and abruptly die.
Also there is a tapping noise in the engine. When I put my stethescope on the right side lower engine, near the oil filter, it is a distinct rapping noise.
So just for fun, I pulled the right side plug wire, which I noticed looked worn. The engine did miss a beat. It runs the same way with the plug wire on as it does with it off. Rpms don't change at all. What is going on? :?:
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Try a new plug on that side - make sure it's actually firing before you screw it in.

The rapping sound may just be the crankshaft being reluctantly pulled along because the right side isn't firing.

What did you end up setting your air/mixture screws on the carbs??
There's a little tab on the float itself which pushes the needle valve closed.
Bend that tab to adjust "float level".
Be sure that the needle valve actually closes - not where the tab just touches the valve.
66Sprint said:
Well, an engine only needs three things to run... Fuel-air mixture, compression, and a spark at the right time.....
The ether provided the fuel-air mixture, You claim to have spark....
You either have a lack of compression, or the spark is mis-timed ........
(or not actually firing...You DO realize that just because a plug will fire in open air does NOT mean it's firing under compression..... Did you try new plugs?)
What were your compression readings?

Well said, Steve.
The compression on that engine read 172 psi, both sides - this was on the bench, right after rebuild - never run, cold.
I'm hoping it increased a bit now.
The cylinder taper was a little high, but Chris just wanted new rings, not a bore job (economics, something we all understand).
The engine also had the valves done by my machine shop buddy - they did not leak, for sure.
OK Chris - this shouldn't be this hard...

Stop, step back, and re-zero here.

OK, left side runs, right side doesn't, it has spark at the right point -

1)After "running" for a minute, check the right spark plug - is there fuel on it at all??
2) Switch spark plugs - any change?? If the right side now runs, it's just a bad plug. NGK B8ES only, no substitutes please.
3) Switch plug wires - just run the one on the left side over to the right side and vice versa - any change??
If the right side now runs, it's either a bad coil, condensor, wire, or cap.
If you have a compression tester, check it (warm engine, open throttle, no choke).
Just to make sure that nothing crazy has happened - I recall you said at first it ran like a raped ape, so check if you can, let's make sure it's still ok.
KERRY said:
You might want to try a compression test before you get into trying to solve a fuel supply problem. Leaking valves, worn rings, holed piston etc. will result in a non-firing cylinder no matter what else you do.

Kerry -

The engine just got new rings and a professional valve job.

I'm looking at the engine this weekend sometime (Sunday I think).
I'll post what I find, I have the feeling it may be unusual...........
mitchellsk said:
Chris Garrett said:
The contact points cover was making contact with the points...
Hasn't happened to me but someone told me about this scenario once... thought I'd pass it along :)
It's actually pretty common on a 450..........
zx12ryder said:
i find this subject interesting...i have had the same intermittant problem. thought condensor was acting up for the one side. I think i will put a thicker gasket on my points cover plate. also......why would they touch?....quirk in the mfg process that was overlooked? Doesnt really matter how but i will def take precautions.

It's easy to put the little spade connectors not quite right when you change points.

Easy enough to diagnose - your problems happen only when the point cover is on.......
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