CX500 _symptom indicative of what?

[True Blue 79]

Hi-

I picked up a 1980 CX500 Deluxe for my boys to use to practice and get their licenses with (actually lent to me by the
owner who didn't feel comfortable selling a non-runner). I got it past the seized engine, found a headlight/taillight to replace fairing, tuned it and it runs okay. However, it seems that only one cylinder is firing until it hits about 4,000 rpm. Then the engine comes fully alive. Does this sound like a CDI or stator related problem? How do I trace it down?

[robin1731]

Sounds more like carburetors to me. Time for a complete tear down and cleaning at least. If not a full on rebuild.

[True Blue 79]

I thank you for the response; help is always appreciated.

However, I thoroughly cleaned the carbs when I went through the bike.
Anything else it might be?

[Papa Bear]

Don't rule put a plugged slow speed. They are tiny, to say the least, and any contaminant from the tank could cause a problem with newly cleaned carbs. Otherwise, points, ignition timing? Advance unit? Not firing until full advance?

For the carbs, if you have an auxilary tank you use for tuning, run some Sea Foam thru the system by passing the bike's tank. If it clears up and runs, you have an indicator that the tank is cruddy.

If you don't have one, they are easy to make:
1. Buy a one gallon plastic gas can
2. Buy a four foot length of 1/4" fuel line, a 1/4" tapered fitting threaded on one side, an in line filter, an inline petcock and a piece of 1/4" OD pipe about 2" long.

Drill a hole a bit smaller than the threaded end of the tappered fitting and screw it into the can. Start small with the hole as you can make it bigger, but not smaller. Put fuel line over taper. Splice in filter then petcock. Install piece of pipe. Add gas and SeaFoam if needed. Insert end in bike's tank/pump to carb line. Open petcock.

This will provide fuel to the carbs with the tank off or pump disconnected. Often makes it easier to do tuning and such. Is very good for determining fuel problems. If it runs good with auxiallary but bad with bike's tank, you have a fuel problem. Set-up is good for priming carb after rebuild, also.

[ritalz]

Rubber plug in the float bowl is probably out. Been there.