Engine dieseling

S

sboricic123

Member
I just took my new 66cc Flying Horse for a ride tonight. The kill switch was working fine until I went for a longer ride before shutting it off. Well, when I got to our driveway and pressed the kill switch, it would not shut off. So I unplugged the spark plug and it was still running, beginning to overheat. I then released the clutch and it shut off. I checked the wires, black and blue, to make sure they were still connected and they were. What may cause this to happen?
 
Just a theory but heavy carbon build up in the combustion chamber can be acting as a glow plug and keeping the engine running after the ignition is off. This could be an indication of overheating too.
The condition isn't common but not unheard of. Pull the cylinder head and have a look at things.
What oil to fuel ratio are you running? Does your engine see any WOT (wide open throttle) conditions or is it just putzing around at half throttle or less?
How many miles on the engine and how did you break it in?

Tom
 
This was it's first run Tom. I'm using 20:1 ratio. I have noticed the rpm's are high when idling. I tried adjusting the NT carb but that didn't lower the rpms. I haven't tried any WOT since I'm breaking it in.
 
As you've probably read here, a fast idle speed can be attributed to an air (vacuum) leak somewhere downstream of the carburetor, or a throttle not returning to full closed.

When it comes to break in I'm of the school that advocates running the engine a little harder than some suggest. My theory is that it is a small 2 stroke engine very similar to a chainsaw or leaf blower used commercially. What wood cutter ever tried to cut down a tree at half throttle with a new chain saw? Few, I'd suspect.

You don't have to abuse the engine by riding at full throttle the whole ride but let it run for some short bursts. Some of us recommend that a new engine be run like you expect to ride it normally. That means some WOT time mixed in with some softer running. Don't baby the engine. It needs to be run hard at least some of the time during break in.

Check your carburetor to intake manifold attachment as well as the intake manifold gasket where it meets the cylinder. The kit gaskets are notorious for early failure and a poor gasket seal.

I would also suggest dropping your oil content down to at least 24:1. 32:1 is even better
Your 20:1 is a little oil rich and can increase carbon build up in the combustion chamber and exhaust system.

Let us know how things go or what you find.

Tom
 
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