screaming engine

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malky
Posts: 1096
Joined: Sat Dec 19, 2009 3:25 pm
Location: swansea south wales

Re: screaming engine

Post by malky »

Iffy crank seal - drawing gearbox oil in and running on that ? Seen it many times with diesels running away the same and you can't even stall them they just keep going until they run out of oil
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Alan H
Posts: 12104
Joined: Fri Aug 05, 2011 6:38 am
Location: Wombwell, Republic of South Yorkshire

Re: screaming engine

Post by Alan H »

If there's glowing carbon in the combustion chamber - or even too hot a plug with oily carbon on the point it'll run on oil from the crankcase/SRIS and CCI and effectively turns into a diesel.
Remember also, that a diesel engine can do the same if it has worn rings and it will keep revving higher as the oil vapourises until it all goes bang. Difficult to stall a high revving diesel. The old diesel engines with mechanical fuel pumps would run in reverse and suck air up the exhaust, so had no throttle control or effective rev limiter.
Proof that four strokes are over complicated
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malky
Posts: 1096
Joined: Sat Dec 19, 2009 3:25 pm
Location: swansea south wales

Re: screaming engine

Post by malky »

Had exactly the same happen to my T500L this afternoon - its never done it before in the thirty two years that I've had it - this happened twice and on both occasions it was just after I'd given it the beans - when I got back to the garage I even had the key out and it was still.red lining and had to be stalled to stop it - the only thing that we could find was that the right hand carb piston had stuck right up in the body due to some varnish coating it and once cleaned with carb cleaner and a bit of WD40 normal service was resumed - what was strange though was that the piston was very dry to the touch - I'm starting to consider putting a very small amount of two stroke oil in the tank with the fuel -not enough to cause a weak mixture but enough to keep the carbs lubricated -anyone else got any thoughts on this idea ?
Mal.
barney01
Posts: 3118
Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: screaming engine

Post by barney01 »

For info the engine can also be stopped by putting the choke on. IMHO I would just occasionally spray carb cleaner onto the throttle valve body and would only ever add a little oil in the fuel whilst running in a new built engine.
NO SMOKE .......NO POKE
Steve72J
Posts: 28
Joined: Fri May 18, 2018 1:25 pm

Re: screaming engine - Throttle alignment pins maybe ?

Post by Steve72J »

I've had these symptoms happen twice. Both times the pin keeping the throttle had backed out allowing the throttle slide to rotate in the carburetor body.

Had to do the same procedure you describe to get home. Hope your problem is the same issue. Cheap and easy fix. I put a dab of JB Weld epoxy over all my pins. All my pins are flush with the carburetor body. If one of them is sticking up this may be the problem.
Steve72J
Posts: 28
Joined: Fri May 18, 2018 1:25 pm

Re: screaming engine ..no not the same thing

Post by Steve72J »

Sorry about "pin" post ...didn't catch the part about not shutting off ..
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