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Author Topic: Jim's Hit & Miss Engine M92  (Read 563 times)

RedRyder

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Re: Jim's Hit & Miss Engine M92
« Reply #15 on: October 18, 2020, 09:49:50 am »
Hi Jan, the Marvel Mystery Oil I use won't gum up so no worries on this end either.


That said, thank you for the info on the no oil added.

tony1951

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Re: Jim's Hit & Miss Engine M92
« Reply #16 on: October 21, 2020, 11:36:28 am »
Up until my ignition black box packed up, my M90 engine ran faultlessly on both zippo, ordinary unleaded petrol and a mixture of both. I don't think fuel is at the root of Raphael's problems with his engine. **

The variables that decide whether an engine will run are:

Compression
Fuel/air mixture
Proper energy of spark
Spark timing
Valve timing
Free movement of engine parts (ie not binding up and absorbing all the energy).

I don't think there is anything else that can stop a working design from working.


My M90 worked great, then it didn't when the ignition unit started to fail. The failure may have occurred because while I was trouble shooting a sooted up spark plug, I may have inadvertently spun the engine over without the spark plug body properly earthed to the engine, because I had the plug outside while I was looking at the spark energy to diagnose the sooted plug. This leaves the HT energy to make its way back through the ignition unit electronics to ground and is a common cause of breakdown and failure in electronic ignition systems. Having been brought up in the robust era of contact breakers and tough as iron coils, I didn't take account of this inherent weakness.

** EDIT.
I have run a little two stroke oil in my fuel - varying from about 20:1 when it was brand new, to about 40:1 after it had run a little while. Mine spits out carbon coloured oil too.

Adirondack Jack

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Re: Jim's Hit & Miss Engine M92
« Reply #17 on: October 28, 2020, 06:23:51 pm »
I’d get off the two stroke oil if possible. That’s the soot, just like you’ll get on the tail pipe of a two stroke bike or leg of an outboard. I’m not seeing much of it from my M91 using a fair bit of marvel mystery oil. Bog standard hydraulic fluid would also work. It’s designed for fairly high heat, high pressure in applications such as high speed hydraulic pumps and rams subject to far worse abuse than our engines. It will leave a bit of slippery slime, but not black, and won’t gum up in storage. A hint of how well hydraulic oil handles combustion. I’ve used it as a bore preservative inside black powder guns, and after a good post firing swabbing, they’re still oily.