ASP 12 problems!
 

I have 2 SC 15s and an SC 12 and all are good engines.

I bought an ASP 12 from eBay for not very much and it looks brand new.

But I just cant get it to stay running the best I get is about 15 seconds it's drawing fuel and I've tried a variety of carbs/venturis but none made any difference.

It's dying before I even have time to disconnect the glowplug.

The compression does feel poor - what do you think?

Has somene tried to run it on some very low oil car fuel and ruined the piston/liner?

Annette

Even on my oldest SC/ASP .12 there is still a pinch around TDC that is easily felt with the plug out. These engines are true ABC and run fine on straight synthetic fuel too.

With a second hand engine you never know how it was treated, but you could check for a pinch around TDC with the plug out, or leave the plug in and check how long it holds the compression at TDC. On a cold ABC engine there shouldn't be any leakage at TDC at all.

There are many other possible sources for poor running. You could check the head gasket (or add one if there are none) and the rear crankcase gasket too.
On my best running engines I have added an extra shim under the head to avoid over-heating. Even on 10% nitro I think the stock compression is a little too high for props around 7x4.

Is the compression leaking out somewhere like the piston cyl at the exh, or just not snappy? You could take out a head shim to step up the compression a bit.Maybe a hotter plug? Also check to see if the plug is flush with the inside of the combustion chamber. A long plug may stick out too far or an OS type may be sunk in too much. It will make a difference with the little guys. It is always a gamble with used motors, I still keep getting them anyway. They are only $30 new, and parts are actually quite reasonable if you do need them though. Oh, I see Mr Cox beat me.

Got it running like a goodun now there were no gaskets in the head so I cut one from a red bull can and for luck used Teflon gaskets cut from non stick baking parchment either side...

Thanks for the help.

Annette