.46 mecoa marine

this engine is so tight at TDC that it will not turn over. have managed to run 14oz.fuel,but it is almost impossible to start. any easy way to loosen this thing up so one person can get it started
thanks
cliff [img]

Loosen the glow plug so it will leak some compression. Once its started pull the plug igniter off and tighten the plug back up.

will only go past tdc with plug completly out.
thanks
cliff

well that doesnt make much sense. If the piston will only go passed TDC with the plug out, it sounds like the reach on the plug is too long and sticking under the button hitting the plug... which would mean that motor has one hell of a small chamber.


Are you sure it WONT do it period, or the pinch at the top of the sleeve is still just really tight.

Cliff,

Sounds as if MECOA has used a HIGH TAPER design with the ABC piston liner, or they just have fitted a slightly too large piston ?

Unfortunately they give the end user little choice but to use a BIG starter and take a chance of breaking crank pin or rod getting it started, or do as most did in the days of KnB building the engines ....

That being, hand lapping the piston too bore fit using diamond lapping compound and a few hours of your time :huh:

Note that NITRO engines use ABC tech, thats ALUMINUM piston, Brass sleeve chrome plated. NO piston ring and a tapered cylinder bore of @ .002 to .005 smaller at TDC that BDC. Piston is VERY HIGH silica aluminum with no taper and a very round shape withing .0002 or less !

What you have going on is pretty typical in nitro class engines and does ease up with a few gallons of fuel run.

Hope this helps ?


Scott

Is there an off-chance that the piston is hitting the plug? What's your clearance? Try using an extra washer on the glow plug, and also check to see if you are using a long plug in an application where a short one would be required. New nitro engines can be a B to get started with the high compression (make sure you have plenty of fuel getting to the motor), but once they are broken in, whether by running or lapping, you'll get the best performance from that motor, probably of its whole life, until you have to replace the piston/sleeve and start over again!