Finally got the boat uncovered, same engine problems

[wingtime]

Backfire of some sort?

[Mike453]

Sorry I'm slow in reposting on your problem ,been working late, Possible backfire,what I would do is drop on carb bowl and see what is in the carbs. H2O will raise hell with a 2 cycle of any size. Keep us posted. Mike

[MarshMarlowe196]

Just spoke with Lewis-

Here's the old ad for the Ficht.  I still have it, though I might be wrong about the year??

PM me if you're interested.

viewtopic.php?f=6&t=4312&p=27315&hilit=Ficht#p27315

-Jessie

[GoneFission]

Bam ain't good.      

Could be you over-advanced the timing and wound up with hot pistons that seized.  Did you actually verify the timing, or just "wing it?"  Remember, most 2-stroke motors since 1970 or so have variable timing to acheive a reasonable idle and good higher RPM performance.  If you optimize for low-RPM idle, you could easily be too advanced at higher RPM and that will lead to very high piston temps.

[Boatdood]

I see it's been a while since you posted this so the problem may have been diagnosed for a while now, but some thoughts for you here.

The high speed timing on those engines must be checked with the engine running at high speed. A static check compared to a full throttle test can vary over 10 degrees. I've seen this many times and it's hard to believe without first hand experience. Too much timing advance will put a bunch of heat on the pistons that two strokes are just not tolerant of. If you're timing is too high and your engine RPM's are lugging, either situation really, it can result in a melted piston starting at the dome. This aluminum can stick to the cylinder wall and lock up the engine, and it can do it temporarily. Surprisingly the compression may not read bad, but a compression gauge is very unreliable anyway. A leak down test will usually tell the tale better than a gauge.

[GoneFission]

Sounds like you over-advanced the timing.  The bang was a piston seizing in the cylinder after overheating and expanding.  Confirmed by the fact it was locked up just after stopping.  If you are lucky, it released without breaking a ring or further piston or bearing damage.  Yes, these motors will fly with the timing advance way out, but that is suicide for the motor.  Set the timing accordin to specs, don't do the "run to the max" timing unless you want a blown motor.