Back of Flywheel rubbing on protruding ring inside stator housing

[akscott]

12ft jetboat, 717 engine, approx. 25hrs on complete rebuild. R&D power plenum, and bored out 1 over size, but otherwise all stock. Engine was running great, recently rejetted to run slightly rich. The other day it died on me after approx 30 minutes of run time. (engine was not real hot to the touch) went to start it and just the sound of the starter bendix kicking out. Took the plugs out and saw no obvious signs of damage.Tried to turn the crank manually w/ the plugs out; it would turn, though not easily, and I could hear a scraping sound at the mag side of the engine.

Took the stator housing cover off, and imediately noticed a small pile of metal shavings. Turned the flywheel by hand and the scraping seemed to be consistent all the way around. Took the flywheel off and could see that the flywheel had been scraping on a raised ring (of the stator housing) that surrounds the stator.

Turned the crank by hand with the flywheel off.. it turns smoothly with no
noise at all.
Do I have a crank bearing problem? Can the flywheel simply be worn out to where it goes back too far on the shaft? The flywheel key was in place and looks fine as far as I can tell.

The only other thing I can think of, is that a couple weeks ago, I removed the entire jet unit, to inspect it, and install another impeller. I wouldn't imagine that in reinstalling and tightening up the jet unit, the crank could have been pulled backwards a tad? (I have a berkely 6JA jet unit which mates with the rotax engine via adpaters that bolt together) The way the crank sits in the engine case this scenario seems highly unlikely to me...

The crank seals front and back look fine, no leaks. The engine was running great before this. Also, I cleaned out the metal shavings, put the flywheel
back on and it did not rub this time. The engine started right up and seemed
to run great on the hose.

Don't want to run it in the rivers until I find out what caused this.
Thanks in advance for any help.

Scott

[akscott]

Re: Back of Flywheel rubbing on protruding ring inside stator housing

Forgot to mention, I checked the compression and it's 149 & 148 PSI.
Took the head off to make sure nothing was amiss and the cylinders and pistons look great.

[1fastski.com]

Re: Back of Flywheel rubbing on protruding ring inside stator housing

check the flywheel , it might be damaged also check the crank end for ware , and check to make sure the sator is seating ok .

[Bill O'Neal1]

Re: Back of Flywheel rubbing on protruding ring inside stator housing

I have seen this many times.

The ring gear is pressed onto the magneto flywheel. The only thing holding it on there is red loc-tite. When it gets too hot, the loc-tite releases the ring gear. It moves back towards the motor until it rubs the engine cases.

Press the ring gear back on the magneto flywheel until it seats against the shoulder. I stich weld it in a couple of spots to hold it, but you can use a punch to put a few dimples around the edges to kinda hold it there and use new Red Loctite under it when you press it back onto the flywheel if welding is not an option.

I take this opportunity to rotate the ring gear on the flywheel so that the starter drive has some fresh teeth to chew up in the future.

[akscott]

Re: Back of Flywheel rubbing on protruding ring inside stator housing

Thanks Bill!
Makes sense... I had no idea these flywheels were not one complete
part. I'll check it out, get it reseated, and see if I can have a friend stich weld it to fix it permanently.

BTW, your recomendations on my carb jetting last week were right on. I increased my mains by 10 points and my low speed by 5, and it made a big difference. Thanks for sharing your expert advice!