1985 35 HP acceptable tolerances

[G DANE]

I've got this 35 HP that unfortunately ate some metal piece, that got into it. One of the cylinders has 3 very small scores, a little chip on edge of a port, and head is banged a bit, one piston damaged at ringlands. I've got 2 used pistons from ebay. Bores are 2.995 and I plan to hone them a bit and round the edges in intake ports. I am not able to measure bores out of round, cross-pattern still intact, this motor sat for years with a bad lower unit. The used pistons measure as follows at skirt: parallel with pins, 2.990, 90 deg to pins, 2.988. How is that, will I be fine with the hone and rering job ??

 

[iwombat]

Re: 1985 35 HP acceptable tolerances

My manual says .001 per 1" of bore. You're at .005 for 3". So, by that standard, I'd say you're out of tolerance. Check your specific manual to be sure though. That being said, this stuff is fairly forgiving for being out of spec.

 

[Paul Moir]

Re: 1985 35 HP acceptable tolerances

You did measure the piston right down at the bottom of it's skirt right? It seems to me that crossflow pistons are always very tapered.

If you can still see the honing marks, the bores can't be very worn.

 

[G DANE]

Re: 1985 35 HP acceptable tolerances

Yes the piston measures are at the very buttom of skirt. Bores are not worn at all, I wonder how much it ever ran. I had it lying in shop for years and the previous owner had it sitting in shed for so many years noone remembers, parts were missing in lower unit. I cant even measure any difference in diameter measure in bores top to buttom, either way, only one got those scores and a little chip missing at edge of intake port, lets say a 3/64 x 3/64 piece. I will round that edge nicely off, hone it and give it a try.

 

[iwombat]

Re: 1985 35 HP acceptable tolerances

So, you're out .005 _before_ the hone? Honing will usually bring that _in_ at least .001 - .002, so maybe not so bad. Worth a shot for sure.

 

[G DANE]

Re: 1985 35 HP now ignition failure !!

Re: 1985 35 HP now ignition failure !!

Finally got the time to put it together, and compression is still very fine indeed. Now to a new problem, no spark at upper cylinder, so I have to troubleshoot that. Coil resistance is fine and all grounds too, zero resistance to ground. Points against defective powerpack or trigger coil. How does the powerpack figure what plug to fire, reversed magnet polarity ?? When I took it home from the trip where it ate a 1/4" washer, spark was fine. Only reason I can think of is if I forgot to ground the plugwires when i took compression readings. Did anyone actually fry a powerpack that way, on a rope start ?? Or is the possibility theoretic . Is the stator grounded thru the cable set to power pack, or did I leave a jumper out somewhere ?

 

[G DANE]

Re: 1985 35 HP acceptable tolerances

anyone ?