390xp missing parts? Base delete?

[Stevetheboatguy]

Ok so I'm doing a down and dirty, hope it works until the new one arrives rebuild. The saw is a late 390xp. It lost the top ring locating pin and ate the cyl pretty good. I cleaned the cyl and have a hyway slug already installed.
I cannot find my solder. Think it will be a head slapper without a base gasket? Don't have much experience with the 390 to know what the norm is.
Second. The guys who took it appart originally. Managed to loose the heat sheild behind the muffler. Safe to run without? Doesn't matter he's going to run it without I'm just curious to know for future reference.


Thank you.

Steven

 

[Funky sawman]

Most of the 372 and 385 family saws have generous squish in the .045 to .060 range. I've only seen one head hitter with a base gasket delete but that was using a Wiseco pop up piston

 

[Ketchup]

You can stick a piece of card stock or something thin like that on the edge of the piston crown and roll the saw over. If it won’t turn over, too tight. Usually the old gasket is around 0.018”.

 

[drf256]

Try to run the heat shield if you can.

The name is a misnomer, it actually is there to allow air from the fan to get diverted all the way over to the exhaust side PTO fins of the jug.

We all know what part of the bore typically gets scored first in an overheated saw. It is almost always the PTO exhaust side.

 

[Stevetheboatguy]

Most of the 372 and 385 family saws have generous squish in the .045 to .060 range. I've only seen one head hitter with a base gasket delete but that was using a Wiseco pop up piston

I knew the 372 was safe but this is the first 390 I've had appart. So no reference to what could be the norm. Thank you.

You can stick a piece of card stock or something thin like that on the edge of the piston crown and roll the saw over. If it won’t turn over, too tight. Usually the old gasket is around 0.018”.

See now that's something so simple I kick myself for not thinking about it myself. Thank you.

Try to run the heat shield if you can.

The name is a misnomer, it actually is there to allow air from the fan to get diverted all the way over to the exhaust side PTO fins of the jug.

We all know what part of the bore typically gets scored first in an overheated saw. It is almost always the PTO exhaust side.

Thanks Al. I know I have a shield for a 372. The muffler pattern is the same. I'll see if I can make it fit. Has to be better than nothing.


Steven

 

[Normzilla]

Never built any, but am definitely a 390 fan
Think some really underate them. I've kept mine around.

 

[Funky sawman]

I normally either get them ported, or do it myself, and the main thing I found when production felling/logging is keep the max rpm no more than 13,500. That is with the black module also, this series of saws seem to rattle apart at higher rpms, cracking mufflers, screws falling out even with red loctite. I got to where I would cross drill the heads of the muffler brace and bucking dog screws and run a piano wire between them to keep em tight