Chainsaw Repair

The coefficient of expansion between aluminum and magnesium is probably insignificant?  Copper would be more significant?

consider the values to be relative but they are actually 10 to the minus 6 per inch per degree Fahrenheit

Aluminum 12.3
Magnesium 14.0
Steel 13
304 stainless 9.6
316 stainless 8.9
Copper 9.3

Quote from: Cut4fun_ on March 07, 2014, 01:58:14 pm

I've only lost 1 piston do to a gasketless build using sealer.   Wasnt a saw I did and took on trade.
 Kept noticing  running odd at times and seemed to have carb adjustment issues. Tried a known good carb swap and samething. Dug deeper and it was a sealer giving out at base gasket area.

I have never had any problems using sealer for crankcase gasket, base gasket, or sealing tank halves that I have applied myself.  But I still prefer a gasket for base, but use sealer when needed.

The crankcase holds what, maybe 10 to 12psi.   I think myself that a good sealer should be able to handle that easy.    Also by using a copper gasket you now have 3 metals with different rates of temperature expansion.

I think it was one of those deals where someone applied it to thin. JMO from looking at it when I pulled it down. 

had a learning curve with some sealers.  my experiences might not be the same as others.

for paper gaskets:  found over course of time, that the old standby 'indian head shellac' is very cheap and always did what i wanted it to do.

for copper gaskets:  spray copper.  this stuff is very messy and runny.  after blowing out head gaskets a number of times, found that spraying the gasket, on both sides.... holding gasket up by a wire through one of the stud holes..... and letting the stuff almost dry completely before install, finally worked.

copper gaskets can be a pain to cut.  tried exacto knives, sharpened pizza cutters, linoleum cutters for these.  cutting them on a mud flap.  i like using them, however because sheets come in different thicknesses.  an assortment of sheets are usually cheap, (or were, have not bought them in years).  as far as copper goes..... i always thought it was used because it was a good thermal conductor.

rtv silicone:  could never get this stuff to seal anything because i was always in too much of a hurry to let it set long enough to get thouroughly sticky before tigtening bolts.  if i use this stuff, i tighten bolts, then take the bolts out to remove excess goo that got squeezed out the sides.

imo, hylomar is real good stuff.  gascacinch will seal anything...... sometimes too well.  if nothing else will seal it, then resort to that.  aneorbic(spelling?) worked well for oil pans, but have not used it for much else.

yamabond: the only thing i ever used it for, was for harley cases.  thought it was kinda thin and very stringy to work with, but it did work well.  can say to use this stuff sparingly, it oozes like rtv.

-joe

In recent years statisics say the number of auto accidents has decreased for drunk drivers but has increased because of distracted drivers .