how do you do it and how many thousandths are acceptable
help how to check the squish
- Thread starter lone wolf
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redlinefever
ArboristSite Operative
I used like #6 fuse wire but u could use thin solder. For what is acceptable depends on the size of the saw!!!!!!!
squish
ms 200t
ms 200t
bitzer
******** Timber Expert
I've used solder and for the most part you want to stay over .020 in. When it starts getting tighter than that there is a greater risk for detonation. I'm not sure about cc range though. On saws 55 cc+ that is what I would go with.
redlinefever
ArboristSite Operative
I have my 026 set @ .015 to .017 the smaller the bore the tighter the squish band can be. But you will need to run premium gas in it. What is your comp. at now????????
dont know saws apart 125- 150 range guessing
redlinefever
ArboristSite Operative
check your squish band and see how much clearance you have. Then measure the gasket. You might be able to go with out one or you might have to make one out of say beer can, shim stock , or something laying around. Just my thought I just got done porting my saw so kinda new to it to.Good luck
Lone Wolf ,
What part of NJ ?
We got lots of NJ members here. all good folks.
Angelo
What part of NJ ?
We got lots of NJ members here. all good folks.
Angelo
mtngun
Addicted to ArboristSite
Yes and no. Very high compression may require premium gas and may result in detonation, but it is possible to have tight squish and low compression, like my lame 066BB.bitzercreek1 said:
In automotive engines, EXCESSIVE squish can cause detonation, even in low compression engines. Excessive as in 0.080" or more. This is a common problem in 1970's era engines like my ancient GMC truck.
The danger with tight squish is that the piston could slap against the top of the cylinder. Bear in mind that the piston will expand with temperature, there may be some flex in the rotating parts, and the piston may cock slightly in the bore.
I agree, for chainsaws.bitzercreek1 said:
Most all of my saws are between .016"-.020". You're not going to have any issues with fuel with just tightening up the squish. BTW, I use soft electrical solder to measure squish.
bitzer
******** Timber Expert
I've read that lower octane fuels can induce detotnation and knock more frequently with a tighter squish.
Could be. I was just saying that premium fuel is all you need. That's all I run in my ported and popup saws
bitzer
******** Timber Expert
Right, 93 is all I run too. I've also read that ethanol is becoming more of an issue with knock and det.
timberwolf
Addicted to ArboristSite
I wonder if they are saying this assuming tighter squish is linked to higher compression?
In general given compression is the same tighter squish = higher squish velocity = reduced detonation potential. The exception to this is when squish is taken well less than 0.020 and the boundry layer gets stripped off the surface of the piston exposing the piston to direct flame which can seed pre-ignition remote from the sparkplug and set up a detonation potential from colliding flame fronts. Tell tail sign of this is a piston crown where the squish band area is covered in minature craters or looks like it has been etched with acid.
In a properly run chainsaw though I think detonation is a very rare event and not much need getting worked up about it.
bitzer
******** Timber Expert
I don't remeber where I read it and I wish that I had now. I believe they did mean tighter squish = higher compression leading to extreme heat and pressures= detonation. It did have to do with a saw I remember and low quality fuel. I would guess you are right in saying that in a properly run saw this shouldn't matter. I was just alluding to the fact that 93 octane should be used and I know there is that squish tightness limit.
timberwolf
Addicted to ArboristSite
More than fuel I was thinking a sharp chain run in the powerband.
But on the fuel, I have run saws even ported ones with compression 40 psi over stock on reg 87 or 89 octane pump gas. Never had any problems.
Not saying it's a good idea, but just never encountered a problem.
Metal base gaskets or non at all for me.
But on the fuel, I have run saws even ported ones with compression 40 psi over stock on reg 87 or 89 octane pump gas. Never had any problems.
Not saying it's a good idea, but just never encountered a problem.
Metal base gaskets or non at all for me.
TW and all,
Wouldn't detonation be more of a concern with a valved engine, as the off-timed secondary detonation wreaks havoc primarily with the valve timings. I know its kind of like saying smoking is only bad for your lungs but I don't think it should be a major concern considering compression in a 2 stroke cycle.
I agree TW a dull chain will cause more damage then high compression.
Just thinking out loud.
Angelo
Wouldn't detonation be more of a concern with a valved engine, as the off-timed secondary detonation wreaks havoc primarily with the valve timings. I know its kind of like saying smoking is only bad for your lungs but I don't think it should be a major concern considering compression in a 2 stroke cycle.
I agree TW a dull chain will cause more damage then high compression.
Just thinking out loud.
Angelo
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