Squish and timing

[KMB]

This is in reference to my 044 with low compression. I believe the reason is in timberwolf's post #7 in this thread: http://www.arboristsite.com/showthread.php?t=103543&highlight=044+compression

With the base gasket (.040") and using a .047" diameter piece of solder, there was no squish when the piston was turned over (full rotation, so squish is over .047"). With the base gasket removed, the .047" solder was to hard to be able to get a squish measurement. I got some .032" diameter solder and did 3 measurements (through the exhaust port with a long enough piece to reach the rear and front of the cylinder...I should also do side-to-side to get more accuracy). For the first measurement, I turned over the piston a few times and got .015" and .017" (on each end of solder). The next 2 measurements were with only one piston rotation, and they were .014" and .020", .015" and .020". From reading, I would need to have about a .005"-.006" gasket to get to a 'safe' squish.

In my reading on squish and how to get accurate measurements, I have seen some mention of the timing being different when removing the base gasket. What is the largest squish measurement difference (between gasket to gasket-less) that will affect the saws performance?

Kevin

 

[gink595]

Hey KMB!!! How did you measure the squish through the exhaust port? Or did I not understand what your saying?

 

[blsnelling]

That's really unusual to see that much variation in squish unless you're working with a poor quality aftermarket cylinder.

Was your base gasket hand made? Most are only .017-.018 thick.

Don't worry about the port timing if all you're doing is removing the gasket. The effects will be negligible.

 

[KMB]

Hey KMB!!! How did you measure the squish through the exhaust port? Or did I not understand what your saying?

For the first gasket-less measurement, I had the cylinder off, so I just laid the piece of solder on the piston (with a dab of grease) and put the cylinder back on. The next 2 times, I pulled the muffler. Cut the right size piece of solder (approximate diameter of piston, making sure it cleared the cylinder walls). Pushed in the solder, and rotated the piston through a full rotation. I'll probably take off the cylinder again to do one side-to-side measurement (or as I've read go through the spark plug hole and bend the solder to each side).

Kevin

 

[blsnelling]

For the first gasket-less measurement, I had the cylinder off, so I just laid the piece of solder on the piston (with a dab of grease) and put the cylinder back on. The next 2 times, I pulled the muffler. Cut the right size piece of solder (approximate diameter of piston, making sure it cleared the cylinder walls). Pushed in the solder, and rotated the piston through a full rotation. I'll probably take off the cylinder again to do one side-to-side measurement (or as I've read go through the spark plug hole and bend the solder to each side).

Kevin

Do your squish measurements through the spark plug hole.

 

[KMB]

That's really unusual to see that much variation in squish unless you're working with a poor quality aftermarket cylinder.

Was your base gasket hand made? Most are only .017-.018 thick.

Don't worry about the port timing if all you're doing is removing the gasket. The effects will be negligible.

The cylinder is stock, but the piston is aftermarket from Bailey's. 'Shorter' piston? Or maybe the amount of carbon on the piston is causing the difference.

I'm not sure what company made the base gasket, but it's not homemade. I just re-measured the gasket and it was .040" on 2 sides and .041" on 2 sides. I still have old base gasket that was on the saw when I got it, and it averaged .043".

Kevin

 

[gink595]

For the first gasket-less measurement, I had the cylinder off, so I just laid the piece of solder on the piston (with a dab of grease) and put the cylinder back on. The next 2 times, I pulled the muffler. Cut the right size piece of solder (approximate diameter of piston, making sure it cleared the cylinder walls). Pushed in the solder, and rotated the piston through a full rotation. I'll probably take off the cylinder again to do one side-to-side measurement (or as I've read go through the spark plug hole and bend the solder to each side).

Kevin

I see, I'm a little slow. I realized after I posted what you were doing It seems like there would be a lot of chance for error on putting the soldier on the piston and refitting the cylinder afterwards. See if the results add up by going through the spark plug hole compared to your other methods.

 

[KMB]

Do your squish measurements through the spark plug hole.

I see, I'm a little slow. I realized after I posted what you were doing It seems like there would be a lot of chance for error on putting the soldier on the piston and refitting the cylinder afterwards. See if the results add up by going through the spark plug hole compared to your other methods.

I'll give it a try and report back. Won't hurt to try. If anything, I hope the results will help someone else down the road who is looking for info on squish and squish measurement.

Kevin

 

[tdi-rick]

Sorry to raise this, are you really sure the base gasket measured 040" ??

That's 1mm thick !!

 

[Tzed250]

The cylinder is stock, but the piston is aftermarket from Bailey's. 'Shorter' piston? Or maybe the amount of carbon on the piston is causing the difference.

I'm not sure what company made the base gasket, but it's not homemade. I just re-measured the gasket and it was .040" on 2 sides and .041" on 2 sides. I still have old base gasket that was on the saw when I got it, and it averaged .043".

Kevin

You have a low compression "bad gas" base gasket.

The standard gasket for an 044 is .5mm (.02 inch).

.5mm Gasket = 1128 029 2301

 

[KMB]

Sorry to raise this, are you really sure the base gasket measured 040" ??

That's 1mm thick !!

Picture of gasket and measurement coming...

Kevin

 

[tdi-rick]

Interesting John.
I'd heard they used to have these available for the 038 but didn't realise they were still available.

 

[Tzed250]

Interesting John.
I'd heard they used to have these available for the 038 but didn't realise they were still available.

The part number for the 1mm gasket is obsolete (1128 029 2302) but he could have ended up with one.

 

[AUSSIE1]

Just remember that the solder will expand giving a false reading.
Turn the piston back and forth a doz times for the solder to settle.

 

[KMB]

Just so y'all don't think I'm crazy.

Old gasket:

New gasket:

As Tzed250 has already brought up (according to the 044 IPL), I had/have the old base gasket size.

I've learned something new today.

Now to finish up my work day...than back to the saw for more squish measurements...

Kevin

 

[KMB]

Just remember that the solder will expand giving a falde reading.
Turn the piston back and forth a doz times for the solder to settle.

Thanks for that tip.

Kevin