Author Topic: Squish  (Read 2482 times)

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Offline joe_indi

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Re: Squish
« on: August 11, 2012, 11:33:14 pm »
Okay Al, EPH,
I did get my ports crossed.
The exhaust port will be retarded because the piston top opens it a bit later now.
The Inlet port gets advanced because it is now a bit lowered and the lower end of the piston opens it a bit earlier now.

Now, coming to the transfer ports, they would have a retarded timing because the piston top opens them, right?
EPH, I have no clue to how much squish this saw should have. I used the squish of the MS460 for a comparison. All this was done in my regular shop where I had a vernier handy to take measurements.
So I used a steel scale instead and found the squish is nearly double that of a MS460.
I often use the 0.8mm gaskets instead of the 0.3mm standard ones to reduce piston damage on old 460s, but at the cost of compression, which often leads to unburned 2 stroke oil.
For the sheer lack of tools at that moment I used up  a couple of depth gauge files and emery paper to lower that cylinder.Well the result was not something to put up in a beauty contest, so I used some Three bond as the leveler and allowed it to dry for about 20 minutes before installing the cylinder.
It was a great relief that there were no leaks.
The first hint of things turning for the better was that the oily carbon blackened spark plug came out looking dry and dark gray after about 5 minutes of test cuts. And, unlike earlier, not a hint of exhaust smoke at anytime.
I tried it with different mixes of two stroke oil, 2% of Stihl oil, 3% of the the local oil and finally 4% of the local oil, the last being the standard out here.
Even with the 4% oil the results are very good.
From a slightly tinny exhaust note the sound has become more throatier.
It has also made the revving more 'linear' (if that is the proper word)


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