Author Topic: Port timing.  (Read 1750 times)

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Online 3000 FPS

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Re: Port timing.
« Reply #90 on: February 23, 2013, 09:20:35 pm »
I think I would try and find out why you only have a 130PSI for compression.   You are never going to get good torque out of that saw unless you bring the compression up to aleast 150PSI or more where it should be.  Or else just run it the way it is and see if it comes up some when you break it in.
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Offline Al Smith

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Re: Port timing.
« Reply #91 on: February 24, 2013, 06:38:27 am »
Well that 130 PSI static isn't helping things for sure .99 opening from 101-102 probabley has little if any effect .

In my way of thinking raising the upper transfers would not be benenficial because of two reasons ,First it would start the transfer at lower crankcase pressure and it conjuction with the exhaust opening there would not be the differentials of pressure existing between them.The transfer pressure phsically at the time of transfer has to be higher than the exiting exhaust pressure or else it just will not happen until it is so .

I wouldn't fiddle with it any more until you figure out why the static pressure is so low .Oh I suppose the intake side of the piston skirt could leak some crankcase pressure but it would really have to be concentric to do that .I mean out of round like a football .I've seen some really  funky pistons do a pretty good job

That flap wheel hone job probabley didn't help things but given enough run time the rings should wear in .Might take a while though .

Don't give up the ship just yet .FWIW the 038 Mag which a lot of folks on this forum have seen in action had a funky intake side from a torn boot .It took me nearly all summer cutting down from a 10 cord pile of oak to seat those rings with 5-10-15 minute run times .When those rings finally decided to straighten up and fly right it was like a jet with an after burner .

New rings on an old cylinder are  not the same thing as a complete new top end .It usually revives them but sometime it just takes longer .

Offline jmester

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Re: Port timing.
« Reply #92 on: February 24, 2013, 06:54:37 am »
Ok, I will keep running it and try to seat those rings. I will keep you posted on what happens with it. This is my first time running a new piston and rings with an old cylinder. So it is a little different to me.
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Offline Al Smith

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Re: Port timing.
« Reply #93 on: February 24, 2013, 07:33:27 am »
I must have missed that part of a new piston just like I missed the part of new rings .Hmm.

Offline jmester

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Re: Port timing.
« Reply #94 on: February 24, 2013, 07:36:59 am »
What do you mean by hmm. It is an oem piston kit.
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Offline Al Smith

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Re: Port timing.
« Reply #95 on: February 24, 2013, 09:11:02 am »
Hmm meaning I missed that part some how .I thought you just tweeked an already good running saw just to get a little more punch out of it rather than to repair what evidently was one with damage .I can't think of any other reason to replace a good piston.  So here is part of an earlier post ----It is 130 with new rings, they should come up some as they seat in. I wonder if we will get 150 out of them.----There wasn't even any mention of a new piston until two posts ago .

Offline jmester

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Re: Port timing.
« Reply #96 on: February 24, 2013, 12:02:29 pm »
You are correct. I did take some measurements on the new piston and it matched the old piston well. The piston I took out of it had some deep scuff marks on the intake. I am thinking dirt or carbon got stuck. There was also some scuffing on the exhaust side as well. All marks where on the pto side of the piston. Would a new piston effect it that much. Will the heat cycles over time distort the cylinder.
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Offline Al Smith

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Re: Port timing.
« Reply #97 on: February 24, 2013, 12:31:50 pm »
Not likely .

Offline jmester

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Re: Port timing.
« Reply #98 on: February 24, 2013, 12:35:20 pm »
I guess I will have to either run it or tear it down.
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Offline 660magnum

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Re: Port timing.
« Reply #99 on: February 24, 2013, 12:46:56 pm »
RUN IT!
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