Author Topic: Port timing.  (Read 5975 times)

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Offline 660magnum

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Re: Port timing.
« Reply #70 on: February 21, 2013, 06:12:55 pm »
It might come up to 140 but that will most likely be it.
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Offline Al Smith

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Re: Port timing.
« Reply #71 on: February 21, 2013, 07:28:24 pm »
If you've already cut the upper transfers you're pretty much stuck with them unless you drop the cylinder more .However if you would have left them alone you could have gotten a few more degrees of blowdown by raising the exhaust .99 won't hurt you though unless it won't come up above 130 PSI static . A new set of rings should jack it back up to 150 or so I'd guess .They're only about 5 bucks a pop for Cabers .

At 102 exhaust it would have pulled good but it wouldn't gain much if any on RPM .99 with good compression should if the blow down isn't out of sorts .That's just my theory which of course is up for debate .

Offline 3000 FPS

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Re: Port timing.
« Reply #72 on: February 21, 2013, 07:35:36 pm »
What did the squish end up at when you measured it.
PP 505, 475, 445.

Offline jmester

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Re: Port timing.
« Reply #73 on: February 21, 2013, 08:04:37 pm »
The squish came in at .025. I could have gone to .020. But I did not want to make it so tight. My blow down should be around 21*. I have 99* on the exhaust and 120 on the transfers.  Al, what do you consider to be good compression.  I should have it together tomorrow. I guess we will have to see.
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Offline 3000 FPS

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Re: Port timing.
« Reply #74 on: February 21, 2013, 08:10:47 pm »
I would think that with a squish of .25" that your compression should be at least 150psi or better.   Sounds like the rings are not sealing for some reason.   
PP 505, 475, 445.

Offline jmester

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Re: Port timing.
« Reply #75 on: February 21, 2013, 08:18:42 pm »
Would it be because they are new.
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Offline 3000 FPS

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Re: Port timing.
« Reply #76 on: February 21, 2013, 08:25:16 pm »
Did you use any 2 cycle oil on the rings or cylinder walls when you assembled it.   
PP 505, 475, 445.

Offline Al Smith

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Re: Port timing.
« Reply #77 on: February 22, 2013, 05:17:51 am »
150 would be good .Lowered cylinder it should be maybe 160 .I'm more inclined to shoot for 180 myself but I'm a little eccentric  just as I suspect those rings are . ;)

The way I look at a saw engine as far as  power curve is you basically have two ranges ,idle and wide open .Something like a bike or snowmobile engine a person might be concerned about mid range for an acceleration shot .On a saw I don't know too many people who run them half throttle .

Offline Al Smith

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Re: Port timing.
« Reply #78 on: February 22, 2013, 05:21:13 am »
Would it be because they are new.
Well if that's the case put  that thing together and stick it in some wood and flog it like a borrowed mule .It'll either seat in or blow up which I doubt .

Offline jmester

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Re: Port timing.
« Reply #79 on: February 22, 2013, 06:05:37 am »
Yes I did coat every thing with oil, pistin,rings, cylinder. May be when I was cleaning the bore up I got it a little out of round and that's why it is low. I used a flap wheel that was half shot. That's the plan, put it together and run it. 
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