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Engine basics => Engine set up tips => Topic started by: Dallas Healey on August 01, 2009, 05:01:04 AM

Title: Bottom Of Piston Uncovers At TDC On ST46
Post by: Dallas Healey on August 01, 2009, 05:01:04 AM

I have two Super Tigre G21/46 motors which I recently purchased and have not yet run. I note that both motors are set up so that the skirt of the piston uncovers the exhaust port at TDC. I have never seen this on other motors. Is this unusual? What effect does this have?

Title: Re: Bottom Of Piston Uncovers At TDC On ST46
Post by: RandySmith on August 01, 2009, 10:33:55 AM

Quote from: Dallas Healey on August 01, 2009, 05:01:04 AM

I have two Super Tigre G21/46 motors which I recently purchased and have not yet run. I note that both motors are set up so that the skirt of the piston uncovers the exhaust port at TDC. I have never seen this on other motors. Is this unusual? What effect does this have?

Hi Dallas

It is common for The ST 46 to have the piston uncovered in just the bottom outer edges (I have seen this many times), but not the whole bottom of the piston, is it possible this is a ST40?
On the ST 46 the small amount of  sub port induction will not hurt the run, If you have a lot of the piston uncovered you will want to use a muffler that does NOT  have  a lot of back pressure, the less amount the better.

Randy
Randy

Title: Re: Bottom Of Piston Uncovers At TDC On ST46
Post by: W.D. Roland on August 11, 2009, 09:31:04 PM

Just don't try to make it idle!
Other than that sub induction is good.
That is one of the mods we did to combat and rat engines.
Worth several RPMs

David
51336

Title: Re: Bottom Of Piston Uncovers At TDC On ST46
Post by: Martin Quartim on August 12, 2009, 10:10:34 AM

Hi Randy,

I got one ST 60 that the piston will do the same, is that also normal for an ST 60 ?


Martin

Title: Re: Bottom Of Piston Uncovers At TDC On ST46
Post by: RandySmith on August 12, 2009, 01:26:00 PM

Quote from: Martin Quartim on August 12, 2009, 10:10:34 AM

Hi Randy,

I got one ST 60 that the piston will do the same, is that also normal for an ST 60 ?


Martin

Yes some of them will uncover in the bottom corners

Randy