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Workshop => Engine and Bottom End => Topic started by: Antimullet on November 26, 2021, 11:19:54 AM

Title: Squish setting on Bored ESR 330 PV (350cc now)
Post by: Antimullet on November 26, 2021, 11:19:54 AM

I have a used, but fresh bored ESR motor, originally a 330PV motor.
Cylinder and piston is now a 76.5 bore, 76mm +4 crank, which equals 349.812 CC displacement.

I have the pump gas and race gas heads, and they are o-ringed, so I cannot adjust squish there.

It currently has a .230" spacer plate on it.

Question, my current squish is as follows.
Race Head = .03"/.762mm
Pump Head = .04"/1.016mm

Compression on the Race Head was 220.

I have not ran it like this yet, as I'm concerned squish is too tight.

Thinking about putting my .250" spacer plate on it and then trying squish measurement again.

Any idea or recommendations on squish, or if I should leave it alone, if not, what is the best method to raise it a bit?

Maybe a thicker base gasket versus the .250 spacer?

Title: Re: Squish setting on Bored ESR 330 PV (350cc now)
Post by: broken1 on November 26, 2021, 01:00:35 PM

Not sure if this helps but there's a ton of good information here: http://www.macdizz.com/update39.html

Title: Re: Squish setting on Bored ESR 330 PV (350cc now)
Post by: Antimullet on November 26, 2021, 06:28:45 PM

Thanks!

Yea I'm wondering what the other guys with ESR cylinders are running for squish as a decent start point.

Title: Re: Squish setting on Bored ESR 330 PV (350cc now)
Post by: Michael88R on November 27, 2021, 10:12:30 AM

So you added the stroker crank?  Port timing must also be set up for the stroke. 

Title: Re: Squish setting on Bored ESR 330 PV (350cc now)
Post by: Antimullet on November 27, 2021, 12:04:45 PM

Quote from: Michael88R on November 27, 2021, 10:12:30 AM

So you added the stroker crank?  Port timing must also be set up for the stroke.

Its one of the newer version cylinders requiring boring of the cases and a stroker, not the old ESR 330 kit that fit in the stock cases. The piston and port alignment looks good. The piston is out of the cylinder at TDC a bit say 1.5mm or so.

Title: Re: Squish setting on Bored ESR 330 PV (350cc now)
Post by: Michael88R on November 27, 2021, 01:01:00 PM

There is a lot more to Port timing than just looking good. If the piston sticking up one and a half millimeter more than before and the ports are off one and a half millimeter, that will drastically change the power characteristics.  You need to talk to a two stroke builder to get it right.  If you don’t it will cost you a lot more in the long run.

Title: Re: Squish setting on Bored ESR 330 PV (350cc now)
Post by: Antimullet on November 27, 2021, 04:03:13 PM

Quote from: Michael88R on November 27, 2021, 01:01:00 PM

There is a lot more to Port timing than just looking good. If the piston sticking up one and a half millimeter more than before and the ports are off one and a half millimeter, that will drastically change the power characteristics.  You need to talk to a two stroke builder to get it right.  If you don’t it will cost you a lot more in the long run.

Trust me I know the concerns so I want to verify everything starting with squish.

I checked all the port and cylinder measurements per some guidance I got from a builder and that is all good. The issue I have is not knowing what ESR sets squish at. 

Title: Re: Squish setting on Bored ESR 330 PV (350cc now)
Post by: Michael88R on November 27, 2021, 04:07:59 PM

Gotcha.  Best to check with the experts.  Let us know what you find out.