Carby Reed Valve on stock Nt carb with billet intake

jaguar

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Putting holes in the piston is essential. The boost port is not essential but does give a mild power gain. Stuffing the crank is essential for top rpm power. If not then all the power gains with a reed are just at low rpm.
 

Rconce01

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Jan 3, 2008
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Putting holes in the piston is essential. The boost port is not essential but does give a mild power gain. Stuffing the crank is essential for top rpm power. If not then all the power gains with a reed are just at low rpm.

Nice thanks! Any top speed improvements or power increase?
 

Fabian

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Sep 8, 2009
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Holes in the piston with a reed valve intake may be beneficial for top end performance but the top end performance requires higher rpm and these chinese made pistons are of questionable quality, especially when causing stress risers in the piston from the drilling process.

Below 5,000 rpm, a piston window may provide little benefit. In saying drilling out the piston is "not essential" for low to mid range rpm operation.

If wanting significantly higher power, together with the higher rpm requirement it's best to overlook the Chinese engine and purchase a Morini engine; designed specifically to be a high power unit.
 

jaguar

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yes the holes benefit top rpm mostly but I think you'd see some difference even at 5000 rpm. These pistons are not any weaker than other pistons. I have one of them that I drilled 14 holes in and had it in an engine that rev'd to 8000 rpm. no problemo.
But these pistons do give two good reasons to seek an alternative replacement. They have 2mm thick rings whereas some pistons have 1mm thick rings. More contact area of ring to cylinder means more friction and wear. They also have excessive ring end gap that means compression loss. I posted about an alternative piston that gives a good compression boost. check it out.
 

Karl Snarl

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Sep 20, 2019
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IMG_20210725_135715.jpg
My latest set up. g2 reed, carbon fiber, and tillson knock off carb. For low end machines, just use fiber glass reeds. These carbon ones are great on the mid to top, but hinder low end and idle because they are a bit stiff. I have to run a high idle to keep it idling or it will just die. With the fiberglass reeds i never had tht problem, instead I had flutter at high speed and it causes it to four stoke at high rpms. still working on the perfect solution for both high and low. An yeah a windowed piston, haven't decided if I wanna boost port yet. It really pulls well without it.
 
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