Thinking abkut a Reedvalve kit but have Concerns

APRules2

New Member
Jun 20, 2019
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I have an 80cc 2 stroke and I'm thinking about a reed valve kit. Im mostly interested in it because I'm looking for more low and midrange power. My motor seems to take forever to get to top speed. I think mostly because its on a beach cruiser and I weigh about 195lbs. The motor is bone stock and has been through 3 tanks of gas. I have 2 concerns I was looking at eBay kits and I've read on posts some of them are for 30cc model engines not out bigger 80cc engines. The other thing I'm concerned about is from what I've read you need to port the motor. Ive heard of people ruining the motor in the process. Also because I'm looking for torque is opening the port going to make me lose low rpm port velocity, like when someone ports a V8 way to much?
 
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FOG

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Mar 3, 2019
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On a straight piston port motor, (non-reed), the piston skirt opens and closes the intake port. On a reed motor the piston going up and down causes the reeds to open and close so the piston skirt just gets in the way. The way around this is to put a "window" in the piston. It's an opening to let air thru whenever the reed valve lets it flow. That's all the modification you should need to go to a reed valve intake.

Here's a link to a picture of a windowed piston to give you an idea ....

 

APRules2

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Jun 20, 2019
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I dont mind spending the $20 is that piston a better idea than trying to port a stock one?
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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up north now
What fuel/oil ratio are you running?

If you're still at 16:1.you can get more power (a fairly good increase) by going with 32 or 40:1. Twice as much fuel in the fuel/oil mix. THEN set your carb so it's running right and the plug looks good. See how you like that before you start tearing things up and throwing money at it.
 

APRules2

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Jun 20, 2019
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I'm actually running Trufuel its 50:1 but I've read its fine in just about everything. I've been running it in chainsaws for years. Only my 16:1 homelite gives me trouble.
 

FOG

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I have heard there are differences in wrist pin heights between pistons? Maybe someone who knows more than me will check in.
 

FOG

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Here we go. Greg 58 to the rescue with a post detailing the pin heights. Post #3.