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Heads and Cylinders All about your porting, compression, rings, cylinder and piston modifications to your bicycles engine

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  #41  
Old 08-18-2016, 10:59 PM
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Venice Motor Bikes Venice Motor Bikes is offline
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Default Re: 34 tooth swap, down hill, new personal best!

Higher RPMs are achieved the same way as in any race car... Large ports for more air flow!
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  #42  
Old 08-19-2016, 02:54 PM
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sbest sbest is offline
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Default Re: 34 tooth swap, down hill, new personal best!

Quote:
Originally Posted by Venice Motor Bikes View Post
Higher RPMs are achieved the same way as in any race car... Large ports for more air flow!
Actually Venice, that is pretty much how I got more rpm initially. I opened up the port windows in the cylinder, but it's not as simple as that. I didn't open up the ports themselves. I have seen a huge number of engines ruined by amature "porters" hogging out the ports. I used base gaskets to alter port timing and a hill and GPS speedo to test.

Steven, do one slight mod at a time, test it, then increase it if it worked.
Otherwise you will never know what works or what made it worse.

It is the scientific method they taught us back in highschool. It works.

Read my sig,

Steve
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  #43  
Old 08-19-2016, 02:58 PM
StevenMain StevenMain is offline
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Default Re: 34 tooth swap, down hill, new personal best!

Yeah, that was how my last jug was. I thought I'll just keep cutting away at it until performance starts to decline again . I got a decent bike that did 46 on level ground and was mostly happy. This time I opened the 2 stroke tuners guide and cut up a cylinder by the book and it's been gutless. I'm hoping it's because of the piston problem I mentioned. I'll have a go at a new piston in a few days, only going to window it. No ramping.
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  #44  
Old 08-22-2016, 07:52 PM
StevenMain StevenMain is offline
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Default Re: 34 tooth swap, down hill, new personal best!

Yea, no luck. Damn these simple engines are complicated hahaha. I went and put the 44 tooth back on and the thing is a rocket... until 9k then wham, it's like someone kills the spark. I have been doing some reading in the 2 stroke tuners guide to get the formulas for correct expansion chamber, basically my **** it just alllll wrong this chamber would only be a very low rpm performer, so I think it's a chamber induced rev limit. I'll wait until after my check rides are complete and end up putting a good chamber on, short pipe, steep divergent cone, short chamber, and a steep convergent cone with a good sized 5/8 ID stinger. (16mm)
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