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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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  #11  
Old 08-12-2016, 11:46 PM
StevenMain StevenMain is offline
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Default Re: 34 tooth swap, down hill, new personal best!

Good idea sbest I'll be sure to try it..... Edit... I was thinking about it though, but technically I raised ALL the ports already with porting so IDK it that would gain me anything.

Last edited by StevenMain; 08-13-2016 at 01:05 AM.
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  #12  
Old 08-13-2016, 01:39 AM
StevenMain StevenMain is offline
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Default Re: 34 tooth swap, down hill, new personal best!




I need this in my life
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  #13  
Old 08-13-2016, 07:57 AM
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sbest sbest is offline
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Default Re: 34 tooth swap, down hill, new personal best!

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Originally Posted by StevenMain View Post
Good idea sbest I'll be sure to try it..... Edit... I was thinking about it though, but technically I raised ALL the ports already with porting so IDK it that would gain me anything.
It would tell you if raising MORE would help.
Awesome picture!
I love it. Are you Canadian?



Steve too (or is that Steve II ?)
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  #14  
Old 08-13-2016, 10:50 AM
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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!

Don't touch the stock port heights!
That changes the port timing, lowers compression (& lowers performance).
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  #15  
Old 08-13-2016, 03:54 PM
StevenMain StevenMain is offline
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Default Re: 34 tooth swap, down hill, new personal best!

No, the above photo is a vintage downhill bike. Just saying I need a fairing like that. That is not me!
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  #16  
Old 08-13-2016, 03:58 PM
StevenMain StevenMain is offline
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Default Re: 34 tooth swap, down hill, new personal best!

Venice motorized bicycle I only changed the exit angle to have the transfer charges converge just below the deck. I'm actually removing the cylinder right as we speak, going to completely full the transfers with JB weld and form an altogether new transfer port shape with correct aim, correct radius throughout, and smooth contours, not like the stock garbage ports which make a hard right 90 degree turn and aren't aimed correctly.

Last edited by StevenMain; 08-13-2016 at 05:06 PM.
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  #17  
Old 08-13-2016, 05:32 PM
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Tyler6357 Tyler6357 is offline
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Default Re: 34 tooth swap, down hill, new personal best!

Quote:
Originally Posted by StevenMain View Post
I have yet to try a cr machine head but I don't know how it could possibly boost any performance.
If your squish gap is about .03" you will get more compression with a FredHead, also, the Fred will run the engine cooler too.


Last edited by Tyler6357; 08-13-2016 at 05:34 PM.
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  #18  
Old 08-13-2016, 05:58 PM
StevenMain StevenMain is offline
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Default Re: 34 tooth swap, down hill, new personal best!

When I finish my CFI training and start flight instructing I'll finally have time and money, something I haven't had in a while as a college student.

I plan to prototype a heavily modified 6 port version of this engine, it will be made from stock parts, I'll tig and re machine them. If it performs amazing I'll try to set up a go fund me or something to see if I can get a foundry to produce new case halves and cylinders the end user can just slap together.
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  #19  
Old 08-14-2016, 02:56 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
Don't touch the stock port heights!
That changes the port timing, lowers compression (& lowers performance).
For a novice, that is very good advice Venice. Typically things only get worse if you touch the height. The goal when raising port height is to trade off torque for higher rpm HP. Touching the exhaust port height with a cutter has always been a last resort for me, and only after testing with extra base gaskets or a chamfered piston.

The exhaust port on these motors are a bit taller than needed for the 38mm stroke crank, so there is lots of room for extra basegaskets. I did find a gain in my motor with extra basegaskets, so I would recommend experimenting with it, at least with gaskets.

Wow! Ambitious work with the JB Weld Steven!
At least it cuts easier than aluminum. I think I would have cut the aluminum first and filled in where needed with the JB Weld. I think the JB Weld will be less likely to come loose doing it the way you are. Keep us informed, great photo!

Steve
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  #20  
Old 08-14-2016, 06:02 PM
StevenMain StevenMain is offline
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Default Re: 34 tooth swap, down hill, new personal best!

I finished the porting and got the bike back together. The ports are just as big as I had them before (BIG) and with the same timing as before, but much much better angles, AND the ports are L shaped from the factory. The added JB weld has made them more of a smooth "j" shape now. They are also angled better to point more towards the intake. I will wait until night to test top speed but one thing I've noticed immediately was that my bike actually idles AGAIN. before this the ports were too big and the L shape made low rpm total garbage and I would have to roll on the throttle slowly to 15 mpg or it would go flat. Now I can slam open the throttle and it just goes. This tells me I'm getting much higher quality flow since the ports are just as big.
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