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Max compression Ratio for piston

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I was thinking about to run Little higher compression then the current piston that i got when i rebuilded my Engine.

 

My bike:

Honda CRF450R-07.

 

Mods:

Cylinderworks Bigbore (488cc) with Vertex 12.1:1 Piston.

Hot Rods +3mm stroker

Hot Cams stage 3 cam

Fastheads Bigbore head

FMF Megabomb + FMF 4.1

FMF Powerflow

 

I was thinking about 13.5:1 CP piston, is it possible to run with regular 95 fuel ? There arent many HC pistons available for 100mm (as far as i was able to find).

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I have almost that exact same setup and have had zero problems with it. Once you figure out how to kick it hard enough to get her started it's a wild ride!

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It'd be a custom piston (they might offer it, but its not in a regular catalog)

 

The issue Id think would be heat. Youve made the engine 10% larger, and bumping the compression ratio too...You'll need bigger rads. But it could be done.

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Thanks for the responds, i was afraid it might get to much compression, but if its possible to run for you Will i order 13.5:1.

Shawn:

Cp have 13.5:1 in stock list for 100mm, i fortgot to mention i have already got "oversize" radiators.

Have got boyesen powerflow waterpump also.

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Man that things gonna be a rocket for real! I like haulin ass but if you don't already you might wanna look into a back up bike for hittin the trails or track

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Man that things gonna be a rocket for real! I like haulin ass but if you don't already you might wanna look into a back up bike for hittin the trails or track

 

I hope so atleast :) Im currently looking for a new bikebuild since this one are soon done. So im already thought about that :)

 

 

A straight up 450 can make more HP.

 

This thread are not about if its possible to make more hp out of a crf450r or not, but im sure there are better ways to get more HP then the parts i have choosen.

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I hope so atleast :) Im currently looking for a new bikebuild since this one are soon done. So im already thought about that :)

 

 

 

This thread are not about if its possible to make more hp out of a crf450r or not, but im sure there are better ways to get more HP then the parts i have choosen.

OK hope you be careful with your endeavers. We use to make 505s out of these and there is a lot more to it, good luck.

Edited by bushman45

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Thanks for the responds, i was afraid it might get to much compression, but if its possible to run for you Will i order 13.5:1.

Shawn:

Cp have 13.5:1 in stock list for 100mm, i fortgot to mention i have already got "oversize" radiators.

Have got boyesen powerflow waterpump also.

 

Well, more compression is going to make more power. Youre going run out of air through the OEM head soon. A little port work does wonders, that and maybe retard the cam 1-2 degrees so it doesnt go flat on you at higher RPM. Id think youve gotta be at the edge of the envelope on the rods ability with that big ass piston and that much compression. The pin in an XR650 is gigantic compared to the CRF and it doesnt even make as much power stock. Food for thought.

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Well, more compression is going to make more power. Youre going run out of air through the OEM head soon. A little port work does wonders, that and maybe retard the cam 1-2 degrees so it doesnt go flat on you at higher RPM. Id think youve gotta be at the edge of the envelope on the rods ability with that big ass piston and that much compression. The pin in an XR650 is gigantic compared to the CRF and it doesnt even make as much power stock. Food for thought.

Oh my bad. The "Fastheads" Bigbore head have got a Port & Polish job done also to it.

Iam not so experienced builder i had got any thought on changing the cam degrees.

 

(Im running with this head: http://www.ebay.com/itm/CRF450R-Extreme-HEAD-Package-Big-Bore-Mods-Oversize-Valves-BeCu-Seats-Porting-/351063870274?pt=Motorcycles_Parts_Accessories&hash=item51bd098b42&vxp=mtr)

 

thanks for taking time and giving me tips, really apriciated since im not the most experienced builder.

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Just put it together with the parts you have as is, you'll be plenty happy. It'll probably scare the shit out of you at first. I know the first 511 I did with a ported head and a stock cam was crazy fast.

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Just put it together with the parts you have as is, you'll be plenty happy. It'll probably scare the shit out of you at first. I know the first 511 I did with a ported head and a stock cam was crazy fast.

It still is, even with it's negligent owner :banghead:;)

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