Powroll 12.3:1 high comp piston

[heybuddy1901]

Anyone have any experience with this?

its a .5mm overbore from stock and is claimed at 12.3:1

[Chuck.]

12.3:1 compression ratio seems high for use with a stock cam since the stock CR is 9:1. Why not ask Powroll for their recommended combinations of CR and cams.

[heybuddy1901]

already have a big cam. need more compression than what the wiseco offers

[heybuddy1901]

anyone?

[Chuck.]

As I previously posted I suggest you ask Powroll; they have a lot of dyno and race time with the two valve engines, including building road race engines for karting and Honda.

Hope this helps.

(541) 923-1290

[heybuddy1901]

already talked to them, want first hand experience, which im guessing not alot of people have since it requires running 100% race fuel..

[JJStunts816]

already talked to them, want first hand experience, which im guessing not alot of people have since it requires running 100% race fuel..

Are you positive? I really don't know much about octanes/compression ratios, but my honda f4i with a 12.0:1 compression only needs 86 octane! I always ran 87 in it. Of course I know its liquid cooled for one, and also the ignition timing and tune make a difference. But hell I even ran 87 octane, with my bike regularly at 240f water temps while running.

Most people think its the most evil thing ever, but you might also consider e85. I personally WANT to build a high compression bike just to run e85 lol

[coeshow]

Its mainly due to the combustion chamber shape. The old air cooled engines have a true "hemi" combustion chamber. All of the inlines and current state of the art 4 stroke dirt bikes have modern quick burn low volume combustion chamber designs. Air cooling doesn't help matters either.

One side effect of the hemi combustion chamber is compression induced detonation. Without proper fuel, compression ratios above 10.5:1 will detonate. Narrow lobe center cams will increase this problem even more.

[hoosierf]

I'm a big powroll fan. Have their cam and wiseco 11.1 in our 230. Have their 175 stroker in our drz125. Did not put their bbk in the 230 'cause I did't want the down time for boring. You will not be disappointed.

[The Demolisher]

I'm a big powroll fan. Have their cam and wiseco 11.1 in our 230. Have their 175 stroker in our drz125. Did not put their bbk in the 230 'cause I did't want the down time for boring. You will not be disappointed.

How is that cam working for you with the Wiseco?

[hoosierf]

Couldn't' be happier. I'd guess we're getting a little over 20 HP out of it...maybe 21.

[heybuddy1901]

Couldn't' be happier. I'd guess we're getting a little over 20 HP out of it...maybe 21.

what cam are u running?

EDIT: nvm, thought u were a different person running the 12.3

[The Demolisher]

what cam are u running?

EDIT: nvm, thought u were a different person running the 12.3

Lol yeah sorry for that thread jack.

To be at least slightly helpful, I emailed Powroll and they claimed their overbore 10.5:1 is about the same as the stock bore Wiseco 11:1 in terms of torque.

[heybuddy1901]

Lol yeah sorry for that thread jack.

To be at least slightly helpful, I emailed Powroll and they claimed their overbore 10.5:1 is about the same as the stock bore Wiseco 11:1 in terms of torque.

im running the wiseco also, and other sources tell me that its not really an 11:1 more like a 9.9 or 10:1. so putting the true 12.3:1 in should net a decent increase ?

[Chuck.]

Go back and read post #8. The 230 and XR200s have similar heads and these engines are not tolerant of high compression or aggressive ignition timing. The ignition timing is fixed on the 230 so the only option for dealing with detonation is race gas. The inlet valve closing, not CR, determines when compression begins so that is why I suggested getting input from Powroll on CR and cams.

The XR200s run 10:1 CRs but with a cam that is more aggressive than a 230 cam. They can run 10.5:1 on pump premium gas (I have one), but 11:1 is pushing it (I have one of those too) on pump premium without retarding the ignition timing.

[heybuddy1901]

Go back and read post #8. The 230 and XR200s have similar heads and these engines are not tolerant of high compression or aggressive ignition timing. The ignition timing is fixed on the 230 so the only option for dealing with detonation is race gas. The inlet valve closing, not CR, determines when compression begins so that is why I suggested getting input from Powroll on CR and cams.

The XR200s run 10:1 CRs but with a cam that is more aggressive than a 230 cam. They can run 10.5:1 on pump premium gas (I have one), but 11:1 is pushing it (I have one of those too) on pump premium without retarding the ignition timing.

i dont understand what you are trying to tell me...

i DO have a cam, i DO run race fuel, i DO have an 11:1 piston...

[hoosierf]

im running the wiseco also, and other sources tell me that its not really an 11:1 more like a 9.9 or 10:1. so putting the true 12.3:1 in should net a decent increase ?

You''ll have to let us know how it works out. Kind of wondering if you'll lose any over rev in your motard runs. What cam are you running?

[Chuck.]

i dont understand what you are trying to tell me...

i DO have a cam, i DO run race fuel, i DO have an 11:1 piston...

I didn't address my comments to you, I was adding some of my experiences to support the excellent description that coeshow posted regarding how sensitive these engines are to detonation.

[heybuddy1901]

I didn't address my comments to you, I was adding some of my experiences to support the excellent description that coeshow posted regarding how sensitive these engines are to detonation.

ahh, quote is your friend, lol

You''ll have to let us know how it works out. Kind of wondering if you'll lose any over rev in your motard runs. What cam are you running?

the most aggressive one coeshow makes + porting