cr 85 to 105 advice?

[scottiedawg66]

hey there. I am racing a class full of built 105s, and 150r with my 2004 cr85. I need more power.

The max power 105cc stroker kit (50mm bore) is $1900 installed, I paid $1100 for my bike.....

There is also a 105cc big bore kit (52mm bore) that is only $600 + labor (which I will do myself)

Can anyone share any advice (dyno graphs?) on these big bore / stroker kits? I am putting down 17.3 hp and 8 ftbls of torque now, there is a built KTM 105 throwing down 25 hp and almost 12 ft lbs of torque in the class. I can get around people on the brakes and with corner speed (supermoto) but I get stuffed and pulled down the straights. I'm tired of getting 4th place! :yell:

 

[Chili]

Talk to Eric Gorr and he'll get you on the right track for pretty much less than you'll spend anywhere else.

http://www.ericgorr.com/supermini144BigBore125service.html

 

[Patman]

Talk to EG, there are less expensive options that will give you a more / better spread of power. Spend the difference on suspension and maybe some help to learn how to use what you have to it's maximum and you'll be leading the bigger dollar bikes.

 

[Wolf]

Eric will set you up!!!

 

[scottiedawg66]

thanks guys, i'll give eric a call. the suspension, is totally trick for supermoto, and I am running bridgestone super soft tires, so were good there. I just need more motor!!

 

[helio lucas]

17 hp seems a little short on power, even with stock engine.
from my experience, stock pipe make the best power (not best peak) and a pwk 30 with some reed mods and ported cylinder would be the way to go.
a bigger bore may not give you more power, just more torque. eric will setup correctly for your needs...

if you are competitive with a 85 against those 105´s on supermoto, congratulations!!!!!!!! :cool:

 

[scottiedawg66]

http://www.youtube.com/watch?v=yYEpTR2t85g

here is a vid from my 1st race, 2nd time on this bike.

I put an fmf fatty pipe on there, and I agree I lost top end, but picked up so much mid range it was a good mod.

Can I expect 25 rwhp and 11 ft/lbs from a 105 stroker or am I dreaming of running with the built 150r?

 

[helio lucas]

you and your bike are fast on that track, specially on the open areas...
i agree with the 52 bore, will give you a lot more punch out of the turns. if you´re not running race gas and it´s legal, go for it. once again, talk to eric gorr. best money you could spend!!!

the numbers are only important if a correct power curve is held. if you are after big numbers alone, you could end with a very peaky, hard to ride, no response, unreliable, engine.

this is what you want: :cool: http://www.dirtrider.net/forums3/showthread.php?t=97637&page=3

 

[scottiedawg66]

thanks for the advice, I tried to call Eric Gorr twice and got a message machine that was full. He is highly recommended, but Id hate to need something and not be able to get intouch with him...as for the class. the only limitation is 105ccs, everyone runs race gas, so im going with some high compression no doubt.

 

[Rich Rohrich]

Eric gets about 9 zillion calls a day, mostly from 13 year old kids who read his books and want help doing a top end. He stops answering the phone at some point to get work done. Best time to talk to him is 6:30am-8:00am CDT or better yet e-mail him at ericgorr @ hotmail.com (remove the space around @)

 

[scottiedawg66]

thank you!

 

[scottiedawg66]

well....i just bit the bullet. Talked with Eric this morning. $525 got me a 100cc big bore kit and a new cylinder. Once I get it on the dyno i'll post the before and after charts.

 

[helio lucas]

scottiedawg, how is the 100 kit going? any report?

 

[scottiedawg66]

I got everything back from eric, looks great. I am going to finish out this season on the stock 85, and run the 100 next season. I will post a dyno graph and what jetting i run but it wont be until winter.

 

[scottiedawg66]

just to close the loop on this build I went from a 19 hp motor (17.2 hp from earlier post was due to a cracked piston) to a 22.5 hp motor. the torque band is much more usable down low and getting a good start is so much easier.

at sea level I run a 125 main jet.

bottom line is it was worth every penny. 3 hours of abuse on it now. If it blows up I'll update, but for now its just a ripper.

 

[helio lucas]

thanks for the update :cool:

i am currently running a hand made rev pipe, v-force reeds and a PWK 30 on mine.
the 30 carb was the second best mod i´ve ever done, after the big bore, they complement each other very well. the hit is smoothed and the powerband is just wider and much more powerfull from low to very extended top end.
i am still on the process of get it running right but at the moment 130 main jet and a 50 slow jet.

despite the fact that my is a 80 and not 85 wich has a stock pe26 and not a pwk 28, i really think the bigger carb will suit your riding and get you some advantage. as a matter of fact i really think it would pull a 32 with no problem.

note that when i say much more powerfull i really meant it. no kidding :cool: :cool: