big bore kits

I just got done building a a 101 mm big bore for a race coming up and installed my 187 cam and what a disaster cold only pull 55 hp from it and know more peak torque than my 450s it did peak a lot earlier but rolled over so bad on the top end i would not consider even trying to run it were going back to the 208 for the 500 its hard to believe only 50 ccs could have such a large affect on the cam shaft actually the bike produces power like a cr 500 which every one is trying to get away from this is thelast year for 500s in our racing so I'm not even going to try to develop a cam that works for them .

wow ! do you think its the reciprocating weight ?or not enough valve area ?

thats holding it back

Strange. I am running an Athena 100mm kit with a Falicon stroker crank 4.6mm, resulting in a 520cc motor, with a Webcam cam and the motor is an absolute bullit for motocross use.

Stock of 450 produced 48.6hp and approx 40nm of torque, the 520 is producing 56hp and 55nm of torque at slightly lower rpm than stock, but not a significant difference.

The motor has excellent bottom and revs well on top. It does not hit a wall and drop of suddenly. If I were to go further with porting, pipe and ignition, well I can only imagine.

well when your use to making 63 hp and 39 pounds of torque with a 450 and since im the guy that desighned the web cam that your using 56 hp does not seem very significant .the head has 38 mm valves and 33 ex the same head made over 62 hp as a 450 with my 208 cam from web cam

I have no doubt you can produce more power with a 450 than the setup I am running, but does the modified 450 have the same area under the curve as the stroked and bored bike. Supposedly, people running the same kit I am running with head porting, pipe and different CDI are producing 70+ hp. Well worth chasing if you are after more power.

I have had customers give feed back on engines that they have built using my components heads 208 web cam which was my original desighn and 501 displacement any where from 66 hp to 70 hp what bothers me is that we race against them all the time and beat them. last year we pulled a full straight on the competition both in our heat race and the main @ peoria one of the bigest races in the US for dirt track the bike resgitured 62 hp on my dyno and hit 108 mph on thre straight away that mph is an indicator of hp .also the point i was trying to get across is that the big engines dont like the smaller cams like my 187 .

we got the 208 cam in the big bore and it likes it .made 5 more hp and carryed the peak with in 1 hp to 10500 with out hurting the torque to much but the 187 cam did make more it basicly turned the crf 500 into a cr500 .

hey RHC, just wait till next week my friend!!!! :D

Yea i know i can see the headlines now The hammer Henry Wiles takes another win @ peoria is he the new prince of Peoria.

Ron, I think you need to be there cause hank is going to need all the help he can get to beat JR :D

well when your use to making 63 hp and 39 pounds of torque with a 450 and since im the guy that desighned the web cam that your using 56 hp does not seem very significant .the head has 38 mm valves and 33 ex the same head made over 62 hp as a 450 with my 208 cam from web cam

yes Ron i know what you mean,

i have done some big bores and strokes for guys , and it would always take alot of screwing around to kinda get them to work.

the 488 kit i don't like at all,

i can take just a 450 and make the dam thing work better and make better usable power , and more of it.

now most of my stuff is mx,

hell i made better power easier with just a 2 mm stroke on the stock bore , than the 488 kit .

but i know if we all keep screwing with it it will come around even more.

i really had a hard time making a 488 with a 2 mm stroke ( 501 502 thing )

to make better power, :D

the problem is that we are still limited in port cross section on these heads with limited space on these bike for bigger carbs if i would have had time i could have welded the venturi up and squeezed 1 more mm out of the carb

the problem is that we are still limited in port cross section on these heads with limited space on these bike for bigger carbs if i would have had time i could have welded the venturi up and squeezed 1 more mm out of the carb

you know you are right on the money Ron. ( as always )

i really want to reweld a head so it wont leak oil ( i have had to weld some anyway because i ground to far, ill bet you have also :D )

but i think i could really get the cross section larger ,

and like you say ----with a larger carb,----and then a larger bore and more duration cam, larger valves ,

i think the dam thing could be made to really fill the cylinder and make good power-- :D

maybe sorta :D

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now