motor is toast

[rathofkris]

so i have been on the boards for a few months and really like the place..i was going to do a full motor rebuild this winter but now i have to. the timing chain decided to strech after 3 months, it jumped timing and now i have a bent intake valve and some scarring on the piston.

plans
kibble white +1 intake and exhaust valves, kibblewhite springs and retainers, wiesco 10.25 to 1 84 mm piston, new timing chain of course and maybe a new cam.
the question i have is about which cam i would want to look into. i do alot of woods riding. i am working on becoming a member of the mansfield motorcycle club and racing in a few c.r.a. events.
any input would be awesome
thanks alot
kris

 

[ratchracing]

In my rappy I had the Kibblewhite springs and the Wiseco piston like your thinking of. I bought 2 cams from WebCams, the midrange and the racing versions. I put alot of hours on both. IMO if the trails you ride are tight and twisty technical stuff go with the midrange cam. If the trails you ride are more open and fast or you ride sand alot go with the racing cam. The midrange cam gives a good all around boost in performance, the racing cam gives a big boost mide to top but you loose a bit on the bottom end.

http://www.webcamshafts.com/

If your running larger than stock valves with the high-comp piston and high-lift cams you need to check your valve/piston clearance when assembling your engine to make sure your not going to have interference contact. I usually clay the piston and install the head, cam, etc, turn engine over by hand, disassemble and inspect tolerances.

Also, I've found with the increase in compression with the Wiseco piston you need to run 91 octane fuel, I tried 87 and it ran like ****.... too much compression I guess. I also prefer the Wiseco piston over the JE or other makes because the wiseco is super light weight and will let the engine rev up quicker.

Hope this helps.

 

[rathofkris]

thanks for the input i really appreciate it. i ride alot of tight twisty trails so i guess the more low and middle range cam would be great. and as for the tolerances, a local machine shop will be assembling the motor so i shouldn't have any problems..

 

[ratchracing]

I think you'll be pretty happy with that setup, these engines rip when they have aftermarket cams. Let us know how it feels when the new parts are in

 

[DeadLastRacing]

I think you'd be happy with the 390 webcam. Cam talk has been had on here dozens of times. Do a little searching and I'm sure you'll find all the info you ever need to know on what cam is right for you.