[Jim]

We've noticed excessive wear on the cam due to heavy duty valve springs. For 2 1/2 years we used nothing but xr70 springs with no trouble. Six months ago we started using these springs and in 40 hours of running time the intake lobe was worn down 1/8". (So far we replaced 4 cams and valve springs) If anyone had a head done by us please check for cam wear. If you have it please contact us for replacement on the cam and valve springs. We just finished our new xtreme 110 bike and went back to the old valve spring set up with no spring lock or flotting of the valves.(which means heavy duty valve springs are not the way to go).

Jim

www.precision-racing-components.com

(Paid advertiser of planet minis)

 

[XmutinymotorsportsX]

Thank god!!! some one else with some common sense.....I have tried in numerous threads to warn people about these.....Maybe now that a reputable company is also putting the word out someone will listen......I have the flat cam to prove it........I would also assume you are using the older wider style rocker arms......If not that would be something to look into........

 

[~E]

Thanks for the word of caution and good business by offering a fix.



bump.

 

[motoguru]

not so fast here guys, we have one guy who built 4 motors where cams went flat. i wouldn't call that a reason to abandon ship. i have been using the takegawa springs (heavy duty) for over a year, the same ones in that takegawa uses in all their heads, with no problems. maybe the difference is i use japanese cams not chinese. i have not used any prc products but have heard good things of them, and i am not saying you are using chinese parts, but it would be more likely for you to get a batch of bad cams than for it to be the springs causing the problem. every industry in the world, automotive & heavy duty, has encountered swiping lobes on cams. and by the way you do realize that those cam springs are directional, they are called progressive rate. if you put them in upside down they have an excessive pressure at first opening and then have less resistance the more the valve opens. remember the painted end goes up.

 

[manwhore]

i use web cams made in the usa i did not have cam problems but it did dish my rocker arms out so i agree do not use them use the xr 70 springs

 

[Huth111]

I have witnessed a warn cam due to this problem, we went to a XR70 style head with the stock springs.

 

[Jim]

We ran a 88cc built up motor for 2 years with xr70 valve springs. When this motor was torn apart there was no ware on the cam lobs or rockers. Since we installed the heavy duty valve springs( the right directional way) we've had nothing but cam noise, spring lock, and cam ware. It is not a cam problem, I took the cam that we ran for 2 years and the cam that was worn and the both bernilled tested the same. What's the problem, the springs and that's all there is to it!!! They are junk!

Jim

www.precision-racing-components.com

Advertiser of Planet Minis