WR YZ oe aftermarket cams?

[keenxxx]

I have a 2007 WR250F that i would like to change the exhaust camshaft. My first choice was to purchase a new oe YZ exhaust cam. I thought i'd do a search which led to many variables. Hotcams kept coming up but it seemed like it really should be run with the intake cam as well. I found posts where YZF guys were running just the Hotcams intake with the oe exhaust cam to help the bottom end. I have not been able to find cam spec's for the oe YZ cams so as to compare to aftermarket cams. WR owners did you go oe or aftermarket? one or both cams?  Thanks.

Edited July 25, 2014 by keenxxx

[MartyMOOSE]

Ive done several with OEM Yz exhaust cams's they have been great worthwhile mod. Not sure on the hotcams never used them.

 

MM 

[genocidal_josh]

I've got yz hotcams on my wr, best thing I ever did.. you will feel like a midget trying to hold onto an elephants trunk the first time you grind open the throttle and got more than enough bottom end grunt

Edited July 25, 2014 by genocidal_josh

[keenxxx]

I've got yz hotcams on my wr, best thing I ever did.. you will feel like a midget trying to hold onto an elephants trunk the first time you grind open the throttle

 

Would those be the stage 1 intake & exhaust?

[genocidal_josh]

Yip stage 1 on both and worth every cent I paid

[genocidal_josh]

If you want to really go all out you should get a hotcams shim kit, not too expensive but its definitely worth having

[keenxxx]

If you want to really go all out you should get a hotcams shim kit, not too expensive but its definitely worth havingI

 

I installed a couple oe cams over the years and as long as the valves were in spec before the swap no shimming was required. Not sure if aftermarket cams are drop in or need a re-shim.

[longerdeeper]

I have hot cams stgv1 inlet stg 2 ex. I like them, bigger bottom end and strong through the middle. The yz exhaust cam swap was the hot mod before aftermarket cams became avaiable and reasonably priced, It will certainly give you a gain over the stock cam.

[beezer]

I tried a YZ exhaust cam on mine and it worked fine.

 

Then I bought Hotcam Stage 1's and thought that worked better.

 

I tried the Stage 2 but the bike got pipey and I took them out and sold them.

[longerdeeper]

I installed a couple oe cams over the years and as long as the valves were in spec before the swap no shimming was required. Not sure if aftermarket cams are drop in or need a re-shim.

after market cams are pretty good as far as tolerance, not hard to get within 0.01mm on diameter in a grinding process. If I check my valves I usually do it on a week night to get measurements, if I need to shim then I work out what I need and then buy what I need when I get to the bike shop saturday morning., guys at the shop sometimes will exchange the shims for what I need but lately I have been keeping the old shims and they come in handy when another valve needs that size. I don't see the need fir a whole kit, many of which you will never use.

[keenxxx]

after market cams are pretty good as far as tolerance, not hard to get within 0.01mm on diameter in a grinding process. If I check my valves I usually do it on a week night to get measurements, if I need to shim then I work out what I need and then buy what I need when I get to the bike shop saturday morning., guys at the shop sometimes will exchange the shims for what I need but lately I have been keeping the old shims and they come in handy when another valve needs that size. I don't see the need fir a whole kit, many of which you will never use.

 

I called Hotcams about the cam spec's and mentioned the possibility of valve adjustment. The tech told me they had bigger lobes so I would probably need to re-shim. Hmm bigger lobes wasn't exactly an in depth answer.

[longerdeeper]

I thought you would get a better answer than that out if them! Yes they will have bigger lobes and different shape to that lobe that is how they ooen the valves more and for longer, allowing more fuel in and therefore a bigger bang .......in oretty rough trems........

but here is the thing, the clearsnce you measure has nothing to do with lobe size and shape because you are measuring the clearance between the valve cap and the backside of the lobe which is a plain radius for maybe 90 degrees of the cam rotation. It will be the size if this radius relative to the cam bearing diameter that determines if the back of the lobe sits in a different position to the previous cam and therefore needs a different shim size.

[longerdeeper]

The first bike I put my cams in I managed to shuffle the existing shims around and only have to buy 2. The second bike I only had to reshim the center inlet, which I had a shim for, and was a little tight on the standard cam when I checked them.... the reason I decided to use the hot cams again.