Ever heard of this happen before?

[m0t0xk1d]

So the other day we finally gave BCS the go ahead and tear and fix the the problem with my engine. What we and BCS thought it was, was a broken 3rd gear. It just ran like **** and we couldnt get it to run right then they changed the oil and chunks of metal came out.

Come to find out the Intake cam had snapped in half. But we didnt know that and it just ran bad so we kept riding it to try to diagnose it. Well now I need a totally new head and anythign else that got damaged while the intake cam was snapped.

the good news is the tranny is goood to go. nothing wrong with it.

[Ex_Rider43]

If you have a built engine with more agressive cams , it can happen after some high-revving , but this is not very common.

If the engine is stock or pretty much stock with a valvetrain thats not very agressive this is not something that will happen except if you really beat on your bike.

[blaster99]

I have cracked a Web cam. I have also heard of guys beefing up the valve springs to keep the valves from dropping, but it then begins to break cams. It may have been a fluke, your motor was stock right?

[m0t0xk1d]

Motor was totally stock. Im running a production class so I need to have a stock motor. It may be my fault, I tend to ride on the rev limiter. Not like just hold it there obviously, but like right before i land jump i get on it to get the rpms up. Its kind of how justin barcia rides. Can this motor not handle hitting the rev limiter alot? I only had 2 rides on it at mx207 before it started happening. Either that or just bad luck and a factory defect because jay said the bike only had 7 hours on it.

Im thinking it came done to bad luck which sucks but whatever. I dont really hear much about cams breaking in half. My love for the bike hasnt gone down yet though, it ran amazing when it did.

[blaster99]

It was probably just bad luck. I ride similar to that with no issues.

[ds19]

I don't think reving it high caused this... I thought reving it high was the only way to ride a 450 lol.

[Justwin]

Yep, I've broken 2 intake cams over the last couple of years. Luckily I had no damage and was just able to swap them for Web cams. There was no journal damage. The bike would idle fine but there was obviously no power as only 1 valve was operating. Took a while to diagnose the first time as leak test and compression test etc all came up ok.

[450Rida]

Originally posted by ds19
I don't think reving it high caused this... I thought reving it high was the only way to ride a 450 lol.
over reving will cause some serious damage, mostly to the valve train and head. ive never seen it in a ds but have on many yfzs. we brake cams on the drag bike once in a while but thats far from stock.

[Lquad71]

Originally posted by m0t0xk1d
Motor was totally stock. Im running a production class so I need to have a stock motor.

You dont have to have a stock motor to run production. You just cant have a larger displacement. Correct me if im wrong but im pretty sure the pros are a production class.

[motomxman450]

Originally posted by Lquad71
You dont have to have a stock motor to run production. You just cant have a larger displacement. Correct me if im wrong but im pretty sure the pros are a production class.

That's correct, no changing the frame geometry either, just gussets.

[motox_rider695]

this doesn't pertain to your question but when you get on the gas before the landing, do you have the clutch in at all or no? jus curious...

[m0t0xk1d]

I have the clutch in. let it go right as i land

[blaster99]

..strange. I don't touch the clutch in the air unless I am hitting the back brakes. And if I do i just let the clutch out after I release the brakes. Any benefit to dropping the clutch before you land? I always thought holding it wide open about 6 inches before you hit the ground was to pull you forward as you land.

[m0t0xk1d]

What i do i pretty much the same thing. except im usually at the rev limiter when i let go. basically i let go of the clutch like 6 inches from the ground too but since the clutch is pulled in it can rev faster because their is no load on the engine. not even the wheels where as with out the clutch the wheels would be spiining. basically the same thing. Im not sure if what i do is right i was taught that way to rev in the air. maybe your way is better

[blaster99]

Makes sense. I thought you landed with the clutch in haha