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Cam Plain Bearing Seizure?

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Yes I have seen this, and have to agree with Aaron_Silidker, Both times were due to over torquing the valve caps. There was a service bulletin shortly after these came out, and it indicating the that 12Nm or 104 in lb noted in the repair manual is incorrect. The correct torquing should be 10Nm. This is the spec we have used and have had no problems.

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It's true that over torquing the cam caps will cause this but it needs to be said that even when torquing the caps to the correct spec. they could still be tight. You should check to make sure the cams move freely without the chain attached. Sometimes the journal is too tight for the cam and you need to machine the journal to the right size. Also cut the contraversal oil groove, These cams need all the help they can get.

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It's true that over torquing the cam caps will cause this but it needs to be said that even when torquing the caps to the correct spec. they could still be tight. You should check to make sure the cams move freely without the chain attached. Sometimes the journal is too tight for the cam and you need to machine the journal to the right size. Also cut the contraversal oil groove, These cams need all the help they can get.

Well said! :banghead:

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thank god i read this thread cause i've just shimed my bike and i've torqued the cam caps to 20nm... 🤣:banghead::banghead::busted::busted::busted::busted::busted::crazy:🤣🤣

Thank god i have run it yet,,, and i have to race tomorrow......

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thank god i read this thread cause i've just shimed my bike and i've torqued the cam caps to 20nm... 🤣:banghead::banghead::busted::busted::busted::busted::busted::crazy:🤣🤣

Thank god i have run it yet,,, and i have to race tomorrow......

Check those cam cap bolts when you re assemble, they can get damaged and break very easily.

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The caps can become permanently deformed by overtorquing, dont think you are safe yet! Thankfully, the caps are so freaking soft when both of mine siezed, I used 800 grit to smooth the bearing bores out and they have been fine since.

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If you have had a seized cam, take that cam in and have it trued back up, the gear on it tends to spin, had it happen to mine, big bill after, best bet is to try n get yur hands on a new cam, and spot weld the gear so it doesnt move

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Mine just siezed again today! Jeesus this annoying, I am gonna split the cases and clean the oil screens.

:banghead:🤣🤣

Hmmmm..............bet it wasn't from overtorque on the cam caps was it?

If not, you obviously don't take care of your bike, because these are GREAT bikes and will provide the expected service if you only take care of them. These ARE race bikes and you need to change the valves, springs, seats, buckets, cams, bearings, and split the cases to clean the oil screens after every race. I mean, what do you expect?

By the way, I am just kidding..............kinda makes your blood boil, though, doesn't it?🤣 That just seems to be about half of the crap I read on here, and quite frankly, it pisses me off. Amazingly enough, I am able to keep my YZF running, and it is a year older with at least 3 times the hours on it. And last time I checked, the YZF was considered a RACE bike too.

I'd be very interested to see what you find when you split the cases. I'd be willing to bet nothing. Let us know if I am wrong.

If you didn't already know, our intake cam previously seized and spun the gear. :banghead::busted:

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