Can The gear spin on the camshaft????

[hondabilly]

Hey ya'll, I got a question about my 07 yzf 250, I keep having problem with My top end, does anyone know how the cam gear is attached to the camshaft itself, is it just a press fit or something. I'm wondering if this gear could spin when a motor locks up. and is there a way to check it. ( I'm just thinking it moved a tiny bit, just enough to mess up my timing), My thought is that it would not move and that the chain would jump first, and maybe push the tensioner back. also does any one else out there have any problems with the valves on these bikes, we have a 06 and a 07, and we can not seem to get our Intake valves to last more than twenty hrs, problems vary from the head of the valves popping off to just plain wacking the top of the piston which cause the shim and bucket to just explode, I've tried several things with little luck, every time I think I've got it figured out it breaks again. any info would be great. and yes I am timing it correctly. and no we are not overrevving these bikes at all. the 07 bike has been worst than the 06.

thanks in advance.

[William1]

Yes, unfortunately, it is possible for the sprocket to slip. It is pressed on. You can check it with a degree wheel.

Lots of valve failures? OEM or aftermarket valves? Who is doing the head and what method is done to prep the seats if any?

[oldnbold]

Yes, unfortunately, it is possible for the sprocket to slip. It is pressed on. You can check it with a degree wheel.

Lots of valve failures? OEM or aftermarket valves? Who is doing the head and what method is done to prep the seats if any?

what springs with which valves?

Frankly, very few are having any trouble at all with valves.

[mkporn]

I would like to know more details also...You say 20hr, for a honda being raced i could see it, but these bikes will usually go for a couple hundred hours many times without needing adjusted. I know that riding higher in the rpm range does tend to shorten life, but not to 20hrs needing replaced. You say poping heads off or hitting piston, the smacking the piston is cam timing (which yes if the cam sprocket has slipped will cause this and it doesn't take much of a slip of the sprocket to make the valve capable of smacking the piston)

Easy way to check the cams is to put it at TDC and look at the cam lobs, they should be facing away from each other (intake lobes to the carb and exhaust loabs to the pipe) and they should both look the same in relation to the flatness of the cam face. in other words if the intake lobe is pointing further down or up rather than straight out and the exhaust is pointing straight out and the marks are correct on the sprockets, you have a problem with the cam sprocket slipping, this goes thew other way around also, inversly for the exhaust cam verses intake came.

[JasonfromMN]

I would like to know more details also...You say 20hr, for a honda being raced i could see it, but these bikes will usually go for a couple hundred hours many times without needing adjusted. I know that riding higher in the rpm range does tend to shorten life, but not to 20hrs needing replaced. You say poping heads off or hitting piston, the smacking the piston is cam timing (which yes if the cam sprocket has slipped will cause this and it doesn't take much of a slip of the sprocket to make the valve capable of smacking the piston)

Easy way to check the cams is to put it at TDC and look at the cam lobs, they should be facing away from each other (intake lobes to the carb and exhaust loabs to the pipe) and they should both look the same in relation to the flatness of the cam face. in other words if the intake lobe is pointing further down or up rather than straight out and the exhaust is pointing straight out and the marks are correct on the sprockets, you have a problem with the cam sprocket slipping, this goes thew other way around also, inversly for the exhaust cam verses intake came.

Could this make a bike run poorly like its hitting the rev limiter early but not really affecting the bottom or mid? I have a 07 WR250F thats been through a couple of shops of people checking the carb, TPS, coil, CDI ect and not finding anything wrong.

[desert-rat660]

have u ever replaced the timing chain?

[offthewall]

Could this make a bike run poorly like its hitting the rev limiter early but not really affecting the bottom or mid? I have a 07 WR250F thats been through a couple of shops of people checking the carb, TPS, coil, CDI ect and not finding anything wrong.

Sounds familiar. A bike my mechanic got his hands on had the same story. This is something your average parts changer at the local shop will never figure out. Never. Check the degree yourself with a degree wheel and your manual. I would be suprised if the bike could run at all though, save for the degree being off only so slightly. It definately could happen though.

[shaunone]

Yes, the cam sprocket can slip on the cam shaft, seen it happen before. No, it cant be moved back. For the cost of replacing OEM, one might look at a pair of HOTCAMS replacements...

[yzfkneedragger]

lol...hell ya it is. I just had to buy a new cam from the previous owner ripping me off due to this fact. check it out.

My crank is at top dead center and so are the lobes but look at the cam gear. The guy crashed a top end and just "eyed it up" for the cam timing. I just got my new cam today and am going to install it right now.

[williamsmotowerx]

I have seen a few of the valve seats move in these heads, causing stress to the valves and breaking them. It typically happens on the exhaust side though.

A good practice I've gotten into is grinding a small line in the cam and gear itself when new. Then you'll know later if it has slipped.

Yes you can repair them if they've slipped.