2006 YZ450F Timing issue

So my bike jumped timing due to a bad cam chain. I dont think that the valves hit the piston when it happened and the bike would kick over and have decent compression. I didn't verify with a compression gauge. 


I put a new cam chain in and when I slowly turn the motor over the piston comes into contact with the valves. Any suggestions on how to check if the cam gear slipped or do I need to pull the head and check the valves to see if there is any other damage? 



Do you have the timing set correctly? Exhaust cam dot at 9 and 12 and intake at 12 and 3?

What about the timing mark on the flywheel? When the timing marks are lined up, how do the cam lobes look? Should be pointing in the opposite

direction at about the same angle.

Any pictures?

The manual has specifications for the cam, you can use that to verify your cam.

Edited by dougla12

The timing is set correctly. I will take pictures tonight.


Cam lobes are pointing opposite directions but not exactly opposite.


So from looking at my pictures and comparing to other pictures it looks like the intake cam gear has moved on the cam. What do you think?

To me. It looks like the exhaust cam lobe is out of place.

Check the manual, or even a quick search on here or Google would give u a better idea of how the cams supposed to look

The exhaust cam is off on picture 1. However, the 2nd pic with the marks lined up, looks to be right on. Not sure how that is so, unless things were mover around between pictures. Where are the marks on the cams when the flywheel is at TDC?

Sorry I meant exhaust cam and not intake. All the pictures were taken at the same time without moving anything.

With he flywheel at TDC and both cams lined up per the manual. The lobes on both cams should be pointed how your intakes are pointed. At least on my bike they are pointed the same only opposite. If that makes sense. Intake at 10:00 & exhaust at 2:00

The, I don't know why my phone replaces "the" with "he" drives me nuts.

Thanks for the help. Is there a way to tell if the cam gear moved on the shaft? 

I have no idea on that one. I've never seen that happen but it is entirely possible I guess. Everything else looks spot on for timing, it is only those exhaust lobes are not in the correct position. The only explanation is that the shaft has rotated inside the gear. I have an old exhaust cam that is in great shape from an '07 I'll look at tonight.

So from looking at my pictures and comparing to other pictures it looks like the intake cam gear has moved on the cam. What do you think?

It's definitely not right.

Intake cam gear spun. Look at the kx250f section theres a write up on a press off, retime, repress sprocket

10 and 2 lobes

Either this or buy new cams/ intake cam

And thats from a cell phone pic, they could both be spun. Its not in front of me but this is it im 99% if your at tdc on flywheel

After looking at my old cam, yours has definitely spun inside the gear somehow. IMG_1476239299.320763.jpg

The lobes on my cam line up with the post on he front of the cam. From the looks of yours, it's off by a tooth or 2

+1 on that the exhaust cam gear has spun on its shaft.

As long as valves didn't hit the piston (which is likely to happen when it slipped) you should be fine after you turned it by hand and felt that.

You would need to remove the top end for inspection to confirm.

And I don't believe you should try reinstalling that cam gear and spot welding. A new cam should be on order...

Ive reinstalled and MIG welded stock suzuki gears before, no problems but I also ordered new hotcams when my gear spun as it was a new issue to me then. While waiting for their arrival, I use an Oreilly auto parts pulley puller, took gear off, matched lobe hole to sprocket hole, pressed gear back on, then mig zapped the size of a skittle. Both cams, both sets. Years ago, many years, many hours with no issues.

Must be a fast zap as to not overheat and warp the cam. But the weld is seriously no bigger than a skittle. No smaller than a tic tac. This hurts nothing. There are camshafts with fixed, bolted on, cam sprockets. If motor is timed correctly, the motor will work as its supposed to. This is a product of heat. Over and over again you heat the motor up. Heat expands metal, metal has "memory", If it was stretched out, itd remember it did that. Even if it cooled off and shrank, it still was overheated and stretched and knows it. Thousandths of millimeters are a big deal to press fits.

The guy on the kxf forum repressed and did not weld sprocket. He has his thought process on it. I have mine.

My opinion visually is its your intake side. This is the side with the tensioners pressure.

I dont know whats more work to you, pressing gears and welding or not, or buying new cams. Nows a chance to gain power with an aftermarket cam. Your choice. Of course a new cam chains a good idea too. Its a ten year old mx bike. They get hot and those cams are up top not at bottom bathing in oil...take plug out and rotate motor by crank by hand, hear if valves are hitting. Might never had. You could take head off and look. But I wouldnt reuse the gasket. And definitely use torque specs in reassembly. Or you could do a compression test to see if the pistons solid or a leak down test to see if a valve bent. My bet is your good. Itd would have stopped working. There are cameras small enough to fit in the spark plug hole. Another oreillys tool rental.

Youre not in bad shape. This happens to the best of us!

There are no issues having a cam gear properly pressed on and welded. The issue is getting the gear indexed to the proper position on the cam. It's usually done by a jig by someone like MMAD in El Cajon Ca.

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