I just 07 450 hard to kick over

I just picked up an 07 450f that has 4 hours on it since new, how hard should it be to kick over? My other bike is an 05 crf450 and it kicks over very easy and always has, am I spoild by the Honda or is there something wrong with my Yamaha? I am 200 lbs and I.really have to put my weight into it

Something is wrong. Is it physically hard to kick over or just hard to get it to fire?

I used to have an 05 CRF450R and now have an 07 YZ450F. Not much difference in starting either bike as far as the leg power needed. One thing with the Yamaha, be smooth when you kick it thru, you don't need to kick it real hard. Both are easy starters (as long as the valves on the Honda are in spec).

It is hard to kick over, it will start but I really have to stand on it. I am going to be the first mxer to blow his knee out starting his bike.

Check your cam timing. Timing affects the operation of the auto decompression unit.

Thanks, I didn't think it was right, from what I have read over the last few hours the cam chain tensioner can go bad allowing the exhaust cam to skip a tooth and making the auto decomp out of time. I am hoping no damage was done from riding it this way.

Before you worry about that, you should check to see if it's even out of time.

Isn't a bad chain tensioner the main culprit to of them being out out of time? If not what else could cause it?

Isn't a bad chain tensioner the main culprit to of them being out out of time? If not what else could cause it?

check the SIMPLE things first !

Simple test #1 pull the spark plug out then kick the engine over.... does it kick way easier ? If it still won't turn over easy, now you have big expensive problems on the horizon (like a partially siezed engine)... did the engine keep stalling when you rode it ?

If it does kick over nice, now you most likely have a cam and or decompressor mech issue of some sort...

Isn't a bad chain tensioner the main culprit to of them being out out of time? If not what else could cause it?
Usually, the culprit is the chain itself. The links can stiffen and start binding under some conditions, which allows it to "fool" the tensioner. The tensioner should be replaced if a faulty chain is found because they are fairly inexpensive, and the possibility exists that they may be damaged when the engine skips time.

The bike never stalled on me once running, but there was some stumbling under acceleration and popping through the exhaust while decelerating, hmm now that I put the two together timing definitely would make sence.

stumbling and popping are more probably the result of lean idle mixture.

I removed spark plug and it turns over pretty easy, i am pulling the valve cover now

Valve cover is off and looks like the exhaust cam did jump one tooth, what would be my next step?

Replace the chain and the tensioner. When reinstalling the cams, be very sure you torque the cams by the book. I actually recommend that you use 75 in/lb instead of the 86 listed in the manual as the torque limit.

Double check the cam timing after you activate the tensioner, and never rotate the engine more than a few degrees either way from TDC unless the tensioner is active.

Thanks guys, blows my mind that a brand new bike would have a problem like this.

Four hours since new? It has been used too little and sitting too long in between. A good recipe for rust.

I agree and don't get me wrong I wasn't bashing the bike, I actually consider myself lucky, when you get into cam chains skipping things can get real bad fast.:excuseme:

I am installing the new cam chain, I had seen a picture of what the cam lobes look like when the bike is properly timed, anyone know where that pic is? I can't find it again

Download a manual here:


I recommend using a 2000 YZ426 manual because the pictures in that one are line drawings and are much clearer than the photos in the YZ400 manuals.

The cams are not timed by looking at the lobes, but the lobes should point outward to the front and rear, and slightly up. Assuming that you have the stock exhaust cam (no automatic decompression), the cams are timed by using the marks on the sprockets. With thew crank at TDC, the "E" on the exhaust cam should be at 9:00 o'clock and even with the head's cam cover gasket surface, and the "I" on the intake cam should be at 3:00, also even with the head surface. Double check after setting the chain tensioner. The marks may not align perfectly. When this happens imagine the mark being on the next tooth and see what that would be like.

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