yzf 450 cam mod

I just did the cam mod on my 02 yzf426. The bike runs great but when I start it the bike backfires just as the engine starts. any thoughts on this anyone. Thanks Mack

Check the timing of the cams -- NOT THE TIMING MARKS -- but the position of the cam lobes.

Then recheck your valve clearances on BOTH cams.

Can anyone give me the correct number of links or pins on the chain that should be between the marks on the spockets?

I know that there is directions but didn't take the time to look. I used the direction that were posted with the two pics showing how to time it by looking at the cams on the right side of the bike. (Exaust side of the bike) If anyone can post them or send to my email I would appreciate it. Mack

Here is a pic...I was too lazy to count the links for you


Make sure the crank sprocket is on the I mark, it's just to the right on the H mark on the flywheel. Set the intake cam as stock (same in picture above) and count the pins in between the top timing mark on the intake cam and the top timing mark on the exhaust cam. 14 pins, not links!

After you set the timing marks. Release the tensioner, check the crank timing mark to make sure it's on the I mark and then look at the right side of the cams. They should look to be at the same opposing angle. Go ride!

Thanks guys for the help. I was off by one tooth. 13 pins the thing starts soo easy now. I will let you know how it runs wednesday night. Thanks Mack :)

13 Pins? Are you sure you installed the YZ cam and not the WR cam? :)

I completed the 450 cam mod. a couple of weeks ago. It starts great once warm but 20 kicks when cold. I have opened it up several times rechecking the installation and clearances. My intake cam is 1/2 tooth off from Satches pictures. The punch marks are not parallel with the case at 3 and 9 oclock. I have run it with 14 pins (1/2 tooth clockwise) and with 13 pins (1/2 tooth counter clockwise) Seems to run the same with either setting. I have ordered a new cam chain, thinking it may be streched. Only about 1,000 miles on the bike. Runs great either way but tough to start when cold. Any ideas?

Funny you ask...mine was getting kinda cranky when cold and would take 5-10 kicks. I did a thorough carb cleaning and it starts first kick when cold. I cleaned mine and installed a fuel filter this time.

As far as the timing...don't want to sound like a know it all but the pic above is absolutely the correct timing. If yours looks different there is a problem.

Is there a shim kit you can get for these or do you have to measure then order your shim?????

the shims are kind of expensive ($3-5 each) so best thing to do (I know it's a pain) is to install the cam...measure the clearances and use the shop manual to determine what shims you need. Then get the ones you need at the dealer...install them and the cam and recheck. YOu should be right on the money. Then you can finish the install. If you don't have the shop manual check Motoman's site ..here is the link: Shop Manual

If you need info on how the check the valve clearances (I used these instructions along with the Cam Mod PDF to complete mine) here is the link to Garrett's instructions ; Adjusting YZF's Valves

each engine is different, so you have to measure your clearances and work out what shims you need after the 450 cam is in for a trial fit...



Some dealers will let you swap your old shims for new ones as well, that's what I did when I installed my 450 cam :)

My last post read the wrong way. I had it at 13 pins. Now I moved it to 14 and the bike runs great. starts cold or hot. I wish I had done this mod a long time ago. To all thanks for your help.

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