426 Cam swap problem


19 replies to this topic
  • shimla4

Posted February 02, 2009 - 05:46 PM

#1

I installed a yz450 exhaust cam in my 2001 yz426. I followed the instructions to the letter. I can kick it thru but it is very hard(no tennis shoe's). Tried to bump starting the bike, that didn't work. Went back check the valves again and re-shimmed. It still kicked very hard, tow started it in 3rd. Ran it for about 10 min(not hard). Tried to kick it agian, no luck.I have read everywhere please provide any feedback you guys might have. I am willing to bring the bike to anybody in FL or south GA that has done this mod.

  • rexbond007

Posted February 02, 2009 - 06:21 PM

#2

i think you tighten down the cam cap bolts to tight, re torque them at 85 inch lbs
for the 10 minutes it ran did you have to be on the gas?

  • shimla4

Posted February 02, 2009 - 06:52 PM

#3

After runnig for a couple min it would idle by itself.What baffles me is why does it kick so hard.

  • 642MX

Posted February 02, 2009 - 07:28 PM

#4

After runnig for a couple min it would idle by itself.What baffles me is why does it kick so hard.


How did you time it?

  • grayracer513

Posted February 02, 2009 - 09:15 PM

#5

It's hard to kick because you timed it wrong:

http://www.thumperta...078#post3706078

http://www.thumperta...040#post5378040

  • shimla4

Posted February 03, 2009 - 07:00 AM

#6

I set the motor to tdc(I) put a pen in the spark plug to make sure. Set the intake cam's marks at 12 and 3(cam lobe facing toward the back of the bike).
Installed the intake cam first at 12 then retarted it counter clock wise 1 tooth(cam lobe facing fwd). Counted 14 pins in between. The only thing that might be is that my intake cam might be turned clockwise one tooth to far but if i retard it it's not on 12 any more.

  • grayracer513

Posted February 03, 2009 - 07:33 AM

#7

Installed the intake cam first at 12 then retarted it counter clock wise 1 tooth(cam lobe facing fwd). Counted 14 pins in between. The only thing that might be is that my intake cam might be turned clockwise one tooth to far but if i retard it it's not on 12 any more.

The intake cam is the one at the back of the head, with 3 lobes on it. It is to be set with the "I" mark aligned with the head surface. Ignore the 12:00 mark for the moment, and don't retard or advance the intake cam from its standard position.

Then set the 450 exhaust cam in so that there are 14 pins between the two 12:00 marks. Back everything up a few degrees and roll the crank forward to TDC again. Check the intake to see if the stock "I" mark is lined up, then verify that there are 14 pins between the 12's. DO NOT worry that the 12's don't point straight up; they won't.

  • shimla4

Posted February 03, 2009 - 08:04 AM

#8

Thank you very much i will go and try that.

  • shimla4

Posted February 03, 2009 - 08:19 AM

#9

Sorry i stated wrong about retarding the intake cam, i retarted the exhaust cam using the intake as a reference point.I timed the intake cam as indecated in the manual.Thank you very much i will go and open it up and look to see if anything has moved. I will double check my intake install.

  • grayracer513

Posted February 03, 2009 - 10:33 AM

#10

Retarding the exhaust cam is the wrong move. If you look at illustration 1, you will see that the 450 cam should appear to be rotated one tooth farther forward, or counterclockwise from the position in which the timing marks line up with the head. This would be advanced, not retarded.

http://www.thumperta...078#post3706078

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  • shimla4

Posted February 03, 2009 - 06:10 PM

#11

I will take some pic's friday or saterday when i open it up.

  • shimla4

Posted February 08, 2009 - 10:02 AM

#12

Posted Image
So i opened it and it seemed that the intake came wasn't correct( as gray said) so i adjusted it to what you see in the pic.
Backed it up and turned it back to tdc all looked fine.The valves were checked and are in-spec, closed it up. First kick was nice and easy second i had use all i had to kick it thru(6.3inc and 270lbs). Same as before towed got it running drove it for 10min.
It idled fine. Killed the bike and tried to kick start it, no good. I didn't change the cam chain could it be that it's maybe to streched and allowing one of the cams to jump time. I will open again to see what happened.

  • grayracer513

Posted February 08, 2009 - 11:59 AM

#13

In the picture, your cams are advanced one tooth. The two cams are in the correct relationship to each. Both cams need to be moved one tooth clockwise from where they are.

  • shimla4

Posted February 08, 2009 - 02:32 PM

#14

Posted Image
How about this i had it like this the first time maybe there is to much slack in the chain.

  • grayracer513

Posted February 08, 2009 - 05:10 PM

#15

The picture is a bit out of focus, but that looks right as nearly as I can tell.

  • shimla4

Posted February 11, 2009 - 06:43 PM

#16

Gray do you think i can turn both cams 1 tooth more,clock wise? I put a brand new plug in.At this timing i still can't just kick it thru or start it,not even push starting it(way to much compression the wheel just drag) needs to be towed. When running it feels so good and idles by it self. I read where you explain about the degree's it needs for the AD to effectively work, i am wondering if it's still only just that 1 tooth off. I am losing hope.:foul:Or $200 for the dealership to look at it.

  • grayracer513

Posted February 11, 2009 - 07:14 PM

#17

What part number is the cam?

  • shimla4

Posted February 12, 2009 - 07:43 AM

#18

Would the part # be stamped some where since i bought this on e-bay?

  • grayracer513

Posted February 12, 2009 - 07:47 AM

#19

No, I don't think so.

  • shimla4

Posted April 04, 2009 - 05:45 PM

#20

Just a quick update, I installed a new cam chain and redid the cam timing.
Buttened everything up and it started after 5 kicks. Rode it around it started from there on easier. Thanks for all the help.





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