Yzf450 timing HELP NEEDED intake cam doesn't line up and backfiring


17 replies to this topic
  • Joeturabian

Posted June 25, 2013 - 06:43 AM

#1

I recently took apart the top end of my 2006 yzf450 to change the shims. After I finished and put it back following every guide I could find telling me to put it to tdc etc. I have done everything exactly the way I should but the intake camshaft does not line up with the head like its supposed to. Now it won't start and it keeps backfiring on me. Yes specs are good, it's at tdc, shims are sitting correctly, chain is on properly everything is done the way it should be. What could be the problem ???

  • Icon

Posted June 25, 2013 - 07:11 AM

#2

Did you replace the timing chain? A worn chain will make it impossible to line up the marks accordingly

  • angelski628

Posted June 25, 2013 - 02:17 PM

#3

wow what a small world! I took apart my carb and cleaned it 3 times this past weekend and my 06 yz450 wont start. I took off the valve cover to see if it was a cam issue and my intake cam is not aligned when my piston is at tdc. just curious by the way if your flywheel has three tick marks instead of one to tell you that you are tdc?

  • grayracer513

Posted June 25, 2013 - 04:12 PM

#4

They all have 3 tick marks. the two at 11:57 and 11:58 are for ignition timing checks using a strobe. Only the one at 12:00 o'clock is TDC.

  • Joeturabian

Posted June 25, 2013 - 05:47 PM

#5

I didn't replace the cam chain, could that cause it not to start and backfire ?

  • goosey

Posted June 27, 2013 - 10:01 AM

#6

Joe did you confirm you're using the mark at 12 oclock as greyracer said?

  • Joeturabian

Posted June 28, 2013 - 04:38 AM

#7

I am using the mark furthest to the right, the I on its own. Shims are perfect, have swapped the crank 360 degrees incase I'm on the wrong firing stroke. Still showin no signs of life at all just backfiring. Has spark, but I put in a new coil pack off the same bike and it started with the help of aero start for about 3 seconds then died again and won't start since. Starts for a few seconds after about 15 minutes of straight kicking. If anyone has any advice would be much appreciated as its not my bike and I was doing the favour for a friend and now I can't give it back to him like that

  • crf450319

Posted June 28, 2013 - 05:59 PM

#8

Put a zip tie or long screwdriver down the spark plug hole so you can visualize TDC, then make sure the marks on the cams/cylinder head deck line up.

The last 4 or 5 times I've replaced my cam chain, piston or my buddies I haven't paid any attention to the marks on the crank. If you can visualize TDC, you're good.

Of course, if you want to see if they (mark on the crank) line up, then do it.

TDC
Cam lobes somewhat opposed at 11 & 2 o'clock (ish)
Mark on each cam at 12:00
Mark on intake cam (at cylinder head deck) to the intake side
Mark on exhaust cam (at cylinder head deck) to the exhaust side

Posted Image

Posted Image

Edited by crf450319, June 28, 2013 - 06:26 PM.


  • Joeturabian

Posted June 29, 2013 - 12:26 AM

#9

Thanks for the photos mate appreciate the advise. But yeah like I said I've everything you said, everything the manual says. Checked valve specs etc everything is where it's supposed to be. However, while it was at tdc it was showing no life at all while kicking just backfiring every now and then. But then I put it at the first line > |-| | of the crank and it fired and ran for about a minute with only the fuel in the carby (tap turned off). Ever since then it hasn't started again on those marks, everytime I take the plug out its soaking wet. Moved it back to the correct line on the right and again no life. I can spin the cam inside the chain so it is daily stretched, and because of that the intake line sits pretty far under or above the flat surface of the head. Could the chain be enough to cause it to be out or time and not start ? Moving it one tooth up brings it way higher then it should be

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  • crf450319

Posted June 29, 2013 - 03:52 PM

#10

Thanks for the photos mate appreciate the advise. But yeah like I said I've everything you said, everything the manual says. Checked valve specs etc everything is where it's supposed to be. However, while it was at tdc it was showing no life at all while kicking just backfiring every now and then. But then I put it at the first line > |-| | of the crank and it fired and ran for about a minute with only the fuel in the carby (tap turned off). Ever since then it hasn't started again on those marks, everytime I take the plug out its soaking wet. Moved it back to the correct line on the right and again no life. I can spin the cam inside the chain so it is daily stretched, and because of that the intake line sits pretty far under or above the flat surface of the head. Could the chain be enough to cause it to be out or time and not start ? Moving it one tooth up brings it way higher then it should be


I should've mentioned that I replace my cam chain every 50 hours or so, as a result I've never had an issue with cam chain stretch. Cam chains are cheap insurance against catastrophic failure and in all of the chains I've removed there is always more than a couple links that bind. Put a new chain in that thing and let us know what happens....

  • NitrousR1

Posted July 05, 2013 - 05:23 PM

#11

That chain could make it not start. I've been writing up a timing chain for every valve adjustment I sell, for $20 it's cheap insurance. U will be shocked how much it's stretched compared to the new one. I myself replace them pretty often, 3 times for every time 1 time I replace a piston. Never had a issue with it myself but fixed many others with a stretched chain

  • Joeturabian

Posted July 08, 2013 - 12:19 AM

#12

I replaced the chain, was soooo stretched compared to the new one. New ones on and everything looks alright, feels slightly harder to kick now but it's still not starting!! Found out today that the owner was riding and the bike suddenly started becoming weird on him, turned it off then took about half hour to start again. After that he said while riding he had to keep the revs way up or it would just die on him. Ever since then hasn't started. Has heaps of compression and everything to do with the motor is all good. I don't think it could be a carby issue because I have sprayed aerostart down the air filter hole and in the spark plug hole and absoloutley no life at all. What do you think ?

  • thefickler

Posted July 08, 2013 - 05:38 AM

#13

How do you know the compression is adequate? I would say perform a leak-down test, and see what those results say. It will be a good way to rule out some of the possibilities.

  • goosey

Posted July 08, 2013 - 07:09 AM

#14

ohm out the coil to spec, and if it looks good, make someting to extend the plug cap to the plug so the plug cap/coil isn't anywhere near the frame or motor - in case it's cracked or ripped and jumping out to ground.

  • Joeturabian

Posted July 09, 2013 - 11:18 PM

#15

I tried a differet coil pack of the same bike. Nothing, not even the slightest little sign of life. I also have a wrf450 2006 that I have repaced the top end. New piston bore resleeved shimed and all new gaskets, put it together and surprise surprise it doesn't start aswell. Same deal everything's to spec, new plug, heaps of compression, even sprayed some aero start in the air box and nothing. They say charge the battery in the wrfs or they don't start which I have done. So what am I doing wrong ?

  • Joeturabian

Posted July 09, 2013 - 11:22 PM

#16

First time I was kicking it, it kept backfiring. So I rotated the timing to the next stroke and still backfiring

  • goosey

Posted July 10, 2013 - 04:51 AM

#17

piston in backwards maybe

  • Joeturabian

Posted July 10, 2013 - 05:40 AM

#18

Deffinetly in the right way





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