2000 426 cam help please... Now with pics...


16 replies to this topic
  • jimmydoorlocks

Posted March 23, 2009 - 06:30 PM

#1

I just spent an hour and a half reading threads about cams and couldn't find the kind of thing I'm looking for, so I'm going to post a question. Sorry if this seems redundant.
A couple months back, I picked up a 2000 yz426 that had dropped a valve and wrecked the top end. I've been slowly getting the parts I need to fix it and finally got the last bit a couple of days ago. Today, I went out to my shop to put the whole thing back together and make it run.:lol: Today was supposed to be the best day ever. Unfortunately, it didn't work out that way.:usa:
To get to the point, I installed the cams according to the directions in the manual. Everything seemed to be going fine, until I noticed that the cam lobes were 90 degrees out of phase rather than the 180 that I think they should be. I double checked everything. The "I" mark on the rotor was lined up with the index mark on the case. Both cam sprockets had the "E" towards the exhaust side of the head and the "I" towards the intake side, and the punch marks were lined up with the top of the head. The exhaust cam is just a regular cam, not one with the auto decom on it.
Is this normal? Did I read something wrong in the manual? Could one or the other be cams off a different bike, even though they fit? Is there a way to set the timing properly in this situation?
I wish I had pics. I was just too frustrated by the end of the day to take any. :lol:
All thoughts, ideas, or opinions are appreciated. :thumbsup:
Thanks!!

  • Birdy426

Posted March 23, 2009 - 07:14 PM

#2

The separation between the lobes isn't supposed to be 180 degrees...it's something like 108 degrees, so it sounds like you are in the ballpark. The shop manual shows an illustration showing how the lobes should look when properly timed.

  • jimmydoorlocks

Posted March 23, 2009 - 07:40 PM

#3

I was so frustrated today that I thought I'd give it a few days before going back to my shop to have another stab at it, at this point, I'm chomping at the bit to get back out there and give it another go.
I've got the good shop manual and I just thought the cams looked wrong (as did my buddy who was helping). They appeared to be almost exactly 90 out, but if they're only supposed to be 108, then maybe they were just a tooth off. I'll try again, and take pics tomorrow.
Thanks.

  • jimmydoorlocks

Posted March 24, 2009 - 10:30 AM

#4

So, I got the day off today and just couldn't resist going out to my shop and tearing into the bike again. This time I took some pics. Here ya go.

Posted Image

Posted Image

Posted Image

What do you make of that? Am I nuts or is something very wrong here? I think new cams are in order, but I'd still like to know whats going on. I can't find anything that looks like that in the manual or on any website.
The pics were taken with the cam chain off (obviously), but I lined up the index marks (approximately) the way the repair manual says to for the pics.

  • spark250

Posted March 24, 2009 - 11:12 AM

#5

I don't think new cams will help here? Assuming these are the right ones for the application I don't see how new ones would change the phase on the cam lobes. You seem to have everything correct on the top.

I'm not positive but I think those cam gear are just pressed on to the cam, so I'm just thinking as I type here, but maybe during the initial engine failure it spun one or both of the cam gears?

so maybe some new cams could help! That would be an expensive guess though.

  • grayracer513

Posted March 24, 2009 - 11:24 AM

#6

Am I nuts or is something very wrong here?

Without ruling out the possibility of there being some problem with your sanity, those cams are pretty obviously not indexed correctly. The gears have both slipped forward on the shafts, and the cams will have to be replaced.

But one has to question why this is so. Did the cams seize in the head?

  • jimmydoorlocks

Posted March 24, 2009 - 01:41 PM

#7

Without ruling out the possibility of there being some problem with your sanity, those cams are pretty obviously not indexed correctly. The gears have both slipped forward on the shafts, and the cams will have to be replaced.

But one has to question why this is so. Did the cams seize in the head?


Thanks Gray! That was the answer I was looking for :thumbsup: ...and we can leave the argument of my overall sanity to my ex girlfriend. She has plenty to say on that topic. :lol:
As for the cams seizing in the head, I'm not sure. I would have to assume that there would be damage to both parts (cams and head) and/or they would have been difficult to remove. In this case, everything seems to be OK but the indexing. Obviously something happened, I'm just not sure what it is.
Could the cams get off like that in very small increments over time, or is it more likely that it was one single major event that caused the movement? I actually did grab the gear with one hand and the camshaft with the other and try to turn it the other day when I noticed the problem, and it didn't move at all. So, at least it isn't noticeably loose.
I'd like to figure out what caused the problem. I have a few ideas, but nothing concrete. Seems like a good time to do the ADC upgrade :usa:.

  • grayracer513

Posted March 24, 2009 - 03:07 PM

#8

...we can leave the argument of my overall sanity to my ex girlfriend.

I'll look her up if I ever need more info on that.

The most probable cause for the cams being that far out is for them to have seized, but there should be some evidence of that. Then again, I'm thinking this may not be the original head anymore, so you would have only the cams to look at in that case. It's possible that the valve head bouncing around in the combustion chamber could have jammed another valve shut when the cam wanted to open it and that that could have caused the slipped sprockets.

But you're right, you may as well go with aftermarket cams and get AD out of the deal.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • jimmydoorlocks

Posted March 24, 2009 - 03:38 PM

#9

Then again, I'm thinking this may not be the original head anymore, so you would have only the cams to look at in that case. It's possible that the valve head bouncing around in the combustion chamber could have jammed another valve shut when the cam wanted to open it and that that could have caused the slipped sprockets.


That's kind of what I'm thinking happened. Did you remember my previous posts and the valve bouncing around in the chamber, or are you just that good :thumbsup: ?

I'm thinking of replacing the cam chain since I'm going to be half way there anyways. Any opinions on cam chain brand? The best price I've found so far is for a YBN on ebay ($36 including shipping). I don't want to replace old with crap, but I'm on a budget.
Thanks again!

  • grayracer513

Posted March 24, 2009 - 07:46 PM

#10

Any opinions on cam chain brand?

Yamaha.

  • gbalias

Posted March 24, 2009 - 08:22 PM

#11

cams:

http://cgi.ebay.com/...sQ5fAccessories

  • yzhaulin

Posted March 24, 2009 - 10:25 PM

#12

Jimmy, It looks like your exhaust cam has moved on the sprocket, I went out and took some pics of my stock cams from an 01 426. Look at the lobe position from your ehxaust cam to my cam compared to the timing marks.
Exh cam pic.
Posted Image
Int cam pic.
Posted Image
Both Cams.
Posted Image

  • jimmydoorlocks

Posted March 25, 2009 - 08:24 AM

#13

Thanks for the pics. That's what I was looking for confirmation of. I think I'm ordering new cams today. Thanks again!!:thumbsup:

  • jimmydoorlocks

Posted April 08, 2009 - 02:53 PM

#14

I'm like a kid on Christmas eve.:excuseme: UPS delivered my new cams, OEM cam chain, and flywheel puller yesterday and I'll be heading to the shop first thing Thursday morning to do the install...and hopefully get my bike running. :confused:
I was just wondering if anyone had any additional tips or tricks for me to ease installation or assembly.
I think I'm pretty well prepared. I have done a fair bit of research on TT (the amount of knowledge on here is unreal), have all the tools I should need, a good shop manual, and all day to get it done. Any advice would be appreciated. :thumbsup: Thanks!!

  • grayracer513

Posted April 08, 2009 - 07:40 PM

#15

http://www.thumperta...405#post3150405

http://www.thumperta...845#post7467845

  • jimmydoorlocks

Posted April 09, 2009 - 08:17 AM

#16

Thanks Gray! :thumbsup:

  • BASSic

Posted April 09, 2009 - 08:39 AM

#17

Do you have a new gasket for the tensioner? I was hoping to reuse it, but I was being careful and it still split into several pieces when I removed the tensioner.





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