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23 replies to this topic
  • feirmeoir

Posted April 25, 2008 - 08:23 PM

#21

Lol...let's crack some of those open and talk about who makes the best oil.



:thumbsup: Yamaha. The answer to your next question is :ride: 20w40.

  • grayracer513

Posted April 25, 2008 - 09:07 PM

#22

The "12:00" marks are NOT significant. Align the E mark on the exhaust cam with the gasket surface, and align the I mark on the intake with the gasket surface. If you are using an old chain, and you really think you have a condition where the cam is just as far off one way as the other, the more retarded of the two is probably where it belongs.

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  • manther

Posted April 26, 2008 - 08:55 PM

#23

The "12:00" marks are NOT significant. Align the E mark on the exhaust cam with the gasket surface, and align the I mark on the intake with the gasket surface. If you are using an old chain, and you really think you have a condition where the cam is just as far off one way as the other, the more retarded of the two is probably where it belongs.


Hey thanks for all the technical info GR. Sorry we got off on the wrong foot.

  • SJMC_DON

Posted May 07, 2008 - 02:05 PM

#24

Let's go back and see if we can start here:
First, the timing chains in these engines are rather long, top to bottom, and a worn chain can cause the cams to retard by several degrees. Secondly, no great care is put into marking the cam sprockets to one degree precision, either. But the cam gears have 32 teeth on them, so each one the cam would be off by would be 11.25 degrees multiplied by the 1:2 ratio to the crank for 22.5 degrees of crank rotation. The marks are placed so that they are near the place where they should be, but hardly ever line up "exactly". Normally, the mark will be a little off, but moving it a tooth either way makes it much worse.

The next thing that must be looked at in timing cams is that the crank can turn nearly 10 degrees without moving a cam if the tensioner is off the engine. When you think you have the engine timed, rotate the crank backward until it starts to move the intake cam, then manually rotate the exhaust cam back until it draws the chain tight, and then do the same to the intake. After that, rotate the crank forward until it arrives at TDC again. This will pull both cams into the actual position they would be in were the engine running, with the front and top runs of chain drawn tight. See what the marks look like in that position. Not doing this screws a lot of guys up.

If you can't get it it to look better in one position than another, and it has been more than 2 years since the timing chain was replaced, you most likely need a new one. The crank gear is cut directly on the crank, and is not something you'll enjoy replacing if it gets eaten by an old chain.


This is by far the most informational post I have read on TT... I am in the process of putting YZ cams in my WR and what you have explained is exactly what I am dealing with in terms of getting everything aligned and timed with the chain tensioner off only to have it go out after install of the tensioner. I am installing a new chain tonight and will use your method described to align the cams with TDC according to the rotor before installing the tensioner... many thanks:worthy: :eek: :p





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