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dvn

Another valve adjustment question

7 posts in this topic

Hi all. Just checked my valve clearance for the first time. They were all in spec just over the tight side of the range. I have around 15 to 20 hours on the bike. My question is this: Do you think that they will get any tighter or should I be past that stage with this many hours on it? One thing that kind of concerned me was that there is no mark on the flywheel that lines up in that opening when the marks on the camshaft gears are lined up with the edge of the head. The bike runs and starts great, so I can't believe the timing could be off. Have you guys found that some of these flywheels are marked wrong or not marked at all? I did see three small lines on the flywheel but they do not line up like the manual says they should. Also the manual shows a large single line as a marker. I hope I'm not asking stupid questions but I'm new to the 4 stroke thing. Any help would be great. Thanks. P.S. This is on a 01' YZ 426.

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My flywheel marks seem to be off also, at least they don't look anything like in the manual. To check my valves I always use the other method mentioned in the manual- make sure the cam lobes are opposing each other. I have well over 100 hours on my bike and I've never had to adjust them. One is getting on the tight side but has changed very little along the way. If they are in spec I will leave them.

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They will almost defintely get tighter as time marches on. Unless, there is excessive cam lobe wear due to insufficient lubrication. If that's the case, you have a much more serious issue to address. Typically, the valves drive deeper into the head as a result of normal riding/racing. As they drive deeper into the seats, they are steadily moving closer to the cams, hence, tighter clearances. The good news is that if one uses quality oil, changes it often, and generally keeps the engine in a high state of tune, the clearance will usually almost stop changing after the first or second adjustment.

I had tried to get a valve shim co-op going here a while back so that we could trade amongst ourselves when we wanted the odd sized shims instead of having to make the .05 incremental steps. I mean, when I need to adjust my valves again and the 1.78's that are on two valves need replacing, someone else might just need these particular sized shims to bring a valve or two right into perfect adjustment. There were no takers.

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From what I gather from reading here, it seems that the values on the pre-titanium valved engines tighten up faster than the titanium counterparts. It makes sense because a heavier valve requires a heavier spring and the extra force will surely cause more wear on the valve seats (assuming the seats are made of the same material). I've got an '01 which I've had for almost a year and they're also getting towards the tight end of the spec but are definitely within spec as of a couple of rides ago. Personally if it's in spec I wouldn't worry, unless you want to order your next set of shims now so that you already have them when you need them.

I too just spun it over until the cam lobes were pointing in opposite directions.

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dvn and MikeOK,

There is no reason not to follow the manual precisely (Ego's suggestion). But to check the clearance, any position of the cam with the lobe fully disengaged will do. They are round except for the eccentric. Keep the eccentric to the side or up and the valve clearance should be the same. The advantage to the book is you can check the intake and exhaust without rotating the crank.

MikeOK,

Next time you have the valve cover off, post what your's looks like.

mwc

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You really can't order the new shims until you know what size you have. It should be done all at the same time. Listen to boit, they will not get looser. :)

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