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foxz

signs for a new cam chain?

14 posts in this topic

Hello there this is for my buddy. Hes got a 01 426 and hes had some problems starting it latley so thought it times for a cam chain. Ive done the ones on my crf's over the years, and wondering what you guys think. As per the manual it says too line it up with the I and have the lobes apart from each other. I have that and the intake cam mark is where it should be, straight up and lined with the mark on the head unit. Now my problem is the exhaust side is off too the right if your looking at it... Sure sign of it being stretched? will this cause hard starting? When i put the new chain on should i mark it all and leave it how they are now or re time everything and have both marks facing straight up. thanks

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The marks will rarely line up precisely. The test is to imagine whether it would be better aligned if it were moved a full tooth either way. The answer is usually no. Cam chain wear will result in the slight retardation of the cam timing, but even in a severe case, it can't be blamed for hard starting. That doesn't mean it shouldn't be replaced if it's been more than two years.

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its been since 01...hes not doin it strictly for this he just doesnt wana screw up the crank gear...so just leave the marks where they are...what would be cause of hard starting then...when he puts a new plug it fires right away...then goes on ride comes back soon as it starts to cool boom she wont go

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He should be using an NGK CR8E or equivalent. Using a colder plug, as some insist on doing, will cause what you're describing.

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yup hes running the plug you said..its got quite a bit of carbon on it and its pretty much brand new...the valves at in spec, so i dono what the problem with it is..any ideas?

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80% of all starting problems in 426's end up being in the carb. Is this something that just started happening when the weather got cold?

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ill have to ask him more details...but in the summer it was fine when we ridin...he also said the bike would rev up and down and choke adj. didnt do anything

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The marks will rarely line up precisely. The test is to imagine whether it would be better aligned if it were moved a full tooth either way. The answer is usually no. Cam chain wear will result in the slight retardation of the cam timing, but even in a severe case, it can't be blamed for hard starting. That doesn't mean it shouldn't be replaced if it's been more than two years.

Wouldnt retarded cam timing result in better top end and a loss of low end power?

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Retarded exhaust , yes, in small amounts. Remember that the YZF exhaust is already retarded relative to the WR by a considerable amount.

Retarding the intake is detrimental. The real issue is lobe centering.

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You can't if it has auto decompression. If it's an OEM YZ426 cam, you can, and you end up with WR timing.

Why not? Curiosity...

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Because when you retime the cam, you retime the AD unit, it doesn't work, and then you can't start it.

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