Timing in a pinch

2 replies to this topic
  • JKep44

Posted May 14, 2005 - 01:08 PM


I recently purchased a 2001 YZ426 with tranny problems. I replaced the gears and now have completed assembly all the way back to timing the cams to the crank using an article in a dirt rider mag for torques. The problem that I have is my manual off of e-bay has not arrived yet and I am unsure of cam positions. Both cam sprockets look the same with three timing marks each. One marked with an E (for exhaust) one with an I(for intake) and another with no letter designation. In addition to this on the flywheel there are three marks with no letter identification. Two of the marks on the flywheel are connected by a horizontal line. I would guess that these are the firing marks and the third mark is the TDC, but I am only guessing. Any help would be greatly appreciated.

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  • grayracer513

Posted May 14, 2005 - 01:35 PM


You are right about the flywheel. Folks here refer to those as "H" and "I". "I" is TDC. To start with, with both cams sitting in place and the slack pulled out on the front run of the chain, the intake should sit so that the I mark is lined up with the top surface of the head. The exhaust cam is where I'm a little foggy on the procedure. I'm thinking that the way it should be done with a stock YZ exhaust cam is to align the E mark with the head surface, but a lot of the guys with 426's count pins between the mark at 12:00 on the timed intake and the mark at 12:00 on the exhaust. That may only apply to using a 450 cam, though.

You can download a 426 manual from http://motoman393.thumpertalk.com/ and clear up the whole thing.

It's in the Misc section on the Tech Articles page. It's in PDF format, so you'll need Acrobat Reader (free from Adobe.com if you don't have it)

Errata:The manual pages are actually in bit map format (.bmp). Any Windows computer will open them without additional software. Mac OSX needs Adobe Reader becasue the native bit map viewer, Preview doesn't like the files sometimes.

  • JKep44

Posted May 14, 2005 - 03:24 PM


Hey thanks a lot for the tip! It doesn't get any easier than having the book.

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