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jameskiehl

which lifters do i use for rebuild?

3 posts in this topic

guys,

when we last talked, i was tearing apart my top end of my 98 wr and in doing so i discovered that i had cooked my piston, thus ruining the piston, cylinder and head assembly including the valves.

i have been diligently purchasing repalcement parts, OEM yamaha , to build a brand new top end. i have the new poston, rings, cylinder, head, valves and assorted hardware. ( i even bought the valve spring compressor to seat the new valves myself...).

I can do all of the work but i am at a loss to figure out this one step. when you look at the breakout of the valve assembly, it shows the lifters and spacers that sit between the valves and cam lobes. when you look at the parts list, though, it lists two different sets of lifters for the same part # with only one distinguishing feature. they show a set of 'blue' lifters and a set of 'yellow' lifters. even the guys at the service shop couldn't tell me the difference between the two. i know there are lots of different sized spacers, but no idea what the lifters mean.

(you can get to the valve assembly breakout diagram here)

i think that in order to do the assembly correctly, i need to put the cams on with the lifters on, measure the clearance, figure out what spacers i need to raise the lifters into specification, install them and reassemble the cam assembly.

can anyone tell me what the difference is in the 'blue' and 'yellow' distinctions of the lifters? or any other info to correct my misguided thinking would help.

thanks a BUNCH,

Jim

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Well, which is your favorite color??????

All kidding aside, I don't know, but guess that there is a slight (.00001) difference between the two to allow for machining tollerances. Need someone with real life experience to weigh in on this one.

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The difference IS in the thickness of the portion of the "bucket" that the cam (and on the opposite side, the shim) ride on. I don't know which is thicker, but I believe it's by about .050 inch. They did this at the factory and select for each valve in each engine to cut the number of shims they need to stock and use in half. Look at what came out of your bike and order what was there...or order all yellows or all blues and if one stacks up too tall, exchange it. With a new motor, it really doesn't matter unless all the tollerances run against you, then one could be too thick or too thin.

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