Top end Q's

So I am in the process of putting my '02 426 back together, and have a few questions. I saw on the Hotcams instructions that basically the break in was to go for a mellow trail ride for a half hour. What about for the piston/rings, will that same break in work?

Also, the exhaust cam has the autodecompress upgrade, and was wondering what do I do with the manual decompress shaft that came with my bike. Does it go back into place, and just not get used, or do I remove it and put a cap on it? There are no specs on what to do with it.


The decomp shaft can go back in place if you choose. Something has to go in there, after all. If you use the old shaft without modification, you need to be sure to include the coiled return spring, too, so the shaft won't rotate and beat on the valve lifter. Alternatively, you can cut off the half-round inner end, cut off the lever arm, and put it in that way. Then, you won't hav eto slide it out of the way should you need to adjust that valve.

You can also spring for one of these:

...or remove the oil seal and insert an 18mm cup plug (automotive freeze plug).

You can even put the whole decomp thing back together, but you'll never use it.

On break in, new cams should normally be kept at speeds above idle for the first 20 minutes, and otherwise treated normally. Rings need pressure to seat. I break all my stuff in by warming it up for the first time fairly gently, then running it pretty hard for the first hour. Avoid lugging the engine around, avoid running near max RPM, and don't run it at more than about 80-85% percent of its capacity. DO NOT take it too easy on it either. After that, ride it.

Sweet! Thanks. It will be back together on Sun.

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