Auto decompression upgrade on 02 wr 426f
Posted February 26, 2014 - 07:12 AM
Posted February 26, 2014 - 07:55 AM
I don't recommend using the stock Yamaha cam for this purpose anymore because the aftermarket cams made for the earlier engine fit them correctly, can be timed in the normal fashion, and are less expensive. During the 3-4 years it took the aftermarket to catch up, it was a good idea, not so much anymore.
It's just a whole lot simpler, and you can select what grind you want (YZ/Stage I or stock, or whatever).
Posted February 26, 2014 - 08:53 AM
Grayracer has provided a lot of accurate and help info over the years. While I agree that the aftermarket cam may "fit" better (I think you mean the tooth pitch in the sprocket), there are quite a few successful updates with the OEM cam. Instructions posted on this site for the update are very good and you only need to change the exhaust so aligning the cam to proper timing is not that hard. Biggest thing here is the cost to value. If your talking new the OEM may be more, but on the used market I haven't seen any aftermarket exhaust only cams for the 400/426 with auto-decompression that are cheaper than the occasional OEM cam. The original instructions were written in '03 and reference using the '03 cam. I think the question here is: if using OEM cam(s) what years work and, if different, which are the better choice?
By the way, my '98 400 has been using an '05 YZ cam for 8-9 years with the OEM Chain and, so far, no problems.
Posted February 26, 2014 - 09:24 AM
Despite any protest to the contrary, everything I said is fact, and my recommendation here stands.
Posted February 26, 2014 - 02:03 PM
No disputing your facts, My comment was in relation to the cost vs. value for a bike of that age. I'm hard pressed to spend a lot of money on my '98 given the resale value. If it's broke I spend the money, that's easy. I the case of replacing the cam for auto decompression , if I can find a used exhaust cam in good condition (good condition in this case is equal to or better that what was working) for 40% of the new part that's where I'm going. And it may only be the choice for me, and that's cool too!
Edited by tcmII, February 26, 2014 - 02:04 PM.
Posted February 27, 2014 - 12:49 PM
I agree with that, but a lot of the used parts I've seen purchased lately have been a little flaky. Cams that have too much wear on the lobe nose can cause problems you don't want, and it's a PITA dealing with the stuff if you have to reject it.
Posted February 27, 2014 - 04:13 PM
Edited by supasupa, February 27, 2014 - 04:14 PM.