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450 exhaust cam in 426?

By schuon,
in YZ400F/426F/450F/450FX

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schuon

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I just wondered if you could put a YZ450F exhaust cam in a YZ426F or do you have to get a hotcam with steeper lobes and sacrifice reliability. It would be kind of nice to have auto-decompression instead of manual. :banghead::banghead:

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Phatjonny

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It will take you a week of blinding headaches to read that thread!! I have but 3 things to suggest to you 1) order it, 2) install it, and 3) enjoy it! :banghead:

Yes...Don't think...just buy it. I pondered over it for way too long. Just take everyones advice and just do it...

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FZ1426

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I just wondered if you could put a YZ450F exhaust cam in a YZ426F or do you have to get a hotcam with steeper lobes and sacrifice reliability. It would be kind of nice to have auto-decompression instead of manual. :banghead::banghead:

Someone can correct me if I'm wrong, but I believe the 450 cam has steeper (more lift less duration) lobes as well. In any case, it won't sacrifice reliability. The intake cam has that kind of profile already. All you're doing is matching them up.

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grayracer513

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Someone can correct me if I'm wrong, but I believe the 450 cam has steeper (more lift less duration) lobes as well. In any case, it won't sacrifice reliability. The intake cam has that kind of profile already. All you're doing is matching them up.
That's sort of a side benefit of the doing the mod. It ends up having more bottom end, if you can believe that, without giving up any of the top end, and gives the bike a wider, more smoothly delivered power curve. All in all, it's probably the single best mod you can do to a 426.
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schuon

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That would be sweet to have more reliability and bottom end. I found that thread kind of confusing, and that's why I asked this question. Is the cam a direct bolt in fit, or is there anything else you have to do other than get a decompressor plug and a cam.

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93gt

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Like you, Im fairly new to the site, and the bike. I did read as much as my eyes could take and found the vitals. Your shopping list will be 1) cam 2) shims. You will need to install the cam for a trial shim fitting before you order the shim size from the dealer. The decomp plug like the one they sell here is totally optional. You can leave the lever on if you want, some ditch it, and some leave it for clearing the cylinder. I think mine is in a box in my shed with the old cam. I have not missed it either. The biggest things to be concerned with is getting your valve clearances right, and getting the cam timed correctly. Print out the instructions to that thread, and read them over and over while youre waiting for your cam to arrive. You may not copmpletely get it from the paper, but when youre looking at the bike in front of you, apart it will all start making sense. Pay attention to the crank shaft timing mark, and the way the cam lobes are positioned as seen from the right side of the bike, NOT the timing marks on the new cam. Good luck, and if you get fumbled up there are some very smart people on here that will help you out. BTW, Im speaking of the 03 Yamaha cam, not the hotcams one.

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Florida_426

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I did the 450 DCM in 2002 :banghead: . Had no shim changes required. I do regular lash checks and change oil, Yamalube 4R every 3 hours of riding. MX rack riding only. So far everything is still in the center of speced tolerances and the bikes response is phenomenal not to mention the ease of starting :banghead: .

I removed the decompression device and lever completely and installed a

TT plug and washer. While I had the bike opened I installed a fresh piston (1 year of use) and cleaned the head, valves, springs and ports. No complaints here. Use Satch's pictures for cam orientation pictures and do the mod. You won't regret it.

Bill

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grayracer513

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Has anyone ever installed the 426 sprockets on the 450 cam?
That would be quite a piece of work, considering that's where the decomp flyweight is mounted. After you met the challenge of fixing it in place so that it worked, there's the issue of counterbalancing the weight. The cam does rotate at more than 5,000 rpm.
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Florida_426

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Tryce,

Some research was done on the grafting of a 450 sprocket onto a 426 cam when this came out in early 2003. Yamaben and Yamaha Dude did some work and measurements as well as extensive comparrisons between the cams sprocket's teeth pitch, the cam chain ride and seat and the durations of the two different lobe profiles. I remember this in the original thread that I believe got lost in a software upgrade and the consensus was it was too difficult to warrant the swap of the sprockets due to the machining and fabrication necessary. The guys at Hot Cams got in on the discussions and their cam was comming out soon. I imagine that the idea lost steam there.

What cams did you use in Stevie's 450 DTX John and I helped y'all pit on at Tunica?

Bill

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