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yzguy459

?? about hotcams going in 01 yz 426

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This is my first time going through the engine, im putting in a wiseco piston and in/ex hot cams on my 2001 yz426. i was just curious about the valve clearance. since the hot cams have slightly bigger lobs on them does that mean i have to get smaller shims to keep the clearance the same? Oh, and i was wondering wat the opinions r on the titanium 4 silencer with a powerbomb header, good sound? good power jump?

Thanks

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The exhaust you mention is a good one, and its biggest benefit is not in th eincrease of peak power, but in how wide and flat the curve will be.

If the increase in lift means anything to valve clearance, it would mean that the shims may need to be larger, not smaller. Why? because there is often a limit to how tall the cam can be for design reasons, and they are often built very nearly that tall stock, again for sound mechanical reasons. In that case, lift is added by making the base circle smaller, not by making the lobes taller. Lift is the difference the height of the cam to the center of the shaft at the low spot, or heel, and the height of the cam from the shaft center to the top of the lobe.

Most times, YZ4** cams are ground with the base circle at a diameter very similar to the OEM cam, so the shims will be very close to, or even the same as, if you're real lucky, the ones you have now. There is, however, no way to know what shims will be needed to adjust the valve clearance without assembling it with the shims you currently have and measuring it.

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While the hotcams have more lift (the "pointy part of the lobe is taller), the base circle (the round part of the lobe) is actually a bit smaller than the stock cam. You will need to reshim, but will likely need thicker, not thinner shims.

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This is my first time going through the engine, im putting in a wiseco piston and in/ex hot cams on my 2001 yz426. i was just curious about the valve clearance. since the hot cams have slightly bigger lobs on them does that mean i have to get smaller shims to keep the clearance the same? Oh, and i was wondering wat the opinions r on the titanium 4 silencer with a powerbomb header, good sound? good power jump?

Thanks

All that stuff sounds good to me. I have a Wiseco piston, hot cams, and the T-4 exhaust with the p/b header.

You will have to shim up for the hot cams. Check with you local Honda shop, they normally have a good selection of shims (same shims as the CRF450).

The FMF exhaust will broaden up the power. Actually, the stock header with the T-4 slip on will have more punch. The p/b header with the T-4 creates a nice smooth hit. I've tried it both ways, and prefer the p/b header. And it sounds great. :thumbsup:

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I had to go with thicker shims as well. The exhuast cam needed the thickest ones compared to the intake. The ti 4 exhaust is really loud. You may want to look into getting a quiet core for it.

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The ti 4 exhaust is really loud. You may want to look into getting a quiet core for it.
That depends on the length of the can. The 17" one on my '03 is roughly 99-100 db.

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I think HotCams does indeed estimate what a shim change from OEM spec would require, and provides a note of this suggested baseline change in the box. This tells you what direction you need to go with shims (for purchase/order), prior to opening the engine up.

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You may want to look into getting a quiet core for it.

The 14 inch isn't that loud when properly packed. Mine is 100 db. :thumbsup:

The quiet cores absolutely kill the bottom end. :ride:

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Did any of you fellas with hotcams degree them in, or just install them with the setting from hotcam?

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I installed per their marks since I don't have the equipment to degree the cam and haven't had any issues... but shoot at your own risk. :thumbsup:

J

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