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wrenchard01

Sign off real early w/ wr timing?

6 posts in this topic

Hey, I switched my 00 YZ426 to wr cam and it seems to sign off real early, riding in the woods, and I cant goose the front wheel off the ground off the bottom like my 02 KTM 300 EXC will, plus I have less top end and have to shift where I wouldn't have to on KTM,this sucks! stock gearing, 14/49 any help Ya'll?

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You did not specify which WR cams you used. The 2000 model was a 400, and would have had milder grind numbers on the cam just because it was a smaller engine, although perhaps not much.

Using WR cams in place of YZs SHOULD produce less top end, more bottom end, and a lower horsepower engine that runs smoother at low speeds. Compare your power output to a WR426, not a 300cc 2 stroke. If you think that it does not compare favorably with a WR, double check the valve timing. Advanced cam timing will add low end at the expense of top. Being a tooth off toward the advanced side on the intake is unlikely, however, since doing so very quickly brings the valves into contact with the piston. There could be some differences in the way the crankshaft cam sprocket is indexed.

Another possiblity is ignition timing, either the static setting, or possibly the mapping used for the YZ could be wrong for a WR.

See if someone who has done this swap responds with more info.

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I'm sorry, I switched the exhaust cam to wr setting by retarding it 1 tooth, this is correct right? seemed to really kill the top and I just can't beleive that this engine is so dead off the bottom being what it is . many made it sound like it would be a handful, on the contrary, where's the beef?

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alright, ive done the switch on an 00 yz426. something sounds wrong. im not sure which way the cams spin :thumbsup:

but when your looking at the index marks on the cams, stock the marks are lined up (at TDC)... for WR timing, you want to rotate the exh cam COUNTERCLOCKWISE 1 tooth so the middle mark is at around 11:30 (stock is 12).

i believe WR timing is advanced 1 tooth, you probably did retard the exh cam. mine has some serious bottom end, and more top and overrev than i really need.

it does anything but sign off early. your timing is off

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just like tool said.

WR->YZ timing retard 1 tooth (clockwise)

YZ->WR timing advance 1 tooth (anticlockwise)

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To help clarify, the cams and crank and chain rotate in a forward direction, like the wheels do.

If a cam is advanced, it means it is getting to the point of opening the valves sooner, in advance of the rest of the engine. Retarded, it gets there late, after the rest of the engine.

Thus, to advance the exhaust cam rotate it one tooth forward while the crank and intake cam stay in position. Backward to retard, as if the engine had moved forward while the exhaust cam had stood still.

Sounds like you went the wrong direction to start with.

NEVER advance the intake cam on any engine without VERY CAREFULLY checking for adequate clearance against the piston as the valves open!!

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