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Auto Decompression cam

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I want to upgrade my 01 WR to use an auto decompression cam. There is one on ebay right now, its from a YZ, I am pretty sure I can use this with out changing the intake cam to YZ also but I just wanted to make sure. What do you guys think and how is the YZ timing going to effect the way my bike runs?

Thanks

TonyC

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tony,

you only need the YZF exhaust cam. intake cam stays the same.

check the exhaust cam part number at

http://www.thumperfaq.com/autodecomp.htm

you want the '03 (or '04...) YZF cam, not the WRF type; subsequently install it to YZF timing per the FAQ page above.

performance with the YZF timing will be improved across the RPM range, provided that you have a more open exhaust than the stock plugged up WRF exhaust. so your exhaust options are: unplugged WRF exhaust (heavy and very loud, but has spark arrestor), YZF exhaust from '01 or '02 YZF (cheap if bought used, light, but still pretty loud, and no spark arrestor), MX aftermarket exhaust like DrD (expensive, light, great performance, no spark arrestor), off-road aftermarket exhaust like the FMF Q (expensive, light, good performance, includes spark arrestor, meets most state's 96dBA sound level limit right out of the box).

the "cheapest" "best" option for trail riding is probably to get a stock YZF exhaust (US$50-75), and then fit it with one of the aftermarket spark arrestor caps.

other than that, you will likely have to tweak the jetting a bit to accomodate the new timing setting. generally this means a bit richer -- start by raising the needle one notch (i.e., moving the little 'C' clip DOWN one groove towards the pointy end of the needle).

after installing the '03 YZF auto-decompression cam you may want to remove the manual compression release lever and cable assembly. as for the manual release mechanism in the head, you can leave that there or remove it and replace it with a machined aluminum plug like the one sold at the TT store. i left the manual release mechanism in my cylinder head for the sole reason that it can still be manually pushed open in the event that i drown my bike and need to get the water back out.

jim aka the wrooster

'01 wr250f

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Thanks WROOSTER! I will use the stock WR exhaust with out the baffle but I do on occasions plug in a promoto billet baffle when I want to be stealthy, would it be ok to run that from time to time?

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Thanks WROOSTER! I will use the stock WR exhaust with out the baffle but I do on occasions plug in a promoto billet baffle when I want to be stealthy, would it be ok to run that from time to time?

hmmm, let me give you an analogy... put on your sneakers and go for a run with a sock stuck in your mouth. let me know how you're feeling after the first 500 meters. your bike will feel the same way.

jim aka the wrooster

'01 wr250f

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well, the point was that human physiology employs the same tract for inhalation and exhalation and thus the analogy was based around your lungs being unable to get rid of excess CO2... but never mind; your post was funnier. :cry: :cry:

jim aka the wrooster

'01 wr205f

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Ok I get it I cant use the baffle if I want the bike to run right. WROOSTER you r analogy was appropriate as for the other analogy, its funny how quickly ones mind can turn to anal! LOL :cry:

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