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02 yz250f auto decomp. cam

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Hi all my son hs an 02 yz250 f, all systems healthy but i'ts crazy bad to cold start. My question is will an auto decompression intake cam solve this problem thanks chuck pittsburgh.

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My buddy has an 01 that we just put an 03 exhaust cam in with the auto decomp and it made a huge difference in starting (decomp is on the exhaust not the intake). That said it dosent mean that is your problem. The cam just makes it easier in the sense that you dont have to mess with the decomp lever and time your kick right. Now if this has been a gradualy problem getting worse all the while i would say its more likely you have a valve issue. Either incorrect valve clearence or poor valve sealing. What is the current condition of the bike and history? Hours, rebuilds?

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Hard starting cold is valve clearance but changing over to an 03+ exhaust cam is a very popular mod. Refer to your service manual to check your valve clearance or do a search. You tube has many videos on how to check and shim your valves

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You will be able to kick it over in your sandles when you are done. It makes it a ton easier to start because you could kick it over many more time with out getting tired. You still need to check the other things mentioned.

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I just put 06 YZ cams in my 02 WR. I can kick it in my nikes. I would not own this bike with the stock cam.

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I'm looking at YZ timing for my '01 WR. No way I'm doing it myself! So my question is..

How much labour am I likely to be up for to do the mod?

Just want to squirrel away some funds for next time I get my valves checked and do the mod at the same time. :bonk:

Edited by Thommo_400f

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I'm looking at YZ timing for my '01 WR. No way I'm doing it myself! So my question is..

How much labour am I likely to be up for to do the mod?

Just want to squirrel away some funds for next time I get my valves checked and do the mod at the same time. :bonk:

Most dealers will not do the timing mod on a stock WR cam. Doing it wrong can cost a lot of money in parts. Your best bet is to do the work your self and find a used set of 03-05 YZ cams or a set of hot cams with auto decompression.

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Got it. That would be a super simple thing to do. It you take it to a shop they will probably charge you a minimum of 1 hour shop time or more just because they could. I would do that myself but I guess it depends on how well you are mechanically.

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Main reason for asking my mechanic would be to guarantee it was done right....I am ok with most mechanical basics but if I get the timing wrong there is a big chance of bent valves or worse and I haven't got money to burn on a rebuild.

I may have a go at it, I'm still getting a feel for the 250f power after moving from a 250 2-stroke. I am thinking I would prefer the power hit to be lower in the rpm range as I mostly ride tight woods and hrdly ever get to WOT.

I am definitely going to look for some '03 cams, even to put away in case I decide to do it.

How do the stock '03 cams differ from Hot Cams (Stage1 & 2), are the stock ones neutral in their power curve?

Cheers.

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Not much from what I hear if all you want is the autodecompression. That is only the exhaust cam. I you want a little more power go with the intake too. I would thing the intake cam profile would work out well without the timing mod you talked about though. I don't know for fact, just guessing.

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Well for now I think I might quiz my mechanic (his son races) about running yz timing as a trial, then if it goes well I might get the '03 stage 1 intake and exhaust combo.

Thanks for the advice.

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Auto decomp cams are great - easy mod to do yourself while you're checking valve clearances, you have to pull the cams anyways if you need to shim and if you don't need to shim then you may as well time it to YZ specs which would take 5 minutes longer that just checking clearances. There's no difference in OEM cam profiles for the WR and the YZ - the difference is one tooth in the timing.

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