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01 YZ250F, Advice would be appreciated!

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Hey My friend is giving me his 01 YZ250F and ulimited money to do a rebuild on his bike, He wants an Athena 290 BigBore kit, and i talked him into getting an FMF powerbomb exhaust header.i have so many questions i dont know where to start. Is athena a good product?

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Athena is a good choice, but you will be setting your self up for failure by just throwing on a a BB kit on a 10 year old crank. You will need to start at the bottom and rebuild the entire motor.

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That was the plan was going to send the bottom end in for crank and bearings.

will the 290 kit require a new con. rod? or will it come with one?

Also will the powerbomb header be breathable for the big bore kit?

what about the carb? should it be bigger?

Edited by GB5291

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and none of you TT Legends give me any of that newb bs. I came to you for advice

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Be patient my friend a lot of the senior guys check this site after they get off of work. They are more than willing to help and give you or anybody else as much advice as possible. The big bore kit will not come with a new crank but you can purchase a whole other rod/crank kit. People have mentioned before that when you do get the kits is to have them sent out to be balanced. You could step up to a stroker kit but a lot of people don't recommend it unless it's done correctly

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so if i send the botom end in i might as well give them the jug, piston, rod bearing ect. to put on? will my stock head go on the big bore kit? with stock valves n cams?

I think someone put an 03 ehaust cam with automatic decomp. in it, because the manual decompression assembly was pulled out and left a gaping hole above the exhaust, and it blew out oil and exhaust. i baught a plug for it on ebay, works fine.

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I wouldn't send it all in. Hot Rods makes a crank kit and they say it is already balanced for a stock piston. How much work are you willing to do? Big bore kits are supposed to be a bolt on kit and no modifications required so yes your stock head should work as far as valves go. Have they ever been shimmed? Have they ever been checked? Some guys say shim them once then replace them after they become out of tolerance after that. If you do replace the valves the seats need to be cut so a machine shop will have to do that. If your buddy gave you an open checkbook there is a lot you can do!!

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Don't want to sound rude but how strong are you mechanically? Go to YouTube and look up Johnnysshop. He does a complete rebuild on the YZ250F and shows how to tear down the whole engine and replacing the crank and all the bearings. There is a whole series of stuff so reserve a couple hours of your day and watch his videos.

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You should be able to find a complete kit online that comes with the big bore kit and a hotrods heavy duty crank. I would do that. Then send the head off to be machined and have new valves installed. For cams, go with stage 2 in. and stage 1 ex. This will really help you get the power out of that big bore kit.

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Get the crank rebuilt, it's about half of buying a new one...unless of course the guy is made of money...but if he does have an open cheque book, why do up a steel framed 01 when he can just buy a new(er) aluminum framed beast.

When you send the bottom end out to be rebuilt you are NOT sending the cases with it, you're just sending the crank....

New crank bearings for sure while you're in there or you'll have a weak link.

Check all the gears, make sure none of the dogs where they mesh are rounding or you'll be back in there before you know it replacing tranny parts.

Big bore kit usually comes with a wristpin and clips so you're good there.

Definitely check your valves because if it has a lot of hours on it - this will now become your weak link.

No you don't need a bigger carb, you might actually have to lean out your jetting by going a jet size smaller to get it dialed in right, but all this will depend on how the powerbomb performs with everything, but you definitely should NOT have to go to bigger jets.

Your exhaust will be fine.

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Hey Ed, I thought it was the other way around. Stg1 intake and Stg2 exh. Am I wrong? Does the big bore perform better with that set up?

Your right, I was confused. Stage 2 ex and stage 1 in. My bad

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Get the crank rebuilt, it's about half of buying a new one...unless of course the guy is made of money...but if he does have an open cheque book, why do up a steel framed 01 when he can just buy a new(er) aluminum framed beast.

When you send the bottom end out to be rebuilt you are NOT sending the cases with it, you're just sending the crank....

New crank bearings for sure while you're in there or you'll have a weak link.

Check all the gears, make sure none of the dogs where they mesh are rounding or you'll be back in there before you know it replacing tranny parts.

Big bore kit usually comes with a wristpin and clips so you're good there.

Definitely check your valves because if it has a lot of hours on it - this will now become your weak link.

No you don't need a bigger carb, you might actually have to lean out your jetting by going a jet size smaller to get it dialed in right, but all this will depend on how the powerbomb performs with everything, but you definitely should NOT have to go to bigger jets.

Your exhaust will be fine.

Unless you have free labor on a crank, the cost are about the same. Another thing to consider is how warn the teeth are on the timing gear. That and I would'nt use anything but a heavyduty crank for a 290 kit.

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Thanks for the support guys. now that you mention it. idk why hes building up this steel framed beast but its his bike n his money. And im doing this for more experience!

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My 400 crank cost $160 including parts to be rebuilt by Eric Gorr (Lukes racing has the parts only for $110 for your bike, pretty sure Eric gets a better price on parts then we do), a new one from Hot Rods would cost you 320 for an 01 250F.

That's a BIG difference and the labor to rebuild a crankshaft is not that much, a decent tech can do it in 20 minutes.

Kit:

http://lukesracing.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=LR&Category_Code=WRKYD

Full crank:

http://lukesracing.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=LR&Category_Code=WCCY

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