02 to a 03 conversion

[sliding15p]

Ok a few quick questions. I have an 02 250 that ive had since new. It seems to be one of those "problem motors". Just cant keep the thing together no matter who builds it. Looking at putting a 03 motor in the frame and just hope to get a decent motor in it. Are there any major (or minor at that) mods that i have to do to make this work ?....I had just bought a FMF fatty for my 02 with the shorty silencer. and curious if it'll just bold right up. I thought i read somewhere that starting from 04 it wouldnt work.

Im in need of some help here to make sure everything will smooth or if id be too much of a hassle and maybe i should just start a rebuild with new 02 cases. ANY help would be appreciated, im tired of seeing this thing just sitting around as pricey paperweight...

thanks again,

john

[kuritaro9]

the 03 motor will drop right into your frame.

[sliding15p]

ok thanks, what about as far as the exhaust. i just bought the one i have for the 02....will that bolt right up to other motors too ? this pipe has like 5hrs on it

[rtv]

Your 02' pipe will bolt right up with no problem. There are only minor cylinder porting and suspension valving differences between the 02' and 03' model years. I had Eric Gorr do the cylinder on my 03' and the difference in power between that cylinder and the stocker were amazing, and For less and the cost of a new pipe.

[Redlined]

Your good to go. The frame never changed from '02-'07, so engines & frames are interchangable within those years.

The pipes fell into 2 groups, '02-'04 are interchangable, and '05-'07 are interchangable. The '02-'04 use a female cyclinder flange, the later models used a male cylinder flange.

Just curious, what keeps failing on your '02 engine?

[sliding15p]

ive had the motor rebuilt three times and everytime something gets to to the crank and locks it up and BOOM there goes the whole damn motor. looks like a chunk of the lobe is missing again and damaged the cylinder a little bit enough to have to to rebuilt also. I just had the cylinder done by millennium bored 1mm over and total reuild on this motor was 5hrs old.....ever since i got this bike ive had problems with it. so im hoping maybe swap the motor to something new and see what happens. Just REALLY frustrated with it, and ready for something to stay together. Ive never had any problems with any of my other bikes. This one just seems to give me fits every yr.

[sliding15p]

also, out of the 02-04 are there really any motor mods that were done, wondering what motor would be the strongest if i do swap out new motors..

thanks for all the help guys

[Redlined]

also, out of the 02-04 are there really any motor mods that were done, wondering what motor would be the strongest if i do swap out new motors..

thanks for all the help guys

There is a sticky above that outlines model year changes. The changes appear to be minor, but the later motors probably have a small advantage. That said, price and condition are obviously more important.

[sliding15p]

yeah i have my eye on a few 03's an couple of 04's...just looking to see what i can get a better deal on....just pretty frustrating about just having the WHOLE motor built and bored and it lasted 5hrs...

[PowerFiend]

Did you use a Honda OEM replacement crank? Are your reeds good? Did you fix the possible airboot leak?

02-04 cranks are basically the same, and this motor is typically stone reliable.

[sliding15p]

No i used wisecos hot rods crank and piston. Complete motor rebuild with wiseco parts. the reeds were FMF carbons that were brand new also. There wasnt any cracks or any leaks in the air boot. I checked all of those things and the motor was brand new from the bottom up. Thats why this was so disappointing, 5hrs on it and this happens AGAIN. i figured it was just "one of those problem" motors. Im lost and dont know of what else it could be. Ive spent WAAAY to much money on this motor and im ready to get one that stays together....

[rtv]

There was a major problem in 02' with the air box sealing to the air boot on ALL cr 250's. The boot and the air box need to be seperated and resealed with RTV or I believe PC racing makes a neoprene seal for that boot to box seal, just for this reason.

Edited July 13, 2010 by rtv

[sliding15p]

is it just on the 02s ? would it be worth buying a airbox off a newer cr ?

[rtv]

It was just the 02's. No it's not worth buying a newer air box, 02'-07's all use the same air box. There was a problem with sealing them at the factory. The fix is cheap and relatively easy. Just remove the air box from the air boot and rtv the lip then bolt them back together and let the rtv dry. Problem fixed, or you can buy the neoprene seal that PC racing makes and do the above without the rtv. It's your choice as to how to fix the problem. here is a link to the PC racing seal kit. http://shop.thumpertalk.com/catalogs/Parts_Unlimited_Offroad_2009/default.asp?p=800 the air box kit is at the bottom of the page.

[H4L]

I must of logged at least 100 hrs. on the 03 & 75 hrs. on the 02 with no issues. Also have at least 30 hrs. on an 07 model I just recently bought with no issues. These motors are very durable with proper maintnance they should last. I would recomend OEM on the bottom ends & OE or wiseco on the topend. Who is doing the work ? There might be something else going on that is causing the failure on the engine. As mentioned above about the air box on the 02 models I got a PC racing one but they no longer make them. Look into the MX Bonz kit I've heard good info on them (Do a search).

[sliding15p]

i had two dealers ( one of which was good sponsor of mine) do the first two. then this last motor, me and my road racing mechanic built it. (more he built it but, i help when i could) hes had MANY MANY yrs of building motors and knows what hes doing, hes a very dependable guy. Im really just lost of what to do, if it wasnt for wiseco being a great sponsor that they are i wouldnt be able to do the rebuilds on these motors. But this is going to be my last if i decide to rebuild. i will definitely look into the mx bonz seal kit, im taking the air box apart tomorrow and really going to inspect it. If i can find a good motor thats ready to install for a good price i may jump on it. If not i can get it rebuilt for a pretty good price too. Just really really nervous about this motor now, im riding it and hoping it doesnt blow up.

[H4L]

I have a buddy that is a certified 25 yr. plus car mech. that has worked at a few dealers. He has done some work for me & my family with bad results. Hopefully that's not your case. What oils & gas are you running & premix ratio ? Is your engine stock ? How often do you clean your air filter & change your tranny fluid ?

[sliding15p]

I have nothing but TOTAL confidence in him, he built my road racing motors for 4 years and never had anything but great results. I also had two other mechanics build the motor and same results. this is why i think its just "one of those problem motors".....I am a road racer and dirttracker, so i maintain all of my bikes after every ride. Its kind of dusty out on my personal track so i had the filter skins on my filters also and i cleaned them after every ride (skins and filter). I run redline lightweight shockproof gear oil (always ran this in my 2strokes). the first two motors were stock and this last one i had it bored 1mm and i did change the jetting that was spot on and i run my premix at 40:1. Ive gone over everything after the first motor gernaded, and im just totally lost what it could be. LOVE TWO STROKES but this is getting out of hand, this is why im considering just getting a different motor and see how it goes. thanks for all the input guys, keep the suggestions coming, maybe ill find something i am missing.

Thanks again,

John

[PowerFiend]

Wiseco had and may still have a bad reputation for their cranks. They have them made in China. You should be able to get an OEM Honda crank for under $250 shipped online.

[sliding15p]

how long ago was this ? ....it looks as if theres a chunk missing off the lobe again. same thing that happened last time. my cylinder really doesnt look all that bad gonna have someone take a look and see but the head has pits in it and so does the top of the piston.....think there could have been a problem with the crank and caused this ?

what kind of problems were there with the wiseco cranks ? they have been nothing but great to me so i want to make sure before i switch back to the OEM crank.