2003 cr250 needs new life

2strokesurvivor · #21 09-01-2008, 02:52 PM

Took the top end apart today, everything seems to be ok. I wanted to post some pics to see if it appears that my cr was running too rich or not. Also, I can see a few shiny lines in the cylinder, and want to hone but need to know if I just do the scotch-brite or brush hone? Where can I purchase a brush type hone? Thanks for any help. I am replacing with a wiseco piston and new gasket kit.

MXracer21 · #22 09-02-2008, 09:51 AM

It looks like that piston was getting a little too hot. I think that is an indicator of it being too lean, but dont quote me on that.

Faded · #23 09-02-2008, 04:22 PM

I've posted plenty on this bike here in years past. The '03 was a good bike and there is really little you can do to make it great. The stock carb and jetting didn't seem to work anywhere except sea level, so you might be okay there. While you have it apart I would turn the base down and raise the exhaust port to help broaden the power spread. The stock pipe is a great performer and there isn't much, if anything to be gained by switching. About the only reason to switch would be to replace a smashed or folded pipe. The SST will get you some noticable power but is a tuning headache IMHO. The stock reed cage is adequate and capable, just keep fresh reeds bolted to it. The head could use a tighter squish band and bit more compression, but if you machine the base you'll already get this one. The big-bore options are not reliable if you plan on keeping the bike more than one or two seasons. Been there...

As a rider, father, and ex-CR250 owner you'd be in good condition with some minor cylinder work (as mentioned), keeping the piston/reeds fresh and saving your money for tires, suspension and practice fees, IMHO.

2strokesurvivor · #24 09-02-2008, 06:10 PM

Thanks Faded. I have read some of your posts on cylinder work and they are very concise and helpful. If you could point me in the direction on how to turn the base down on raise the exhaust port that would be great. I had to replace the exhaust..if you look at previous pics posted it shows where the pipe was slightly smashed and had almost cracked all the way through(I don't know how long I was riding like that). I have had this bike sitting for some time, do not race, just looking to have reasonable reliable power and a bike I can ride on the few free weekends I get as a new father. Also, you think that v-force reeds are not worth the money for the '03 cr250? I don't need to waste money, so I appreciate the honest opinions. NICE RIDE!

Faded · #25 09-03-2008, 11:15 PM

You can turn down the base by using a lathe and an expanding mandrel to clamp the bore of the cylinder. Use a dial indicator to check the run-out at the base and shoot for something less than 0.004"...less is better. This will set the base perpendicular to the bore and allow you to square it up. From there you start cutting until you're happy.

Raising the exhaust port will require some porting tools...more specifically a right angle porting tool, along with some knowledge/experience. Not only do you have to 'raise' the port, you have to worry about the shape/size, roof/floor angles, chamfering the port when finished and not chipping the plating while grinding.

These are usually better left to those that have the tools and are experienced, but if someone is determined then more power to them. There are more than a few capable guys out there that I would trust though.

I liked the Boyesen Rad Valve over the V-Force on my '02 but felt that neither of them were really worth the money in the end. The stock '02 reed cage suffered from a poor design so I replaced it...the slight increase was a small bonus but I was more interested in getting longer reed petal life. The '03 is a much better design and is worth keeping, at least for the time being, IMHO.

2strokesurvivor · #26 09-04-2008, 08:47 PM

Thanks for the explain Faded. I have neither the tools nor the know how to do this. I think I am just going to have the cylinder honed and put a new top end in for now. I am putting on the Fatty w/silencer and some new bearings, controls, and maybe have the suspension set up. I am only looking for some good seat time, and will eventually be getting a thumper, just not right now with the new addition to the family. I said it before, but I really do appreciate the time that the regulars on this site put in to help out however they can..

Faded · #27 09-04-2008, 09:49 PM

AT LEAST order yourself the base gasket off of an '05 or later CR250 and use that instead of the supplied gasket.

EDIT: I forgot to answer some of your other questions in your original post so here's a few other things...most of it is cheap and easy.

Pull that air box apart, clean it up good enough to eat off of and make sure it's sealed up tight when you put it back together. A fresh motor deserves fresh, clean air.

Get the '04-up front fender, it makes the bike look newer. If you get a 'kit' it's all the same from '02-'07 except for the front fender; example: you could get a kit to fit an '06...or an '05, etc.

For gearing I would run a 14-53 combo.

Definately hone that cylinder before assembly. If you need a post on cylinder bore prep let me know and I'll get you a link.

I recommend the Wiseco piston, it solved the piston slap issues some of the bikes had with stock pistons and is more durable. The only drawback is that you have to get in the routine of properly warming up your bike before you beat on it. Small price to pay for reliability though...

MXBonz.com sells exhaust spacers that are fun to play with when trying to make the power band suit your riding style. Add spacers to move the power down lower. Start with 2-3mm, if that's not enough then go with 5-6mm. After that top-end really starts to suffer.

That's what I can think of off the top of my head for now...

B_Rad · #28 09-04-2008, 10:19 PM

What's the idea behind that FADED?

Faded · #29 09-04-2008, 10:23 PM

Quote:

Originally Posted by B_Rad

What's the idea behind that FADED?

It's a thinner (0.010") rubber coated steel gasket vs the old fiber ones that were approximately 0.020" thk. It'll help just a little bit and it's better than nothing.

B_Rad · #30 09-04-2008, 10:41 PM

Hmmmmm

. I'm still trying to rid my detonation problem so I don't think a smaller gasket is the go for me.
And sorry for the capitals on that last post.

Kinda looks like I'm yelling at ya.

P.S. I

love your bike

Faded · #31 09-04-2008, 10:48 PM

Quote:

Originally Posted by B_Rad

Hmmmmm

. I'm still trying to rid my detonation problem so I don't think a smaller gasket is the go for me.

I might be just the ticket.

kjjz28 · #32 09-05-2008, 11:53 AM

2 stroke survivor...not sure where you are in Dallas but I can recommend heading up 75 to Cycle Gear in Plano. Ash, Dave and the other folks are very helpful. I ordered new '05 plastic there for my '03 and it does make it look better. They also occasionally have after hour sales with 10% off on anything in the store as well as special order items. If they don't have it, they can get it pretty quick.

2strokesurvivor · #33 09-05-2008, 09:25 PM

Thanks for the detailed info Faded, I am ignorant on some of the lingo about the base gasket you are talking about. Is this the gasket in the cylinder head (to close the gap to the spark plug), or the gasket on the base of the cylinder? What function does the smaller gap serve? Sorry, I just do better when I have an understanding of the how/why of things..allows me to make better sense of what I'm trying to accomplish with this motor. Btw...I am going to pull apart the air box in the morning, maybe some lunch off of it if all goes well..

Faded · #34 09-05-2008, 09:34 PM

The base gasket goes between the case halves and the base of the cylinder. The thinner gasket will do three things, change port timing to favor low end, tighten the squish clearance and increase compression. The thinner base gasket will be a slight improvement over the standard one. We are not talking a huge change here, the difference is very little. The change is so small that you won't have to run race gas, it won't totally change the power and you won't lose top-end...it'll just be a nice little boost everywhere that is most noticable on the bottom end.

2strokesurvivor · #35 09-05-2008, 09:40 PM

Nice..just the thing that the '03 needs. I am planning on taking the cylinder to a shop tomorrow to have it honed..does anyone know of a place in Dallas where this can be done on site? Dallas Honda recommended Motorcycle Specialty.