'02 CR250 Porting & Head Shaving

[Nuts]

I just bought a '02 CR250, saved a thousand dollars from an '03, I put a FMF SST pipe, FMF shorty silencer and Delta V-Force reeds on it. I was what difference porting and shaving the head would make. I would like to see a increase in power over the whole powerband - I'm trying to avoid a high, hard hitting power band. Has anyone made these mods or have any comments. Any input would be greatly appreciated.

 

[Jman271]

Yes! EG did mine for mo better everywhere porting, let me tell ya, it was a ripper form bottom to top. I had a PC pipe and shorty, V-Force,(low tension) and a leaner needle,380 main, stock gearing and there was no comparison to the stock motor at all. Pulled like a tractor and rev'd to the moon. I know he shaved some off the base and head, did some transfer work,etc. Run, don't walk to the post office, send your jug out today,,,,

 

[john stu]

eric also did a 2002 cr250 for me and it pulled from a lower rpm than stock and seemed to pull longer than stock i wouldn't say it was unbelivable difference but i will say its well worth what he charges.i would do it again

 

[Faded]

Don't worry about getting something with an uncontrollable hit, my 265 w/mo betta still doesn't hit, but I have more than enough power on tap w/out it! :aj:

 

[strublized]

I had the mo better done to my 02 CR 250 and am very happy with it. The mod added power across the entire rpm band. The most noticable difference for me was how fast the motor reved. It has made me keep my bike for another year because it is so much fun to ride. Go for it and send in your jug.

Matt

 

[markymark77]

I had it done as well. Its all good. :thumb:

 

[Nuts]

I was just quoted 500 canadian dollars - works out to be about 360 USD for the porting and head shave. Just wondering if this is an alright deal. The mod shop is going to take my whole bike - I don't have to tinker with a thing, they will even do the jetting. I was wondering if this would be a good time to replace the stock piston with an aftermarket one - wiseco? I have about five hours on the motor.

 

[Faded]

Sounds good if they do a good job and get the jetting right. I think you'd be okay with the stock piston, but if it is anything like mine then the piston slap is a little bothersome and since you have it apart it might be a good idea to replace it. Either way, good luck!

 

[endurohero]

I would be leery of many if not all 2 cycle tuners in Canada only for the lack of work, practice makes perfect especially when it comes to tuning 02 and newer CR 250s not all tuners can deliver an interpritation of type of power you want most will tell you what their last cut n geuss was but can explain why or how they arrived there.If you get the chance to ride an identical bike to yours that was done recently and you found it ideal then your money will be well spent.I personnally have modified 11 02 and 03 cr250s and am still learning. dont be sold on promises.

 

[Faded]

endurohero,

I'm just probing here, but what is it that you find most challenging with the '02/03 CR250s?

 

[endurohero]

I found four issues with these crs 1 power valve open and return speed changes dratically with age , not carbon fouling but cable maintenance and inconsistancy between actuator motors some faster than others . 2 carburation , good luck getting a modified engine to run reasonable through all circuits bottom to top there is always a small hitch just as the slide moves from off idle to about 1/8 open thank you mikuni . 3 exhaust port outlet size, limited to pipes and spigots available , a shade on the small size for shreeking top end. 4 reed cage included angle and distance from crank shaft, every thing has to be comprimised to really get working better than stock. There very good in stock form (03) so major improvements are not easy.My comments about our tuners in Canada doesnt reflect to jobs done by everyone just the most popular guys to whom i have to redo there work after the customer gets their motor back, dont like it and have no support to get help, just the standard reply" thats the way we do it youll have to pay again for us to fix it ".

 

[Nuts]

Endurohero who do you recommend to do the porting and head work? I was talking to the guy who wants to do the porting and he gave me some numbers for some of his past customers with the same bike as I have. So far I have talked to one guy and he is happy, I'm going to phone a few more and hopefully someone will let me pilot their bike. Also has anyone heard of the HRC kit available from honda? This kit apparently includes a cylinder, a pipe, valves, piston & rings, gaskets, ignition box and jets for about 1600 USD. I read about this in the June Dirtrider magazine, Lars Lindstrom was running this kit as a privateer. Just wondering if anyone has tried it.

 

[john stu]

my 2002 cr250 was a much harder to jet than bikes i've had in the past but i totaly disagree with endurohero that you can not jet the mikuni carb to run perfect.mine runs awsome after porting and head mods and with much more mods and it ran awsome stock after many long hours of tinking with the carb and many jets nozzles ect. it did take a lot of work and carb parts that you usualy don't have to change like nozzles (s-8) you can do it it just takes some work. my bike does not have ANY carb issues like it did stock i can honestly say it runs perfect but i do agree the mikuni runs like crap the ways it comes on the bike and it needs magor work to get it to run good and lots of parts you think they would fix it, i am very good at tuning carbs and it was hard for me but i really feel bad for the average person who has a new cr and doesn't know alot about tuning a carb because they are in for a nightmare.

 

[Nuts]

I tried to PM you John Stu but that option is not enabled yet. (I just downloaded the membership form - I will sign up on the lifetime membership) I want to make sure my carb is tuned correctly and would like to know in more detail what I should do. I'm fairly sure that I will trust my cylinder to the mod shop I have in town but want to make sure that he tunes the carb properly. If I know a little more about what should be done to the carb I will have a little more leverage on this guy. The mods I currently have are delta v-force reeds, FMF sst pipe and shorty silencer. Could you let me know what areas need to be changed and what you are running ? What is the difference in running the reeds in the low or high postion - right now the reeds are in the high position.

I appreciate the help/input fom everyone. The membership is worth every penny.

Go ottawa senators!

 

[tomoad]

where can you get the hrc kit???

 

[Faded]

Originally posted by john stu
but i really feel bad for the average person who has a new cr and doesn't know alot about tuning a carb because they are in for a nightmare.

Yea, that's me to a 'T'. Then add another 15ccs to the mix and weather that can vary 20 degrees from one day to the next...it has been an experience and continues to be one, but someday I hope to be able to accomplish what John Stu has. You're my hero man.

 

[endurohero]

Icant recommend anyone, with a good concience for the exception of eric gorr because he has been a big help to me in understanding some aspects of design and tuning of pipes, cases and cylinders. Most tuners egos get in the way of the facts and really dont understand what does what.Sorry.

 

[john stu]

nuts
as far as carb tuning you i doubt you will end up running the exact jetting (because of altude,fuel,rider,ect) that i am but i can tell you that the s-8 nozzle made the biggest differance in getting the bike dailed in for me. i did get the bike to run great on pump fuel but it was still finiky with temperature on pump fuel i think the bike runs very close to detionation stock and to keep it safe honda jetted the bike rich. if you lean it out to run clean at 90 degrees when the temps fell to 70 degrees the bike would ping and i would have to go richen the jetting to stop the detention and then when the temps went back up to 90 it would be rich so i would have to lean it back out ,the easy fix for me was to run race fuel i was planning on using it anyway after having it ported so i gave it a try(vp c-12) then with the race fuel i could lean the bike out just enough so it would run clean when it was 90 degrees but then if there was a cool day the bike would not detenate and ping so if you want your bike to run perfect and not have to mess with jetting all the time for me the answer was race fuel but to be honest i don't think it was the carbs fault i think it had to do with the bikes compresion ratio because just increaing the octain fixed all my tuning isues. also i ran the bike at 50/50 race fuel and that was all it took. i really didn't want to have to run race fuel all the time but after seeing how good ny bike ran after trying it i just couldn't go back and after all its probuly better for it anyway.and as far as the reed tension i tryed the high and low back to back and the top end seemed the same but when set in low tension the bike seemed to come on the pipe sooner to low is where is stayed.i think i ended up with a 400 main, 72 needle,s-8 nozzle and a 30 pilot with the air screw set at 1 1/2 turns out but like i said the s-8 made the differance in getting the run clean and the race fuel keep the detionation away.after erics porting the bike seemed a little lean so i have been making my way closer to stock again on the pilot and i went up to a 410 main now i would recomend you to send you cyl to eric he's cheap and he did exactly what i asked for witch was some more bottom end with out losing any top and i ended up with some more bottom end with it seems like more top end too!!!!you really should give the race fuel a try just lean the bike out untill it runs clean and then run the race fuel 50/50 problum fixed.i have checked my plug all the time and its always tan even after hard full throttle runs or after just some trail riding i have had the same plug in the bike all summer and it runs great stock the bike always wanted to foul if i went for a trail ride just for 5 min. now i can put around all day with my nephew (9 years old)and it doesn't miss a beat and then after hammering down a 5th gear straight wide open i can pull the clutch in and kill it and check the plug and its still tan.it doesn't get any better.also add one tooth to the rear sproket it helps a lot as far as being in the right gear it seems to make the bike pull better especialy when short shifting to third .

 

[parkerCR]

John Stu,

Fantastic post one of the most helpful I have ever found on this site in two years! Thank you I have had tremendous problems jetting my 01 CR250
I just got it back from Eric Gorr with the mo better porting. I am at sea level -2000 ft, at about 55-80 degrees in and around Washington state so a fair amount of humidity. I am definitely taking your advice on one tooth larger rear and 50/50 race gas. I currrently run

410 main
30 pilot
s-7 nozzle
stock clip on third position

The s-7 nozzle replaced the stock s-9 and the impression from the other folks on dirtrider seemed to be positiive with this mod. I am thinking that the S-8 may give me a better baseline. where did you find this part?
Thanks for all the info!

 

[VintageTech]

Parker,
The S-8 nozzle is out of a 1996 YZ125 (perhaps other years, also). I believe the part number is 3TC-14141-S8-00.
Retail is around $20.

Hope it helps

 

[motometal]

parker, I think you are on the right track with your jetting.  Have you tried a 27.5 pilot (or for starters just turning the air screw 3 turns out)?  Maybe it's too lean this way.  I have jetted a few 'o1s for 800 ft elevation, and ended up with a 25 or a 27.5 pilot.

 

[Curt_704]

Parker,

I've struggled with the jetting on my 01 CR250 for two years now, but I think I've finally got it. In an attempt to become spooge free I created a lean condition that left several deep scratched in my cylinder wall, so I've found the lower limit and adjusted up from there. I'm running the exact same jetting you are with one exception - a 430 main.
The S7 nozzel creates a lean condition somewhere near the top that I believe I've corrected with the 430 Main. I've also switched oils to Mobil 1 mxt2, from Honda hp2, and adjusted my mixture to 40:1, from 32:1. With this set-up my plug looks great and I'm pretty much spooge free.

 

[motometal]

in your opinion, is that mx2t an improvement in the spooge factor?  I'm currently using Suzuki CCI, which has been great oil in many respects, but I suspect it may spooge more than some oils.

Regarding the mid range to 3/4 throttle jetting, I think the needle clip position also plays a big role in that range (along with the nozzle or needle jet).  In other words, you should be able to re-compensate for the leaner 1/2 to 3/4 throttle condition by adjusting the needle clip position.

 

[parkerCR]

It sounds like running 50/50 race gas with super will help us all in our jetting struggles according to john stu's post. I think I might try this. Motometal do you have a porting job on your CR?

 

[Curt_704]

I was told that mx2t oil burned at a lower temperature than the hp2 oil, I was using, and this would help clean up my spooge issue. I can't confirm the burn temp, but my bikes exhaust is clean.