CRF230F Motor Mods


12 replies to this topic
  • endurokids

Posted 21 August 2009 - 02:56 AM

#1

I just picked up a CRF to race in H/S in Wisconsin, Illinois and Indiana. It has a Works Pro Shock, R T Emulators, piped, jetted and air box opened up. The motor is stock. I'm a +50 A (back in the day) Enduro rider. I rode the bike last weekend at the Hill & Gully Enduro and felt that I could use more power to stay in 3rd gear but ended up abusing the clutch to the point that I feel it needs some help.
What do you suggest on the clutch part of it?
What mods to the engine do you suggest for more power without loosing the rev out or top end? Which big bore kit?
What do you think of doing just a carb swap and a cam?
Which ones and why?
I want to keep the dependability of the motor intact.
Dwight, I've been following your posts but would like to hear about your conclusions.
PS. (Dwight, I'd go with the WR300.)

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  • ve3rqm

Posted 21 August 2009 - 04:23 AM

#2

You may want to change your gearing on the rear sproket.
http://www.sprockets...Optimizer2.aspx
here is a calculator for checking out different combos
I had too high rpm in 2nd gear and was just screaming the bike
and not enough rpm to ride well in 3rd gear. I added 4 teeth to the rear sproket. Keep in mind this will lower the top speed of the bike and increase each gears rpm to do the same speed. but for woods riding it was a great improvement.

there are other gear and sproket calculators that factor in rpm just do a google search.

  • 4strokeridertt

Posted 21 August 2009 - 08:51 AM

#3

I'd start with an Engines Only 250 bore kit and a light port and match job on the head.
The extra CC's and stock carb will really help the bike work on a Hare Scrambles course espescially in the tighter sections. If you still need power a cam and carb can be added later without having to tear it down to far.
Great bike for us 50+ guys to run a long race with out getting beat up like riding a big 450.

  • vmeadows

Posted 21 August 2009 - 07:58 PM

#4

the xr250 carb conversion helps on the midrange.
Also try running a mix of race gas with regular gas. In theory it should not help, but it DOES.

I have been looking at internal engine mods. I have not made a move yet.

I have researched several companies and decided on Engines Only. They are the only company that backs up their claims with actual dyno charts. Its easy to claim big HP numbers.....they are the only ones i have found that will prove it.

I am not going to go with big bore, I am going to install a cam and head mods and high compression pston. this in conjunction with the 250 carb should really bring it to life.


Good luck ad welcome to the 230 club

  • heybuddy1901

Posted 21 August 2009 - 08:07 PM

#5

i have the set-up that vmeadows is talking about.

except coeshow not engines only.

it definately pulls harder than stock, i cant vouge for the carb because i did everything at once. (high comp piston, extensive head mods, porting, carb)

i would try moving the gearing around first though.

when i used to race h/s i was running a 14/49 set-up and it was perfect. (still using that ratio for supermoto)

  • crf150f guy

Posted 21 August 2009 - 08:38 PM

#6

i have the set-up that vmeadows is talking about.

except coeshow not engines only.

it definately pulls harder than stock, i cant vouge for the carb because i did everything at once. (high comp piston, extensive head mods, porting, carb)

i would try moving the gearing around first though.

when i used to race h/s i was running a 14/49 set-up and it was perfect. (still using that ratio for supermoto)


so thats how you were able to pull away from me so easily.

  • heybuddy1901

Posted 21 August 2009 - 09:02 PM

#7

shhh :thumbsup:

  • endurokids

Posted 22 August 2009 - 05:08 AM

#8

Thanks to all that replied! I was wondering if you have the make and model of the carb that you describe as the XR250 carb?
I may be able to find it thru Ebay easier that way.
I just finished my TTR125's carb swap to an XR200 unit and it makes a noticeable difference on it.
What kind of modifications are needed to complete the task?
What jetting do you suggest to start with?
Why would'nt you go with the big bore since you had the top end apart anyway? Just curious.
I really like the bike the way it is, but would like more power overall for racing.
What weight savings measures have you taken? If any.
I had some issues with top heavyness but I'm sure I can get used to it the way it is. :thumbsup:

  • heybuddy1901

Posted 22 August 2009 - 07:58 AM

#9

because i race in a displacement limited class.

max 230cc air cooled.

and didnt want to go with a cheaper BBR piston, wanted to stick with wiseco.


plus to get a 250 big bore out of a 230 you have to split and machine the cases.

not nearly as simple as just removing the cyl. and piston/head like i did, haha

  • endurokids

Posted 23 August 2009 - 03:57 AM

#10

That make sense to me. I'll probably go the same route as to High Comp piston and porting.
Anyone use Thumper Racing's High Comp kit? Gary Hazel is an old midwest competitor from the 80's and it's good to help out people you know in the biz.
Thanks again.

  • vmeadows

Posted 31 August 2009 - 09:07 AM

#11

I would buy a new 250 carb.

I bought a used one for 75 bucks on ebay,

but then i spent almost another hundred on parts. if the ruber diaphram is bad it is over a $100.00 by itself..

If i remember correctly u can et a brand new 250 carb for around $250.00

Look in the thumpertalk OEM parts store.

The only issue with mounting is the gas line conection. It interferes with the frame a little. I well placed whack with a ball peen hamer will give u the clearance you need.

I do not remember the exact jetting requirements for the 250 carb..............i know that it is critical that you use the right mix of needles and jets to make it work.

  • heybuddy1901

Posted 31 August 2009 - 09:21 AM

#12

not sure what pilot im running, but i am using my 230F needle (2004 needle with 4 or 5 clip positions) on the 3rd clip down i believe.

and a 132-135 main (depends on the altitude)

cant remember what pilot im running, i think a 48.

and yeah, i had to do what vmeadows did, just smack the upper tube with a hammer a couple times to make clearance. my fuel line is squeezed in there, but not pinched, and it works fine.

  • TrikeKid

Posted 31 August 2009 - 05:44 PM

#13

I run an XR250 carb with a 42 pilot, 120 main and it starts and runs very well but is just slightly rich with the needle as far down as it goes. It runs great everywhere I go so I'm not going to mess with anything. There is a fitting you can change to not have to go cave man on your frame to get the fuel line to clear. Search for the info nw56 posted on that part.





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