CR250 with NO low end

[tlstandup]

My 2002 CR250 has a huge power loss down low when accelerating out of corners and in tight woods trails. I bought the bike used with "fresh top end" and it has the stock pipe and silencer (freshly packed). It seems to run good right as sonn as I start it (starts on the first kick every time), but when it warms up, it runs like trash down low. :ugg: When I clutch it into the midrange it will pull happily into the high RPMs with no problems. I have cleaned the carb and checked the reeds, which appear to be new carbon fiber replacements with no gap at the ends. I have played with the mixture screw and the needle clip positions but to no avail. Please someone throw me a bone on this one, it would be very appreciated. Also... I have a new DEP pipe and silencer ready to put but I dont want to do that until I take care of the original problem. Thanks alot.

 

[Adrian591]

Make sure your power valve is operating and adjusted properly.

http://www.motocrossactionmag.com/m...0&tier=3&nid=F6E595A399B64522B984C9F052329215

 

[tlstandup]

I have already adjusted the cables as per the Honda manual(guess I should have said that), but still no change--I appreciate your help though!!!!! Any other CR owners out there with this problem???? Your advice would be greatly appreciated!!! By the way---anyone know the stock jetting for this bike so I can double check this??? Hows about jetting for a DEP pipe(at sea level)? Thanks again!

 

[tony91]

How is your jetting? I came off a 92 CR before my 03. Before I got it dialed, it felt like the low-end was non-existent. I was thinking power valve too....but it was just terrible jetting. Do you know what you have for needle, pilot, nozzle, and air screw adjustment?

 

[Sandy Whoops]

Stock jetting is 380, 32.5, 6BEY30-74 2nd from top, 1 1/2 turns out on the AS.

Stock jetting tends to be slightly rich at idle, lean at 1/4 throttle (typically knocks on pump gas), and slightly lean on the main jet. The perfect needle is elusive. A number of owners have tossed the Mikuni and replaced it with a Keihin.
Another possibility is to contact James Dean. I think JD has a jet kit for the '02 CR which includes a custom needle or two.

The '02 CR250 is notorious for lack of lowend grunt. Best bet is to send the cylinder & head to Eric for a little of his porting magic.

 

[pro2k]

from service manual:

Poor performance at low and idle speed
Check ignition timing (faulty ECM or alternator)
check air screw
check for leaking intake pipe
perform spark test
Check RC valve system (excessuve carbon build up)


hope this helps

 

[Thumpdaddy]

I had a similar problem on my 02 and chucked the Mikuni for the Keihin. There is a good thread on the 02/03 CR carb so do a search.

 

[tlstandup]

Thumpdaddy---which carb would you be referring to? Which Keihin did you go to, and what was your jetting on it?

 

[Thumpdaddy]

I have the Keihin PWK carburetor that came stock on the 2000 CR250. You can order it from Service Honda for $155 and it bolts right up with no problems - make sure you order it for MY 2000. I installed it 2 weeks ago and have put about 5 hours on the bike. The flat spot off idle has lessened greatly and there is smoother acceleration. I am running with the stock jetting at sea level and have a Procircuit pipe with Boyesen reeds.

T-Diddy

 

[tlstandup]

Thanks to everyone who has helped me with this! Thumpdaddy--I will be ordering that carb this week as the general concensus is that the stock carb is trash and is impossible to tune correctly. I appreciate the assistance! :cool:

 

[mtk]

Yes and yes. I just put the PWK from my 2000 on my 2002 myself. It slips right in.

 

[tlstandup]

Thanks again to everyone who helped me with this problem, hope I can return the favors one day. I have the Keihin on order now and will install it soon along with the DEP pipe and silencer. Still debating on the V-Force3, anyone got praise for it, or dislikes? Also, has anyone tried the MXBONZ torque spacers, and if so; improvement or gimmick? Thanks alot guys.