2003 Cr250 Bogging Down ,,, Please Help,,,,

[moffman250]

HELLO THERE EVERYBODY I WAS WONDERING IF YOU CAN HELP. I HAVE PURCHASED AN 03 CR250 TO TRY AND GET BACK INTO MOTOCROSS AFTER A FEW YEARS OUT.
I BOUGHT THIS BIKE AS IT IS IMACULATE AND IS WELL SORTED BUT AFTER RIDING IT YEASTERDAY IT SEEMED TO BOG DOWN WHEN I WENT TO GIVE IT FULL GAS IN AROUND 4TH GEAR, I DROP THE THROTTLE AND IT SEEMS TO CLEAR OFF. LOW DOWN ITS GOOD I HAVE NO PROBLEMS, ONLY WHEN I GO TO CANE IT AFTER SAY A CORNER OR BEND THEN HIT THE STRAIGHT.....
I WAS WONDERING IF ANYONE COULD TELL ME IF THEYVE HAD SIMILAR EXPERIENCES WITH THESE BIKES AND THEIR OUTCOMES. ALSO, IVE READ ABOUT THE AIRSTRIKER CARB CHANGE ETC WOULD THIS TOTALLY BENIFIT MY YEAR OF BIKE AS IVE READ ABOUT THESE PROBLEMS ALOT???? but ive had a few Hondas and like them so I chose this knowing there may be issues down the line!!!!!

the gut I bought it from says it was running fine and he gave it a good caning and never had problems, he lives near a track which has open straights.

I googled his altitude this morning and is 433 feet-131 metres.

mines is 590 feet - 180 metres

could this be the cause?????


ive not checked the plug yet will inspect over the weekend as I know this would be the first place to look but would be grateful for any other info regarding jetting the carb etc as this is where my knowledge is limited. I will find out my main jet size and notch positions as well for reference and post!!!!!

MY BIKE SPEC......

FULL HINSON RACING CLUTCH
STOCK CARB
FULL DEP NICKEL PLATED PIPE AND DEP SHORT SILENCER
V FORCE 3 REEDS.

all the gaskets on bike look sound and relatively new.
the carb is tight on the reed block clamp also and reed block gasket is new and tight!!!!

im new here so any help would be much appreciated guys thanks., moff

 

[arnego2]

The cause could well be a worn top end and in your case I'd have a look int the cylinder.
Take off the expansion chamber and look at your piston. You see a lot of black or scratches you need at least a new piston.

 

[SQUIRLEYMOFO]

Extremely hard to jet with out porting......had one never liked it. Fat, lean no bottom end no top end. Get it ported, fixed.......on the upside great brakes, suspension etc. I'm either going to buy a YZ or a 4 stroke.....or a RM 2 stroke if it's cheap

 

[jaguar]

If you have to roll the throttle open then it's too lean. Just raise the needle one notch.

 

[BSWIFT]

I've recommended this many times. Read "Eric Gore's Jetting Guide" that is pinned at the top of this forum. If your CR has a good top and bottom end, you can have it jetted perfectly within 2 hours. Just follow the guide and only make one change at a time.
However, if you have other issues, worn top end, leaking seals, etc., you will need to fix those items first or you will just chase your tale when jetting.
http://ericgorr.com/techarticles/carbtuning.html

 

[jaguar]

That carb tuning page is no longer on that site. This one is:
http://ericgorr.com/incl/pdfs/carb cleaning and jetting.pdf

 

[motometal]

Regarding the carb...don't give up on the stocker too easily...it can be made to work fine. Stock pilot is fat and some folks benefit from a smaller needle jet which is the brass tube the needle passes thru. But it sounds like as others stated, you may have problems besides jetting. Someone experienced with these bike can tell if it has decent compression just by feeling resistance on the kick lever...no need to dis assemble anything...Also keep in mind...resistance on the intake side or the exhaust can make it do just what you describe. Make sure air filter is ok and nothing is plugging the exhaust. Seems like a long shot but I've seen stranger things.

 

[kneedrag05]

I have done countless hours of research on these bikes as I have an 06 CR250 and they are often lumped in the same category as the "3rd gen" CR250's (there are significant differences)

A couple things you need to do to get some things figured out.
1. Replace the plug (and get a few spares) from the auto parts store. they have the same NGK plug at half the price.
2. Check the air filter. clean and re-oil at least and possibly replace.
3. Inspect the reeds. Cracked, chipped or frayed reeds are no good.
4. Do a compression check.
5. Change your transmission fluid and measure the exact amount you put in. Ride it for an hour or so. Drain the fluid and measure it. If there is a significant difference in the amount then you have a bad crank seal.

Once you have done all the base line/cheap/easy stuff, then look at jetting. Jetting is more of an art than a science but there is science to it. You will need to re-pack your silencer, start with a new plug, and go to stock settings as per the manual. Something else you might want to consider is switching to an '05-'07 base gasket. They were thinner slightly raising compression and improving bottom end response. You will want to do this before jetting though.