Does anyone have any experience with big bore kits for 98 cr 250's.I am looking at the rpm 285 kit and forward motions 265 kit,what kind of powerband and horsepower do they have?
I don't have a '98, but I do have Eric's 265cc setup on my '01 CR250, with low-mid porting. Horsepower/torque were 45/32 at the rear wheel, with the hp. peak at 6500 rpm. Very nice smooth curve, with almost no hit at all...just smooth progressive power.
Basic setup at dyno time:
EG 265 cylinder w/ low-mid porting
Stock pipe/silencer
Stock carb, 370 main, stock needle in 3rd clip, 25 pilot jet
VP C12 mixed 40:1 with Maxima Castor 927
Dyno runs were done this summer, around 80F/80% humidity or thereabouts.
I had both the 265cc(2mm) and 275cc(3mm) setup on my 1997 and 2000 CR250. I liked the 2mm over setup better on both bikes. The 3mm over cylinders just didn't perform to my liking even after many different porting changes.
However, I really like the 3mm over cylinder on my 2002 YZ250. :thumb:
Thanks for the help,I am a long time big bore rider at 250lbs i was looking for a little help for the 250.I currently have a rad valve,pro circuit pipe combo with an fmf turbine core silencer along with many ergo mods to fit my 6'6" frame,I would like to stay with pump premium fuel.I taked to eric today and he was a huge help!
Hey Smarttoys:
Do happen to recall the jetting you used for your 1997 CR265? I've got the same setup and having jetting woes. Did you stay with the PowerJet or did you unplug it and go with a bigger needle? Did you go up on your Pilot Jet? Trying to jet at near sea level and am looking for a baseline that has worked with the 265. Any help would be great. email: bryans@itiblades.com
dat dude,
I haven't had the bike for quite awhile but I believe I used a 175 main, cut the slide 1mm, stock needle 2nd or 3rd position, 50 pilot and disconnected the powerjet. That was for 1500ft elevation and 60+ degrees.
Sweet, thanks for the reply...175 sounds a bit small for the main (185 stock) but I'll give it a shot. I went with a larger needle per Eric Gorrs advice, but still need to fiddle a bit. Haven't heard about modifying the slide though. Why would you do that, and if necessary, is that something that a local machine shop can handle or did you have to send it out?
I used basically the same jetting on my '97 and '00 CR's. Big bore cylinders usually require a little smaller main jet. I cut my slide to help clean up a small stumble in throttle response that needle and pilot jet changes didn't fix. If you have good response at 1/8 to 1/4 throttle then you won't have to do anything with your slide. You can cut the slide yourself if needed. Do a search since it has been covered a few times before. ;)
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