2000 CR250 now at 5,000ft. from 800ft elev. - jetting suggestions?

[g_man80]

I just recently moved from about 800 feet above sea level to 5,000 feet. I realized that I would lose power being higher up, but the bike seems gutless. I jetted the bike for 5,000 to 7,499 feet based on a tuning chart I got from a local honda dealer. Pilot - 48, Main - 175, Needle clip - 3rd, and 2 turns out on the air screw. I was actually running a 175 main jet back at 800 feet and it ran great. Does anyone have suggestions for a different set up? Perhaps I should go to a 172 or 170 main jet? I'm also thinking of moving the needle clip up one notch. I've already put a brand new twin filter on it and that seems to help get it some more air. Any help would be great.

Thanks,
G

 

[pace]

My riding is all at 5,500-6,000ft. I run the PWK from the 2000 CR on my '03 with the specs below. I use the 91 octane oxygenated piss they sell at the pumps here, and mix 36:1 Amsoil synthetic):

#172 main
#42 pilot
needle clip up one position from the middle
air screw at 2.5 turns out

I'm on the stock #7 slide and stock A715/289R/A327/A487 needle. I could probably go leaner, but I like to err on the side of caution on pump gas.

This will probably get you in the ballpark. I'd have a couple of jets on hand to bracket the specs above (ie. 170 main and 175 main, etc.)

This bike will still feel gutless. Welcome to thin air. ;)

-pace

 

[g_man80]

Thanks for the reply. Sounds like I'm still a little too rich. It seems hard to compensate for the thin air up here. I'm thinking of going to a 4-stroke next year. Right now it feels like I'm riding a 125cc. The power loss doesn't bother me as much in car, but then again I don't expect the same rush out of driving to the grocery store as I do riding. I'll keep messing with the jetting. Hopefully I'll get some decent results.

Thanks again for the info,
G

 

[pace]

Four strokes suffer from the effects of low barometric pressure just as do two-strokes, but of course you're starting off with more power so that may offset the perception of it feeling slow. Remember that the thin air affects everyone else's bike also and you'll soon get used to the reduced performance. You can compensate a bit by raising static compression to squeeze more (mass) air through your combustion chamber.

Anyway, try leaning her out a little more. Judging by my piston crown which only has about 5 hours on it, I'm still running a little rich somewhere. Your '00 CR should rip, even up here.

-pace

 

[mtk]

Pace is right; a four-stroke isn't going to magically solve the elevation problem for you. The only cure for that one is to move to a lower elevation or start with a bigger engine.

 

[Shig]

I ran a 172 in my 00 CR250 at about 5,000 feet. I didn't mess with the pilot, but the needle clip went back and forth between the 2nd and 3rd slot. When I rode it in the mountains above 8,000 feet I would go as low as a 165 in the summer. If you think its gutless at 5,000 feet, then try it at 10,000 feet. I'm totally with you on the 4-stroke logic. Here in Colorado it is getting hard to find a competitive 250-class rider (Mx and HS) above 170 lbs who's not riding a 450. I know that Pace is gonna blast me for that comment, but the thumpers have taken over the Rockies like Kudzoo in the south.

 

[pace]

I know that Pace is gonna blast me for that comment..

Nope, 'cos (a) I weigh 160lbs, and (b) I'm not competitive. :laugh:

I agree though.. ALL the top A and B class riders are on thumpers up here.

But I've found the 450F advantage to be marginal on the straightaways. They don't pull on the 250s the way I'd expect them to. Up the hill at Lakewood for example, it's easy to keep similar ability or slightly better 450F riders behind the 250, and I can often catch and pass the 250Fs.

-pace

 

[g_man80]

Thanks for all the input. I realize that a 4-stroke isn't going to solve the power loss problem. I guess I shouldn't have mentioned it in that context. My thoughts on a 4 stoke is just that it's something different and instead of upgrading to a newer 2 stroke I might want to try something new. I spent a few minutes on a yzf426 and I was quite impressed. Plus, that was a few years old with a lot of time on it.

Anyway, it looks like I have a few months to mess with the jetting. Everything is pretty much snow covered and I don't think it'll be melting for a while. Time to start looking for a snowmobile :p .

Shig, how do you like your 450?

Thanks again,
G

 

[Shig]

Hey Gman,
Actually, I love my 450. In 2000, I was the biggest smack-talker when it came to thumpers. I bought into all of the stereotypes. Since I've owned two CRF 450s, I've changed my tune. I prefer my 450 to a 250 for everything but freestyle. I still can't whip a 450 like my ol 250, but I'm trying.

Pace makes a great point about the 250s. I'm about 210 lbs, and before the 450, I couldn't get a decent start to save my life. The 450 has evened the playing field for me, but a light enough rider on a 250F (or even an 80 for that matter) can pull big hills and long straights just as well.