elevation change corrections...

[jhendr3702]

if you were going to a riding place that is 4000 - 5000 ' higher than you normally ride and probably 30dg cooler, what changes would you expect to make on 2 stroke ?

we ride at about 3600' here in amarillo, but our air is horrible.. we went to red river and i think the highest peak was just over 10000.. the bike is a 2007 mc250 which runs great here.. i dropped main from a 165 to a 155.. pilot from a 40 to a 38. tried cek needle in all different positions.. air screw also.. got it "rideable" but was not great..40:1 mix and it spooged down the silencer so bad it covered the swing arm within about 10 miles..

just wondering.. never really had an issue before, but i dont think i was as picky as i am now.. on my older bikes we just dropped the main 10 points and rode and i guess it was fine..

[Rick]

Originally Posted by jhendr3702

if you were going to a riding place that is 4000 - 5000 ' higher than you normally ride and probably 30dg cooler, what changes would you expect to make on 2 stroke ?

we ride at about 3600' here in amarillo, but our air is horrible.. we went to red river and i think the highest peak was just over 10000.. the bike is a 2007 mc250 which runs great here.. i dropped main from a 165 to a 155.. pilot from a 40 to a 38. tried cek needle in all different positions.. air screw also.. got it "rideable" but was not great..40:1 mix and it spooged down the silencer so bad it covered the swing arm within about 10 miles..

just wondering.. never really had an issue before, but i dont think i was as picky as i am now.. on my older bikes we just dropped the main 10 points and rode and i guess it was fine..

I would use this as a base line. My owners manual for my 200 has pretty much the same table. http://www.iwt.com.au/mikunicarb.htm

[jhendr3702]

Originally Posted by Rick

I would use this as a base line. My owners manual for my 200 has pretty much the same table. http://www.iwt.com.au/mikunicarb.htm

pretty good read.. i guess i should have taken one more step leaner..

thanks rick.. we will go back in the fall, i will be more prepared..

[AZRickD]

Temps will drop 3 to 4 degrees F (depending upon humidity) for every 1,000 feet. Temp changed affect jetting much less than altitude changes. Do a search on Density Altitude calculator to prove this to yourself.

For my summer change of Phoenix 2,000 feet and 100+F) I will drop one or two on the main and pilot when I travel to Flagstaff 8,000+ and 80F).

But I have an RB modded AS1 and head. The jetting is quite a bit tighter.

[jhendr3702]

Originally Posted by AZRickD

Temps will drop 3 to 4 degrees F (depending upon humidity) for every 1,000 feet. Temp changed affect jetting much less than altitude changes. Do a search on Density Altitude calculator to prove this to yourself.

For my summer change of Phoenix 2,000 feet and 100+F) I will drop one or two on the main and pilot when I travel to Flagstaff 8,000+ and 80F).

But I have an RB modded AS1 and head. The jetting is quite a bit tighter.

mine is an mc250 with an rb modded as1.. we are 3600' here.. i have a bud who runs a pro stock car.. he has checked it here and our "corrected air" can be 5000' on some days..

my "thinking" is that i am on the rich side here, so even dropping what i took with me, i was still on the rich side.. it was not horrible, but could sure have been better.. i wonder how much of that is the taper of that needle

[Rick]

Originally Posted by jhendr3702

pretty good read.. i guess i should have taken one more step leaner..

thanks rick.. we will go back in the fall, i will be more prepared..

Just a rule of thumb.....Like I should be throwing out suggestions...I jet and leave it! The 200 is more forgving than my 125, which I now own a ton of brass!

I hate JETTING!!!

[jhendr3702]

Originally Posted by Rick

Just a rule of thumb.....Like I should be throwing out suggestions...I jet and leave it! The 200 is more forgving than my 125, which I now own a ton of brass!

I hate JETTING!!!

me too... jakobi is going to make us learn tho....

[Jakobi]

Buy a smart carb?

Seriously,

What I would do i just take it up there with a couple of needles. Maybe a couple steps different on the needle diameter, and a half clip adjustment or so. Start the bike and run it. Jet it like you just bought it.

Put in a main you think will be ballpark (see correction table), AS1.5 Start it and ride it. If its fluffy off the bottom, open the air screw half a turn. If its still too rich go to a leaner pilot. Continue until you get a nice idle and off idle response. Then clip position until it revs nice. If its still burbly just off idle that you can't address with the air screw or pilot, go a leaner diameter, bump the pilot up one, and test again. When done, DOCUMENT your findings in your notepad and keep it for next time you head up that area and you'll have a ballpark setting to start from.

No fun wasting the first hour jetting, but maybe better than dealing with a poor running bike for a ride?

Elevation wise here I only see 0-1000M (approx 3280ft), so I don't have to do this myself at all

[jhendr3702]

thanks jake... no funds for an sc... so... I will jet on..

took a lot of time since I got the bike home working on getting my jetting here lined out.. I think that will help when I go back up.. I am leaner on the pilot than I was 38 instead of a 40.. air screw seems good at 1.75. have not messed with main, but put the 165 back in.. I have a ddk in it ctr clip that came in a lt kit I bought a long time ago..

I have 2.5 acres, so I have a diagonal across it that is a 4th gear wot run.. it now pulls a lot stronger off idle and easily lofts front wheel.. when I get to the end, I no longer can see the cloud of 2 smoke oil I used to.. pulled the plug and it is tan, no lean surge at idle, no bog at all..( the neighbors really like it when I do that....)

the "problem" is the bike has run good with anything in it, so I have not really messed with it.. it has been ok around here.. I will keep messing with it.. I have plenty of brass, need to put some seat time and figure out needle..

I have a cek, ddk, nedh, nedw, n3ew, and oh yea a real nice n1ee....