'02 CR250 Porting & Head Shaving

[trout]

I did lots of putting around this weekend on an 02 right off the showroom floor. I didnt foul one plug with stock jetting and pump gas / hp2 @ 32:1. The book says it jetted for 0-999 ft elevation, I live on the coast so I guess I fit in that category.

Did you guys suffer jetting issues right off the bat or after a few rides?

 

[motometal]

Parker, no I don't have port work on either CR (I currently have an '01 and an '03).  You are making a good point, this could affect jetting.  I still think if you really want it crisp you might try going even leaner on the pilot if you haven't already.

Trout, the majority of the mx bikes running around out there are jetted way rich.  As long as the owner of the bike is happy, than so be it, but they are missing out on throttle response and a few hp here and there.  Some of the bikes I have re-jetted ran pretty well before the change, but ran that much better afterwords.

For example, I had a '99 Kx100 that was ported, and ran pretty hard, no plug fouling or sputtering.  One day I put in a leaner main jet, and gained an instant 1,000 rpm on the overrev and probably a few hp in this upper range.  I just wish I hadn't sold it!

 

[whitesands26]

Moto are you currently at 800ft. elevation ? Temps ? What size main jet are you currently running on Your 03 ?

I'm at about 400 ft. and the temps are in the 90's and I just went to a 410 on the main from the stock 120 and turned the air screw out 1/4 turn.

 

[motometal]

i'm not exactly sure on the elevation, but for jetting purposes our elevations are similar.  Temps have been 70-90 F.

I'm running a 390 main, 27.5 pilot, air screw 2 - 2.5, stock needle in between the 1st and 2nd position from the top (it's shimmed with a washer).  With Sunoco Standard at 32:1, it runs very crisp and responds like no other CR I have ridden!  In sand or cooler weather I would richen it up a bit to be safe.  I wouldn't feel comfortable with this jetting with 91 octane premium (it might ping).

 

[whitesands26]

Originally posted by whitesands26

I'm at about 400 ft. and the temps are in the 90's and I just went to a 410 on the main from the stock 120 and turned the air screw out 1/4 turn.

Oops...I meant to say that I went to a 410 from the stock 420 main and turned the air screw a 1/4 more of a turn from stock....Right now I'm having to run 93 octane pump until I can find some C12 or something comparable.