jetting for mods

[parkerCR]

I have an 01 CR250, this sort of question has probaly been asked
several times but the search was to no avail. I have a V-force and just purchased an FMF fatty pipe. I just drove back from Florence oregon where I was riding the dunes. Everything was ok for the first day but then the bike turned lean. The plug was white as the day got later. I looked at FMF's specs for jetting and I even went richer on the main one and one clip on the needle. It would seem
that the temp of 50-65 degrees and a relative humidity of 70% would make the bike run rich. I also have an S-7 nozzle which may be part of the problem I am not sure.

I just can't figure out how it was running so lean if I am jetting with specs from So Cal at 70 degrees, sea level, and 0% humidity.

Any of you jetting gurus shed some light on what may have happened?

Thanks

 

[parkerCR]

Sorry
My jetting was:

S-7 nozzle
410 main
stock needle third clip
30 pilot
2 turns out on AS

 

[karterron]

Mod Edit - This is NOT the For Sale forum

 

[jmics19067]

sand clogging up the screen in you fuel petcock?

 

[john stu]

s-7 nozzel ? maybe try the s-8 i would try a bigger main one size will make a difference but not a lot. if you are riding in sand that puts a big load on the motor and might need a bigger main than you would need i the dirt.what nozzle does your bike come with stock?it could be an air leak check all conections on the carb and reeds and check the left side crank seal.i would bring some bigger main jets and tools to where you ride and try them after making sure there is no air leaks.one more thing what plug are you running i think it should be a ngk br8eg or equivalant if its a 7 go to an 8

 

[parkerCR]

My bike comes with an S-9 stock, would it be better to put that back in the carb?

 

[hotrodvw]

ParkerCR......I ride in Florence all the time, and I had the same prob you did. It's not the elevation, it's not the temperature. It's the Humidity. High humidity = high air density. You need to go one to two steps bigger on the main. On my KTM I run a 178 main. I originally ran it lean, got hot, and fried the ignition. I bet yours ran like a bat out of hell, eh? Best thing is to ask around with the other guys out there riding a bike like yours........similar mods. Generally, you only have to change the main down there. Easy swap for a fun day! Good luck. Eric

 

[parkerCR]

Eric

Thanks a lot. It was probably the main.

 

[PT cr]

More humidity means less oxygen in the air which makes the bike run rich.
Whatever works I guess?

I have had my own problems jetting my 01 CR250, and I've found the S7 nozzle to run lean (pinging and run on). I use it now with race gas and it seams to work OK.
Good luck

Parker