Lean in cold weather conditions?

[1998RM250]

In previous posts I was worried about the crank bearings being bad on my 02' cr 250, but after having numbers people check it out they said I am just being too meticulous. Last night here in FL the temp went from 84 degrees to 54 degrees. The airscrew was set at 1.75 turns out, and it was idling a little high and "felt" lean. Also I noticed it has a bad o ring on the header pipe and was leaking a tiny bit, would this effect the jetting? I feel like when I am cruising long straight away's on the 2 stroke that I am going to blow it up as I've heard that is bad for these motors, and it seems to lean out even more when cruising in 5th at lower rpms. Carb was completely cleaned as well as air filter before the ride, I've also heard the 02' CR's come jetted actually lean from the factory?

 

[julien_d]

Yes, you'll be running leaner in colder temperatures. Not sure if it's a problem for you, depends on how close it's currently jetted.

 

[_JOE_]

Drop in a size bigger pilot and raise the needle a clip if temps stay cooler.

 

[1998RM250]

Sweet, If i can find some VP 110 technically that would make it run a tad richer even correct? I'm new to the TMX, I've heard of some swapping them with a Keihin PWK setup.

 

[High Lord Gomer]

Cruising while on the gas is not bad for the motor but coasting IS! Many people will get to a high speed and then coast. The bottom end is still turning at a high rate and if the throttle is closed, you're not getting gas NOR OIL to the bottom end. If/when you do slow down, pull the clutch and blip the throttle as you slow.

 

[BSWIFT]

OH so true, Gomer. Nothing like siezing a perfectly good motor because of stupidity. If your jetting at 84F is spot on, you may want to make the carb a bit rich know in colder weather. If you are rich at 84F, I would just ride and have fun.

 

[1998RM250]

Well I pulled the plug yesterday after about two hours ride time on trails, looks slightly lean and running cool, what do you guys think?

 

[2-Strokes 4-ever]

The photo looks like a flesh-tone color?... which would be about right. If it looks like it's leaning towards white, I'd go one step richer with the pilot. We tune the pilot so we get a temporary bog for a minute or so after start-up (after the choke's off.) Although the pilots real focus is 0 -1/4 throttle, it does effect the entire range.

Tune the pilot first, then the needle. Once the needle is correct, you may want to go back and check the pilot again.

We've never relyed on plug checks too much for the pilot and needle (mainly a sound and feel thing), but plug-chops work well for the main jet IMO.

We change the pilot and main three times per year because the years riding temps go from 30* - 100*.
Richest when 30 - 55.
Middle when 55 - 80.
Leanest when over 80.

 

[1998RM250]

Thanks for the great info as always, it seems when crusing in midrange rpms it wants to lean out a bit and when you pull in the clutch the idle is a bit high. Before it is completely warmed up it has the "slight bog" until you clear it out then it rips.