I've been using a 20-50w Castrol semi-syn, but lately with OAT's running in the mid 40's up to around 60 F I've noticed that up shifting seems to be a bit clunky. Adjusted the slack in the clutch cable play to the .12" that the manual advises, with no change. Is it likely that this grade is the cause even though it falls within the use range in the manual? Would going to 10-40w make any difference? Seems like the engine and oil temps would be sufficient that it wouldn't make any difference, or am I missing something?

 

I've noticed my bike has a harder time firing up on cold (30's) mornings too and I'm using Mobil 1 synthetic 10-40w. I would think with 20-50w it's got to be worse. I'd try going down to the 10-40w.

 

I'm getting a good easy start and after warm up drive away is normal. Just the shifting seems a bit clunky even after 30 min. of riding. That's the part that doesn't make sense. Maybe it's something else?

 

My 2012 250s factory manual calls for 10-40. Have you ever noticed that every racer who pays for they're own motors uses Red Line oil? I thought " Let's ask a person that really knows about oil". I found Red Line's phone #, left my # and soon got a call back from Dave, an engineer at Red Line. Very nice guy. Very smart guy. He answered all my questions and I learned quite a bit about oil. I love this forum but there are people out there that are a lot smarter than us. It's easy. Just ask them. They LIKE being asked about the field they spent 4+ years in college to learn. It's also their job. P.S. When you phone these people be prepared. Think about your questions and write them down. These folks are very busy. Don't waste their time.

 

Another thought. Oil needs to get hot enough to evaporate (atomize ) the water in it. That means a water temp of 180 to 210 degrees. Go look at Thermo Bob's research on klx250 water temperatures. I'm shocked that these bikes run as well as the do.

 

I've been running in -10º - 0ºF all week(that's before wind chill). Once I get it started...I let it warm up for 4-5 minutes, running 10W-40, and have no shifting problems at all.
The only time I had bad shifting was when I needed an oil change, after slipping the clutch (a lot) up some big rocky hills trail riding...or when I didn't notice the shift lever getting loose.

 

20w-50 seems to be a bit excessive IMO, especially at those temps. If you were bombing through death valley in the middle of the summer with the engine running hot it might be okay, but in the cool weather like that were the bike is unlikely to really even heat up fully thats probably a bit too viscous.

Just as an FYI on oil rating, the first number is the viscosity rating in winter (hence the W) at 0 degrees F and the second number is the viscosity at operating temp 210 degrees F.

So a multi-viscosity oil like a 10W-40 will behave the same at 210F as a 5W-40 oil. But at 0F the 10W will be "thicker" (more viscous) than the 5W oil.

 

that is what it comes with from the factory...but, the klx250s/sf manual gives you the recommended oil weight for different weather situation..the recommended varies in the manual...i'm currently using 10w-40 yamalube semi-syn...but, after it runs out...i have jug of rotwella 5w-40 full-syn next...5w should help with cold starts..

 

I just put redline tranny and gear oil in my car...
What did they recommend for the klx?

 

I'm an engineer and if you call me at work I'll tell you how great my product is and all the benefits my stuff has over the competition. You buy my stuff, I pay my bills. I've been at it for 20 years and haven't really been challenged by anyone that calls. I don't lie, but I stack the cards in my favor. Knowing this, I'm not real inclined to ask a manufacturer what they think about their own product since I know I'm getting a biased opinion.

I've notice my shifting gets clunky when my bike is hot. Doesn't matter what oil I use.