Just picked my new 2014 klx250s. Going to put a couple miles on her to break it in a little. The first oil change and check up she is going to the dealer for look over and I am going to have them install an exhaust and jet kit.

The two exhausts I am considering are either the FMF (should I get the header too) or the two brothers? Jetting Dynojet stage one or two. I will also get a K&N filter.

Thanks

JamieD

 

Dyno jet kit comes with both stage one and two. If you get an aftermarket pipe use stage two. Instructions are included. The only difference is in stage two you use bigger main jet.

 

There are lots of slip-on options available to you. Do a search and you'll find them on here. I went with the FMF because it's suppose to be a little quieter than some of the others. If you do just the FMF slip-on there is no need to rejet. However, adding a header and/or air filter mod will require rejetting.

 

Perhaps only if he is at a very high altitude. 2000 and below the bike needs to be re-jetted stock.

 

Cheapest slip on is the DG-R ($150) but it's nice and loud - I love mine.
Do the MCM cam mod - rejet to stage 2 using the 132 main jet if your near sea level - pull the airbox lid off - put on the DG or FMF slip on - and you'll have a completely different bike. You'll have about 20% more horsepower and (more importantly) 27% more torque than stock. It'll wheelie on engine power alone in first gear.

 

Yes!!

 

The one point that is often mentioned with both the 250 and the 300 is the small ID head pipe. You should do a head pipe for sure - full system if you have the money.

I know TNC is using a Muzzy system with a stepped head pipe, pretty trick stuff, if it is still available. The stepped head pipe is used on the primary tubes of exhausts on NASCAR and other such racing machines. The head pipe on my KLX650 uses an increasing radius drawn tube instead of stepping up the size, but the effects are the same. I have a larger straight gauge head pipe in the garage for my 250, knowing what I know about them and the 300s.

Back about 9 years ago the trick for the 300 was a full exhaust and a flat slide carb for the best bang for the buck. Of course you could have done both for about $500 then. Seems the carb and pipe strangled them a bit. Same is true with the 250s. I think it is slow carb reaction due to the CV and the small head pipe doesn't allow adequate flow at mid-high rpm.

Right now I am waiting for better weather (unheated garage) to check valves, do the cam timing trick I think, and set up for the head pipe and Pro Circuit slip on I picked up. If the money appears I may do the flat slide TM36 too, but who knows.

When it comes to jetting I take a different tack here than most - I use the Dial-A-Jet because of personal experience. The reviews in the ATV industry back it up as do a few of the motorcycle media, but everyone still likes to shuffle brass. I like to take a carb off once, install the enrichener set up, bolt it on and go. It has worked fine from stock to big bore with a full exhaust on the 650 without any changes, not to mention from 18 degrees F to 95 degrees F and sea level to over 5000 feet again with no changes. Plug is perfect, exhaust is same. Never too rich, never too lean. Makes it my choice over all. About $80 and an afternoon's work. Easy since the bike is jetted lean to start with.