Hi Guys,

I am new to this forum, and am just about to plunk down the cash for a new KLX250S.

Can someone put together a KLX250S Mods Bible/Primer of some sort that everyone can agree on? All this info is overwhelming and confusing. I have pages and pages of info and one guy says one thing, another guy something else, and nobody can seem to get the part numbers right. I have seen and used documents like this on Thumper Talk with great success and happiness. This forum seems to be the place for the 250S though…

As far as I can tell, the following is what needs to be done to the stock bike to increase performance:

• Remove the snorkel
• Drill the slide valve vent hole with a #30 drill bit
• Re-Jet carb 122.5 Main Jet - Drill slide vent hole with a #32 drill.
(so which is it? #30 or #32 drill bit?)
• Install 120 jet (again, 122.5 or 120??)
• Install a bigger yet imaginary tank
• Drill out the first deflection plate in the exhaust with a 1/2' drill
• Drill out the Crank-Case Vent Hose fitting in the Lower Front Air Box to 3/8" (huh?)
• Install 13 tooth front sprocket and 45 tooth rear and install new chain
(But where can you order all three? What are the part numbers??)

Can someone just put together a complete kit containing all the frickin parts plus instructions and sell it on Ebay? I would buy for sure!

Or better yet, when will they make a dual sport straight from the factory with a big enough tank that doesn’t require any mods??!! Do you have to smuggle one in from Japan or what??? One that you don’t need to be a mechanic/engineer/MacGyver/just plain lucky to be happy with. Is the stock bike really that bad?

 

The bike is great stock, some people just want more lol, mine is stock apart from the Pelican case on the rack. Having said that for the dirt it really could use lower gearing, sump guard, barkbusters and maybe radiator guards, but thats true of virtually all dual purpose bikes. After all they are dual purpose

 

The bike is great but for my style of riding i wanted lower gearing 13/ 45 i may do carb work later down the road. I have been making baby steps first 13 tooth sprocket put 100 mile on it that way. Now i have gone to the 45 rear and just got back from another 100 mile ride. much happier with this set up. It is each there own and you do what you want to do. You will not be disappointed at all if you decide to this bike. All this info can be overwhelming. That is my 2 cents hope that helps.
FYI, At this time i do know the front sprocket is a pbi po45-13 pro or 50-045-13 you can obtain that thru Dualstar the rear at least what i used is a jtr460.45 can get at local shop and then a new chain 520 108 links

 

I am leaning toward not actually doing anything else besides the pelican case on the back and the 13 tooth on the front. I'm the kind of guy that likes leaving things as stock as possible. Hey Scott when are you going to get a photo gallery up so we can see more pics, of the bike, trail pics or anything. "GO SEAHAWKS"

 

mrphone, I would suggest lower gearing 13/45(requires 108link chain), works fantastic for scat and I. Just the gearing improves the bike immensely. Dual-Star can get you what gearing you want, not in their catalog yet, but they can take care of you if you call them. If you want more mods ask after gearing down.

 

The bike's great right out of the box. However, it's also got a lot of additional potential once you uncork it a bit. Gearing helps (13/42 or 13/45/with chain).

I just love to mess with mine. I enjoy working on stuff and I'm an engineer so I tend to like to take things apart and try to improve them.

I'll try to answer some of the questions you had:

The jet size (120, 122, 125, 128, etc.) is really going to depend on how much you open the airbox and exhaust. Plus it depends on what altitude above sea level you ride. The stock main jet is a 118 so going up a size or two with simple airbox and exhaust mods is going to work for most people. More fuel will be required on the high end (thus a bigger main jet) if you really open things up.

The slide vent hole can be drilled with either a #30 or a #32. However, finding numbered drill bits is difficult unless you have a speciality (old fashioned) hardware store nearby. So...a 7/64th splits the difference nicely.

The crank vent hose drilling is a simple matter. The crank case is vented to the airbox. They put a tiny hole at the end of the hose (where it connects to the airbox on the right side of the bike behind the carb) to prevent oil from flowing into the airbox too quickly if you lay the bike flat on that side. However, this tiny hole can cause pressure to build up in the crankcase which reduces power. Drilling it out to 3/8" or 1/2" prevents this pressure build up. Just be aware of the fact that you don't want to leave your bike laying on the side for too long.

There are two gas tanks known to fit this bike. Acerbis makes a 3.7 gal and IMS makes a 3.2. The Acerbis is on backorder here in the states until April. The IMS may require some minor mods to the bike to fit. This remains to be seen.

The part numbers you seek are all available in this forum. Just check the threads on 13t sprockets and the one called "opening up the KLX250s"

Enjoy!

 

Thanks for answering all my questions, you guys are great! It’s all much clearer now! I feel confident I can open the bike up. I appreciate you all taking the time to share your knowledge. There isn't a huge dual sport following here in PITTSBURGH, so I need places like this to get info and hear from others. I will share pics once I get the bike, just have to sell the one I have now…


This one's for you deej: