I guess I won't be getting my KLX250S till around mid November, so lets talk about stuff I can do to it after I get it? I'm talking about the MODS!

I've seen a lot of posts about Big Gun and Muzzy exhaust, are those the only ones available for it? Or just the best ones.
Also about the 300cc kit, where do you buy that, I'm having a hard time finding online stores that really have any KLX250 parts/accessories.
The IMS fuel tank seems to be a big modification around these boards, after all 1.9g is kinda wimpy.

The main thing I'm really interested in would be suspension modification, how tough is the bike stock? Will it stand up to some decent jumps without breaking in half? I notice it has a steel frame compared to most modern dirt bikes which are all crazy aluminum deals now. Not that it would make it weaker, just heavier then a modern aluminum frame I'm sure.

Is there anything else that really can be done to these? Jet kits?

 

Goodness, where to start? Big Gun or Muzzy or ??? Some folks have used a While Brother's pipe and reported that it was great. In generally, I think any aftermarket pipe that is a "full system", i.e., header, and silencer that works on a KLX300 will work on the KLX250S. What you need to be careful of are the KLX300 "slip-on" pipes. These are designed to fit onto the KLX300 header and replace the KLX300 silencer section. But the KLX250S and KLX300 headers are different so the KLX300 slip-ons don't quite fit. But a KLX300 full system that replaces both the header and the silencer will work. If you want a slip-on, you will need to get a KLX300 head pipe - shouldn't be too hard to find, try e-bay for that. That will open the door for all the slip-on options.

300cc kit - just buy the individual parts from some place like RonAyers.com. Parts list is in the common part numbers thread. WARNING: if you don't plan to do the install yourself, check with your dealer or your mechanic to make sure they will install the parts that you purchased. Some dealers / mechanics may insist on sourcing the parts themselves. I did mine myself, so I just bought them the cheapest place I could find them which happened to be RonAyers.com.

IMS tank - moderate install. But I think more folks have installed the Acerbis tank since it bolts on with no mods. I did the IMS, I just liked it better and the Acerbis was no where to be found at that time, though there seem to be a few more popping up recently.

Regarding other stuff - you can take the bore size to 330cc without much trouble. You need to buy the 300cc cylinder and have it bored out to 330cc. Check kustom-kraft.com for that. They do the boring, plating, honing and other prep and then supply the piston, rings, and gaskets that you will need. Also, one can replace the carburetor with a pumper carb. I've got one on order, but it is back-ordered. I'm bummed about that, but it's going to be a while since I can ride now so I guess there's no sense complaining too much.

Regarding suspension, it is really pretty decent on this bike but is set up for a 150 lb rider. So depending on your weight, it may be perfect or require some adjustments. Some folks here have replaced the springs with stiffer spring rates to match their riding weight and report good results. There are several adjustments possible with the stock suspension, though, to fine tune it including pre-load, compression, and rebound adjustments for the rear shock, and compression adjustments for the front shocks.

Jet kits: jetting is pretty much one of the first things you'll want to do. Jetting, airbox, pipe - the standard low-cost mods to open the bike up. KLX300 jet kit works, I personally just bought the jet sizes and parts that were recommended here from the parts list thread and saved a few bucks.

There are tons of variations of mods to do, ranging from simple and ecomical to expensive and more complex. Just pick your poison, there are lots to choose from.

 

Wow Nobrakes, you have it all covered. You just made me want the bike even more!!

I was actually just looking at a KTM 450 EXC-G Racing but that thing is expensive (2x that of the Kawa), and I still question KTM's long term reliability from friends personal experience. I think I'll be much happier with a KLX250 with a 300cc overbore.

 

Kawasaki KLX250S 300cc Kit

1 x barrel p/n 11005-1983 = $309.93
1 x gudgon pin p/n 13002-1109 = $9.63
1 x set piston rings p/n 13008-1071 = $36.66
2 x gudgon pin clips p/n 92033-1054 = $1.68
1 x Head gaskit p/n 11004-1314 = $37.31
1 x cylinder gaskit p/n 11060-1740 = $5.16
1 x Piston p/n 13001-1463 = $62.64

Total = $463.01


So how much power does that add for $470? A noticeable amount?

 

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But that wouldn't be my first mod - if I were you I'd do the carb jetting, airbox, and pipe mods first. These will reclaim some horsepower from the EPA restrictions. Depending on your riding, you might also consider a gearing change which will increase torque, but will not increase power.

The 300cc adds horsepower which you will feel as more power = higher torque across the throttle range, similar to what the gearing change does, but it doesn't it by increasing power, as opposed to changing the gearing ratio. But if you don't jet and open it up first, you most likely will not see all the benefits.