More Bottom End '05 KX250

[Kawabunga]

I recently purchased an 05 KX250. The bike has a few mods from stock including VForce 3 Reeds, Pro Circuit Works pipe. It also has a new Vertex piston/rings ect...

Its the first KX I've owned in many, many years. I'm coming off an 00 RM 250 I set up for woods riding. Mainly single track in the mountains of WV. I lowered the gearing and added a flywheel weight to tame the hit of the RM.

I have very liitle time on the KX but already see I need more low end grunt. I need more lugging power. If this bike falls off the pipe its over. It simply will not lug down and come back from it without a handful of clutch. Then the monster hit comes on in the mid range, the rear wheel breaks loose and its over. (It feels more like an extremely hyper 125 than a 250.)

Could this be a mechanical problem, power valve/carb or is it the nature of the beast?

I like everything else about the bike and would like to keep it. Its in excellent shape and I like the suspension/handling of the bike. It turns great and feels stable at any speed.

Has anyone added a flywheel weight and a FMF Gnarly to an 05? I'm hoping these changes with lower gearing will get more out of the bottom of this bike. I hate to spend the money and still not be satisfied though.

Any advise or direction would be appreciated.

[The Flyin Hawaiian]

I have heard that this is the nature of the new style engines. My 04 is smooth and torquey. My girlfriend, who also rides a 04 250 and competes in enduros, just picked up a 07 and we were a little concerned about the type of power it puts out. Its still in the protective plastic wrap, fresh out of the crate so we havent ridden it yet. The Gnarly worked well on my 03 KX, which I thought was lacking in the lowend dept., also the V Force and fww along with 13/52 gearing helped. The FMF Q or the Pro Circuit 296 helps smooth the low to mid transition, I prefer the 296 because of durability issues with the Q.

[Jeeks]

You need a stock pipe on that,  3rd gear berms all day.

[makKX250]

I dropped to a 12 tooth counter sproket and added an 11oz FWW. It helped with it's lugging ability and really helped tame it down in the mud/ice/snow/rocks and other muck we have here in the rain forest they call the PNW. The VForce 3 on my YZ125 really helped with the low end throttle response so that is going to be my next mod. Then if that doesn't do it I'll look into a Gnarly pipe. Funny, I stall in the really tight stuff on the 250 probably five times as much as I do on my 125 which doesn't stand to reason since I weigh 210 lbs.

[Dutch-K5 Fan]

Ad a spacer to the VForce 3 Reeds, and a 10 or 15 mm long pipe between the cilinder and exhaustpipe.
Longer frontpipe gives more bottom end.

 Dutchie

[Kawabunga]

You guys have confirmed what I was afraid of. Seems it is the nature of the new style KX engine. The very reason I decided to upgrade from the RM was I needed a better low end for the tight mountain single track I enjoy riding so much. I read the online reviews of the '05 and all kept talking of the this excellent power throughout with a smooth hit to the mid. (I guess the MX guys and woods guys have a very different view of smooth.)

Don't read me wrong; I love the hit of a 2 stroke coming on the pipe but I need something below that hit also. I've ridden smokers for many, many years and will continue to do so. This thing right now is either on or off. No in between and no room for error without grabbing the clutch. My old RM actually had more lugging ability than this bike. (Bummer)

A quick stab of the clutch and the bike is ready to roar but this is the last thing you need when riding slick rocks, roots and mud on an off camber single track trail in the mountains. I'm sure its great on the track though. The thing is a beast in a drag race for sure!

I'm not giving up on it just yet. I'l be dropping a tooth on the front sprocket for this weekends ride. The PC pipe must also go and a fww is on order.

Never tried the spacer on the exhaust before. I'll look into that. I'm thinking the V force Reeds are already spaced back??

TFH - I hope your girlfriends new bike fits the bill perfectly. I heard the 07's have been tamed a bit to reduce the enormous hit in the bottom of the mid range.

Thanks guys. I'll keep you updated with my changes to the bike.

[dmstarr]

I just picked up an '06, and it seems to have a ton of low end. Of course, maybe I am confusing that low-mid transition hit as low end. The problem I have with it is when I am in tight stuff and let off the gas, it wants to stall - even with a FWW. I never had this problem with my '97.

[SLOWPOKE]

Hmmm I went the other way with it.(gearing)  I run AA in the missouri series and love this bike after coming off a 06' 300 KTM. 
What has worked for me to tame it down was,

13 oz FWW (tried the 7 oz its for sale)
V force reeds
Gnarly Pipe
FMF shorty
13 front sprocket and 48 rear (this helped the most taming the hit and spreading out the power a bit,  Did not hurt lowend at all)
JD jet kit was spot on, it also helped a bunch!
But most of all you must carry speed on this bike and use a little clutch.  Ride it more and more and you will adapt just fine it just takes seat time thats all, but in the long run you should be faster from corner to corner on this bike then any other IMHO!

[Kawabunga]

UPDATE:

Problem found. Power Valve not functioning correctly if at all. Cleaned entire assembly and replaced the valve assembly. (By longtime KX racer/mechanic in the area.)

Its like riding a different bike now!

The 13oz. fww also tamed the enormous mid range hit. I'm a bit too low in my gearing now but still prefer a littler lower than stock. I can manage the hit by riding a gear higher and now being able to lug the bike a little in the slick/nasty stuff.

I'll probably end up at 13/52 or 53 if I can find one. The 12/51 is too low.

Now that I have a little confindence in the bike, I'll be replacing the PC pipe with a Gnarly very soon. I'm excited with this bike now!

[kaw rider]

they change the spring on the new motors. i would stiffen up the spring alittle.