new guy here, need some more low end kx250

[SHMEE]

just bought a 99 kx250 mainly ride trails and canyons. i was wondering if anyone had some ideas. thinking about a flywheel weight and vforce 3 reeds. thanks

 

[mattb348]

just bought a 99 kx250 mainly ride trails and canyons. i was wondering if anyone had some ideas. thinking about a flywheel weight and vforce 3 reeds. thanks

Don't forget to gear it down, along with putting a low end pipe/silencer on it.

I'd go with FMF for low end probably.

 

[SHMEE]

if you look at fmfs dynos there pipes only help top end. iv had a lot of pipes and personally i like the stk one. thought about going to a 13/50 gearing, prob do that to. thanks for the reply

 

[kshackleton]

I have a 2001 KX250 and I went with a 12/54 gearing from the stock 13/49. Changing the rear by just one tooth is a waste of time. I also added a 13 oz flywheel weight and I now have a bike that went from unbearable to excellent on the trails. The gearing really improved the climbing and slow speed and I still find that I am almost never in top gear....so I still have all the top end I need.

I am also thinking of replacing the transmission gearset and primary gearing with that from the 2002 KX. That will change the primary from 2.75 to 3.00 to 1 and give me a wider ratio transmission.

I am also looking at the FMF Gnarly.....for now the exhaust is stock.

 

[kshackleton]

if you look at fmfs dynos there pipes only help top end. iv had a lot of pipes and personally i like the stk one. thought about going to a 13/50 gearing, prob do that to. thanks for the reply

If you looked at the FMF Gnarly pipe you would have seen that it moved the entire HP curve into a lower RPM range, the peak HP is higher than stock and it is generated at 7300 rpm instead of 8400 rpm for the 2001 KX 250.

One look at that dyno curve has convinced me to go with the FMF Gnarly for my KX.

 

[SHMEE]

stock is 13/49? mine has 13/48 i was going half. 1 tooth front =4 in the rear. if i wanted to go 4 then just change the front 1 tooth, plus the smaller front sprocket, the tighter the chain gets going around the sprocket, "takes up hp" and where did you find a 54 rear sprocket? thaught a 51 was the biggest?

 

[KXtrailrider]

In the 99-01 KX250 you can put in a 98 1'st gear(2.13 compared to 1.80) 2'nd-5'th are the same as the 99-01. I have this setup in my 250, in my 310 I have a 98 1'st 2'nd and 02 3'rd 4'th 5'th. There is a little gap between 2'nd and 3'rd but the 310 pulls it well. I use both primary ratios 2.75 and 3.00 depending on how low I need to go on 1'st. If you use 12 tooth counter shaft sprocket with an o-ring chain it can rub on the case by the seal, I don't like that so I don't go lower than 13. I get most of my stuff off egay. The most low end I have come up with is 98 ignition, rad valve,PC pipe, and 13oz weight. I don't have any FMF pipes but I have a stock and a PC on my bike the stock makes more top end and the PC more bottom end. I most often run a 13-49, I do alot of Idaho singeltrack. BTW I most often run the stock pipe , I like the overrev, always the fly wheel wieght and rad valve. Ed

 

[KXtrailrider]

I forgot but also you should strongly think about an Eric Gorr 310 setup for low end. I love my 310 and it is very FUN. Ed

 

[kshackleton]

stock is 13/49? mine has 13/48 i was going half. 1 tooth front =4 in the rear. if i wanted to go 4 then just change the front 1 tooth, plus the smaller front sprocket, the tighter the chain gets going around the sprocket, "takes up hp" and where did you find a 54 rear sprocket? thaught a 51 was the biggest?

Stock for mine was 13/49...and one off the front is like 4 added to the back...true. I bought the 54 tooth rear and the 12 tooth front from the dealer....along with a new chain.

The radius of the turn for the chain is a little tighter around the 12 tooth front sprocket, but the chain moves quite freely and if it has taken away any HP....it sure isn't noticeable. My final drive ratio went from 3.77 to 4.50. By going from 13/48 to 13/50, your ratio will change from 3.69 to 3.85....not a huge difference.

 

[Bandit9]

I second the 310 kit. I put a FMF Gnarly on it and it has greatly enhanced the low end. The Gnarly is thick tough pipe. It holds up well to off road abuse. The stock pipe is good too, but it is so thin, that it gets bashed up pretty easily.

 

[Noeboy89]

Not to hi-jack the thread, but what does the 310 kit cost?
Thanks,
Terry

 

[kx250kev]

In the 99-01 KX250 you can put in a 98 1'st gear(2.13 compared to 1.80) 2'nd-5'th are the same as the 99-01. I have this setup in my 250, in my 310 I have a 98 1'st 2'nd and 02 3'rd 4'th 5'th. There is a little gap between 2'nd and 3'rd but the 310 pulls it well. I use both primary ratios 2.75 and 3.00 depending on how low I need to go on 1'st. If you use 12 tooth counter shaft sprocket with an o-ring chain it can rub on the case by the seal, I don't like that so I don't go lower than 13. I get most of my stuff off egay. The most low end I have come up with is 98 ignition, rad valve,PC pipe, and 13oz weight. I don't have any FMF pipes but I have a stock and a PC on my bike the stock makes more top end and the PC more bottom end. I most often run a 13-49, I do alot of Idaho singeltrack. BTW I most often run the stock pipe , I like the overrev, always the fly wheel wieght and rad valve. Ed

Wow, it sounds like you've really given your KX some TLC. Sounds sweet, lets see a picture.

 

[KXtrailrider]

Thanks. I'm not much of a computer guy and haven't figured pictures out, but it's just a clean looking 99KX. Right now it is in dirt mode but I have also put UFO turn signals and lights and have a NV. plate for it. Some day when it's back in legal mode I will have my wife try and put up some pictures of it. Ed

 

[SHMEE]

whats the deal with the 98 ign? and a PC? iv been out for a while so sorry. last two years i was big into my bomb "ds650" trying to beat every other fourstoke out there. to many dollers there so i sold it.

 

[KXtrailrider]

Many say the 98 was the best KX motor. The main difference between a 98 and 99 is the ign. and carb, They use the same cylinder and porting. So i got a 98 ing. off egay and tried it with my 99 carb without the throttle position sensor pulged in and it worked great, the 98 didn't use a throttle position sensor. It makes more low end and less top end it seems to me, not worth it if I was paying full price for it though but watch egay there are tons of good KX parts to try. I bid low and lose most of the time but stuff keeps showing up and I keep bidding and have got a lot stuff cheap. I like the 02 ing. may be the best it seems like more low than the 99 and about the same top end. on all the KX ingnitions they need the wiring harness also. PC is Pro Circuit. The boyesen rad valve helped low end to and I like it, again egay, I use it and the flywheel weight all the time. Also for a little more low end you may try advancing the ingnition at the stator. BTW with the 98 ing. you need the 98 stator because it is wired in to the harness with no plugin. Also the 98 had the lower 1'st gear but the two motors are close to the same just many people feel the 98 was better. And to Noeboy 89 click Eric's icon on the left of this site. Call Eric and talk to him, he is a very nice guy and does the best work. Ed

 

[Gibby]

One tooth on the front is like 3 on the rear. I run a 13/51 in the woods and does great! Also for sure go with the FMF Gnarly pipe you wouldn't believe the difference!! The flywheel weight is also a plus(although I didn't like mine). You could go with some FMF torque reeds and a carb spacer as well. Just my 2cents....