Low End Power/Torq

[thumpy3]

I want to know what is best to improve low end power on a 2005 KX 250 R1
What Pipe?
What, if any, fly wheel weight?
FM Gnarly or Pro Circuit Works series?
With gearing of 1451

I'm a big guy who is used to racing an XR650R in Best in the Desert and I'm trying to build an Enduro bike out of a KX250.

[hughes]

FMF Gnarly or Pro Circuit Platinum 2 These two pipes are low-mid range pipes.
Flywheel weight would make the bike have less hit and more traction. I am unsure of what weight (ounces) would be best.
I think a v-force reed system would work really good.
I think moose makes a reed block spacer your could try.
Last chance would be porting.

Is this bike going to run in the desert or in the woods?

[TPhill]

I have a 91 KX250 with a Pro Circuit Works pipe and an Answer spark arrestor (with a top end porting job) and my wife has a 2000 KS 250 with and FMY pipe and silencer. Mine has better bottom end, but will still pull the front tire in 4th gear. Hers seems to have a little less bottom end, more power on the top end. I dont know if its the exhaust set-up of the fact that my engine has had a porting job done to it, but it really pulls nice down low (for a 2 stroke that is).

[eprovenzano]

I have a 99 KX250 with a PC pipe.  I too was looking for more low end grunt.  I've changed the front sprocket from a 14 to a 13.  I also am adding a 11oz flywheel weight.  The gearing made the bike much easier to ride in the woods.  I haven't installed the flywheel weight yet, but am looking for more traction, making the tight woods easier.

A friend of mine has a YZF450.  He took my KX for a spin, he said if he knew he could get that kind of low end power our of 2 smoker, he would have not spend the $$ buying the thumper.  He wants to ride it again after I get the flywheel weight installed.  Maybe I'll be able to bring him back from the dark side and back onto a 2 smoker....

[FPMXer]

Pipes and flywheel weights will help the motors power output and can be tuned to your liking. If your looking for good pull out of the hole or a corner add some teeth to the rear sprocket and hang on. I had a 48 on the rear of my 125 and it had great top end. I put a 51 toother on the rear and dang what a difference out of a corner and the hole. You will give up some of the top end but even a 50 toother will suit your taste. Instead of buying them borrow them from a friend if possible and figure out which one you like the best.

[kx666]

For the most partthere is not much porting that can be done to a modern bike that will not kill reliabillity. ususally you loose low end power from porting, it is difficult to gain low end.

flywheel weights are a good way of gaining low end, so is milling the head.  just keep in miind you will be creating much more heat. milling a head is one of the easyest modifications you can do, and it will only cost a new headgasket. (if you are milling your head make sure to take your measurements with the gaskets you are planning on using. most builds can safely run a .060" quench band)

you can allways remove more so dont get too greedy. good luck on your build, i hope it is better than my spelling

[eprovenzano]

I recently changed my gearing to 13 front, 50 rear.  I couldn't wait to try it out.  I changed from a 14 to a 13 front about 4 months ago.  Loved the change.  The rear sprocket and the chain was due to be replaced, so I went from a 49 to a 50 rear with a new chain.  The only problem I have on long hill climbs is trying to keep the front wheel down....  I keep riding up on one wheel.  While everyone thought that was great, let me tell everyone here, that wasn't my intention...  at least at first.  But after a few runs, I would pick up the front wheel just to see how far I could carry her...

Yes the gearing is low, but for woods riding, its like a tractor.  All I need to do is point, and the bike will go where I want to go.

This bike has never failed me...  (now that I said that, it will die on me deep in the woods...)

What sprockets are you running?  This is the easiest and least expensive way to get the low end tourque your looking for, of course you sacrifice some top end...  (but I'm too d**n old to go as fast as I did when I was 15...  plus its takes a lot longer to recover from an oops)

[Mudshark]

As far as flywheel weights go, I have been reading lot on this subject (I want to
do the same to mine) From what I read, 9oz is the way to go. This will still leave
you with snap, but keep the motor turning over the hairy slow stuff, without
having to ride the clutch.

[eprovenzano]

I purchased an 11oz, but haven't installed it yet.  The bike runs so well, I'm not sure if I'm going to install it or not...

I'm not in too big of a hurry, as I did an endo last weekend, and was planted into a hill side. Its been 3 day's and I'm still in excruciating pain when I take a deep breath.  Can you say cracked rib(s).  So I will not be on the bike for a little while...