kx 125 '02: best mod for $100 for more low-mid power?

[binthedirtnow]

I have a 2002 kx 125 which I really like, but it could always be bettter!! Right now it has: new topend; Pro-taper bars; fmf fatty pipe and spark arrester; boyesen dual stage reeds; 12/51 gearing; uni air filter. Otherwise, the motor is stock. So, for $100, what mod could I do to increase the low-mid power? :aj:
B.

 

[keithb7]

Flywheel weight.

 

[binthedirtnow]

Flywheel weight?? I thought that just smoothed out the power hit for better traction? I'm looking for a low-mid boost...
B.

 

[Studboy]

Porting is about all you can do, but you will lose some topend if you port for low/mid.

 

[ellandoh]

uhh.........250 :clue:

 

[gowen]

uhh.........250 :clue:

:cool: That is the best answere I've read so far. But, the porting is the second.

 

[bikepilot]

You could find or make a thinnner base gasket, which would raise your comp raito and lower the ports a little:)

 

[Chili]

At $100 your pretty limited, porting will be more than your budget. I'd look at going larger on the rear sprocket if your looking for more pull.

 

[kuchera89]

a powernow. i would make it if i were you but if you want the real thing its right at $100.

does anyone know the website on how to make it yourself?
i've seen it before, but i lost it :|

 

[Rutbuster1]

Get a Moose Torque Spacer Kit. They run about $30 at Dennis Kirk. You place it between the carb and reed valve. It gives you more bottom end. Used one for years on many bikes. Even have one on my sons RM 85 for woods riding! You can also go down a tooth on your countershaft sprocket. You'll almost get the same effect but you'll be shifting a bit quicker.

 

[Chili]

You can also go down a tooth on your countershaft sprocket.

He's already running a 12 tooth CS I'd be very reluctant to run an 11, hence my suggestion to go up on the rear sprocket.

 

[binthedirtnow]

Great suggestions!

Well, hummmmm... PowerNow, reed spacers, add a tooth on the rr cog.... Well, if someone has a 250 for $100..... Or, I could sell my 125... but I like the 125......I'm a little too broke at the moment for porting.....decisions, decisions.....

I heard the powernow doesn't work. Anyone here that can give an opinion in its favor - did it make a difference for you?
B.

 

[bikepilot]

Save your cash and get good using the clutch, there is nothing wrong with slipping it a little to keep the motor in the powerband while not putting too much power to the wheel. clutch plates last an amazingly long time even with a lot of use and are cheap and easy to replace:)

 

[binthedirtnow]

Good response. Actually, I'm gonna hold off and save my money for now. I got a good idea today - why don't I just save my money and learn to use the clutch better? LOL I even have a new set of replacement plates I bought recently because I thought I roasted the existing ones. It turns out the existing are almost new!! Interesting to note though that the recommended amount of tranny oil isn't enough - I was getting a lot of noise until I put in a full liter as recommended by the kdx guys here on DR net. That fixed the problem and now the clutch works great again.
B.

 

[flyinzuki]

I would like to add two more options to help with low-mid power...Just in case...

1. MX Bonz exhaust spacer.
2. Carbon Tech low tension reeds.

Like bikepilot said, a thinner base gasket. :cool:
Cometic will make one for about $8 (base only).

And like Rutbuster1 said Torque spacer. :cool:

Total would be just over $100

That take you from Brrrrrrrrrrrraaaapp to Braaaaaaaaaaaaapp :laugh:

 

[binthedirtnow]

OK. Now these are some good ideas!

I like these... I was looking for these type of suggestions....Tuning tricks!!! I may try some of those ideas! Hey where can I get one of those exhaust spacers? And what reeds would you recommend? All these mods together might provide an honest shift in the powerband, it sounds like.... :aj:
B.

 

[viking20]

If you havent done so already , make sure the bike is jetted properly....Can make a big difference , and its almost free....

 

[NacNac250F]

I had an 01 KX125 which is very similar to yours. for $100 buy a reed spacer from moose, get the head shaved but not so much that you can't run pump gas( maybe .001 or a little more, figure 10lbs of compression for every .001 of an inch) and double up on the copper exhaust gasket. It all costs less than $100 you should have enough left over to go buy premix 5 gallons of gas and a couple spark plugs. The only thing you should really need to change is maybe a size on the pilot or raise the needle. You will feel a noticeable difference with those three things.

 

[binthedirtnow]

The bike is jetted awsome right now. And I always check my air screw settings throughout the day, each day I ride - it can change half a turn sometimes on the same day.

But I think I will get the torque spacer. The torque spacer increases the plenum volume, correct?

Aha!!! I thought that's what the exhaust spacer kit is - same as adding copper gaskets. Well, I'll probably do that one first since I have at least two of those gaskets available.

I don't know if I want to cut the head because that is irreversible. But I'm giving serious consideration to trying the thinner base gasket - that should acheive the same basic goal right? Except that will also change the port timing a little and increase the crankcase compression ratio a little too, right? This is really interesting guys. These are the kind of tuning tricks that make a difference in rideability that the average guy never realizes. Also, this is why I love 2 strokes. Thanx all... :cool:
B

 

[flyinzuki]

The stock washers are probably more economical but you can find the exhaust spacers --->HERE

 

[binthedirtnow]

Installed the washers today....

I had two extra exhaust washers so I put them on. I could be wrong, but it seems like the throttle response is better snapping the gas even with the bike on the stand.

Please inform me about this: If I install a thinner cylinder base gasket, will I have to use race gas? I don't want to use race gas. Also, to offset a compression increase I don't think I can install 2 head gaskets because the '02 kx 125 uses a steel shim gasket and, let me know if I'm wrong, I think using two would invite leaks. But, I just thought of something - I might be able to get a thicker head gasket from cometic, but that might be defeating part of the gain (increased compression) from using a thinner base gasket? True??

Now, I have a question about the torque spacer: How does it work?? It seems like it would reduce the crankcase compression by adding volume which could reduce the bottom end power(?). So, what change does it bring about as opposed to not using one? Unless I am totally wrong, but it seems that the spacer is installed between the reed block and the case, which would increase crankcase volume? Or is the spacer installed between the carb manifold and the reed block, increasing the volume behind the carb? I might forward this part to Rich....
B.

 

[bikepilot]

I don't under stand the tq spacers either. Also, how does the exhaust spacer help low end, I thought a longer effective head pipe lenght (prior to the expansion chamber) typically moved the power band up a bit and lessend low end power. Do I have this backwards?

thanks,

 

[KX02]

I don't under stand the tq spacers either. Also, how does the exhaust spacer help low end, I thought a longer effective head pipe lenght (prior to the expansion chamber) typically moved the power band up a bit and lessend low end power. Do I have this backwards?

thanks,

Yeah, you've got that backwards. A shorter header will move the powerband up the RPM range.

 

[Vic]

A shorter header will move the powerband up the RPM range.

Keep in mind that this is just a generalization. It doesn't hold true for every application. Sometimes it will just make the engine run worse. You just have to try it and see what happens.

 

[bikepilot]

Thanks:) I'll try a spacer on the KX100 and see what happens.