Kmx more power?

[uk_kmx]

What mods can be done that aren't a 200 conversion? I've done air filter and exhaust, I'm also running a 13t front sprocket.

[bladerunner]

What kind of speed are you getting at the mo? And has the kips valve done the usual trick of shearing?
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[uk_kmx]

Well the exhaust hasn't arrived yet, but I seem to be getting 70 on average, powervalve assembly is relatively new and opening at 7-7500. I'm not too worried with top speed it's just the fact that to wheelie in second I have to near on redline before popping the clutch.

[Boxing]

If you're going it for more power to wheelie, then you want to just get it up in first and go through the gears whilst in the wheelie.

No point in really doing wheelies on a 125CC. You get points on your license if you're doing it on the road, and if you mess up it costs money to fix fairings etc.

If you want to do it off road, get a 125CC 2-stroke like a KX 125, lean back and it'll wheelie on the throttle.

[stevo as b4]

I take it with the 13T front sprocket your going for acceleration and not top speed, seeing as they run 14/48T as std, and in full power form are a fraction undergeared for road only use in that they run into the red in top.

Is the bike in good condition, with good compression, and been properly maintained within accordance to the service/maintainence schedule? If so and it's full power I am quite surprised your not finding first and second gear wheelies reasonably easy especially with a 13T front sprocket. You can certainely wheelie in 1st/2nd on the KMX without needing the clutch, but it's down to preference. If your slipping the clutch near the red-line, I suspect it's more your technique that you need to work on and not the bike.

What exhaust system do you have? new expansion chamber and silencer or has just the silencer been changed?

The Gianelli system gives the bike the most top end power of the two available aftermarket front pipes, but for say an extra 0.8bhp-1bhp more at the top end your lose a lot of low down power compared to a std de-restricted pipe.

What airfilter or airbox mods have you done and what jetting are you running at the moment?

You can get around 27-28bhp (crank figure) or 23-24bhp at the rear wheel with some fairly easy tuning mods and a few aftermarket parts, reedblock, airbox mods, and a bigger 28/30mm Flatslide Mikuni. With light cylinder porting and skimming and re-profiling the head to raise the compression slightly you should manage around 30bhp the same as the 200cc engine that's in a lower state of tune, but with a far more peaky delivery and less usable power by comparison.

I personally think you can make a KMX125 go very nicely with some careful simple mods, as mentioned, and be happy with the performance. The 200cc conversion is an alternative route, but my preference would be to buy a complete 200cc motor and re-build that, instead of converting your 125 with a 200cc top end and all the hassle and different bits that you need to do it.

Lastly get some pics up of your KMX so we can see another example of one of the best 2stroke 125 trail bikes ever made.

[Compo]

My lads KMX is running standard gearing and will power wheelie in 2nd no clutching it up, off the power with a timed pull on the bars.

Standard front pipe with DEP rear exhaust standard carb with Boysen reeds 112.5 main and a 27 pilot and the thing carbs nice with the airbox lid opened up match the full internal diameter of the air filter. Tried a VM28 but lack of time stop me tweaking the jetting so went back to standard.

Bike will just touch 85mph, power band seems to start at 6500 and really come in at 8000.

Are you sure the exhaust has not still got the restrictor washer in it as it does seem a little under powered ?

[uk_kmx]

Yes it's still restricted in the pipe, I'm waiting for a new pipe, would derestricting the standard one with a new silencer be a better option?
I can only power wheelie in first and even then it doesn't have enough power to tech the balance point, it's not my technique as I can wheelie other 125s without too much trouble.

[bladerunner]

See how you get on with the new pipe first I would expect a good condition kmx125 to pull 80 on the flat before you run out of revs with your gearing now. When you fit the new pipe check the kips valves are working and setup right whilst you can see up the exhaust port by pulling the activation lever by hand.
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[Compo]

We tried a big one front pipe with the dep rear and all i can say is dont bother the standard de restricted front gave a much better power spread and the band came in harder.

I was told by the manufacture the front pipe for the 125 & 200 were the same just the exhaust stub at the front where the front pipe slip onto is different. Ask anyone on here and they will tell you a one size fits all front pipe wont work. The 125 and 200 need a different pipe i asked Gienelli and the standard 125 & 200 exhaust have different internal volumes. I got it from RPM in wales they were useless just box shifters they are.

[uk_kmx]

Ok, looks like I'm gonna get another stock pipe (mines so rusty it nearly failed MOT!) where can I get a cheap stock pipe? I've looked on eBay but decent ones are hard to come by for a good price.