kips derestrictions.

[ultraculture1...]

Im picking up the kmx on saturday and the guy who owns it says he hasnt touched the powervalve.
Its an 88 he said he has drille out the airbox or something like that and it has a big one exhaust, i know there is lots of info online about this but this seems to be the best forum, so can i please ask for the definitive kmx derestriction guide please?
Will i need a new softer spring for the kips? Is there anything else i need to know?
Also is the rear shock damping unit adjustable, can i fit aftermarket, Marzzochi, forks for a plusher ride, how easy is a supermoto conversion.
Please dont comment if you're going to tell me to get a bigger bike, i have been looking into this for a while and i like the idea of rinsing the bejesus out of the little 2 stroke engine.
I know there are a couple of real experts here ,(dangerous dave?) Please give me your knowledge and experience, again i know this has been asked before but i read a few vaguely different stories.
Thanks

[stevo as b4]

A lot of points mentioned there in one post! But a quick reply to some of them:

1, The Powervalve. I too have heard the rumour of KIPS valves needing different springs and even shims on the early bikes to effect de-restriction, but I've never really bought the idea myself. This is due to the fact KIPS is an open/closed system, not a progressive or 2-3stage PV, so I can't see how it should need altering to give best performance.

2, The Big One pipe should have done the de-restriction thing for you. The std one has a restrictive collar fitted for the 12bhp B-versions. Even the jetting is the same, so nothing else should need to be changed IMO.

3, The Airbox? It's not restricted as such, but the intake silencer/snorkel is much smaller than the 200's one. It has been experiemented with by using the 200 airbox lid or cutting removing the 125's lid, that some extra power might be found. It does seem to need 2-3sizes up on the main jet, so the fueling must be affected by this change. Some people on forums have claimed +1.5-2bhp more by modding the airbox and re-jetting.

I'm hoping to find out if it has any effect soon when I get some dyno time with my 125, before the new carb and reeds are fitted.

4, The 1990 or maybe it's 92> rear shock's are remote reservoir units, and had a re-bound damping adjuster on the bottom of the shock. When new it probably makes some difference to the ride/damping. You will want the pre-load on a std shock adjusted closer to max if your are say 12stone>. Most KMX's lead hard lives and anything with plenty of mileage on it will be screwed now. I'm not so sure how re-buildable the std shock is or not? There's aftermarket options from around £160-500 though.

5, Forks are a bit soft as std for road use or even faster off road riding. new springs, pre-load spacers and thicker oil might help but would need experimenting with depending on your useage for the bike? KMX200 forks and yokes can be fitted and are 3mm bigger in fork leg diameter and have air valve adjustment on them too.

For supermoto conversions I would say USD fork conversions are a good bet, to get a bit more ride height to compensate for the 17" wheels. There's a few ways to get different USD forks to fit, but hopefully Dave will along to explain more.

The wheels can either have new wider rims laced to the OEM hubs, or aftermarket hubs, or you can go the route of cast alloy wheels.

Wheels that have been made to fit the KMX are, NSR125 wheels, GS500E, or GPZ500S wheels. The front brake can be upgraded with bigger diameter discs and caliper spacer plates and or twin pot front calipers. The KLE500 300mm disc seems to fit the KMX200 hub as well.

If your only riding on the road then a supermoto conversion would work well like it does on the DT125R's, but it's much more expensive to sort out and get the bits for and make it all fit, than it is to use road tyres on std wheels.

But most people would like a bike they can do both gentle off roading and road riding with. There's plenty of people that can advise you of suitable tyres for a compromise depending on what your looking for?

I have used Pirelli MT60's before and found them good on the road, and ok on gravel tracks or dry green lanes etc.

[ultraculture1...]

Cheers steve, you were the other resident kmxpert i was thinking about
Im not that bothered about converting to sm, but might be handy to keep a set of road wheels and knobblies, but probably cheaper to go dual purpose.
As far as kips springs, i woukd imagine perhaps stiffer spring stops the valve from fully openening? I will have to wait and see, there isnt a definitive video in you tube showing exactly how it can be manually adjusted, the bike im buying is quite old but looks extremely well cared for.

[thx1138]

I had a stupidly quick KMX 125 when I was a teen. Bought it 2nd hand though.

[stevo as b4]

There is technically no adjustment on the KIPS system or in the linkages though. The spring people mention I feel is more to do with changing the speed that the governor operates at. The valves are either closed and the resonator chamber open/ or the valves open and resonator chamber closed.

It's exactly the same system as used on the KR1/S, but without electronic actuation.

The valve should open at 7000rpm, that is the linkage arm under the RHS cover moves out to the right.

[dangerousdave]