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Can anyone tell me if the KIPS cover spacer (homemeade 10mm spacer) that was used on the early air cooled KDX,s (1988) to give more bottom end will work on the water cooled models (1997) ?

We had this discussion recently, I think. There should be a thread around here somewhere. In theory, it should. Give it a try and let us know?

Hello there,

In answer to the question - yes a spacer plate on the KIPS expansion bottle should make a performance improvement to the water cooled as well as the air-cooled models.

Essentially the resonator bottle or expansion bottle is lengthening the exhaust pipe when open, so that you now have two different length pipes depending on revs.

Exhaust pipes are designed to only one rev range (for example 7000rpm) where they will perform best and everywhere else is a compromise. The longer the pipe the lower in the rev range it is tuned to. Typically road pipes are tuned to perform best well below the red line where the manufacturer deems most riders will be cruising (and to discourage you from holding it next to the redline where longevity is compromised). Performance pipes are typically shorter and work best closer to the redline (more rpm, more bhp).

Having an expansion bottle allows you to have two rpm's where the pipe is close to ideal, giving you a boost in mid-range performance.

In fact for whatever reason on a few models (the KDX and KMX notably) the bottle was not quite big enough to produce best spread of power and this becomes more pronounced with a shorter performance pipe. Quite why they did this is anyone's guess, but reducing the visual 'barnacle' effect may have had an influence.

The above is not a thorough technical rendition, there is a lot going on there but it gives those that don't know a good grip on the situation. As mentioned by someone else before on a previous thread; once the KIPS resonator is closed you are back to normal so there is no compromise of top end power for this low to mid 'boost'.

In bhp terms the improvement will not be astounding (at low revs the engine isn't making much power anyway), but in terms of percentage it is significant for the cost and ease of fit and makes the bike more forgiving and flexible.

If it is of interest to any of you we produce a CNC machined spacer plate for these now with machined faces for good seal (gasket goo is fine), as the result of demand. If you don't have the facilities or motivation to make one up yourself then give us a call - if someone in Norfolk or thereabouts wants to bring their bike down to us we will arrange to have a before and after dyno comparison done.

All the very best,

Brock
01508 481713

Good post Brock. Really appreciate the information.

I assume the numbers after your name is a telephone number. Could you post additional contact info? Not being a supporting member, we are not able to send you PMs through this forum.

Good information in these posts. Anybody do this on a KX125?