KX65 Expansion Chamber or similar?


Sep 25, 2017
Hi Everyone,
Wanting to buy a expansion chamber for my bike as im still using the stock one with no baffle and holes drilled in it. What are your recommendations?
I saw a post where someone said they put a kx65 econ there bike but they didnt give any info, i can weld btw so that isnt a problem. It is going to go on my '80' cc motor or what ive heard are actually 66cc so not sure.


Well-Known Member
May 17, 2010
they arent designed around the porting on these engines but are better than most of the other pipes sold that arent even designed at all... you can always tweak the ports a bit... also, kx should be running reed valves and a boost port. again, the pipes designed specifically for a particular engines port timing and RPM. you wont ever get the same performance from a china girl...

as long as you can get it to fit and dont have to change anything with the main chamber, then they work fine. ie, dont get tempted to try and squash that chamber, it ruins them.

mount them with springs, a pipe thats bolted on and all welded up solid will quickly break from fatigue.

just have a go at making your own pipe specifically for the engine, if you can weld. twostrokewizard works. javapipe is...questionable. but free. trying to do the maths itself is too hard. let some software do the number crunching.


Well-Known Member
Nov 29, 2017
If you don't have much done to the engine look into the Zeda 88 or CDH 66 expansion chambers. They are the same or very similar to each other. I'm running one on my case reed engine until I finish welding up the MZ65 chamber. That is another pipe to look at.