KMX 125 Exhaust restriction?

[sam_w]

Can somebody please confirm for me that this is the exhaust restriction on a kmx 125. from what ive read online it is a washer welded in. this does not look like a washer but defo looks restricive.

https://i97.photobucket.com/albums/l203/sam_welsh/PICT0096.jpg

if this is the restriction would somneone also confirm the main jet size that i would need if i take the restriction out.

thanks

[carlperkins00...]

bit of a rough picture...
looks like a restrictor that is permenantly welded inside the exhaust..
but its a very blurry photo so thats just a guess.

[stevo as b4]

Hard to see from that pic, but there is more of a sleeve or collar than a washer fitted, and it's about 1.5" into the expansion chamber from the flange. If there is a step down in diameter then that is your restriction.

TBH you could get an aftermarket front pipe instead if you like? The Giannelli system seems to add about 1.5-1.8bhp from 6k upwards.

Jetting should not change for a de-restricted exhaust on these machines. They are much more sensitive to intake than exhaust changes, as i suspect that is where they are fairly restricted in terms of being able to make improvements.

[sam_w]

yes i agree its a bad picture. that was the best pic i could get for some reason.

i have already bought a new pipe. the one in the pic is the pipe that i had on the bike. it has got a hole in the side so needed replacing. the pipe i have bought is a stock kmx pipe, but that sleeve or wotever it is in the pic is not on the new exhaust. the reason i asked wether it was a restriction on my old pipe is because i thought my bike was already destricted due to it having a big one end can already fitted when i bought the bike + my kmx already seemed quite nippy.

[ben350]

I always thought that KMX's were restricted via the KIPS valves = never owned one but think the springs needed changing
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[stevo as b4]

I heard this as well for early KMX's, but im 100% that later 96> one's wern't restrictricted this way. And if you look at how the mechanism works then it really is only open or closed like YPVS, AEC, ATAC systems. There is no half open position, so you either have a resonator chamber which is linked to the exhaust port via a small passage, or else the valves turn 90deg to block off the resonator chamber passage, and simultaneously open the 2 exhaust auxillary ports, which are timed to give more exhaust port area than the main port, to suit 7000rpm>.

The jetting is the same in the kawasaki workshop manual for a de-restricted std exhaust as for a 12bhp version. The bike was probably always jetted to run best in full power form, and the exhaust just restricted as an afterthought TBH.

Of course with any aftermarket pipe you should check the jetting, and be prepared to make changes, but with a full power std pipe, i don't think you need to.

[sam_w]

well, went the bike shop yesterday to pick up some oil and explained about the thing in the exhaust. the guy said it was a restriction and i would need to re-jet. so got a 110 main jet and fitted that. drove to work and back today and big was running like sh*t, spluttering and felt like it had no power. so ive now swapped back to the original main jet (102) and its running great. checked me plug and its a nice golden brown colour. i think my old exhaust was defo restricted cos u can defo feel the difference in performance now, especially when the power valve opens. the bike used to have a few pops in the exhaust at high revs aswel. this seems to have disapeared now. thanks for your input m8. u was right afte rall