KR-1S.co.uk Forum

corvine wrote:Yep OK it's my turn! will find a cheap one on ebay.

S'alright Mick.

I'll see if any of my local bike shops have one I can compare this weekend. If not, there's new pattern ones for sale on Ebay for £26.50 incl. P&P. That's a small price to pay if it means KR owners have a source of new pistons/rings again. If not, I s'pose I'll have to find a cheap KMX125 on Ebay to use it in...

Just found out kmx bore/stroke = 54x54.4 not sure if this is true, so you will have to be careful!
Unless this is your way of getting another bike!!

Went to my local bike spares place yesterday. He didn't have an oversize KMX piston in stock, but he had an ordinary one and was happy to help me measure and compare it to the genuine KR one I took with me.

It looks the same ! Same overall height, gudgeon pin is in the same place and same diameter and the ring pegs are in the same place too. The only visible difference is that the KMX piston doesn't have the strange hole above the gudgeon pin (see previous photo) - I don't know what it's for, is it just some kind of lightening/balancing thing ?

So, it looks good to me. KR owners all over the world owe Tambo a pint. Just don't forget to get the 2.0mm oversize one or it'll be a bit rattly...

And here's a bloke selling them on Ebay. Ignore his photo though, that's a piston off something else.

Well done that that man, men!! Will the price of KMX pistons now rocket?
The hole must be for help oiling the little ends. Which piston did you look at genuine/pattern?

corvine wrote:Which piston did you look at genuine/pattern?

I was comparing my genuine KR piston with a pattern KMX one. I think so anyway - it wasn't in a 'Kawasaki' box, although it was priced at £44 !

I guess we won't know the answer for sure until someone fits a pair and canes their bike for a couple of thousand miles without a problem. Over to you Mick !

I was thinking maybe the kawa part has the proper oilway?

corvine wrote:I was thinking maybe the kawa part has the proper oilway?

Yeah, maybe. We need to see a genuine KMX125 piston then. There's no chance my local K dealer will have one in stock though...

Hard to tell for sure, but the photos of the pistons in the KR factory workshop manual don't appear to show an extra hole ?

Yes I know what you mean but if my memory's correct it's the same picture/s used in the KR1 manual!!!

today I saw the guy that imports Wiseco in Belgium and asked him about KR250 pistons/rings.

if he has a piston, he could look for rings, don't know if you have an old you could send him ?

he said that they can make any piston you want, as long as they have an example. asked him about prices, and they depend of course on the number off pistons you order. if you would order 20 pistons, he figures it would come to about 130-140 euro/piston including rings and the small-end.

I'll see him again on sunday. if you are interested, or have any questions, let me know

JanBros wrote:today I saw the guy that imports Wiseco in Belgium and asked him about KR250 pistons/rings.

If he has a piston, he could look for rings, don't know if you have an old you could send him ?

he said that they can make any piston you want, as long as they have an example. asked him about prices, and they depend of course on the number off pistons you order. if you would order 20 pistons, he figures it would come to about 130-140 euro/piston including rings and the small-end.

I'll see him again on sunday. if you are interested, or have any questions, let me know

I do need to find a source of new pistons/rings that I can point KR owners at, so yes, all help gratefully received.

I can't remember if I have an old piston/rings lying around but if I find one, I'll be happy to send it to him so he can tell me what he thinks. I'll let you know. Thanks.

StrokerBoy wrote:I can't remember if I have an old piston/rings lying around but if I find one, I'll be happy to send it to him so he can tell me what he thinks. I'll let you know. Thanks.

I've got a couple, well messed up (dunno where the rings are!!?) that i could send somewhere. Took 'em out to compare with flat top CR125, and DT125.. 130 euros is about $260NZD... but i'd still be keen for some if that drops the price.
Is a KMX125 powervalve?

Kwakka KE125s have the same 56 x 50.6 bore and stroke as a KR250, and they were disk valve too.. I'll see if i can get one.

nzkrnut wrote:Kwakka KE125s have the same 56 x 50.6 bore and stroke as a KR250, and they were disk valve too.. I'll see if i can get one.

Found a bloke on Ebay selling KE125 pistons, and have asked him for some pics so we can compare them to stock KR250 ones. Hopefully he responds. [-o<

I also put it to my engineer (who knows KR's well) and he advised against trying to sleeve it up to 350cc, as the bottom end and gearbox wouldn't be able to cope.

Has anyone measured up RGV250 pistons
The bore is right at least, and from the few pics I've found on the net, they look similar......

In the end, I think we need to find someone who'll let us search through their aftermarket piston catalogue. Any volunters (I don't have the conections). I did the same with car pistons years back.

Good news people.

After speaking to my engineer, I've had it confirmed that the hole above the gudgeon pin IS for feul transfer as I had suspected. Pistons that don't have these origionally can be modified, meaning the 2mm o/s KMX125 pistons are a definate option. The only problem is that because the difference between KR250 and KMX125 piston castings, means that the hole size needs to be re-calculated to suit.
I'll be getting a pair of pistons soon and taking them to my engineer so he can calculate the new hole size and modify the pistons. Once they're finished and I have them back, I'll measure the hole size and post up all the details along with pics of the modified pistons.
It will be quite a while b4 I fit them to a bike though, as I am only just finishing my first KR build. I intend to do a complete rebuild on the next engine to cope with a serious increase in horsepower.