KR-1S.co.uk Forum

might be of interest to anyone : all the dimensions of a KDX125 piston.

http://users.telenet.be/jannemie/KDX125.pdf

seems about spot-on with KR1 piston's , except they are 4/5mm shorter. benefit would be that they are available in oversizes. Woessner and Mitaka make them.

I'm sourcing other piston's as I need replacement's for my Woessner's with pin's in the incorrect position.

Sadly Wiseco don't make these. the Woessner-impoter (who also import's Wiseco) is going to supply me 2 piston's of my choice for the bad Woessner's, but since I don't fancy using Woessner again, I'm trying to find a suitable Wiseco (can't expect him to pay for 2 Mitaka's )

edit : link is now on the 2nd page

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the KDX125 from Wossner has the pins in same location as their KR pistons
the ring lands are slightly different (no effect)

[attach comparison]


post a picture of the dud pistons ring pin location
because if it was a bad batch you should just get the correct replacement.

KR-1R wrote:.
post a picture of the dud pistons ring pin location
because if it was a bad batch you should just get the correct replacement.

I've had 3 of them : the 2 I already used and a new one. All 3 of them had the pin's on "different" locations, meaning somewhere where they should be, but not exactly where they should be.

It's not just a "batch-problem" since they were all 3 different. I don't have them any more, they were al 3 send back to Woessner, together with a cylindre and an original piston to show them where they were wrong, but all they say is they never had any problem's with them and that ...

by the way : your comparison is not showing

lubrication holes at +/- 45°




ring peg gap at ~+/- 30° there could be variances



the shorter skirt on the KX/KDX pistons puts it close (<4mm) from the bottom edge of the exhaust port at TDC

The KR-1(S) piston being approx 4mm longer skirt (than KDX/KX) has therefore approx 8mm below bottom of main exhaust port.

It also means that on a B model barrel the siamese boost port (lower one) will be below skirt edge if it runs the shorter skirt

Tnx for the pics

KR-1R wrote:
the shorter skirt on the KX/KDX pistons puts it close (<4mm) from the bottom edge of the exhaust port at TDC

it would be 3.5mm and shouldn't be a problem according 2 reliable sources

It also means that on a B model barrel the siamese boost port (lower one) will be below skirt edge if it runs the shorter skirt

I'm running B's. but I don't thinck that has any effect, since the piston closes the top boost port.

Still in doubt as to what piston's to use.

first option was to use KX125 88-89, but 2 things bother me : if I can't make the insert's working, I will have to have another head completly welded up and make new chambers for the dished piston, but mostly since the flat part of the crown is only about 3.5-4mm thick (I thinck judging from pictures), not much room for squish.

secondly , YZ125 89, but compression height is only 28.50 (Mitaka source) or 28mm (Woessner source). on standard barrels might be ok (i.e. slightly raising ports), but my KIPS port's are already raised, which would give me exhaust timings off +/- 192.6° (28.50) or 194.8° (28.00). 192 would be ok, but from what I read/know, 195° would be too much (specialy for a road bike).

you happen to have the YZ Woessner to measure it ?

third are the KDX125's

Do you sell piston's ?
there are some other Yamaha piston's but it's almost impossible to find correct data/keep them appart ... DT125(R), TZR125/250. You happen to have checked these out ? Woessner nr's 8002,8003,8006, Wiseco''s 679,684,236

I only have one of each so cant even make a comparison between 2 KR pistons from Wossner

KX pics from the net... single and 2 ring domed (I think shorter skirts)

Single ring domed...

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youre could go wrong with KX ones as on some of them the lubrication holes run centre for a bridged exhaust

I think you should just get some new for new KR-1S ones - if they dont meet spec ask why - or resell new and recoup your money as possible
but if there is a variance in the ring gap location on these it needs to be addressed

MJ and Loz/2TI and other run pistons with 6 o'clock gap, down centre of port

Kx125 (81-86) has a comp height of 30.50, and total height of 54.50, so the skirt is even shorter at the bottom (only about 2mm). + as you pointed out : the oil-holes in the middle off the piston.

The 87 is dished down, and has a hole in the piston at the back, in stead of a cut-out.

I'm not going to oder KR1's in the hope I get 2 right ones, and then sell the bad ones to some blok I know I'm gonna screw with them ...
neither is my importer gonna order a bunch of them, he to knows they are crap now ...

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the early eighties KX are also piston ported?
as well some RD and DT?

8002DA slightly higher comp height? +0.5 = 3mm dome
is that pistons's dimple a belly button or anus?

just had him on the phone, and asked him if he could measure the compression height of Wiseco YZ125 '89. It should be 29mm (Mitaka 28.50, Woessner 28.00).

So YZ's it will be . pffww, after 2 weeks behind the PC searching for piston's, I'm glad it's over

Which pistons did you use in the end? i had a kr that someone had sleeved and that ran tzr250 2ma pistons if thats any help? i dont know what the specs on them are though

I went for the YZ125 '89 piston's.

mainly because everybody makes these piston's, and they are available in many oversizes.

so if i have a standard size kr1s barrels what would i order because sometimes they want to know the in's and out's of a cats arse, what colour is the bolt that hold the thigh bone to the knee bone or is it leg bone, get my meaning cheers

did anyone on herer save the file in my first post about the KDX125 poston ?

I haven't got it anymore

Hi Jan,
Frank from Nikon said they used to use the DT125 pistons.
Cheers
Bernie

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pretty useful 3D views now available on the Wossnerpistons.com

KR compression height 29.5mm, domed
http://www.wossnerpistons.com/images/st ... 8043DA.swf

DT twin ring Domed 29.9mm, Domed, long skirt
http://www.wossnerpistons.com/images/st ... 8002DA.swf

TZR twin ring Flatish 29.9mm, Flat, long skirt
http://www.wossnerpistons.com/images/st ... 8006DA.swf

KX single ring Domed 29.7 undrilled, short skirt... 8211DA
http://www.wossnerpistons.com/images/st ... 8211DA.swf

KX single ring Flat (dish) 29.5 undrilled, short skirt ... 8130DA
http://www.wossnerpistons.com/images/st ... 8130DA.swf

^^^ pick your squish or compression