Pistons KR1S

sauvage84 · Post by **sauvage84** » Sat Jan 19, 2013 1:49 pm

Hi, i m french and next year i ll race in France with my KR1S in e new categorie VMA evolution
i ve a bad english, so i ask in french :
je recherche des pistons pour ma kr1s, quels pistons sont les meilleurs ? forge ou coules ? ou les acheter ?
j ai eu une proposition de PJME pour des Wossner (forge)
merci, thanks
JR

mj43 · Post by **mj43** » Sat Jan 19, 2013 5:54 pm

Hi
For racing I would recommend using Yamaha TZ 250 pistons type 26J.
They are available in the UK from Clive Padgett http://www.padgettsmotorcycles.com/

They are expensive but you will not have problems with piston ring pin failure which I have seen with all types of standard piston including replacement types.

For best results it is worth getting the head reprofiled as the dome radius on the TZ piston is shallower than the stock piston.

PM me your email address and I will send you details of the modifications I do.

Regards

MJ

JanBros · Post by **JanBros** » Sat Jan 19, 2013 8:21 pm

Woessner sont des tres bonnes pistons, mais moi j'ai ue des problemes aves leurs piston de KR1 : les "pinnes" pour les segments sont pas parfaits ou ils doivent être alors une étais completment cassé et de l'autre les segments commençait a se détruir parce que ils entraient dans le ports de transfer.

j'ai trouvé la faute apres que je commendait un autre piston pour remplacer selui qui était cassé : comparer tous les trois avec un original, la conclusion était que dans les 3 Woessner, les pinnes étaient dans des differentes positions, et aucune correspondaient avec la position original.

l' importateur Belge a reconnu la faute il ils ma proposer de donner des autres pistons de mon choix. Il est aussi l'importateur Wiseco donc j'ai choissi des pistons YZ125 '89 de Wiseco (ils sont 1mm moins de hauteur, donc il faut adapter ou les cylinder, ou la culasse).

Les Woesner sont des bons pistons, mais si tu choissi de les utiliser : mesure bien les pinnes et est sure qu'ils sont dans la positions ou ils doivent être

sauvage84 · Post by **sauvage84** » Tue Jan 22, 2013 11:20 pm

Thanks you
i have some problems to connect the forum
and today i send my cylinders to have a new nickasil and new pistons
i choose Prox from KX 125 with mono ring and i ll change them every 4 or 5 races
sorry for my bad english

sauvage84 · Post by **sauvage84** » Sun Jan 27, 2013 11:12 pm

je suis a la recherche de pistons "coulés" (not forged), personne n en a en France !!!
is somebody know where i could find it ?
i was looking for Prox or Namura

dave32 · Post by **dave32** » Sun Jan 27, 2013 11:25 pm

Out of curiosity what year KX pistons are you planning on using,90 or 91?
If you do a search there was a very in depth topic on the pros and cons of various pistons,the conclusion was either YZ125 (87?) or TZ 250 (not sure what year) were the prefered route.
Cheers
Dave

sauvage84 · Post by **sauvage84** » Sun Jan 27, 2013 11:39 pm

in france i ve read : KX125 82-86 with mono ring
on this forum i read : TZ 26J, i think it s year 81-82 ( i have 2 new pistons for my TZ !!)
if i use YZ piston, i need a longer con rod

JanBros · Post by **JanBros** » Mon Jan 28, 2013 12:58 am

here a comparison between KR1 piston's and KDX125 piston's. mainly the biggest difference is that the KDX is shorter at the bottom :

viewtopic.php?t=7562

also lot's of other data about KX and YZ pistton's

pm me your email if you would like the technical drawing of the KDX piston's

you don't need longer rods if :
*you can live with them being shorter on top (meaning : if you haven't raised your exhausts already, then they might become too high). just shorten the barrel at the top
* you shorten the barrel at the bottom, then you keep your timiongs, BUT you'll weaken the barrel

if you need it translated, pm me