Motos rusas

¡Hola Homer!
Como me imagino que rectificarás el motor en un Taller Especializado, si les suministras los pistones de sobremedida y demás, ellos mismos establecerán las tolerancias.
Al menos a mi siempre me lo han hecho así, al margen que después montes tu el motor.
Un abrazo y adelante.

Hola Homer:
Si te interesa, tengo un juego de pistones y aros de primera sobremedida nuevos sin usar, creo que son de 78,18, me los vendió Piotr pero uno de los cilindros tenía tanto desgaste que no fue suficiente y tuve que pedir una medida más.  Son de alta calidad ovalizados y con los segmentos cromados, solo pido lo que me costaron.

He encontrado esta informacion sobre los pistones originales, con mi ingles poco me entero, pero con el traductor automatico menos, ¿hay algun alma caritativa que pueda explicarlo-resumirlo de forma algo inteligible?

hello how to say it \i dont want to mix your feeling but dont think ukrainian pistons are the best because they are not I know bit about them as this was my first research about their structure which mean cut the piston and then \i polish surface and put under the microscope of course chemical analis was made and becasue i compared them with other pistons made in poland and even china i can say one conclusion Im not sure if you are interested in metalurgy or material science but in brand new piston there was a lot of substance called well sorry i dont know this english world but faza miedzymetaliczna which is part of the alloy but have much diferent mechanical properities so this piston from the begining have structure which is just bit after eutectic point and as you know material for piston should have at least 16% of Si which mean stronglu after eutectic point in proper structure we should see dendritical alfa and needle eutectic of Al+Si of course it can be modyfy as it was in k-750 and then eutectic have diferent structure .as for the end of this message what i will sugest ... try to buy chinese but only as set up with piston pin and remember that to chose piston you have to know the piston pin size before buyng it because you can have problem like it wont suit to push rod head so check the mark on push rod up end and then check in table from factory which size it is then find piston pin which is cuitable and for piston pin find right piston with size which you actualy need , with chinese is problem at least here in poland that they seel it sometimes with piston pin but not always and what is more anoying they can give you two diferent piston from piston pin group and of course with wrong and not equt piston pin which should be same for two pistons
there is also polish pistons which im actualy using they are from Almot and i think they cost with piston pin and piston rings about 140 zl at least i pay this much and well this piston i will sugest there is only one piston pin size group so maybe there can be problem wit suit but i didnt have it it was completly ok and realy nice worling they have which is diferent from all piston i seen for k-750 surface which is harder that deep part of material which mean more sizsitant for stuck in the cylinder if you need them i will show you auction and then ......
i can tell here also about piston for cossac they was worst and im not sure if you have this problem well when you fix your bike dont you have this problem of geting warm easily very fast and sometimes piston surface start to touch surface of the culinder? well i know this is always conected with depr or cossac bikes which ever you will call them reason is same belive me i check cylinder is worth shit i couldnt figure it out why only in denpt there is so many cases of stuck piston isnie the cylinder durning exploatation and of course piston was set up properly on the push rod up end so why this is happening? well you have to know when piston work it's temperature is about 400 degre celcius (673 K) so it need to give all this warmt for cylinder which take it and give for atmoshpere by rigs on it's surface so it wasnt completly piston fault that's why i cut culinder which is mage drom well special czugun as it's called in russia żeliwo in polish and well sorry maybe in english iron but inf act it's iron which have more Fe3C that 2,11% so pipe is made from iron but surface from ALSi alloy bu special method of production this AlSi alloy should stick to iron but because what;s my opinion not good preparation ot his iron pipe maybe to cold before maybe dirty the alloy AlSi surface dont stick to iron which mean there is big buble of air which as everyone know isolate not transmit the heat in this case piston work not in 400 but in higher temperature which is not good becasue structure change and from alfa start to go out faza miedzymetaliczna which as i wrote before it's not so good if it amout is biger than predicted by factory ( when this amout is smal hardnes and mechanical properities are better but if to much then everything go down including hardnes) and also this is the reason of piston geting biger and stuck iside the cylinder
so K-750 piston only Almot not this ukrainian this is my advice
as for denpr same piston made inf actory i mean specialy for dnepr ( this is big company not some smal manufacture so it can be trusted) and of course cylinders from same company which are much more better .
on the end i have to say i examine cylinder and pistons from bikes used on ukraina and also on belarus so maybe quality of machines which go for export are better i didnt check them co dunno but if you have problem which i described before then you know the reason .....


PD: vaya tela, menuda parrafada....

Modificado por homer (2009-04-17 09:39:35)

Para los que no les apetezca leerse el chat, ahi va:

debe ser un individuo que se ha dedicado a hacer lo que yo hice en polonia en ratos libres, composiciones quimicas de los componentes, este en concreto lo ha efectuado a los pistones y se ha dado cuenta que las fundiciones ucranianas y polacas no son de buena calidad, y te recomienda que uses pistones de procedencia europea o originales de la fabrica dnepr por que se supone que tienes mayores garantias

Para que luego hablen mal de las Chinas,jajajaja

mahle sí es una marca conocida y seguramente una de las mejores marcas que fabrican pistones, si tienen unos para K-750 que cumplen los requisitos antiguos, claro que valdrá la pena ir por ellos, depende del precio también claro pero yo también prefiero poner una cosa cara que no se va a romper que una más barata pero menos segura, de hecho al final se puede ahorrar bastante con esto, lo que no sé es si mahle se dedica a reproducir unas tecnologías antiguas
otra cosa es que si producen kits de cilindros, pistones etc., entonces a lo mejor le servirá la tecnología más moderna, pero todavía hay el sistema de lubricación por salpicar, la baja presión de la bomba de aceite, el material de las bielas, etc. lo que influye todo el proceso de funcionar del kit...

lo de las medidas esta claro,el rectificador dirá si una u otra, lo que no tengo claro es si el piston por ej mide 78 ¿Cuanto debe medir el cilindro?

gracias Ribben, Si , hay un cilindro bajo de compresion, de momento va bien, pero tengo que cambiar uno de los empujadores de las valvulas, no  porque empuje mal, sino porque la tuerca para cogerla es cas redonda asi que cuando desmonte veré como está todo y quiero estar preparado para ello, lo hare despues de la kedada.

alguien mas tiene alguna experiencia con la tolerancia del piston? no se si dejar 0,06 ó 0,08, en cada sitio dicen una medida...

homer dijo:

Al fin lo encontré, si se quiere terminar con los problemas el piston a montar es Mahle-Nr.: 021 79 00     79 de diametro y 21 de bulon

tres preguntas:
¿tienes mucha experiencia con estos pistones?
¿has montado un montón de ellos y nunca te han fallado?
¿por qué crees que son mejores de los que tengo en venta yo?