cylinder/piston clearance

Begonnen von gordinir8, 27 April 2016, 10:15:29

« vorheriges - nächstes »

0 Mitglieder und 1 Gast betrachten dieses Thema.

gordinir8

Unfortunately my con rod failed and metal particles destroyed also the cylinder and piston. I will buy new oversize piston and rebore the cylinder. According to r25/2 manual, clearance between piston and cylinder must be 0,06mm or 0,07 mm if sidecar is used. Is that clearance the same also for r 25/3? I am using a sidecar so i want to known how bigger the cylinder should be for correct installation.


gordinir8



OldsCool!

Usual clearance for standard original pistons is 0.06mm for the singles. Cylinder oversizes are usually even sizes in 0.5mm steps. (68mm, 68.5mm, ... 70mm).

Best regards,

Steffen
Ich bin auf dem Dorf aufgewachsen. Ich wurde nicht erzogen, ich habe ÜBERLEBT!

gordinir8

Yes I know that, mine is already 68.5 so I guess I will jump to 69mm for piston and 69.06 for cylinder bore.

Zitat von: OldsCool! am 27 April 2016, 11:09:43
Usual clearance for standard original pistons is 0.06mm for the singles. Cylinder oversizes are usually even sizes in 0.5mm steps. (68mm, 68.5mm, ... 70mm).

Best regards,

Steffen

OldsCool!

#3
You will not get an off-the-shelf piston with 69mm. That is the next cylinder size, 69mm. The matching piston is then 68.94!
Sometimes the pistons are labeled according to their matching cylinder size. So if you buy a 69mm piston, it is actually 68.94 but the cylinder has to have 69mm.

Alternative: bore your cylinder to the custom size you like and get a custom piston which matches (2x price).
Ich bin auf dem Dorf aufgewachsen. Ich wurde nicht erzogen, ich habe ÜBERLEBT!

gordinir8

This is very usefull information, i didn't knew that thank you. The best spot to measure the piston is right above the piston ring area across the gudgeon pin or is it at the skirt lower end?
When i rebuild my engine 15 years ago i put a new piston and new cylinder sleeve. Problem was that my engine had always lot of smoke coming out of the exaust, spark plug and head was always oily inside, i am now pretty sure that the cylinder sleeve was lot more than 0.06mm
I will try this time and find a good machine shop to rebore my cylinder as close to that 0.06 dimention.

Similar topics (1)

Begonnen von Garnet Grylls


Hauptmenü

Anleitungen & Bücher Baureihe Specials Startseite Vergleichsliste

Presse & Wissen

Bauzeiten & Stückzahlen Historisches Liste der BMW Modelle Presseberichte Prospekte & Plakate

Foren & Literatur

Bildergalerie Bildtafel-Suche Forum: Boxerforum Handbücher Servicedaten

Allgemeine Infos

Bildtafelsuche Glossar Impressum Kontakt Sitemap

Tipps & Service

Dienstleister Händler Märkte & Museen Tipps Verschleißteile & Werkzeuge