Running in a brand new piston?

[BakerNinety3]

Hey,

Details about how this happened aren't really necassary but I have a nifty little pen holder now in the form of an 80cc piston .

I had to replace the piston on my TZR50 with an 80cc bore kit (If that makes any difference), now the rest of the engine is run in, but the piston is brand new, how would you say is the best way to run in the new piston?

I've heard high gears and full throttle for 30 second bursts over a 5 mile stretch and also 300 miles at 5k revs (half the redline).(Which is also 30mph, which I don't feel completely confident doing in 60-70mph zones)

Thanks

[JimR]

Hey,

Details about how this happened aren't really necassary but I have a nifty little pen holder now in the form of an 80cc piston .

I had to replace the piston on my TZR50 with an 80cc bore kit (If that makes any difference), now the rest of the engine is run in, but the piston is brand new, how would you say is the best way to run in the new piston?

I've heard high gears and full throttle for 30 second bursts over a 5 mile stretch and also 300 miles at 5k revs (half the redline).(Which is also 30mph, which I don't feel completely confident doing in 60-70mph zones)

Thanks

Hi,

ummm so you have fitted a big bore kit ? the running proceedure could depend on the bore/piston clearence a slack bore need very little running in but if too slack the piston will self destruct in no time but Yamaha supplied the following info with 2 stroke moter produced there as the TZR motor is an eyetie (Italian) production the guide lines may be different

Yamaha Guide lines read :-

0~300 m

Avoid prelonged above half-throtle operation. It is good for the engine if it is allowed to cool about 10 minutes for each hour of operation. It is recomended that during this period the engine not be operated at a constant speed. Vary the speed occasionally. Do not exceed 1/2 throttle.

300 ~ 600 m

Avoid prelonged full throttle operation. Avoid cruising speeds in excess of 3/4 throttle vary speeds occasionally.

Above 600 m

The engine can be operated occasionally at full throttle but becareful of the engine condition and check for noises, etc.

End of Guide lines

When at the factory in Japan in 1980 each bike was red lined in each gear (up & back down the gearbox) as a final test from the production line so from that I would guess if the clearences are right on the piston/bore and piston ring/bore are correct you can thrash the nuts out of it ... I must stress that this is from Japanese production and not European but I would suggest Minnerilli would have to produce the engine to the same tollerances as the Japs.

Remember if the big bore kit was from another manufacturer there is a chance that the tollerances & materials used may not match the O.E.M spec.

Regards Jim

[BakerNinety3]

Thanks, mate, it's a Polini piston in a Polini bore, I've been told to do 100 miles at 5k revs and below before i can open it up, but it's going back to the garage anyway, the pillock that did it a so called "bike specialist" put the fuel and oil mixture way to rich and hasn't tightened the plug on the head properly and it started pi$$ing liquid after running for about 5-6 at idle. =/

[muttey]

As a guide, half max revs, but don’t let the engine stress up hills (Change down and use more revs for a short time if necessary) and build up revs after a few hundred miles rather than just open it up all the way. Most important is that you do not let it overheat during this time, and mixing with a higher than normal octane fuel to avoid engine knock can help a bit during this time.

[Ryan09]

Theres a few different ways people say. Iv known people on ktm exc300's to rebuild then race next day and be fine and other people to baby it for 600miles but you will need to rev it a bit otherwise the piston will be shocked when you redline it and not be used to expanding due to the extra heat.