Yamaha TRX850 Enthusiasts Forum

Just done a rebuild on the top end, new valve stem seals, rings etc. I was just wondering what kind of running in I should do and how far before the piston rings are bedded in. I couldnt believe how good the bores were after nearly 30k...mind you the bill for the gaskets came as quite a shock. Thanks again David.

Key factor I always found was take it for a good ride and vary the revs.. To prevent glazing ...I had a new z750 that I put 200km on the odometer and then took it for a track day around Lakeside. I then did head work at 10,000km so a chance to see inside and bores and rings where not an issue....

I agree with the above.

After 878JE piston rebore and head rebuild (cam chain & guides, valve seals etc) I did about 600 road miles gradually increasing the load on the motor. Didn't go near the redline obviously but did vary revs constantly.

Then I went to Mallory, did a few slower sessions before revving flat out in all gears. Have not had it apart since however but it seems healthy.

The genuine Yamaha gasket prices shocked me as well but thought better pay up than use potentially crap pattern parts.

You don't need to 'run it in'. Just ride. Simples

No kid gloves. The rings need to be loaded and unloaded during the first 50-odd ks to bed in to the bores. Otherwise bores just glaze up, and power will be down and oil consumption up. You don't thrash it or lug it, but you've got to load it. On and off the throttle on a well warmed-up engine seems to be the concensus. A long highway trip "to run it in" is bullshit. You would be better off commuting in moderate traffic. Then an oil change at the 50k mark to get rid of all those bore "high-spot" scrapings.