Running in a new piston and bore

[Sigean]

Hi,

I have just rebuilt my 350 Condor engine with a new standard Ducati piston (from the excellent Lacey Ducati) and a rebored cylinder. I am currently trying to "run in" the engine. In March 2013 StewartD wrote regarding running in techniques:

"Initially when riding use the motor for lots of engine braking. The throttle closed causes a high vacuum in the combustion chamber and oil is sucked up past the imperfectly bedded in rings. This ensues that the top ring gets plenty of oil.

After 100km or so, if the motor seems to be running ok, you should heavily load the motor for short periods. This should be done when the motor is at normal running temperature. By heavy loading I mean going up a steady climb but allowing the motor to stay in a higher gear than you would normally use. Slog the motor at about 3000 to 4000 rpm. The effect of this is to pressurize the rings and force them into heavier contact with the cylinder wall. A very good match of the ring to bores imperfections is thus made."

This seem like good advice and it it seems to reflect the type of riding I have been doing before I came across this advice. My running-in technique for the first couple of hundred miles has been to keep the revs down by setting myself a speed limit of around 40mph and am about to increase the nominal top speed for the next couple of hundred miles. But I wondered if there was any more advice about the length of time such running in/bedding in procedures should be followed.

Any thoughts or advice welcome.

Peter

[CaptonZap]

http://mototuneusa.com/break_in_secrets.htm

CZ

[Samurai]

Don't overthink it. The main point is to vary the engine revs and not to Labour the engine in any gear.

Modern rebore machining is more accurate than it was years ago and as a result the length of running-in is less critical than it once was.

If you stuck to the same engine speed for long periods or lug it around in a high gear, then the freshly honed bore will glaze over and you'll start to burn more oil. Plus, once that happens you'll never run it in properly unless you re-hone it.

Starting off with a sensible top speed limit like you have is fine, but gradually increase it as you feel the engine start to loosen up over the course of a few hundred miles.

Don't panic of you exceed what you think is your upper rev limit a few times, during the course of running in, it won't do any harm.

Common sense rather than slavish devotion to some mantra is the key IMHO.

[Bevel bob]

Vic Camp's mechanic Bert told me that some new 250's took 2000 miles to fully run in . One of my bikes had light use for years and suddenly developed high compression and a real snarly exhaust note after a good blast around Brands Hatch race track. Do not slog it, keep revs over 3000 if you want the big end to get oil.

[Nick]

Gas it!

[Sigean]

Many thanks for all the thoughts. After a couple of hundred miles, with the engine running quite freely, I think some slightly harder use might be appropriate as some replies have suggested. I am hoping for some good weather tomorrow!

Kind regards,

Peter