Running In

[neo]

Hi All,

Got the 125 back on the dirt last night. She started second kick and a she's purring like a kitten. But I kept the revs real low while I plodded around on the grass.

I was just wondering if I need to be taking it easy for the first few hours/days???....What's the best way to run this engine in...if at all?

Best of balance.

Neo

[copemech]

Fresh bores and new piston sets require the most break in time. If you did what I think I understand, and freshened the mains, and installed new rings, then other than the initial set of the rings to the bore(minimal) there should be nothing special here, and the rings are pretty much set in to the old bore after the first ride.

Does it sound better?

[neo]

Thanks Cope,

Yes she sounds creamy smooth. ...can't wait to try her on the rocks this afternoon.

Best of balance.

Neo

[copemech]

Well, that is good news then!!!!!

You see, as things go, I still have open issues in my mind regarding these piston noises and other engine noise on the bikes. Add the fact that these things get beyond the ability to diagnose long distance.

Coming from an old background of aircooled MX'ers where all was the same but different, we got 3 races on a piston, couple of pistons then a rebore so things fit, and so forth.

These plated watercooled things are different, yet ?

Tolerances can be held tighter, the bores are tough but not bulletproof, the pistons still are the sacrificial unit, as well as the rings, as I do know well enough one must run the soft rings in a hard bore(chrome or nickel) and visavie.

Then you get into the dirt issue, ruining both components potentially, yielding much wear and slop(and noise).

Coming into the trials realm this decade, I admit I was a bit biffed by some mentions of freshoning up the bikes with just rings? Ok, I can understand that to a certain point of wear on the components, but just how effective is it?

In other words, will a new ring set stabilize a piston that is somewhat worn enough to tone things down and keep them from rattling? Your case is an example. What actually fixed the noise?

Then I get into normal wear, even on a good bore, how often should it be done?

My 2.9 has a bit, I have run it hard at times during testing. Never kept one this long either. As I still consider this long term testing and have not had it apart. The 125 would normally get more revs and abuse than a 2.9 I would think, and require more maintenance.

Others can chime in about simple ring replacement and their experience.

[neo]

What actually fixed the noise?

It was the main bearing on the flywheel (left) side. But not the rollers. Its seems that the sand worked it's way between the crank shaft the the inner cylinder of the bearing. Fortunately the shaft must be harder then the bearing and sustained minimal damage. But the bearing was buffered back to what looked like a bronze/cooper layer of it's metal. And it could slide on and off the shaft with ease.....While the replacement bearing was as tight as ducks a..e.

The bearing seal on the other side was also in bad condition. And I suspect it was letting small amounts of gearbox oil into the crank case area.

Many thanks to everyone for all their help.

I was just thinking about this today.....seems like the only job I haven't done on a Sherco yet is de-coke the exhaust system....so what do think is coming next

Best of balance.

Neo