Running in after a rebuild

[Danger]

The 02 KTM had a good quality piston. I think they changed it in '03. Apparantly once your replace the original with what they now give you over the parts counter your in for more frequent rebuilds.
I only did the topend because the bottom end needed rebuilding. Silly not to do it while its apart.

[camchain]

Wow, nice work reckless. I was just about to dig out the same link. I read that article a few months back and liked/saved it. This principle about getting enough combustion pressure going to force the rings to the bore and bed in properly made a lot of sense to me. Before that I was in the run it in like a granny camp. I think the warm up cool down thing seems reasonable as well.

Running in used to be a lot more important in the old days of sloppy tolerances/machining/surface finishes and shaky engines. Thanks, Japan.

[Reckless]

yes I agree. The two main things that have changed are the metals we now use are much much harder. i.e. Niksel and crome molloy rings etc. Nikasel aimed to never wear out and the ring and piston aimed to be the bit that is replaced. And the tolerances are much better as you say. So you don't need to be so careful.
Added to that, are the oils are so much much better, with synthetics etc. We used to run in all our engines in on castor based old castrol R. But if your using say a Motul 800 or a fully synthetic 2smoke oil you need to give it a bit of shit to get it to bed in properly because the oil is so much better.

[camchain]

I still remember the sweet smell of that castor oil. 'Chase and Sniff' when gunning down modern two strokes isn't as rewarding as it once was (sigh).

Good point on modern harder bore materials. It seems to me that without hone marks to help bed the rings (on well used engine) running in can't be as critical or possibly even very effective when replacing rings? Do the modern bores even have hone marks in them?

[cheese]

Crikey mr CR has done 50 and I'm about to rebuild it.

[Danger]

Yeah my mates '05 CR250 has had about 3-4 pistons replaced in the time I've had my RM. And he does not ride as much as me.

[oldguy]

Ok guys thanks for all the advice, got it sorted and back together, ran the engine as advised, check over all OK.
Just the other day, I noticed an oil leak, on close inspection I find its coming from the seal around the front sprocket.
How easy is it to replace.????
Is it just a matter of hooking it out the old seal with a screwdriver and pushing the new one into place or is there more to it.

cheers John.

[Buddy L]

what type of work did the bike shop do? if they split the motor , maybe it might be under warrenty?

[Danger]

No need to split the motor to do a front sprocket seal. Might be a seal and an oring that need replacing and possibly a bush. Depends on bike.
Some bikes don't like aftermarket front sprockets which can be slightly thinner and these place less pressure on the oring and thus they leak. Anyway east to replace these parts and cheap. Check circlip if it has one and if its notched flip it over, this might preload the oring so that it does not leak. Again depends on bike. Quite common for some bikes to leak here.

[oldguy]

what type of work did the bike shop do? if they split the motor , maybe it might be under warrenty?

I got them to split the bottom end, I had supplied bearings, and gasket set, got them to replace what was need and put it back together for me, I just had to put the top end back together with new piston and rings.
got the seal out so I guess its just a matter of sliding the new seal on.

[oldguy]

sweet as all done.