Ripping

[vtrn_raptor]

Has anyone ripped their bike under 400 miles on a new piston as I'm on 200 now but 400 seems a little excessive

[Calum]

What work did you have done to it.

It's your bike, but it's a minefield.

The last thing you want to do is glaze the rings all the wall.

By 200 miles you can vary the RPMs, don't feel you have the keep it under 6k. Just vary the revs.

[vtrn_raptor]

Just a new piston and rings and put it back on the servo as was pinned and has a full dep

[vtrn_raptor]

And thanks man need to open it up a bit and see if it pull properly

[Calum]

Did you not hone the bore?

[vtrn_raptor]

No mate was I suppose to

[Calum]

@vtrn_raptor Depends whether the bore needed doing.

If you didn't hone it or bore it and merely changed the rings, then 50 miles would suffice.

You should be free to rip roar now mate.

When you hone or rebore it I'd recommend 300 miles. 1000 on a fuel rebuild. But rings, 50 miles will suffice.

[Glynn123]

3 heat cycles, gentle hour odd ride, another couple rides varying the revs and then I just hammered mine, that was after a fresh bore, wossner piston at 0.2mm clearance as recommended. Bike still runs great and pulls strong. I've only done a total of about 150 miles on my DT since I done the engine, was probably hammering it at about 30-40 miles, but I mainly ride offroad so you dont rack up the miles on trails, the main thing to do in a break in is heat cycles, I know many people who do 3 heat cycles and then go for it but id rather be abit more careful.

[Jens Eskildsen]

Any source for the benefits of doing heat-cycles?
Have seen it mentioned from time to time, but never seen anything to back it up.
Thanks man

[Calum]

@jens-eskildsen I've seen it mentioned...on RC cars.

[Glynn123]

Heat cycles will help bed in the piston skirt gently, along with the rings id imagine, allows the piston to expand gently without being under any load, load is the worst thing possible on a fresh engine.

[Irongamer727]

@calum 1000 on a rebuild? That seems a bit much. Do you mean with new bearing and stuff?

[ricky0115]

How do motocross bikes go about running in their engines 200 miles on a track would take months

[Calum]

@ricky0115 MX aren't built to last mate. You can't compare a road going engine, to an engine that is only supposed to last 40 hours lol.

@Irongamer727 Yeah, on a full nut and bolt road going rebuild, crank, mains, gearbox, I would put a 1k miles into before I'd saying it's run it.

You may be misinterpreting the run in procedure for an engine. Which I am not going to describe, lots of conflicting information about that elsewhere, but it doesn't mean drive like your nan for 1k miles.

[ricky0115]

@calum ah explains it all

[Jens Eskildsen]

MX bikes runs way bigger piston to cylinder tolerances last time I compared