How do you break in your fresh re bores

declan

How many miles/ hours do you guys spend breaking in your fresh piston and re bore?

Darty

@declan Around 500 miles -

Just concentrate on getting a few heat cycles in first,

then low to midrange running only.

It's about wearing in the Piston Rings to the bore not the piston.

declan

@Darty 500 miles seems overly excessive

Darty

@declan Why?

declan

@Darty well the heat cycles are important I get that but 500 miles what if it's not an on road bike it would take me all year to break it in

Calum

Ahh well you're posting this question on a DT forum.

I agree with @Darty 500 miles of different riding styles with the first 100 miles being gentle.

On a DT it's about reliability.

On a crosser it's about not glazing the cylinder walls and losing compression. So would you really break an engine in on a offroad bike. Probably not.

Darty

It has to be said,

It's about the Clearances, they are not like your MX engines...

You go out with some full beans with fresh rings and you will begin to melt the edge of them before they have worn,

Excess heat from friction will score the bore, and you will seize, I've seen a few seize within 50 miles!

It's worth taking the time with it, it should last over 10,000 miles after that!?

You can't really run these in unless it's under load either, Steel liners and so...

Shame, good ol' YZ engine can be run in on the stand, in the garden...

NINJA

@Darty said Shame, good ol' YZ engine can be run in on the stand, in the garden...

Man that's insane, so MX bikes are pretty much low use then rebuild em? I guess that's why their usage is measured in hours then???

declan

@CYBER-NINJA well they don't have clocks so they only have hour meters

Darty

@CYBER-NINJA 120 hours Max for an Enduro 125,

but if you're a racer, more like 35-50 hours

Mx bikes can last 5 hours sometimes

Calum

I mean a fresh piston rebore. 500 is a lot. If it was full rebuild then I would err on the 500 side. As long as you give enough miles for the rings to bed into the cylinder walls and don't glaze them you will be fine.

declan

@Calum well as you might know I'm yet to ride mine but the shop has to bore 1 and a half mil I think not fetched it yet but quick side question for you will this add any torque or power now I'm not asking will it be on the back wheel in every gear I'm asking if it would make a difference no matter how small just curious

Calum

@declan No.

declan

@Calum figured so thanks