250 Big Bore kits

[crackerjac]

Anyone know if there are any Big Bore kits for the air cooled Zongshen ZS169FMM engines? Stock they are 232cc (69mmx62.2mm) even though they call them 250s.

I know they sell 300cc kits for the water cooled version of this engine.

[pete]

Originally Posted by crackerjac

Anyone know if there are any Big Bore kits for the air cooled Zongshen ZS169FMM engines? Stock they are 232cc (69mmx62.2mm) even though they call them 250s.

I know they sell 300cc kits for the water cooled version of this engine.

18cc or 13% more capacity... if it's more than a straight rebore it's hardly
worth it... if yer have to go to a bigger sleeve... that means boreing the cylinder
block for the bigger sleeve , opening up the crank case opening to take the bigger sleeve..
so a full engine strip...


...

[crackerjac]

Originally Posted by pete

18cc or 13% more capacity... if it's more than a straight rebore it's hardly
worth it... if yer have to go to a bigger sleeve... that means boreing the cylinder
block for the bigger sleeve , opening up the crank case opening to take the bigger sleeve..
so a full engine strip...


...

Looks like most of the kits for the water cooled version come with everything. I'm guessing these particular air-cooled motors would get too hot for this kind of conversion and the cooling fins would have to be huge. I think this motor is a copy of the Yamaha XT250 rather than the Honda but don't quote me on that. If that is the case I wonder if anything interchanges as the XT250 is a true 249cc motor and not a 232cc and also they sell a stroker kit for the XT250. Anyway, just thinking of some what if's.

https://www.aliexpress.com/store/pro...746771916.html

[pete]

The XT225 sarow had a 225cc motor...
So could be the 225 copy already over bored...


..