250cc to 300cc Big Bore Kit
 

What’s everybody’s thoughts on a big bore kit from Amazon for our Chinese 250s?

67mm Engine Parts Big Bore Cylinder Piston Gasket Kit Replacement Set for CG250 250cc Air Cooled Vertical Engine Chinese ATV Dirt Bike Engine USA Stock (Silver) https://a.co/d/gIiA54l

I'm pretty sure that is the stock 229 jug, and piston. I think the CG300(250cc) kits are 70mm

Ah, I see. I’ll keep digging. Anybody done the swap and kept OEM crank?

72mm head diameter in this product, but fitment is my next question. Time to check out the Zongshen 250cc Head bolt pattern info.

72mm Cylinder Bore Top End Piston Gasket Set Replacement Kit for Cfmoto 250cc Honda Helix CN250 JMstar 250 https://a.co/d/1R1Qmmr

This is a water cooled head, anybody done that swap?

72mm Cylinder Bore Top End Piston Gasket Set Replacement Kit for Cfmoto 250cc Honda Helix CN250 JMstar 250 https://a.co/d/1R1Qmmr

A lot of people on some of the Facebook groups use, or at least buy the kits. On some kits the lower skirt of the cylinder sleeve needs machined to around 73mm OD, but AliBaba sells some that already have a 73mm OD skirt. You need to be sure the piston in the kit has a 16mm wrist pin. They is a guy on the ChondaRiders Group selling a kit with a 72.5mm bore, and people are buying them, but I don't see how they can possibly be turned down to 73mm OD .

This was just covered a couple of weeks ago in this thread here
https://chinariders.net/showthread.php?t=31864

This is for the OHV 229cc engine though. Not sure if it applies for you

Yes. You have a 72mm diameter head. Those kits for ZS167 (67mm, 14hp) don't apply to your engine.

The water cooled engines have different frame mounting points. BEST option if you want to increase HP is head work. I have no leads for porting. I did buy a dremel kit to do it myself, but haen't had the time.

If you hear about anyone adapting a different motor to the frame, please share. You have the ZS172FMM-3A engine. It is awesome!!!!!

I got it to hit 70mph, pretty wild. I think I’m happy with performance for now. Thanks, all!

Hey. I have 2019 apollo 250 db36 deluxe street legal. With ZS165FMM engine. I wanted to know if the ZS172FMM would fit and have same exact mounting points. I also wonder if the ZS169FMM would fit exact mounting points.

Just my thought its not worth the time and money,don't think you would even notice any more power.

Hi guy, I just installed the 300cc big bore kit but from the one the oil ring gave me issues. I took the cylinder and ring to a mechanic to be fitted and he trimmed the oil ring. Long story short, I just finished installing the 300cc big bore kit and the bike is smoking line crazy. Does any one know where I can get a set of 300cc rings. I see some on ebay that are 67mm others 72mm but I'm not sure which is the right size for a 300cc jug. Can you guys help...thank you so much

I found a big bore kit for the ZS172FMM-3A makes it a 264cc. they had some other engine parts to.
AJ1 dirt bike .com / it is actually aj1moto.com


https://aj1moto.com/collections/zscb249f-engine-parts