Does anyone know the bore size on a bt80?

[GW's Motorized]

I'm currently looking into hopping up my BT80, and I want to get a windowed piston to add a cdh power reed. I am unsure the bore size and I don't want to tear it apart until I replace the piston

 

[DAMIEN1307]

I'm currently looking into hopping up my BT80, and I want to get a windowed piston to add a cdh power reed. I am unsure the bore size and I don't want to tear it apart until I replace the piston

This was the only information I could find for the BT-80 motor that I found on bikeberry's website.

Note: Due to the design of this engine, most parts (including cylinders, pistons, cranks, and gaskets) and performance upgrade parts (including upgraded mufflers, carburetors, cylinder heads, and case covers) do not fit on this engine. DO NOT purchase parts or performance upgrades designed for non-electric start 2-stroke bicycle engine kits.

Down through the years China bicycle engine manufactures have advertised their biggest engine as 80cc, therefore we have listed them in the same way on our website. However, the bore and stroke of an 80cc being 47x38mm equals 66cc. Therefore the true displacement of the 80cc bike motor is 66cc.

 

[GW's Motorized]

I am aware of the warnings, but I am smart enough to tell if a part will screw my engine. As far as it looked when I put the jug on the internals are the same. I will most likely order the 47 mm windowed piston and size it up to the stock one. I would love to put a reed and jog pipe on this engine especially since I haven't seen it done before. If all else fails I will try my hand at making a replacement windowed piston. I will also measure the studs to make sure the reed will fit. As far as the pipe goes I will have to build a manifold to adapt it to the more dirt bike like exhaust port.

 

[GW's Motorized]

I just priced it. A standard 66cc engine windowed piston, CDH reed block, and jog pipe will run me 150 bucks. I will probably also order a set of jets for my BoFeng carb to get my engine dialed in

 

[Chainlube]

Take the head off and measure, then you'll know.

 

[GW's Motorized]

Take the head off and measure, then you'll know.

It's a one piece jug. I'd have to tear it all the way apart. I'm willing to gamble it's a standard size piston

 

[Chainlube]

It's a one piece jug. I'd have to tear it all the way apart. I'm willing to gamble it's a standard size piston

Actually, if you just lift the jug up a bit to expose the piston then you can measure the piston. Most likely 47mm.

 

[Greg58]

You can get a close measurement by removing the exhaust and sticking a soft piece of wood in the cylinder and rotating the engine a few time to mark the wood, it’s not perfect but will be close

 

[GW's Motorized]

You can get a close measurement by removing the exhaust and sticking a soft piece of wood in the cylinder and rotating the engine a few time to mark the wood, it’s no perfect but will be close

That's an awesome idea. I already have the exhaust off right now because I am rebuilding my bike. This will give me a good enough measurement to guess since is is probably in the 47-50 mm range

 

[Greg58]

That’s how I checked the Chinese chain saw that was advertised as a 62cc, I used a drinking straw to check the bore and stroke to dispute their claim.