CG125 Engine conversion to 250 Help

Gooseberry · 08-13-2020, 04:51 PM

Hi

So I have been looking at buying a 230cc - 250cc engine that will bolt into my CG125T frame as a fun project. I was originally looking at an overbore kit but looking at research its a one way ticket to a melted engine.

Looking at multiple sources I found a couple of brands to look that being Loncin, Shineray and Zongshen. They all appear to have 250cc engines that follow the same design as the CG125 engine but I am uncertain if the dimensions line up. I'm aiming to have as simple time as possible changing over the engine so no mounting brackets/aligning the chain sprockets.

Basically what I'm trying to find is just an engine that will bolt directly in, hopefully has a bit of power behind it (well whatever a 250 can deliver) but also reliable, price isn't too much of an issue.

Any help is welcome.

franque · 08-13-2020, 05:08 PM

As long as it isn't counterbalanced, any of the 'normal' 250s (that is to say not a true 250), even the OHC models, should bolt right in. You might need to make a different top mount, but that should be really easy.

Gooseberry · 08-13-2020, 05:16 PM

Why do I not want it to be counterbalanced? I do actually have a spare Honda CB250 nighthawk engine that might be able to fit in.

franque · 08-14-2020, 07:41 AM

I'm only taking about Chinese made motors. I have no clue about Nighthawk fitment (personally, I hate those motors, too much vibration and too little power for it to be worth it, also not worth the extra weight, to me). You don't want a counterbalanced motor because it protrudes more in the front, meaning it might either hit the lower downtube, or require you to fab up a new front mount. From what you were saying, I assumed you're looking for the easiest bolt-in possible, so I was giving you the option with the least amount of fabrication.

Mister104 · 08-14-2020, 05:12 PM

A cg250 will fit into a cg125 without issue. Assuming the lower crankcase profile is the same it should bolt up using the same front engine bracket.

Mister104 · 08-14-2020, 05:23 PM

FYI I have a cg300 engine, in a CG125 frame.

08-13-2020, 04:51 PM	#1
Gooseberry Join Date: Aug 2020 Posts: 8	CG125 Engine conversion to 250 Help Hi So I have been looking at buying a 230cc - 250cc engine that will bolt into my CG125T frame as a fun project. I was originally looking at an overbore kit but looking at research its a one way ticket to a melted engine. Looking at multiple sources I found a couple of brands to look that being Loncin, Shineray and Zongshen. They all appear to have 250cc engines that follow the same design as the CG125 engine but I am uncertain if the dimensions line up. I'm aiming to have as simple time as possible changing over the engine so no mounting brackets/aligning the chain sprockets. Basically what I'm trying to find is just an engine that will bolt directly in, hopefully has a bit of power behind it (well whatever a 250 can deliver) but also reliable, price isn't too much of an issue. Any help is welcome.
	0

08-14-2020, 05:23 PM	#6
Mister104 Join Date: Nov 2019 Posts: 23	FYI I have a cg300 engine, in a CG125 frame. Last edited by Mister104; 08-14-2020 at 06:49 PM.
	1

08-13-2020, 05:08 PM	#2
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	As long as it isn't counterbalanced, any of the 'normal' 250s (that is to say not a true 250), even the OHC models, should bolt right in. You might need to make a different top mount, but that should be really easy.
	0

08-13-2020, 05:16 PM	#3
Gooseberry Join Date: Aug 2020 Posts: 8	Why do I not want it to be counterbalanced? I do actually have a spare Honda CB250 nighthawk engine that might be able to fit in.
	0

08-14-2020, 07:41 AM	#4
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	I'm only taking about Chinese made motors. I have no clue about Nighthawk fitment (personally, I hate those motors, too much vibration and too little power for it to be worth it, also not worth the extra weight, to me). You don't want a counterbalanced motor because it protrudes more in the front, meaning it might either hit the lower downtube, or require you to fab up a new front mount. From what you were saying, I assumed you're looking for the easiest bolt-in possible, so I was giving you the option with the least amount of fabrication.
	0

08-14-2020, 05:12 PM	#5
Mister104 Join Date: Nov 2019 Posts: 23	A cg250 will fit into a cg125 without issue. Assuming the lower crankcase profile is the same it should bolt up using the same front engine bracket.
	0