CG250 big bore kit? Did I find it?
 

https://produto.mercadolivre.com.br/...8-de68efc7ed4c

I was looking at this Brazilian website for upgraded engine parts and it looks like I found a bigger bore cylinder. Its a 70mm cylinder. The hawk 250's engine is a 67mm bore. Thats turning the 229 cc engine into a 250 cc engine.

SOmething I might wanna get...

Ide wait till experienced people here can look at it ,maybe tomorrow.If not mistaken hawk engine was already bored out to what is now, 3mm ant much but bored out more might be to much.

I think you will find this is a Big Bore for 150cc to 220cc
South America mostly gets 150 and stuff tends to relate to that.
I thought the CG250 had a 70mm bore already?

65x67 stroke by bore.

That is an OHC cylinder in the picture. Chain tensioner hole/mount on the side.

What you found is a kit for the OHC CG 150 Titan. Around 2011 Honda went from OHV to OHC for the CG150 and the XR 150.
It takes the 150 to 220/229

You can look all over South America and you will never find a 250cc kit for a CG. The max it can go be reliable and run forever is 229cc. They used to sell kits to 250cc but they were just grenades so they stopped making them...
Plus you should be aware that some of kits you will find in South America, are made for racing and will have the life of a racing engine...
There is a 400cc for the Honda XR 250 Tornado, that kit only last 30 hours before you need to rebuild the engine.
Same goes for those 70cc piston kit for the CG 150, they are meant to be abused and rebuild.

This what they use those 70cc kits for
https://www.youtube.com/watch?v=lNX7ztjMiN4

Of course the "230" is not a real world speed, but an "ideal world" test no weight and no air dragging



You want or need a real 250cc? Then you need to look at a new complete engine or another motorcycle.

I want to aim somewhere between Full racing engine and reliable, lol. I love my hawk, and its insanely cheap to work and upgrade.

I expected a 250 to bore be a pipe dream lol. I am looking into getting a hotter cam, roller rocker arms, and chrome moly pushrods. The cams from brazil are super cheap its just decifering it and figuring out which one. haha

I have my eyes on a couple different ones.

In this video, this guy is showing headwork where he completely cut out the valve guides that were visible in the cylinder, Is this a viable practice? anyone know? It makes sense in opening it up a lot.
https://youtu.be/POgqCFZeut0?t=1015

That’s an OHC Cg 150 not an OHV. Most of the mods you will find that above 230cc are for the OHC variant.

There is an "easy" way to get to 250 or slightly more cc without a stroker crank. Machine out the cylinder liner and have the bore industrial hard chrome plated. When a factory (like Briggs & Stratton) does this, they use reverse polarity at the very end of the plating process in order to roughen the bore enough to hold trace oil. I would imagine you can do the same thing with a hone VERY carefully applied....ARH

I know i sound like a broken record but...

Every design has it limits, in the case of the CG 125, 230cc is the max. In this part of the world, people been messing with them for over 40 years.
To begin with Honda never sold an OHV CG 150, 200 or 230cc they were 125, the "CG 150 TITAN" is an OHC and it's a whole different animal, to begin with it was born as 150.
The OHV CG 150, 200 and 230 are chinese copies, that are just overbored CG 125, with little to no difference. You can do a lot of things to get more power but overboring it more, will just break the engine.
Just trying to save you from a big headache.

Please understand, this is a "you're on your own" modification that I'm talking about. Yes, you can get to 250 cc or a little more. But I can not predict the life expectancy of this modification. It will work, but for how long? And remember, the finning on the barrel is on the skimpy side. ...ARH :hmm:

Cylinder thermal control is the reason cg250 big bore kits never stuck around. Just not enough thermal mass or cooling area to absorb and shed heat efficiently enough.

The CG 125 is just like an AK47, it was made to be cheap to make, cheap to maintain, reliable and just like the AK47 it was cloned to death...
But most of the design there is a limit of the thing they can do... You are not going to win a bench rest competiton with an Ak47, in the same way you are not going to outrun a real 250cc with a CG250. As it is, it's quite impresive that the CG 125 can be bored to 230cc and be reliable...

Like i said in other post, people used to sell 250cc for the OHV Cg 125.
Then the history would go like this:
-Kids dreams to beat his older brother that owns a CBX250
-Kids gets the CG 125 to 250
-Kids challenges his brother to race both bikes
-Kids ends up crying once his engine grenades out.
-Dad takes his Kid to the store who sold the kit and wants a WHOLE NEW ENGINE!!
-Dad leaves the store without any money, because it was stated that those kit have a low life before needing rebuid..

After a while, they get feed up and will only sell 230cc no more overboring to 250cc...

Black sheep really exists: TMX 155 (58.5 x 57.8 mm) in the Philippines.

In the same way you can find crappy Aks clones. It will depend the factory that cloned it.