Cg 300 cc kit

[Ol,fart]

I've read post about this kit. Has anyone actually used it ? Is it bolt on, links ? I have a hundred questions. Sorry search forum does not work on my phone

[alex_in_az]

Originally Posted by Ol,fart

I've read post about this kit. Has anyone actually used it ? Is it bolt on, links ? I have a hundred questions. Sorry search forum does not work on my phone

I have a CG "300" jug and piston that I plan on using when I re-build my "250". IIRC the cg300 is only about 255 or so, like the cg250 is 229. The cyl liner needs to be reduced in diameter or the case mouth needs to be opened up to accept it. there was talk a while back that opening up the cases might be problematic due to oil passages that might be broken into

[Wild Dog]

Originally Posted by alex_in_az

I have a CG "300" jug and piston that I plan on using when I re-build my "250". IIRC the cg300 is only about 255 or so, like the cg250 is 229. The cyl liner needs to be reduced in diameter or the case mouth needs to be opened up to accept it. there was talk a while back that opening up the cases might be problematic due to oil passages that might be broken into

There is also a 72mm version, that's a bit cloer to "300" at 265cc.

Do yourself a favour, don't use it. It's pointless and it will trash the engine.



Those kits are mostly made for brainless kids in latam, that can't afford a 300 or anything bigger.



Then they use the kit, do that kind of stupid thing...
Of course, they engines lose any kind of reliability...

It's the worst of both world...
It has the reliability of a F1 car, after one race it's done for
and
It has the final speed of a rabbit that had a stroke.

[Megadan]

There are quite a few guys with 70mm cylinders that have been running for a couple of years now. Two are well known and respected members that used to frequent the forums but are mostly active on Facebook. They get ridden all the time and have had zero reliability issues to date. J have one sitting in a box waiting for me to eventually do something with it lol

[Ol,fart]

I thought if it was actually bolt on and close to 300cc I would try it. But I think I'll just ride it instead. ������

[Dusman]

I have a CG300 head sitting in my basement. I haven’t bothered to install it as my Hawk comfortably runs 65-70 mph all day long with the current mods. I just sort of say “why”? at this point since it runs so well thus far with the current mods.

[Megadan]

Originally Posted by Ol,fart

I thought if it was actually bolt on and close to 300cc I would try it. But I think I'll just ride it instead. ������

The CG300 cylinder is 3mm larger in bore diameter than the CG250. When installed on a CG250 it takes it from 229cc to 249cc making it a true "250" It technically is a bolt on affair. Not even every cylinder needs to be machined down for the sleeve to fit the block. Every engine is just a bit different in how it will fit due to very loose machining tolerances on the case halves. The potential is there to need it though

It does make a difference but like with any modification the individual effect is smaller while the accumulative effect is greater. If I were to do a single upgrade to a CG250 it would be a ported head.

[Ol,fart]

Originally Posted by Megadan

The CG300 cylinder is 3mm larger in bore diameter than the CG250. When installed on a CG250 it takes it from 229cc to 249cc making it a true "250" It technically is a bolt on affair. Not even every cylinder needs to be machined down for the sleeve to fit the block. Every engine is just a bit different in how it will fit due to very loose machining tolerances on the case halves. The potential is there to need it though

It does make a difference but like with any modification the individual effect is smaller while the accumulative effect is greater. If I were to do a single upgrade to a CG250 it would be a ported head.

I currently have a ported head shaved 1mm and a 4degree advance key. 110 main jet with 1 washer added to the needle. It would have to be a pretty big difference for me to mess with it any more. I have developed a high rpm miss over the summer. At around 3000 miles between 7 &8000 it starts cutting out ( like it's hitting the limiter) but that's close to 9000. Tried plug, coil, plug wire. Planned to change cdi at the same time but the one from csc had one connector different.
Anyway abandoning the big bore idea for now
P.S. these little bikes would be perfect for a 400 parallel twin !

[Wild Dog]

Originally Posted by Megadan

There are quite a few guys with 70mm cylinders that have been running for a couple of years now. Two are well known and respected members that used to frequent the forums but are mostly active on Facebook. They get ridden all the time and have had zero reliability issues to date. J have one sitting in a box waiting for me to eventually do something with it lol

I guess it's like they say, "Your mileage may vary"
I wonder how they did set their engines.

The reputation and track record here for the 70 and 72 cylinders is not good, in fact most sellers dropped them.

[Megadan]

Originally Posted by Wild Dog

I guess it's like they say, "Your mileage may vary"
I wonder how they did set their engines.

The reputation and track record here for the 70 and 72 cylinders is not good, in fact most sellers dropped them.

These current 70mm cylinders aren't just bored over 67mm cg250 units like the days of old. These are actually different in a few key ways. They are a bespoke casting (cg300) with more aluminum in the main body and the fins are slightly bigger. The iron sleeve is also thicker by 2+mm, which is why some machining may be required to fit. I have one myself for an eventual build/upgrade. I can't speak for the longevity myself, but others I have talked to have been doing alright thus far.

[alex_in_az]

Originally Posted by Megadan

These current 70mm cylinders aren't just bored over 67mm cg250 units like the days of old. These are actually different in a few key ways. They are a bespoke casting (cg300) with more aluminum in the main body and the fins are slightly bigger. The iron sleeve is also thicker by 2+mm, which is why some machining may be required to fit. I have one myself for an eventual build/upgrade. I can't speak for the longevity myself, but others I have talked to have been doing alright thus far.

which head do you plan on using, cg250 or cg300?

[Deckard_Cain]

Originally Posted by Megadan

There are quite a few guys with 70mm cylinders that have been running for a couple of years now. Two are well known and respected members that used to frequent the forums but are mostly active on Facebook. They get ridden all the time and have had zero reliability issues to date. J have one sitting in a box waiting for me to eventually do something with it lol

Originally Posted by Megadan

These current 70mm cylinders aren't just bored over 67mm cg250 units like the days of old. These are actually different in a few key ways. They are a bespoke casting (cg300) with more aluminum in the main body and the fins are slightly bigger. The iron sleeve is also thicker by 2+mm, which is why some machining may be required to fit. I have one myself for an eventual build/upgrade. I can't speak for the longevity myself, but others I have talked to have been doing alright thus far.

Maybe not well-know nor respected... but <Raises hand> Got one. lol.

I'm the guy on the fb group who had the tip of my pick tool fall into the case and chew up the cam and crank timing gears... split my cases and cleaned it all out during the CG300 parts swap. (Doh!).

I can attest, the newer cast CG300 cylinders are quite good. I've got about 1000 miles on mine right now (with all the other major upgrades as well). No reliability issues at all.

It's a fairly beefy jug compared to the stock CG250 unit. Piston was even ceramic coated, which was unexpected.

But I also second Dan's comment, if there was a single upgrade to do it would without question by a ported head. Plus whatever carburetor tuning and exhaust mods needed to support that. Biggest gain in power without compromising reliability.

[Megadan]

Originally Posted by alex_in_az

which head do you plan on using, cg250 or cg300?

250 head is more than sufficient to get the job done.