Hawk 250 DLX 300cc big bore kit.

Newell99 · 11-13-2022, 10:42 PM

Hello, I'm new to this forum and I recently bought a 300cc big bore kit off of AliExpress and I just wanted to ask if anybody else on here has had any experience doing this to these bikes and has anybody had any issues with it, I also have an oil cooler witch was recommended by some people on YouTube. Anyways here is the link for it in case somebody is interested

https://www.aliexpress.us/item/32568...andl_shipto=US

Thanks to anybody who responds.

XLsior · 11-14-2022, 02:51 AM

The jug OD skirt will need likely machined down to aprox 72.8mm to fit in the case recess.

The piston wrist pin which the link specifies is 18mm this I believe is to big for a hawk CG250. Pretty sure you need a 16mm pin kit...

also the stock photo showing inside cylinder diameter only appears to be 67mm...which is a stock cg250 piston diameter...

Sorry to pop a bubble there.

Megadan · 11-14-2022, 04:05 AM

This kit has the right pin diameter AND comes with the sleeve OD machined for a CG250 case. It costs more but also requires no extra work.
https://www.aliexpress.us/item/32568...91969978%21rec

One thing you may want to consider is that a larger bore on the EFI system will likely cause fueling issues.

Newell99 · 11-14-2022, 05:07 AM

I checked what I received with some calipers, and it is a 70mm bore and a 16mm pin, was also told by seller that the one pictured is a 250 but I did receive the 300. I also saw some guy on YouTube did it and showed the whole install and had no trouble, and that's where he put the link where I got it.

XLsior · 11-14-2022, 06:39 AM

Well that's somewhat a relief.
the original link had some questionable details.

your only other possible conflict is the outside skirt diameter.

If its 73mm it should be fine otherwise you might need to get it machined down to size.

Newell99 · 11-14-2022, 08:13 AM

Just checked and its 73mm. So, I think I won't have too much trouble.

Thumper · 11-14-2022, 11:23 AM

Quote:

Originally Posted by Newell99

Just checked and its 73mm. So, I think I won't have too much trouble.

The listing shows 67mm internal diameter. Oh I see they had the wrong photos there. Glad you got the correct bore.

I ordered a big bore kit that I think should fit my 249cc ZS172 (72mm bore), but it looks like it is a modest increase to 74mm which is maybe a 260cc displacement. It says it is a 300cc kit, but I don't think so. I will find out when I get it. I will probably go ahead with it, and while I am at it, port the head. I got a set of grinding bits for the dremel for that. I can also install an advance key this Winter, and work on the exhaust. All together, this should make a big difference. I will probably need to bump the jetting up a bit as well.

Texas Pete · 11-14-2022, 12:00 PM

Quote:

Originally Posted by Thumper

I ordered a big bore kit that I think should fit my 249cc ZS172 (72mm bore), but it looks like it is a modest increase to 74mm which is maybe a 260cc displacement. It says it is a 300cc kit, but I don't think so. I will find out when I get it.

I for one am hoping your AliExpress listing just had wrong numbers from sellers not knowing what they are dealing with but you do get a 300cc kit when you actuallt get to measuring with calipers. You can always message the seller on AliExpress to confirm. AliExpress sellers are usually pretty responsive.

CheapThrills · 11-15-2022, 09:18 AM

Following, thanks for link to jug requiring least amount of mill work. However, please confirm this, when it says 300cc's, it's calculating total space including the head area, not just the cyclenger/jug area(the compressible area)?

So 300cc's on the ad is much less in real life?

Thx!

Deckard_Cain · 11-15-2022, 09:39 AM

Quote:

Originally Posted by CheapThrills

Following, thanks for link to jug requiring least amount of mill work. However, please confirm this, when it says 300cc's, it's calculating total space including the head area, not just the cyclenger/jug area(the compressible area)?

So 300cc's on the ad is much less in real life?

Thx!

CG300 jug on the CG250 engine takes it from 229cc to 249cc. So it essentially turns it into a "true" 250.

I have it on my engine. It's nice. Kind of the end of the road sort of thing to do once you've done everything else, in my case. It's not as mind-blowing of a difference as porting the head with a full exhaust was, but it's a bump in power.

11-13-2022, 10:42 PM	#1
Newell99 Join Date: Nov 2022 Location: Ohio Posts: 3	Hawk 250 DLX 300cc big bore kit. Hello, I'm new to this forum and I recently bought a 300cc big bore kit off of AliExpress and I just wanted to ask if anybody else on here has had any experience doing this to these bikes and has anybody had any issues with it, I also have an oil cooler witch was recommended by some people on YouTube. Anyways here is the link for it in case somebody is interested https://www.aliexpress.us/item/32568...andl_shipto=US Thanks to anybody who responds.
	0

11-14-2022, 04:05 AM	#3
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 8,029	This kit has the right pin diameter AND comes with the sleeve OD machined for a CG250 case. It costs more but also requires no extra work. https://www.aliexpress.us/item/32568...91969978%21rec One thing you may want to consider is that a larger bore on the EFI system will likely cause fueling issues. __________________ Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124
	2

11-15-2022, 09:18 AM	#9
CheapThrills Join Date: Jan 2021 Location: Lehigh Valley Area Posts: 148	Following, thanks for link to jug requiring least amount of mill work. However, please confirm this, when it says 300cc's, it's calculating total space including the head area, not just the cyclenger/jug area(the compressible area)? So 300cc's on the ad is much less in real life? Thx! __________________ - My 2 Bikes: TaoTao TBR7 Boom Vader Gen 2 (BD125-10) Testing a YouTube Channel
	0

11-14-2022, 02:51 AM	#2
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,296	The jug OD skirt will need likely machined down to aprox 72.8mm to fit in the case recess. The piston wrist pin which the link specifies is 18mm this I believe is to big for a hawk CG250. Pretty sure you need a 16mm pin kit... also the stock photo showing inside cylinder diameter only appears to be 67mm...which is a stock cg250 piston diameter... Sorry to pop a bubble there.
	0

11-14-2022, 05:07 AM	#4
Newell99 Join Date: Nov 2022 Location: Ohio Posts: 3	I checked what I received with some calipers, and it is a 70mm bore and a 16mm pin, was also told by seller that the one pictured is a 250 but I did receive the 300. I also saw some guy on YouTube did it and showed the whole install and had no trouble, and that's where he put the link where I got it.
	0

11-14-2022, 06:39 AM	#5
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,296	Well that's somewhat a relief. the original link had some questionable details. your only other possible conflict is the outside skirt diameter. If its 73mm it should be fine otherwise you might need to get it machined down to size.
	0

11-14-2022, 08:13 AM	#6
Newell99 Join Date: Nov 2022 Location: Ohio Posts: 3	Just checked and its 73mm. So, I think I won't have too much trouble.
	1