Hawk 250 piston change or bore

Hawkwind · 07-10-2016, 12:55 PM

just wondering if anyone has changed the bore of the hawk 250 ? If so what size and where to find piston and rings ?

Ariel Red Hunter · 07-10-2016, 01:31 PM

Quote:

Originally Posted by Hawkwind

just wondering if anyone has changed the bore of the hawk 250 ? If so what size and where to find piston and rings ?

I suspect (but don't absolutly know) that this engine has been already bored out to quite close to the maximum. That said, there used to be a company, in California I believe, that used to manufacture stepped crankpins for small Honda engines. I do not recall the name of the company, or if they are still around. In theory, stepped crankpins are a poor idea, but I never heard of any engine problems from those modifications. This machine shop did the work in house, to make sure the crankpins were installed correctly. If I recall correctly, they bored the flywheels for an over sized crankpin which was machined for an off center big end bearing. The magic words "stroker crank" is how they were known among the motorcycle gear heads of the day.

humanbeing · 07-10-2016, 02:40 PM

http://www.chinariders.net/showpost....67&postcount=2

Hawkwind · 07-10-2016, 02:42 PM

I kind of figured that the cylinders were maxed out, I remember hearing about Japanese enduros from the 70's were made a lot more powerful with a larger bore, but if the hawk was bored out from an earlier version of a 200cc design then it wouldn't be possible without designing a different head for the motor.

darmst6829 · 07-10-2016, 03:12 PM

http://www.ebay.com/itm/262490844536...%3AMEBIDX%3AIT

pcspecialist · 07-10-2016, 03:43 PM

Quote:

Originally Posted by darmst6829

http://www.ebay.com/itm/262490844536...%3AMEBIDX%3AIT

doubt that would fit a Hawk frame

BlackBike · 07-10-2016, 04:07 PM

Quote:

Originally Posted by darmst6829

http://www.ebay.com/itm/262490844536...%3AMEBIDX%3AIT

So roughly 18hp for $1000, ouch

Edit $790

humanbeing · 07-10-2016, 04:13 PM

Quote:

Originally Posted by pcspecialist

doubt that would fit a Hawk frame

http://www.zse.cc/Upload/motor/CG250-09500646783.jpg vs http://www.zse.cc/Upload/motor/CB250DG-09475128876.jpg

darmst6829 · 07-10-2016, 08:54 PM

Quote:

Originally Posted by pcspecialist

doubt that would fit a Hawk frame

"It is a direct bolt on replacement for most Chinese dirt bikes running 200-250cc single cylinder air cooled motors."

Kdburtch · 07-11-2016, 08:30 AM

I was wondering this as well. A big bore kit would be a nice addition to these bikes.

Ariel Red Hunter · 07-11-2016, 12:08 PM

Quote:

Originally Posted by Kdburtch

I was wondering this as well. A big bore kit would be a nice addition to these bikes.

I'd like a stroker kit even more.

07-10-2016, 12:55 PM	#1
Hawkwind Join Date: Jul 2016 Location: Idaho Posts: 7	Hawk 250 piston change or bore just wondering if anyone has changed the bore of the hawk 250 ? If so what size and where to find piston and rings ?
	0

07-10-2016, 02:40 PM	#3
humanbeing Join Date: Mar 2008 Posts: 2,436	http://www.chinariders.net/showpost....67&postcount=2 __________________
	0

07-10-2016, 02:42 PM	#4
Hawkwind Join Date: Jul 2016 Location: Idaho Posts: 7	Hawk piston size I kind of figured that the cylinders were maxed out, I remember hearing about Japanese enduros from the 70's were made a lot more powerful with a larger bore, but if the hawk was bored out from an earlier version of a 200cc design then it wouldn't be possible without designing a different head for the motor.
	0

07-10-2016, 03:12 PM	#5
darmst6829 Join Date: May 2016 Location: Redmond WA Posts: 42	http://www.ebay.com/itm/262490844536...%3AMEBIDX%3AIT
	1

07-11-2016, 08:30 AM	#10
Kdburtch Join Date: May 2016 Location: Kansas Posts: 31	I was wondering this as well. A big bore kit would be a nice addition to these bikes.
	0