Hawk 250 New piston and rings

zach3697 · 01-19-2018, 11:01 AM

Hello everyone! Im looking for a new piston and ring set for the Hawk 250.

I know the Hawk engine is an upscale honda 125 but I cant find any information on these parts.

Does anyone have any experience rebuilding this engine or finding parts for it?

Thanks!

Weldangrind · 01-19-2018, 11:06 AM

Welcome!

The engine is referred to as a CG250; use that as your search criteria on eBay. Measure the bore of your engine to ensure that you're ordering the correct parts.

Ariel Red Hunter · 01-19-2018, 11:06 AM

Quote:

Originally Posted by zach3697

Hello everyone! Im looking for a new piston and ring set for the Hawk 250.

I know the Hawk engine is an upscale honda 125 but I cant find any information on these parts.

Does anyone have any experience rebuilding this engine or finding parts for it?

Thanks!

The easy way is to get the parts from CSC (California Scooter Co.). The piston and rings are the same as in their TT 250...ARH

zach3697 · 01-19-2018, 12:12 PM

Quote:

Originally Posted by Weldangrind

Welcome!

The engine is referred to as a CG250; use that as your search criteria on eBay. Measure the bore of your engine to ensure that you're ordering the correct parts.

Quote:

Originally Posted by Ariel Red Hunter

The easy way is to get the parts from CSC (California Scooter Co.). The piston and rings are the same as in their TT 250...ARH

Thanks Guys! ill take a look at some parts!

zach3697 · 01-21-2018, 12:28 PM

Quote:

Originally Posted by Ariel Red Hunter

The easy way is to get the parts from CSC (California Scooter Co.). The piston and rings are the same as in their TT 250...ARH

So heres an update guys. I got a used Hawk 250 off craigslist and started troubleshooting why it wasnt running. The odometer says it has 638 miles on the motor. Did a compression check and it only has 60psi which is way too low. I assumed it needed a piston and rings but after I took the head off the cylinder wall is marked up. So im thinking Ill just buy a new block from CSC for 44.50 and a piston and rings for 12.50

http://www.cscmotorcycles.com/TT250-...MBLY-s/311.htm

My question is I just wanted to make sure that this block will work on the hawk 250 motor?

Thanks!

Megadan · 01-21-2018, 01:42 PM

Just out of curiosity, did you make sure the valves were adjusted properly before performing that compression test? I ask because the number one most neglected and overlooked thing with these bikes when they are assembled is that the valve clearances are never checked or set, and they almost always come from the factory with no clearance at all, or even tight. After a little bit of riding, the valves will actually stretch a little during break in, and cause all sort of issues from not sealing with the head. A poorly adjusted valve can cause all sorts of issues, including extremely low compression.

zach3697 · 01-21-2018, 01:57 PM

Quote:

Originally Posted by Megadan

Just out of curiosity, did you make sure the valves were adjusted properly before performing that compression test? I ask because the number one most neglected and overlooked thing with these bikes when they are assembled is that the valve clearances are never checked or set, and they almost always come from the factory with no clearance at all, or even tight. After a little bit of riding, the valves will actually stretch a little during break in, and cause all sort of issues from not sealing with the head. A poorly adjusted valve can cause all sorts of issues, including extremely low compression.

That's a great thought! I haven't checked the valves yet but I will do that after work today. Thanks for the suggestion!

Ariel Red Hunter · 01-21-2018, 08:31 PM

Quote:

Originally Posted by zach3697

So heres an update guys. I got a used Hawk 250 off craigslist and started troubleshooting why it wasnt running. The odometer says it has 638 miles on the motor. Did a compression check and it only has 60psi which is way too low. I assumed it needed a piston and rings but after I took the head off the cylinder wall is marked up. So im thinking Ill just buy a new block from CSC for 44.50 and a piston and rings for 12.50

http://www.cscmotorcycles.com/TT250-...MBLY-s/311.htm

My question is I just wanted to make sure that this block will work on the hawk 250 motor?

Thanks!

What do you mean by the cylinder wall is marked up? If it sat for a while with dirty oil in it, the cylinder often gets stain marks where the piston comes to rest. 638 kilometers (bikes odometer reads in kilometers) is not even broken in, really. Cheaters break in new rings by starting the engine and feeding a pinch of Bon-Ami through the carb and then ride it for a short time, immediatly changing the oil when getting home. That's known as a FWIW....ARH

letsride · 01-21-2018, 09:37 PM

I second what Dan Said, Practice the K.I.S.S principle before going off all half cocked wanting to rebuild the top end. You just may get lucky and find out it was something simple. It may very well need a top end rebuild, but for now lets hope not. These engines are notoriously tough as nails. But there are folks buying these bike that don't know much about maintaining them. Keep us posted on what you find. AND, round here we LIKE PICS!

zach3697 · 01-22-2018, 12:30 AM

Quote:

Originally Posted by letsride

I second what Dan Said, Practice the K.I.S.S principle before going off all half cocked wanting to rebuild the top end. You just may get lucky and find out it was something simple. It may very well need a top end rebuild, but for now lets hope not. These engines are notoriously tough as nails. But there are folks buying these bike that don't know much about maintaining them. Keep us posted on what you find. AND, round here we LIKE PICS!

Sounds good. Im going to work on the bike some tomorrow and ill be sure to take some pics!

zach3697 · 01-22-2018, 10:07 AM

So I did the value adjustment and it still only has 60 psi.

I think at this point I'm going to have to work on the top end?

Here are some pics

zach3697 · 01-22-2018, 01:21 PM

Inside the head

zach3697 · 01-22-2018, 01:23 PM

Wear?

Megadan · 01-22-2018, 03:31 PM

There is a little evidence of some debris scuffing going on, and maybe a little evidence of some mild overheating as well, but the fact that the cross hatch is still visible in the cylinder wall where the scuffing occourred tells me that this wear isn't that severe and shouldn't contribute to such a drastic loss in compression. The rings look to be in decent shape as well.

What interests me more is the evidence of poor valve sealing, especially on the exhaust valve.

If it were me, and I didn't have the proper gauges to check the cylinder, then I would likely take the cylinder to a local shop, have them check and hone the cylinder. Either get a new piston and rings, or clean up the current piston and get new rings - the difference in cost is pretty small between the two.

The last thing I would do would be to clean up the head, check the head to ensure it isn't warped, and lap the valves.

The poor valve sealing doesn't surprise me. The head I bought and ported showed very poor valve to seat contact from the factory, and I had to lap the valves starting with a coarse grit to get a full seat contact, and then finished with a fine grit compound. This is a good affordable little kit of tungsten carbide lapping compound, comes with a small amount of 100 and 240 grit, which is still way more than needed for this head (you could probably do 50+) https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Beyond that, new base and head gaskets obviously.

zach3697 · 01-22-2018, 05:36 PM

Quote:

Originally Posted by Megadan

There is a little evidence of some debris scuffing going on, and maybe a little evidence of some mild overheating as well, but the fact that the cross hatch is still visible in the cylinder wall where the scuffing occourred tells me that this wear isn't that severe and shouldn't contribute to such a drastic loss in compression. The rings look to be in decent shape as well.

What interests me more is the evidence of poor valve sealing, especially on the exhaust valve.

If it were me, and I didn't have the proper gauges to check the cylinder, then I would likely take the cylinder to a local shop, have them check and hone the cylinder. Either get a new piston and rings, or clean up the current piston and get new rings - the difference in cost is pretty small between the two.

The last thing I would do would be to clean up the head, check the head to ensure it isn't warped, and lap the valves.

The poor valve sealing doesn't surprise me. The head I bought and ported showed very poor valve to seat contact from the factory, and I had to lap the valves starting with a coarse grit to get a full seat contact, and then finished with a fine grit compound. This is a good affordable little kit of tungsten carbide lapping compound, comes with a small amount of 100 and 240 grit, which is still way more than needed for this head (you could probably do 50+) https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Beyond that, new base and head gaskets obviously.

Perfect! I have gaskets and a new piston and rings on order. Got lapping compound from a local store and im going to lap the valves tonight.

The only thing im concerned about it the warped head. If it is warped can it be fixed myself or would a machine shop have to get involved?

Excited to get this motor running!

here are some pictures of my cylinder wall

01-19-2018, 11:01 AM	#1
zach3697 Join Date: Jan 2018 Posts: 43	Hawk 250 Top end rebuild. New piston and rings Hello everyone! Im looking for a new piston and ring set for the Hawk 250. I know the Hawk engine is an upscale honda 125 but I cant find any information on these parts. Does anyone have any experience rebuilding this engine or finding parts for it? Thanks! Last edited by zach3697; 01-22-2018 at 02:54 PM.
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01-19-2018, 11:06 AM	#2
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Welcome! The engine is referred to as a CG250; use that as your search criteria on eBay. Measure the bore of your engine to ensure that you're ordering the correct parts. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

01-21-2018, 01:42 PM	#6
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 7,953	Just out of curiosity, did you make sure the valves were adjusted properly before performing that compression test? I ask because the number one most neglected and overlooked thing with these bikes when they are assembled is that the valve clearances are never checked or set, and they almost always come from the factory with no clearance at all, or even tight. After a little bit of riding, the valves will actually stretch a little during break in, and cause all sort of issues from not sealing with the head. A poorly adjusted valve can cause all sorts of issues, including extremely low compression. __________________ 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2010 VFR1200F - http://chinariders.net/showthread.php?t=20708
	2

01-21-2018, 09:37 PM	#9
letsride Join Date: Oct 2013 Location: Leesville SC Posts: 832	I second what Dan Said, Practice the K.I.S.S principle before going off all half cocked wanting to rebuild the top end. You just may get lucky and find out it was something simple. It may very well need a top end rebuild, but for now lets hope not. These engines are notoriously tough as nails. But there are folks buying these bike that don't know much about maintaining them. Keep us posted on what you find. AND, round here we LIKE PICS! __________________ My Stable- 2022 Lifan KPX250 , 2023 Royal Enfield Himalayan, 1992 Honda GL1500 Goldwing, SSR 70 Auto, Kymco Mongoose 90, Honda Four Trax 300
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01-22-2018, 03:31 PM	#14
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 7,953	There is a little evidence of some debris scuffing going on, and maybe a little evidence of some mild overheating as well, but the fact that the cross hatch is still visible in the cylinder wall where the scuffing occourred tells me that this wear isn't that severe and shouldn't contribute to such a drastic loss in compression. The rings look to be in decent shape as well. What interests me more is the evidence of poor valve sealing, especially on the exhaust valve. If it were me, and I didn't have the proper gauges to check the cylinder, then I would likely take the cylinder to a local shop, have them check and hone the cylinder. Either get a new piston and rings, or clean up the current piston and get new rings - the difference in cost is pretty small between the two. The last thing I would do would be to clean up the head, check the head to ensure it isn't warped, and lap the valves. The poor valve sealing doesn't surprise me. The head I bought and ported showed very poor valve to seat contact from the factory, and I had to lap the valves starting with a coarse grit to get a full seat contact, and then finished with a fine grit compound. This is a good affordable little kit of tungsten carbide lapping compound, comes with a small amount of 100 and 240 grit, which is still way more than needed for this head (you could probably do 50+) https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 Beyond that, new base and head gaskets obviously.
	0