Hawk 250 New piston and rings - Page 3

Megadan · 01-23-2018, 09:32 PM

The problem with checking the ends of the cylinder is that most oblong wear tends to happen more in the center of the bore. I knew the chance of it being out of round was minimal given the lack of miles on the motor, but the debris scuffing on the cylinder walls was pretty severe. I agree with Jerry about honing it a bit more until those vertical scratches are gone. They aren't very deep looking, so your piston clearances should still be ok. They are usually loose on an aircooled engine anyway.

As far as the piston, yes, that is a good way to check them for any taper wear.

I would definitely take the time to clean the heck out of that cylinder. I usually clean with warm soapy water, and then wipe down with clean rags and WD-40 until I get nothing to wipe off on the rag anymore. Then coat the cylinders with a thin coat of assembly lube (it sticks better).

This would be a good chance to try and flush out the crankcase and clear the centrifugal oil filter as well. Might as well start with as clean of an engine as you can.

zach3697 · 01-30-2018, 10:21 AM

So I finally got some time between classes to resurface the head and wanted to make sure the surface finish looked to be a good mating surface for the gasket.

Any opinions?

**JerryHawk250** · 01-30-2018, 11:44 AM

Looks pretty good. But me being OCD I would do it a little more to get rid of that last bit of gasket ring mark.

Megadan · 01-30-2018, 02:04 PM

Quote:

Originally Posted by JerryHawk250

Looks pretty good. But me being OCD I would do it a little more to get rid of that last bit of gasket ring mark.

X2. It shouldn't take much more to get rid of that last ring mark on the head surface.

pistolclass · 01-30-2018, 02:49 PM

For my education, can you point out the residual gasket ring mark? TY.

zach3697 · 01-30-2018, 02:57 PM

Quote:

Originally Posted by pistolclass

For my education, can you point out the residual gasket ring mark? TY.

Its the dark mark on the left of the head right between the two stud holes

zach3697 · 01-30-2018, 02:59 PM

I went ahead and took care of that gasket residue. I just got the piston and rings in today as well. Went ahead to gap the rings and at both top and bottom I was getting a ring gap of .016 inch which from what I read about ring gap should be acceptable. Does that sound to be okay?

Megadan · 01-30-2018, 03:53 PM

Looks good to me. The cg125-150 specs are.
First ring = .15 to .35mm
Second ring = .15 to .30mm
Oil rings = .20 to .50mm

zach3697 · 01-30-2018, 07:42 PM

Quote:

Originally Posted by Megadan

Looks good to me. The cg125-150 specs are.
First ring = .15 to .35mm
Second ring = .15 to .30mm
Oil rings = .20 to .50mm

So my first ring is .016in (.40mm) should be okay? It's .05mm out of spec

humanbeing · 01-30-2018, 08:08 PM

Basics: http://www.dansmc.com/pistons.htm
1 of the 67mm application (LY200 is a Yamaha clone / most CG250 also use same size rings http://www.anerda.com/html/ProList.a...=0,283,&Page=9) :

Megadan · 01-30-2018, 08:46 PM

Quote:

Originally Posted by zach3697

So my first ring is .016in (.40mm) should be okay? It's .05mm out of spec

I wouldn't sweat .05mm. Keep in mind that those are cg125 Honda specs. The larger bore of the 250 means the ring has a bit more metal to expand. Plus, I personally prefer my first ring gap a bit on the loose side with aircooled motors. Unless somebody had cg250 specific information they can post up, but it is unlikely.

As humanbeing stated, the other option is to use another 67mm bore aircooled engine as an analog.

zach3697 · 01-31-2018, 12:35 PM

Went ahead and cleaned the cylinder and head, installed the piston into the cylinder with assembly lube and was going to torque down the bolts and I wasn't sure how much to torque them down to? Found a service manual for the cg 125/150 and it says 21-25 nm

Thanks!

**JerryHawk250** · 01-31-2018, 01:13 PM

Quote:

Originally Posted by zach3697

Went ahead and cleaned the cylinder and head, installed the piston into the cylinder with assembly lube and was going to torque down the bolts and I wasn't sure how much to torque them down to? Found a service manual for the cg 125/150 and it says 21-25 nm

Thanks!

Should be 22-24 ft.lbs. I personally torque to 28 ft.lbs

Megadan · 01-31-2018, 01:35 PM

Quote:

Originally Posted by JerryHawk250

Should be 22-24 ft.lbs. I personally torque to 28 ft.lbs

Again, this. Just make sure to stage it in at least 2 steps and tighten in a cross cross pattern like you would a 4 lug car wheel.

zach3697 · 01-31-2018, 03:10 PM

After I torqued all the bolts down im getting 200 psi compression. Could it be so high from the assembly lube?

Thanks!

01-23-2018, 09:32 PM	#31
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 7,953	The problem with checking the ends of the cylinder is that most oblong wear tends to happen more in the center of the bore. I knew the chance of it being out of round was minimal given the lack of miles on the motor, but the debris scuffing on the cylinder walls was pretty severe. I agree with Jerry about honing it a bit more until those vertical scratches are gone. They aren't very deep looking, so your piston clearances should still be ok. They are usually loose on an aircooled engine anyway. As far as the piston, yes, that is a good way to check them for any taper wear. I would definitely take the time to clean the heck out of that cylinder. I usually clean with warm soapy water, and then wipe down with clean rags and WD-40 until I get nothing to wipe off on the rag anymore. Then coat the cylinders with a thin coat of assembly lube (it sticks better). This would be a good chance to try and flush out the crankcase and clear the centrifugal oil filter as well. Might as well start with as clean of an engine as you can. __________________ 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
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01-30-2018, 11:44 AM	#33
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,545	Looks pretty good. But me being OCD I would do it a little more to get rid of that last bit of gasket ring mark. __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
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01-30-2018, 03:53 PM	#38
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 7,953	Looks good to me. The cg125-150 specs are. First ring = .15 to .35mm Second ring = .15 to .30mm Oil rings = .20 to .50mm __________________ 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
	0

01-30-2018, 08:08 PM	#40
humanbeing Join Date: Mar 2008 Posts: 2,436	Basics: http://www.dansmc.com/pistons.htm 1 of the 67mm application (LY200 is a Yamaha clone / most CG250 also use same size rings http://www.anerda.com/html/ProList.a...=0,283,&Page=9) : __________________ Last edited by humanbeing; 04-12-2018 at 09:11 PM.
	2

01-30-2018, 02:49 PM	#35
pistolclass Join Date: Oct 2015 Location: connecticut Posts: 978	For my education, can you point out the residual gasket ring mark? TY.
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01-30-2018, 02:59 PM	#37
zach3697 Join Date: Jan 2018 Posts: 43	I went ahead and took care of that gasket residue. I just got the piston and rings in today as well. Went ahead to gap the rings and at both top and bottom I was getting a ring gap of .016 inch which from what I read about ring gap should be acceptable. Does that sound to be okay?
	0

01-31-2018, 12:35 PM	#42
zach3697 Join Date: Jan 2018 Posts: 43	Went ahead and cleaned the cylinder and head, installed the piston into the cylinder with assembly lube and was going to torque down the bolts and I wasn't sure how much to torque them down to? Found a service manual for the cg 125/150 and it says 21-25 nm Thanks!
	0

01-31-2018, 03:10 PM	#45
zach3697 Join Date: Jan 2018 Posts: 43	After I torqued all the bolts down im getting 200 psi compression. Could it be so high from the assembly lube? Thanks!
	0