CG250 Head - A Closer Look. - Page 10

Megadan · 01-12-2018, 10:32 PM

Quote:

Originally Posted by JerryHawk250

Looks good

kind of tempted to bolt that baby up aren't you? Lol

You have no idea....

On the plus side, it is allowing me to really take my time and make sure it is all correct. I would have lapped the valves already, but I found that I am out of prussian blue to check the seating surfaces. So I will leave that for a project next weekend. I could use Sharpie, but that dried out as well lol.

I also have my VM30 jetted and ready...with exception to the UFO setup. I accidentally ordered the wrong slide for it. I bought a right side idle screw, and I needed a left... Luckily the company I ordered it from is being rather cool and letting me just swap it out. I have to pay shipping again, but oh well.

I am so antsy to try out this head and the VM30 together. I have a feeling only good things will come from it. If not, I have my new main jets in for the VM26 as well.

**JerryHawk250** · 01-15-2018, 08:50 AM

I had a busy weekend and finally had a chance to look at this on my PC. Comparing your head to mine. At first look it looks like you took more than 1mm because most of that ring was removed. Then I look at the holes were the bolts pass threw and can still see the bevel on a couple of them. That ring on your new head must of had less bevel to it than the stock head. I guess that shows how non consistent the casting and machining is on these engines are. Can't wait to see the dyno results. I don't know how you can take all the stress of looking at your work and not being able to test it out right away. lol

Megadan · 01-18-2018, 06:06 AM

Quote:

Originally Posted by JerryHawk250

I had a busy weekend and finally had a chance to look at this on my PC. Comparing your head to mine. At first look it looks like you took more than 1mm because most of that ring was removed. Then I look at the holes were the bolts pass threw and can still see the bevel on a couple of them. That ring on your new head must of had less bevel to it than the stock head. I guess that shows how non consistent the casting and machining is on these engines are. Can't wait to see the dyno results. I don't know how you can take all the stress of looking at your work and not being able to test it out right away. lol

The bevel on this heads combustion chambers was very shallow, as were the chamfers for the head bolt holes. You can tell by simply looking at how that bevel is cut closer to the valve seats on the stock head compared this one one before I did any work.

This could be a good or bad thing for me. It means I was starting with a smaller combustion chamber to begin with. So that means I will suffer less compression loss from material removal around the valves. That also means the loss of that bevel when I milled the head also decreased the chamber size again, roughly .3cc if my math is accurate.

I do plan on CCing the head for sure, but if my rough estimates are anything to go by I will be looking at about 10.2 - 10.4:1 compression. A bit more than I was planning, but I won't complain either.

Should be nice and thumpy.... If it's going to be any higher than that, then I am going to take the head to a shop with a bridgeport mill and have them cut a bevel back into the head.

Speaking of consistency. I got the new valves lapped with the seats. Prussian blue was a life saver, because the contact with the seats was pretty bad. I had to start with 100 grit for a little while to cut back the seat and valve face enough to get a full 360 contact. Then finished with a 240 then a 500. Cleaned up the head and assembled it with some leftover redline assembly lube, then did a valve seal test with some light cutting oil in the ports. Not a single drip past the valves, so at least I know all the gasses will stay where they should.

I can't take the stress of looking at my work and not being able to run it, but I don't have the time to do much else with it at the moment anyway. I guess it's a good thing lol.

Megadan · 01-18-2018, 06:14 AM

I think this picture from before best shows just how shallow of an angle that chamber bevel was cut on this head and how much further away from the valve seats it is. This is the intake valve seat and you can see a good bit of material between the outer edge of the seat and the bevel.

**JerryHawk250** · 01-18-2018, 07:52 AM

Yes that is definitely shallower than the stock head. Honestly I think you will be okay with a little higher compression. You will have the dual oil cooler to help with cooling. Depending on if the fabricator gets my skid plates done this week or not. More like he may not. The cold weather has his shop shut down right now. I may have a chance to install the other cooler over the weekend.
Why couldn't you slap it on there and start figuring out the carburetor situation. Get it all tuned up then go put it on the dyno, Then just put the stock head and carb back on and dyno? You already have the stock head and carb tuned. The new head and carb may take some time to tune to get it just right.

Megadan · 01-18-2018, 01:04 PM

Quote:

Originally Posted by JerryHawk250

Yes that is definitely shallower than the stock head. Honestly I think you will be okay with a little higher compression. You will have the dual oil cooler to help with cooling. Depending on if the fabricator gets my skid plates done this week or not. More like he may not. The cold weather has his shop shut down right now. I may have a chance to install the other cooler over the weekend.
Why couldn't you slap it on there and start figuring out the carburetor situation. Get it all tuned up then go put it on the dyno, Then just put the stock head and carb back on and dyno? You already have the stock head and carb tuned. The new head and carb may take some time to tune to get it just right.

Mainly because my plan was to dyno it with the VM26 before and after. I didn't plan on putting the VM30 on the dyno

Sochin · 06-01-2018, 11:48 PM

I'm gonna order a new head too it looks like, one of the exhaust studs broke off, I tried to trill the sob out and use a torch and an easy out, but it wouldn't budge and my "easyout" broke off too.

Megadan · 06-02-2018, 01:17 AM

Quote:

Originally Posted by Sochin

I'm gonna order a new head too it looks like, one of the exhaust studs broke off, I tried to trill the sob out and use a torch and an easy out, but it wouldn't budge and my "easyout" broke off too.

That sucks. One of the many reasons I decided to upgrade certain fasteners. The studs were one of them.

I tried to find you a good price on a cylinder head, but there must be some sort of shortage, or they suddenly became made of gold, because the cheapest price I could find was $154.

The only sub $100 option for a new head would be to order a TT250 head through CSC. http://www.cscmotorcycles.com/TT250-...p/zt38-101.htm

If you order it along with something else for another $15, then it would likely be cheaper than just the head + shipping. since shipping is free for orders of $100 or more.

zippy · 06-02-2018, 08:36 PM

There is enough room on the head to drill and tap holes for new studs beside the old ones that are broken off. Here is a picture of how I was able to fix mine. The newspaper blocks shavings from falling into the head.

Sochin · 06-02-2018, 10:00 PM

Thanks, Zippy.....this might be worth a try.

Dan, will this head fit you think? https://www.ebay.com/itm/292266378421

Megadan · 06-03-2018, 12:47 AM

Quote:

Originally Posted by Sochin

Thanks, Zippy.....this might be worth a try.

Dan, will this head fit you think? https://www.ebay.com/itm/292266378421

Going by their measures, and off my not so great memory, I would say no. The only way to know for sure would be to measure.

IMHO, I would say to try the Zippy fix (official name of that repair now lol) before plonking money down on a new head.

If all else fails, when I get my new Hawk in I plan on installing my ported head. If it goes according to plan, I will have a zero mile stock Hawk head sitting around. I was planning on porting it and not decking it, but your need is greater than my tinkery experiments, and you are welcome to it, again assuming all goes according to plan.

Sochin · 06-03-2018, 02:49 PM

Well, if I end up needing a new head. I appreaciate the offer Dan.....I'm off to buy a thread and die set now at o Reillys

1600degrees · 11-06-2018, 11:44 AM

Did this thing ever make it onto the dyno? Or get installed at least? I'm dying to hear the conclusion to this!

ben2go · 11-06-2018, 06:30 PM

Quote:

Originally Posted by 1600degrees

Did this thing ever make it onto the dyno? Or get installed at least? I'm dying to hear the conclusion to this!

MegaDan got his bike together and going but it was unfortunately stolen before he could get it on a dyno. He has since replaced it with another Hawk, but work is keeping him over the top busy for now.

Marvin610 · 08-11-2021, 12:52 PM

Sorry to hear about the bike, just got done reading through all the old post. But I've built a lifan 250cc swapped Honda z50 monkey. The lifan 167ffm is pretty much the same engine the hawk/Apollo bikes have. But I'm not sure why my the cylinder and head have different head bolt patterns. Also it for some reason has much larger valves, roughly 2mm larger intake and exhaust valves. At first I just increased the ignition timing to 30°, and add a huge oil cooler. But I've now done quiet a bit of extreme port work, pretty much 32mm straight shot all the way to the intake valve. The exhaust port is about a 28mm straight shot out to my 2" exhaust. I've also milled the cylinder about 0.04" and the head about 0.02". Now The edge of the piston is flush with the cylinder, and the dome protrudes. I've been running it for about a month now on E85 with 32mm flat slide carb. It makes incredible amounts of power and will easily do 70+mph. It's an absolute monster

01-15-2018, 08:50 AM	#137
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,545	I had a busy weekend and finally had a chance to look at this on my PC. Comparing your head to mine. At first look it looks like you took more than 1mm because most of that ring was removed. Then I look at the holes were the bolts pass threw and can still see the bevel on a couple of them. That ring on your new head must of had less bevel to it than the stock head. I guess that shows how non consistent the casting and machining is on these engines are. Can't wait to see the dyno results. I don't know how you can take all the stress of looking at your work and not being able to test it out right away. lol __________________ 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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01-18-2018, 07:52 AM	#140
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,545	Yes that is definitely shallower than the stock head. Honestly I think you will be okay with a little higher compression. You will have the dual oil cooler to help with cooling. Depending on if the fabricator gets my skid plates done this week or not. More like he may not. The cold weather has his shop shut down right now. I may have a chance to install the other cooler over the weekend. Why couldn't you slap it on there and start figuring out the carburetor situation. Get it all tuned up then go put it on the dyno, Then just put the stock head and carb back on and dyno? You already have the stock head and carb tuned. The new head and carb may take some time to tune to get it just right. __________________ 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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06-01-2018, 11:48 PM	#142
Sochin Join Date: Jul 2017 Location: Montucky Posts: 209	I'm gonna order a new head too it looks like, one of the exhaust studs broke off, I tried to trill the sob out and use a torch and an easy out, but it wouldn't budge and my "easyout" broke off too. __________________ 1991 Kawasaki KLR250
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06-02-2018, 10:00 PM	#145
Sochin Join Date: Jul 2017 Location: Montucky Posts: 209	Thanks, Zippy.....this might be worth a try. Dan, will this head fit you think? https://www.ebay.com/itm/292266378421 __________________ 1991 Kawasaki KLR250
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06-03-2018, 02:49 PM	#147
Sochin Join Date: Jul 2017 Location: Montucky Posts: 209	Well, if I end up needing a new head. I appreaciate the offer Dan.....I'm off to buy a thread and die set now at o Reillys __________________ 1991 Kawasaki KLR250
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11-06-2018, 11:44 AM	#148
1600degrees Join Date: Oct 2018 Posts: 11	Did this thing ever make it onto the dyno? Or get installed at least? I'm dying to hear the conclusion to this! __________________ 2018 TaoTao Hellcat Looking for a good oil? try Amsoil http://www.amsoil.com/index.aspx?zo=5178398
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08-11-2021, 12:52 PM	#150
Marvin610 Join Date: Jul 2021 Posts: 3	Sorry to hear about the bike, just got done reading through all the old post. But I've built a lifan 250cc swapped Honda z50 monkey. The lifan 167ffm is pretty much the same engine the hawk/Apollo bikes have. But I'm not sure why my the cylinder and head have different head bolt patterns. Also it for some reason has much larger valves, roughly 2mm larger intake and exhaust valves. At first I just increased the ignition timing to 30°, and add a huge oil cooler. But I've now done quiet a bit of extreme port work, pretty much 32mm straight shot all the way to the intake valve. The exhaust port is about a 28mm straight shot out to my 2" exhaust. I've also milled the cylinder about 0.04" and the head about 0.02". Now The edge of the piston is flush with the cylinder, and the dome protrudes. I've been running it for about a month now on E85 with 32mm flat slide carb. It makes incredible amounts of power and will easily do 70+mph. It's an absolute monster
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