|
![]() |
|
![]() |
|
Thread Tools | Search this Thread | Display Modes |
|
![]() |
#1 |
Join Date: Sep 2019
Location: Machesney, IL
Posts: 30
|
Contemplating milling the CG head .030 to raise compression – Any input?
This winter I may try purchasing a new head assembly for my 250 Hawk DLX and milling off .030 to raise the compression. Will also probably clean up the ports and polish the exhaust port. Has anyone out there tried this on the CG engine? Hoping to gain some incite from others who have tried this.
I seem to have a lifetime issue with stock performance, even at 60 years old. Need counseling, surely…. Examples: 2010 Dodge challenger purchased new (added): 6.1 Hemi, Kenne Bell supercharger, Meth injection, Corsa exhaust, custom interior and generates 650 HP with a 3:91 gear – 6 speed short throw Hurst shifter. 2016 Dodge challenger purchased new (added): Ray Barton built 392 HEMI Kenne Bell supercharger, Meth injection, 200 shot Nitrous, custom exhaust, Paramount transmission, 1500 hp drive shaft-axles and generates 1388 HP– 8-speed automatic. Worlds fastest Scat Pack record set in 2016. Car was in 4 magazines in 2017. Road racing VW cabrio: won mid-west GP class 2016. My list could go on but this is about the BIKE! Please help – Is it worth doing the head work on my Hawk? |
![]() |
![]() |
#2 |
Moderator
Join Date: Oct 2016
Location: Houma, La.
Posts: 11,654
|
We have a few that have done it. Me being one. Best mod ever. Megadan put all the information and links into one thread to make it easier to find. http://www.chinariders.net/showthread.php?t=23004
__________________
2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 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 |
![]() |
![]() |
#3 |
Join Date: Aug 2013
Location: Goodyear, Arizona
Posts: 412
|
is it possible to remove the cylinder head with the engine still in the frame?
__________________
2020 Tao TBR7 9.3:1 PnP head CRF230F exhaust 4 degree advance key 290 degree cam Nibbi PE30 and cone filter Front fork brace |
![]() |
![]() |
#4 |
Moderator
Join Date: Oct 2016
Location: Houma, La.
Posts: 11,654
|
On the Hawk you can for sure.
__________________
2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 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 |
![]() |
![]() |
#5 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
|
Jerry beat me to it, but I can comment on the milling. I took off .039 (1mm) of a non stock head that had a smaller quench ring than the standard head and ended up at 10.3:1 static compression. If you do the standard head to .030 you should end up roughly around 9.8:1
Definitely invest in cleaning up the ports. Mostly cleaning up around the valve guides will make quite an improvement, especially on the exhaust side around the bowl and roof, and then smoothing all of the transitions to finish it off. Nothing fancy, but quite effective. The intake side needs very little in terms of material removal outside of opening up the port at the flange and smoothing that in, and obviously cleaning up around the guide again into the bowl.Pair it with a 30mm smooth bore carburetor and it takes the Hawk to quite a new level of performance. The PZ30 and VM26 clones are just too restrictive once you open up the breathing. Seeing as you have the EFI bike, it would depend on the size of the throttle body. Is it worth doing? Absolutely. Will it give you the top end performance you are likely seeking. Yes, to a point. I have discovered the final limitation to top end performance to be the cam. Without changing the cam, what you end up with doing a ported/decked head with a larger carb like my PE30 or Jerry's PWK30 is a noticeable gain through he RPM range, but a big boost between around 4000-7000rpm. After that point the power starts to fall off due to the cam profile. What it does do is make the bike much stronger to pull taller gearing. I am waiting on a new cam from Brazil as we speak to solve that last issue. Like you, I don't tend to do stock very well lol. Absolutely. I have a video where I did just that. No problem.
__________________
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 |
![]() |
![]() |
#6 |
Moderator
Join Date: Oct 2016
Location: Houma, La.
Posts: 11,654
|
Liferider,
Do you know right off hand if the throttle body on the EFI is 28mm or 30mm? The ECU should adjust to the changes. 30mm throttle body would be perfect.
__________________
2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 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 |
![]() |
![]() |
#7 | |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
|
Quote:
That is one area where us carby heads are in the dark. We don't know enough about the DLX to offer much insight.
__________________
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 |
|
![]() |
![]() |
#8 | |
Join Date: Aug 2013
Location: Goodyear, Arizona
Posts: 412
|
Quote:
I also don't do stock and am in the process of getting a webber DCOE45 dialed in on my '74 MG
__________________
2020 Tao TBR7 9.3:1 PnP head CRF230F exhaust 4 degree advance key 290 degree cam Nibbi PE30 and cone filter Front fork brace |
|
![]() |
![]() |
#9 |
Join Date: May 2013
Location: finger lakes NY
Posts: 2,060
|
i would be interested in the cam ordering as well...LOL
|
![]() |
![]() |
#10 |
Moderator
Join Date: Oct 2016
Location: Houma, La.
Posts: 11,654
|
The thing to do would be to have someone duplicate it here in the US.
![]()
__________________
2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 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 |
![]() |
![]() |
#11 |
Join Date: Sep 2019
Location: Machesney, IL
Posts: 30
|
Thank you everyone..... This has been very enlightening. It amazes me the amount of knowledge resource here. I will need to find more info on the throttle body.
This stuff is cheering me up on the winter project. Nasty weather ahead here in the midwest, so I need give my 2 wheeled summer babies some love. |
![]() |
![]() |
#12 |
Moderator
Join Date: Oct 2016
Location: Houma, La.
Posts: 11,654
|
The 28mm throttle body would probably be okay. The 30mm would flow much better.
I'm 61 myself. Just reading your first post I think we have the same sickness. lol Can't leave anything stock. My last daily driver was a 6300 lb. 2000 3/4 ton long bed Chevy with Turbo charged 6.0L that was pushing just over 500hp That ran 13.90's at the track. I would have to leave the 5th wheel hitch in the back to help with traction. I've been involved in racing since the age of 13 with my older brother have a few race cars. Then in my early 20's was dating Leonard Hughes of Candies and Hughes race team' Daughter. Then at 30 I met my wife who's Uncle is the Late Paul Candies of Candies and Hughes. That was awkward. lol So yeah racing and modifying engine is in my blood too. lol Paul Candies two sons PB and Brett still race along with Brett's wife and son. Candies Family Motorsports. You'll find the little CG engines are fun to fiddle around with.
__________________
2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 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 |
![]() |
![]() |
#13 |
Join Date: Sep 2019
Location: Machesney, IL
Posts: 30
|
Where do you suggest that I can purchase a spare head assembly and gaskets? Would like to get these on order.
|
![]() |
![]() |
#14 | |
Moderator
Join Date: Oct 2016
Location: Houma, La.
Posts: 11,654
|
Quote:
__________________
2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 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 |
|
![]() |
![]() |
#15 |
Join Date: Jul 2018
Location: NEPA
Posts: 273
|
Things I noticed after .040 was nocked off and the ports were opened up. It finally kick started easily. The starter motor has a workout now as it passed the compression stroke at TDC. The exhaust note at idle and at RPM was cleaner you can really hear it breathing now and no crack/pop on idle. It also feels like it added 1/4 of the bikes HP range. And you WILL be rejetting for you carb guys. Valves needed to be readjusted. Head gasket was reusable. Porting tossed metal chips EVERYWHERE, head cleanup was a bitch so over to a bath in the ultrasonic tank.
![]() If you are comfortable popping an engine head off and have basic hand tools be clean and methodical and you can do this too. Tho you’ll have to earn it - it’s one of the best mods you can do on a Hawk. I worked slowly and it was a 7 hour Sunday job start to finish. Decked & Ported.
__________________
2018 Hawk P&P Decked .040 off the head. 17/43 D.I.D. 428, NGK Iridium plug, DeCat, Wrapped pipe, Custom S.S. Muffler core, Nibbi PE30 115/35, L.E.D. Lights, Digital Cluster, USB port, Cutting Bord skid plate, Oil cooler w/ custom CRF oil filter inline, 5Wt fork oil, Rear Shock, CNC Back Rack, 30mm FAT bars, Bark Busters, ProGrips, Adjustable levers, Shinko 700’s lots of Loctite! |
![]() |
|
![]() |
![]() |
Tags |
cg250, dlx, hawk, head |
|
|