Project: Hawk Stage II - Head Work and Nibbi

[Baskt_Case]

The plan is to port (including matching) both intake and exhaust, polish the exhaust, mill down for compression bump, and install a Nibbi PE30.

I am using the "improved" Rato CGP head that is equipped on the Brozz and TT250, among others. I will be employing the use of A.P.E. Racing for my head work.

My project was conceived after exhaustive reading both here and elsewhere and was originally thrust into light in the Hawk 250 Enduro Owners Group on Facebook. I would like to share here as well, especially considering that the largest part of the technical knowledge required for this project has been gleaned from members and projects right here on Chinariders.

I would also like to share a highly inspirational article on serious CG performance:

How to set a land speed record on a $3,200 motorcycle.

Am I Bonneville bound? I'll never tell!

My current inventory of project parts...

Brozz Head and Gasket:
https://shop.brozz250.com/eshopprod_...r_Assembly.htm

OEM Style Gasket:
https://ebay.us/VnECnk

Nibbi PE30 Carburetor:
https://www.amazon.com/gp/aw/d/B07P2VY8NC

Nibbi Intake Adapter:
https://www.amazon.com/gp/aw/d/B07PCN9MQW

Generic 30mm CG Intake Adapter:
https://www.amazon.com/dp/B07JG3M1T5

Nibbi Pod Filter:
https://www.amazon.com/gp/aw/d/B07KQZMVF3

UNI Pod Filter:
https://www.amazon.com/gp/aw/d/B000N5UCEG

Jet Kit:
https://www.amazon.com/gp/aw/d/B077BVZVQZ

Other miscellaneous items still yet to be purchased for this project are fuel line, fuel filters, torque wrench, 16T sprocket, calipers, extra plugs for tuning, and filter oil.

[Megadan]

That's not an EGR port. Just so you know. That port is for the air injection. Not one of these bikes has EGR.

Glad that my own efforts have inspired you forward, as have those of JerryHawk250 and a couple others. That's the whole point of this forum.

Surprised you haven't looked into a camshaft as well. One of the biggest limitations to these CG engines making power is the camshaft. Once you go past 7500 rpm, the power delivery still falls off pretty quickly. Even my own bike will usually top out right at 8000rpm in 5th. Honestly, that "improved" head could probably make great use of the Ressalto cam profile I picked for my bike with just a little cleanup work.

In any case, I am subscribing to this thread. I look forward to the progress and your impressions of the results.

You should take a moment to install and get the PE30 running on the stock head just for a comparison. It would be nice to have an opinion of the PE30 without port work.

[Baskt_Case]

Thanks Dan, my blunder for perpetuating the EGR myth. It doesn't help that CSC specifies it as such in their own documentation, tutorials, and parts listings. Add that to the fact that alot of us in less restrictive parts of the country have never had the pleasure of physically dealing with an emissions equipped Chinabike.

Indeed, I would not be at my current point of progress in my endeavors without the prior countless hours of research, experimentation, and work performed by you and many others here on the forum. I am very grateful and only hope to expand the knowledge base, and have alot of fun doing it!

Ahh yes, the cam. I am eagerly following your thread for your results and impressions. It is definitely a possiblity for the future, perhaps a "Stage III" project. My plate is comfortably full at the moment with just the head and carb upgrade. However, I am definitely watching you closely, especially since you have started talking about a 32mm carb. Have you read the article from CCW that I linked above?

Upon my initial inspection of the CGP head, I was quite pleased with the factory port profiles compared to my stock head. Its not a massive difference, but plainly visible. Others have suggested the same as you, that just some touch-up work and matching alone would probably yield a significant improvement over my stock head. However, I am "committed" at this point, my heart is set on professional head work. I just wanna see where this goes. In regards to a future possible cam upgrade, heavier valve springs are definitely on the table with the builder.

Originally I was going to wait to install the carb simultaneously with the head but as you and one other individual have pointed out, it would be nice to quantify the gains of the carb and head separately. So carb installation will commence soon!

-Aaron

[Megadan]

Originally Posted by Baskt_Case

Have you read the article from CCW that I linked above?

Yeah, I read it a couple of years ago. It's what actually inspired me to take it further with the head work, cam, and carb. I won't be trying to go 90mph, but I would love the added acceleration and some more high rpm power.

[Baskt_Case]

So today I was able to nail down specifics with the engine builder regarding exactly what work will be performed. I should have the head shipped out in the next day or two.

I will be using A.P.E. Racing in Rosamond, CA. These guys didn't even flinch when I said it was a CG motor. Communication with them has been nothing short of professional.

1. Disassemble, Clean, Inspect.
2. CNC Porting (plus match to my gaskets).
3. Polish on exhaust only.
4. Unshroud valves and address quench gap.
5. Multi-Angle Serdi Valve Job
   • Bronze Guides
   • Stainless Valves
   • Heavy Duty Springs
   • Titanium Retainers
6. Deck 0.8mm (.031").
7. Assemble and Flow Bench

$439 Shipped (both ways)

For comparison, they will sell you a brand new ready-to-race CRF250 head for $945 + Shipping.

[China Rider 27]

I would want to get some objective and quantifiable performance measures of my motor to do a comparison of before and after. Dyno?

[Baskt_Case]

Originally Posted by China Rider 27

I would want to get some objective and quantifiable performance measures of my motor to do a comparison of before and after.

I have put alot of thought into this, as I too would like to quantify my gains. In lieu of a stationary dyno, I'll have to rely on the open road and data logging. I have a 30 mile loop with 220 foot elevation changes that I will be using to track everything.

First graph is the entire 30 mile run. 15 miles out, 15 miles back. You can see my turnaround in the middle, and the results of traveling both against and with the wind.

Second graph notes my worst speed during the entire trip, at the highest elevation, pushing against the wind.

[Megadan]

You will definitely have the most prepped head of anybody on this site. That is race level stuff through and through and not the typical budget DIY job.

[alex_in_az]

Originally Posted by Baskt_Case

I have put alot of thought into this, as I too would like to quantify my gains. In lieu of a stationary dyno, I'll have to rely on the open road and data logging. I have a 30 mile loop with 220 foot elevation changes that I will be using to track everything.

First graph is the entire 30 mile run. 15 miles out, 15 miles back. You can see my turnaround in the middle, and the results of traveling both against and with the wind.

Second graph notes my worst speed during the entire trip, at the highest elevation, pushing against the wind.

what did you use for data logging?

[Baskt_Case]

Originally Posted by alex_in_az

what did you use for data logging?

Its just called Speedometer GPS in the Google Play Store

https://play.google.com/store/apps/d...speedometergps

[JerryHawk250]

Originally Posted by Baskt_Case

Its just called Speedometer GPS in the Google Play Store

https://play.google.com/store/apps/d...speedometergps

Thanks. I've been looking far a good app. The last one i installed worked similar but for whatever reason it away displayed in KPH no matter what it was set on.

[China Rider 27]

Originally Posted by Baskt_Case

I have put alot of thought into this, as I too would like to quantify my gains. In lieu of a stationary dyno, I'll have to rely on the open road and data logging. I have a 30 mile loop with 220 foot elevation changes that I will be using to track everything.

First graph is the entire 30 mile run. 15 miles out, 15 miles back. You can see my turnaround in the middle, and the results of traveling both against and with the wind.

Second graph notes my worst speed during the entire trip, at the highest elevation, pushing against the wind.

I might also consider any other means of measurement that could lend a specific comparison. Top overall speed is always the number one and maybe a measure of acceleration between two known points in terms of time and or speed. That being if you can safely obtain those measurements.

[Megadan]

Originally Posted by China Rider 27

I might also consider any other means of measurement that could lend a specific comparison. Top overall speed is always the number one and maybe a measure of acceleration between two known points in terms of time and or speed. That being if you can safely obtain those measurements.

Top speed is not really a good quantifier on these bikes unless you really gear them up, and I can explain why.

My bike with it's current gearing, which with all factors involved is essentially running the equivalent of a 17 front 45 rear sprocket, on flat ground and zero wind will hit 74 mph at 8000rpm, and then it runs out of steam. If I re-install my taller rear sprocket, which would be the equivalent of dropping 2 teeth in the rear, it will hit 79mph... at 8000rpm. With a 17 front and 50 rear equivalent, it did 67mph, at..... 8000RPM!

Basically the engine runs out of cam. It can roar to 8000, and the power just falls off too fast and it can't pull anymore. With that taller rear sprocket you can really feel where the power curve peaks too. That 79mph is probably just about all it had to give with my big fat butt on it, and it took the starts aligning and the gods smiling for that run to happen. Toss an even taller sprocket on there and somebody like Jerry's size and it might even surpass 80, but I can almost promise you it will halt all progress at right about 8000rpm.

Even with the sprocket combination I am running I still can't hit 74 if there is a decent head wind. In fact, the best I can pull with a decently strong head wind is 65-70mph, which is dead smack on the peak power RPM range. That actually happened to me today just a couple of hours ago. 8-12mph winds out of the north west. tapped out at 70mph.

That is the reason I am installing a cam, I want to shift the peak power up and broaden the high rpm power. Even then, I still won't gear it any taller than I have it now. I just wish my flywheel puller would show the hell up.

[China Rider 27]

[QUOTE=Megadan;338111]Top speed is not really a good quantifier on these bikes unless you really gear them up, and I can explain why.


Yes I agree and certainly no comparison between two different bikes. Searching for a quantitative measure though, maybe it can tell us something about performance modification comparison on one bike if we have one or two variables in the absence of a better measurement such as a dyno?

[Baskt_Case]

Originally Posted by Megadan

...I still can't hit 74 if there is a decent head wind. In fact, the best I can pull with a decently strong head wind is 65-70mph, which is dead smack on the peak power RPM range. That actually happened to me today just a couple of hours ago. 8-12mph winds out of the north west. Tapped out at 70mph.

^^^THIS^^^

This is precisely why I started on this project in the first place. I am after more highway cruising power. Terminal velocity is fun, but the ability to maintain respectable cruising speeds uphill and/or into the wind is most important to me. I live in rural central Kentucky, a.k.a. "hill country" and most travel around here is on 55mph state highways.

Close examination of those graphs will show precisely the effect of elevation changes. It wont be a horsepower number but rather a recorded speed on a given incline. It will be a pretty satisfactory metric for me. Especially when I start comparing back to back results at the same exact geographic location. Sure, I cant control wind or temp, so averaging multiple runs will be the best I can do but I'm pretty sure its going to illustrate "real world" gains or losses.