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 (http://www.aperaceparts.com) 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. (https://www.rideapart.com/articles/254553/how-to-set-a-land-speed-record-on-a-3200-motorcycle/)

Am I Bonneville bound? I'll never tell! :lmao::hmm: :crazy::lmao:

My current inventory of project parts...

Brozz Head and Gasket:
https://shop.brozz250.com/eshopprod_cat_5820373-5934482_product_8486237.Cylinder_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]

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 (http://www.aperaceparts.com/) 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.



Disassemble, Clean, Inspect.
CNC Porting (plus match to my gaskets).
Polish on exhaust only.
Unshroud valves and address quench gap.
Multi-Angle Serdi Valve Job


Bronze Guides
Stainless Valves
Heavy Duty Springs
Titanium Retainers

Deck 0.8mm (.031").
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]

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]

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]

what did you use for data logging?

Its just called Speedometer GPS in the Google Play Store

https://play.google.com/store/apps/details?id=luo.speedometergps

[JerryHawk250]

Its just called Speedometer GPS in the Google Play Store

https://play.google.com/store/apps/details?id=luo.speedometergps

Thanks. :tup: 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]

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]

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]

...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.

[Megadan]

A dyno would be the best way by far, but for many the access to one is either limited, or otherwise impossible. Only one in my city, and you have to book it 8-10 weeks in advance, and even then there is no guarantee of getting the day you scheduled because they don't run the dyno if the temps go above 90F outside, or below 50F.

What is kind of funny is the influx of bigger carb installs and ported heads as of late. My first year or so on this forum, the biggest and baddest mods people ever talked about was exhausts or decats, VM26 car clones, airbox mods or pod filters.

Then one day I post a thread about head porting after buying a head, then a couple other guys, ie Jerry, Silva, and at least one other I can't remember all decided it was a good idea too, and thus in a short span all of us had ported heads. Not one dyno.
No quantified results with a dyno or otherwise, just people taking our word for it, and the proof was in the pudding.

Then for a while, nobody else really dove in right away. Not sure if they were too afraid or what, but it stayed pretty mute.

Then Jerry installed his PWK carb, and not long after I installed me PE30. I made a couple of videos and posts here exclaiming "Holy Moly!" at the increase in power and torque across the entire rpm range. Up to that point I was running the PZ30B, and with the ported head it felt decently stronger than before, but the result felt about the same as installing the exhaust on the bike. A good increase, but nothing too outrageous on its own. Once I gave the head the air to actually breathe, it was a completely different story. Jerry posting similar results with his PWK carb.

Within a few months of us posting our results, a few more popped up here and there and they back up our own words, and thus a chain reaction. Now it almost seems like everybody with a chinabike and a youtube account has to follow suit or be left in the dust. Especially after Redbeard's Garage posted his video of the ported head install on the Motomax, although he is still running a weaksauce carb.

Would I like to know what I got for all of my time and money? Sure, I guess, but to tell the truth I don't really need it. I know how the bike felt with every change, and I know that compared to my last Hawk, the current one is much more powerful. Top speed is a little better, maybe 5mph faster more consistently with the same gearing. The real difference is the acceleration and tractor factor pulling up hills. Something I got to witness first hand with a stock TT250 slowing down up a fairly steep hill that I had to let off just so I wouldn't hit the guy because I was still pulling, with basically 5 less teeth out back than him, a heavier chain, and about 80lbs more weight.

If anything I often have to temper peoples enthusiasm with the gains in question and the idea that they formed in their head of what it is like vs. reality. Especially with the younger guys. They seem to think big carb and head porting will turn an anemic air cooled 229cc OHV engine into a 90mph capable dual sport. We all know that isn't the case, which is why I tend to underplay it a bit, and try to shift the focus away from top speed and more toward pulling power. Going faster than 70 on one of these bikes isn't for the faint of heart, which is why I have mine geared the way I do.

[Baskt_Case]

Well said Dan, keeping traffic off my tail in hilly 55 zones is one of my top goals here.

[Megadan]

Well said Dan, keeping traffic off my tail in hilly 55 zones is one of my top goals here.

I can pull most hills in 5th at 55mph until we start talking steeper grades like 6%+, or one heck of a head wind on a milder grade. Even then I can usually still hold 55, although I might be pretty pegged lol. Again, gearing plays a factor, and never forget that I am a big heavy guy, so smaller people may struggle less on inclines. I am literally the worst person to put on one of these bikes for a top speed or hill test :hehe:

[China Rider 27]

I have only been around here for a little over a year and I can see, you and Jerry, Silva, and others have been the innovators on the head porting and other performance improvements. I mean we all copy and follow you guys! Imitation is the best form of flattery! We do all admire your work and appreciate your knowledge, suggestions, and assistance.

Head porting is going to be a big thing in the future and the PE30 carb arrangements too. That is due to you and Jerry Hawk some others. Good job!

I agree about top speed, it does not really mean much and depends on so many variables. People will always be interested in top speed at the expense of other considerations. Speed is thrilling. It is something people just got to know. On my HAWK it is sketchy at WOT and I agree frankly without some good suspension modifications not somewhere I want to spend a lot of time, nor do I recommend other do either. My real interest is as a measure of performance. "Experience" is just as valuable and real as a number and maybe at the heart of satisfaction. If it feels like it is going fast and your satisfied, do you really need anything else.

One day I will be in the Head porting club!

[Megadan]

I have only been around here for a little over a year and I can see, you and Jerry, Silva, and others have been the innovators on the head porting and other performance improvements. I mean we all copy and follow you guys! Imitation is the best form of flattery! We do all admire your work and appreciate your knowledge, suggestions, and assistance.

Head porting is going to be a big thing in the future and the PE30 carb arrangements too. That is due to you and Jerry Hawk some others. Good job!

I agree about top speed, it does not really mean much and depends on so many variables. People will always be interested in top speed at the expense of other considerations. Speed is thrilling. It is something people just got to know. On my HAWK it is sketchy at WOT and I agree frankly without some good suspension modifications not somewhere I want to spend a lot of time, nor do I recommend other do either. My real interest is as a measure of performance. "Experience" is just as valuable and real as a number and maybe at the heart of satisfaction. If it feels like it is going fast and your satisfied, do you really need anything else.

One day I will be in the Head porting club!

Just like when I arrived here and borrowed ideas and upgrades from those before me. It's the evolution and progress at work lol. A vast majority of my Resource guide is information passed on from other guys that I just collected.

I look forward to your thread on it. Just as I can't wait to see the results from this one. This is the first bike where somebody decided they were going to go all out. Most of us just took the cheap bastards route and made the most of what was already there.

[China Rider 27]

There is nothing wrong with the cheap route, that is why we are all here. Thinking about this testing issue some, and I have to say, High speed testing is to dangerous. Especially with these head ported, compression stoked, engines. Baskt case I suggest what you should do is set some assessments based upon speed going up hills and just control for everything but throttle application. Similar to a Dyno, you could apply all out throttle in each case. That way it would be at a slower speed overall speed depending on the hill but give a good comparison.

[TheChairman]

Just want to say that this thread here is one of the reasons I bought this bike. These super simple engines are always good candidates for building on because it doesn't take a small nestegg, a ton of experience, or specialized tools to get inside there. If you ruin a part, the replacement is cheap and easy to install. 1 or 2HP gains can feel huge.

You mention a cam. Is there a cam available, or is this something that will need to be custom ground? So far the only off the shelf aftermarket performance I've come across is exhaust, intake, and ignition modifications.

[Megadan]

You mention a cam. Is there a cam available, or is this something that will need to be custom ground? So far the only off the shelf aftermarket performance I've come across is exhaust, intake, and ignition modifications.

It's buried back on page 15 of my "New Hawk, New Adventures" thread where I go over the cam I have, how I ordered it, how others can order it, and other related information.

http://chinariders.net/showpost.php?p=323576&postcount=221

[Baskt_Case]

This is the first bike where somebody decided they were going to go all out.

Well, this project sure didn't start out that way, but things kinda got outta hand and now I'm just goin with it!

If the weather cooperates, today is Nibbi day.

OneLeggedRider gave me the fantastic idea to check port volume on the Brozz head before I ship it off. Has anyone checked port volume on a stock Hawk head, or can they? I'm gonna grab a big syringe and some ATF this morning.

And I just found these incredibly helpful calculators this morning. Calculate HP from E/T, Speed, and Weight. Need to find a good app that logs speed vs. time better. My current app only has 1.0 second resolution.

http://www.wallaceracing.com/Calculators.htm

[OneLeggedRider]

Glad I could be of assistance Basket_case. It's actually pretty common to check head and port volume with a graduated buret and ATF in high performance cylinder head work, especially on multi cylinder engines, besides Flo-bench testing.

Do you need dyno testing to tell if you're making more power? No. But it's the only accurate way to measure gains. When I lived in Florida I had regular access to one thanks to becoming very good friends with Don, my former high performance instructor who had worked for some of the biggest name drag racers. That taught me you can't always go by "feel", which is often inaccurate.

And you gave me an idea on weighing the rotating mass before and after on the trike project. And it got me to thinking about selling the 200X rear end and buying something newer that came with 12" rims because of parts availability and the ability to buy much larger aftermarket rims that I can mount DOT approved tires on.

I haven't been posting much because of being sick for 3 weeks and working on my cabin. And also I'm a little aggravated with this site and uploading pics. Even on poor service days I can upload multiple pics to FB in less than a minute, but on here one pic might take a half hour or not at all, which seems screwy to me. :crazy:

[JerryHawk250]

I haven't been posting much because of being sick for 3 weeks and working on my cabin. And also I'm a little aggravated with this site and uploading pics. Even on poor service days I can upload multiple pics to FB in less than a minute, but on here one pic might take a half hour or not at all, which seems screwy to me. :crazy:
I was just about to text you to see how you wee doing. Hoping you're doing better.
Yeah, uploading pictures to this site takes longer because it resizes the picture. Even on high speed internet it takes time to process it.

[Baskt_Case]

Was finally able to at least get the Nibbi mounted and briefly run the motor before I ran out of daylight. Lots of loose ends to tie up tomorrow. Throttle cable was too short, carb touches frame, barely got air filter on it. I sent the Nibbi intake to the builder so I'm using the shorter generic rubber Amazon one. At least the rubber filter adapter is now cushioning the carb against the frame. Longer Nibbi intake will put the bowl on the frame. Not sure what I will ultimately do. Also need to stretch out the spring on the idle knob, or add a star washer. The knob vibrates a ¼-turn either way.

Initial jetting is 40 slow, 115 main, clip in middle, 1½ turns out, 700 feet elevation. Have not been on the road yet. Snap throttle off idle has a tendency to kill it. It'll pop occasionally on come down. Plan to install 45 and 120 and methodically work each. I had not started the bike in a week. Pulled plunger, hit starter, instantaneous light-off. She runs. Would probably get to town in an emergency. I'm tickled for the moment. :yay:

Head is on its way to California. Now I wait. Dont ask how long, were just not gonna talk about that right now. However, I did get a chance to measure port volume before I packed it up...

Intake = 51 cc
Exhaust = 24 cc

[Megadan]

I found a 40 pilot to be way too big and I am at 1100ft. I was running a 35 for a while but it proved to be a hair lean at part throttle in these cooler temps and just recently upped to a 38 at 2 turns out on the air screw. Admittedly, my intake is longer than the one you are using and that may affect jetting slightly.

The frame issues you are having are the same ones I was having. That is the reason I ended up running the rubber CQR 250 intake. Unlike the Nibbi one, it doesn't put the carb into the frame. All of the shorter angled intakes I tried were even worse.

[Baskt_Case]

...just recently upped to a 38 at 2 turns out on the air screw.

Would you kindly expound on the logic here? This is the first carb I have ever tuned in my life. So now I am applying the sum of six months of learned theory. I'm assuming the 38 was then a hair too rich for your liking so you used the air screw to effectively split the difference between 35 and 38?

[Megadan]

Would you kindly expound on the logic here? This is the first carb I have ever tuned in my life. So now I am applying the sum of six months of learned theory. I'm assuming the 38 was then a hair too rich for your liking so you used the air screw to effectively split the difference between 35 and 38?

Ok, so the slow jet, aka pilot jet, is primarily responsible for the majority of fueling from just barely off idle to about 1/8 throttle, and about half of the fueling from 1/8 to 1/4 and then it tapers off to a minimal amount after that.

The air screw for the idle mixture only affects the idle circuit, with the throttle closed. The pilot jet does affect how much fuel can flow through the idle circuit, so with the two different sizes, a different setting is required, but that's about where it stops. With the 35 I needed around 1 1/2 turns out while the 38 required about 2 turns out. The more turns out on the air screw, the more air is allowed into the idle circuit, which leans the mixture.

The reason I switched to the 38 had nothing to do with the idle mixture itself. Either jet had a setting that allowed for a proper idle mixture. The reason I swapped up to a 38 had to do with light throttle going lean.

When a pilot jet is a little lean, what you will run into when either maintaining a low speed in a higher gear, or just slightly applying throttle on a down hill, usually about 1/8th throttle or less, you will get some bucking, hesitation, and even afterfire from the exhaust as the mixture goes lean. I was getting those symptoms with the 35, so I went up a size. Now they are gone. I ran into the same issue with the VM26 Mikuni after installing the exhaust and a 25 pilot jet. I had to up to a 27.5. Idle was fine, but light throttle was lean.

The main thing to remember about these types of slide valve carbs is that the main and pilot jets have their own main purpose, but also affect another circuit or jet. The main jet is primarily there for fueling from beyond 3/4 throttle to full throttle, but the main jet size can also affect the amount of fuel that flows through the needle jet, and thus alter either the needle setting itself, or possibly even requiring a different needle jet in some circumstances. You most likely wont ever run into that here, but if you really delve into hardcore carb tuning, it all plays a role. Even the angle of the cutaway on the throttle slide affects the jetting in a certain portion of the throttle sweep, causing a weaker or stronger pull on the jets.

[Baskt_Case]

Thanks for the insight. This afternoon should hopefully provide some nice tuning weather. Just picked up some K&N filter oil for my pod and I've been doing some additional reading this morning. Its always nice to wake up and have fresh perspective after the previous days experiences have had time to simmer in the brain overnight. I often lay there and replay the cause and effect of dozens of events, slowly piecing together a larger picture until I feel that I understand things well enough.

I may try to get the longer rubber CQR intake, but for now things are ok. My filter neck is actually insulating the carb very well. I haven't decided the fate of my now unused airbox yet. Storage, battery, complete removal? Idk. Leaning towards tool storage and battery box.