My Top Speed Is...

[Mudflap]

07 Lifan 200 GY5 (CG200) stock gearing 17/46, derestricted exhaust, jetting, pod filter, ~65mph.

68 Trail 90 with Lifan 140 17/45 gearing ~55mph.

[CaesarVis]

OOOOK, I'm truly baffled now! I replaced my exhaust with the typical, cheap CRF230 eBay/Amazon exhaust this weekend (which is disgustingly loud, btw...any way to quiet it down???). I bumped my main jet to 115 and added another shim to the needle, for a total of 2. Pod filter intake. My top speed is still pretty pegged at 65mph. Do I need to loose 80lbs before I can get it to go 70? What's the deal???

[Goob]

My top speed is 66-67. This is not GPS, but based on 70mph indicated minus 3 to 4mph. This is what the speedo is off when I pass one of those radar signs for speed...it is the same in a 35 zone and 45 zone...so I think this is close.

Bike is a 2018 CSC TT250. Aftermarket exhaust, Mikuni VM26-606 carb, Uni filter, 47 rear sprocket, Conti GO! street tires, large Nelson-Rigg Panniers, RX3 windscreen. I am 173 lbs, 6 ft.

Changing out to a VM28-49 carb soon, so will see if this makes any top end difference. Don't really care, just want some more punch. https://www.denniskirk.com/165143.sk...ikuni+VM28-49&

[CaesarVis]

Originally Posted by Goob

My top speed is 66-67. This is not GPS, but based on 70mph indicated minus 3 to 4mph. This is what the speedo is off when I pass one of those radar signs for speed...it is the same in a 35 zone and 45 zone...so I think this is close.

Bike is a 2018 CSC TT250. Aftermarket exhaust, Mikuni VM26-606 carb, Uni filter, 47 rear sprocket, Conti GO! street tires, large Nelson-Rigg Panniers, RX3 windscreen. I am 173 lbs, 6 ft.

Changing out to a VM28-49 carb soon, so will see if this makes any top end difference. Don't really care, just want some more punch. https://www.denniskirk.com/165143.sk...ikuni+VM28-49&

How do you adapt that to the intake manifold with the 2 holes that comes on all of these bikes? Is there an adapter or something?

[culcune]

Originally Posted by CaesarVis

OOOOK, I'm truly baffled now! I replaced my exhaust with the typical, cheap CRF230 eBay/Amazon exhaust this weekend (which is disgustingly loud, btw...any way to quiet it down???). I bumped my main jet to 115 and added another shim to the needle, for a total of 2. Pod filter intake. My top speed is still pretty pegged at 65mph. Do I need to loose 80lbs before I can get it to go 70? What's the deal???

Weight (yours) and power will be key. Also, do you lay down forward for aerodynamics? You could try a new head or porting your stock one. The thing with Chinese dual-sports is most people do what you did with yours, exhaust, carb, and gearing, but you don't necessarily get much more top speed out of them, but rather lower revs, making your ride a bunch more comfortable, but not much faster, at top speed. Megadan has advice on the matter based on his Hawk, and he uses a Nibbi carb and has done head work on his Hawk.

[Megadan]

Originally Posted by CaesarVis

OOOOK, I'm truly baffled now! I replaced my exhaust with the typical, cheap CRF230 eBay/Amazon exhaust this weekend (which is disgustingly loud, btw...any way to quiet it down???). I bumped my main jet to 115 and added another shim to the needle, for a total of 2. Pod filter intake. My top speed is still pretty pegged at 65mph. Do I need to loose 80lbs before I can get it to go 70? What's the deal???

Your overall gearing (sprockets and tire diameter), the mods, and the engine in question... 65-68mph is about right.

Some things to consider.

1. How/where the CG250 makes power. Unlike the OHC "CB250" engines like the ones found in the Apollo DB36, or the Venom X22R, the CG OHV engine, especially the 230cc variant, is a low reving motor that makes good strong low to mid range torque and mid range hp with the top end HP tapering off fairly quickly past the peak at 7000-7500rpm. That means that even though the Rev limiter for the CG250 is 8500rpm, it doesn't really have the power to pull itself there, especially in a higher gear with taller gearing. Top speed is all about that high rpm energy, something the CG250 engine just doesn't quite have.

2. The setup of the bike in question AND the rider. Because the CG is not a high RPM power making engine, the compromise that is often made is to gear the bike taller with bigger front and smaller rear sprockets. This works well for the CG since it is such a torquey engine. The downside is, that there is a limit to how far you can gear these machines up before it negatively affects that power as delivered to the rear wheel.

Then there is the rider to consider. My top speed seems relatively low for my mods because it has me on top of the bike, a man the size of an NFL lineman. Compare my work to JerryHawk250's bike, the difference in gearing, but most importantly, the difference in the two riders. I have an easy 100lbs of weight on Jerry, if not a bit more AND I am a good half a foot taller than he is. I have to keep my bike geared shorter (bigger rear sprocket) than he does, which if you do the comparative math I would have +5 teeth out back vs. his setup . If I try to gear my bike like his, I actually lose top speed simply because the bike can't push me through the air. He is actually able to more consistently hit higher top speeds because of it.

Just to bake your noodle even more, we can compare my current bike to my last Hawk.

All things being equal, my last hawk was only maybe 3mph-ish slower than my current one in terms of consisten top speed. And that bike only had a Mikuni clone carb, pod filter, and ebay exhaust. It could generally hit 65-68mph vs my current bike consistently hitting 70-72. Gearing between them is nearly identical.

So why did head porting, a cam, and a bigger carb only net a couple of mph? Simple, the motor is still hitting peak power around 7000-7500rpm. The cam helped stretch the power a bit past that point so it doesn't fall on its face quite as fast and I can stretch it to 8000rpm in 5th, but it still lacks that top end power that is really needed to push higher speeds more effectively.

What's the difference between the two bikes then? Well, top speed doesn't accurately measure the real difference. My current bike would leave my old bike in the dust getting up to those speeds. Acceleration is effortless compared to my last bike. My old bike would struggle to climb certain hills that my current bike just tractors me up without skipping a beat. Basically, I make more power within the same power curve.

Plus, there is also basic physics at work too. The Kinetic energy needed is the square of the factor of increase in velocity. Or as often heard in simple terms, it takes 4 times the power to go twice as fast. So, in the grand scheme of things, I have maybe added 4-5hp to my Hawk with all of the work I have done, which is a respectable 25% increase and nothing to sneeze at.

If we actually do a little analysis of a stock Hawk, of which the fastest I have ever gotten one to go with a properly jetted carb and different sprockets (same ratio as current bike) was about 63mph. Fair assumption is that a Hawk with said properly jetted carburetor makes right around 14.5-15hp. That means that if I wanted my Hawk to top out at 93mph it would need 30hp (this is all oversimplified obviously, but it illustrates the point). Since I have added maybe a third of that amount of power, it stands to reason that my top speed on my current bike would be *drum roll* about 10mph faster (7.75mph if you do the proper math), which it more or less is.

I say this with the utmost respect, so don't take this the wrong way, but if your goal was to have one of these bikes carry you along at 70+mph on the highway for any length of time, you are barking up the wrong tree. Dual sports are very non-aerodynamic and their large diameter spoke wheels with heavy tubes and off road tires have a high moment of inertia that saps kinetic energy. Combine those facts with the relatively low power output of these little engines, and they just can't achieve what you are after. You can make one go 60-65mph all day, but beyond 70 is asking just a little too much. If you need more evidence of this, look at the CRF250L and its top speed of 80mph. That bike makes 10 more hp than our bikes do from a proper OHC 249cc liquid cooled motor.

[lilgman]

Thanks, Megadan, for that explanation!

[Wild Dog]

Originally Posted by Megadan

You can make one go 60-65mph all day, but beyond 70 is asking just a little too much. If you need more evidence of this, look at the CRF250L and its top speed of 80mph. That bike makes 10 more hp than our bikes do from a proper OHC 249cc liquid cooled motor.

Another example:

Honda XR 650cc estimated top speed 110mph

Yamaha MT03 321cc estimated top speed 110 mph

Dual Sports are just not meant to be fast motorcycles

[CaesarVis]

Wow, that is some great information. Thanks for being so thorough. I definitely don't plan on trying to drive for long periods at even 60mph, I was just hoping it would be able to hit 70mph if needed. I will say that since the exhaust I did notice it is definitely more lively. I was just shocked about the top speed not changing.

Also, I didn't know the Apollo DB36 had a different, arguably better, motor. I would have probably gotten that bike instead of the Bashan Storm had I known that!

[CaesarVis]

Also, where does one get this CG250 performance cam I have seen mentioned a few times? I cannot find any information or where to purchase it.

[culcune]

Originally Posted by CaesarVis

I didn't know the Apollo DB36 had a different, arguably better, motor. I would have probably gotten that bike instead of the Bashan Storm had I known that!

I wouldn't consider the Storm inferior to the Apollo Deluxe by any means. The CGs and the CBs are two different engines is all with each having their pluses and minuses.

[lilgman]

Originally Posted by CaesarVis

Also, where does one get this CG250 performance cam I have seen mentioned a few times? I cannot find any information or where to purchase it.

I think both Megadan and JerryHawk250 have done this. Maybe others. Megadan's thread is here:

http://www.chinariders.net/showthrea...=23546&page=18

I'm not sure what page the information is on. The whole thread is worth a read, though!

[JerryHawk250]

Originally Posted by lilgman

I think both Megadan and JerryHawk250 have done this. Maybe others. Megadan's thread is here:

http://www.chinariders.net/showthrea...=23546&page=18

I'm not sure what page the information is on. The whole thread is worth a read, though!

I haven't done the cam on my Hawk yet which is a CG engine But have install the Honda CRF230F cam and 11:1 Piston on my X22R which is a CB engine.

[Goob]

Originally Posted by CaesarVis

How do you adapt that to the intake manifold with the 2 holes that comes on all of these bikes? Is there an adapter or something?

The PO had it on mine when I got it, but I am pretty sure the following link is the part. There are straight ones available from Mikuni (thru Jetsrus.com), but they won't work because we need the angled ones to get the carb to fit. They range between $6 and $12 or so.

https://www.ebay.com/itm/30mm-Motorc...sAAOSwFfZetSqW

[alex_in_az]

Just got back from a speed run, got it up to 76mph per GPS at about 8500rpm. This is with the new cam and 4 degree offset key. It was starting to get kind of loose at the front end and I don't think I want to go much faster than this on it. It might be time to up the gearing so I can cruise in the 60-65mph range.
The new cam and key really wake it up in the mid range, it was pulling a lot harder from about 4500 all the way to 9000 in the lower gears.