Hawk 250 power/gearing downfall?

Weazler · 03-18-2019, 08:10 PM

So, I've done a fair amount of looking around, on various different sources. I know the 17/45 combo is the tested and true go to for these bikes. I've heard people claim they have had luck with other combinations as well. The lowest ratio I've seen verified was 17/40, but only with claims of top speed improvement, and no mention of the effect to the low end of the power band. I cant find anyone that can verify a particular gearing ratio of 17/34 (2.0 final drive). In theory, according to online calculators, with a feather light rider, this combination could reach 100mph+!!! But my fear of this ratio is that the little single cylinder would just fall on its face trying to spin the rear wheel. Would you lose all acceleration from this and spend days trying to get up to speed? Or is this little 250 with say, a carb and exhaust actually up to the task?

roundhouse · 03-19-2019, 07:10 AM

I do not think that the bike could do 100mph regardless of ratios. Just too much wind resistance and not enough HP. I also think it would KILL your starts in 1st. I have 17/43 and it is good. My speedo broke so I have no idea what I am doing but I can get on the freeway for a exit or two and not be run over.

Alpha Reign · 03-19-2019, 09:00 AM

With sockets you will have to choose if you want speed or torque. If you increase speed you will have a decrease in torque. You just got to find a good combo. I run a 17-40 for street riding, it does okay off road too. I do switch to a 15-40 combo when I am planning on doing harder off road sections, which works fine for me.

bogieboy · 03-19-2019, 12:54 PM

i am a big guy (6'2" 280#) and on my Ninja rim conversion supermoto i am running 13-38 in #50 chain instead of #428... thats a 2.92 ratio, and i very much like it... it does get wound out on the top end cruising at 60, but it also can cruise at 60 yet.... so

yeah. it gets off the line decent too....

**JerryHawk250** · 03-19-2019, 12:59 PM

Quote:

Originally Posted by Alpha Reign

With sockets you will have to choose if you want speed or torque. If you increase speed you will have a decrease in torque. You just got to find a good combo. I run a 17-40 for street riding, it does okay off road too. I do switch to a 15-40 combo when I am planning on doing harder off road sections, which works fine for me.

^ This is what I do too^ and the 16/40 works well for light off road and back road riding. You just have to gear it to what type of riding you planning on doing.

Ariel Red Hunter · 03-19-2019, 03:41 PM

Quote:

Originally Posted by Weazler

So, I've done a fair amount of looking around, on various different sources. I know the 17/45 combo is the tested and true go to for these bikes. I've heard people claim they have had luck with other combinations as well. The lowest ratio I've seen verified was 17/40, but only with claims of top speed improvement, and no mention of the effect to the low end of the power band. I cant find anyone that can verify a particular gearing ratio of 17/34 (2.0 final drive). In theory, according to online calculators, with a feather light rider, this combination could reach 100mph+!!! But my fear of this ratio is that the little single cylinder would just fall on its face trying to spin the rear wheel. Would you lose all acceleration from this and spend days trying to get up to speed? Or is this little 250 with say, a carb and exhaust actually up to the task?

100. No. 80 plus? Yes, with a full head porting (especially on the exhaust side), a very good exhaust system, and a carb that is jetted right on the money. Peak torque is at just below 5000 rpm. Peak power is at 7500 rpm. It will pull tall gears ok, but you will have to use the gears more. If you ride it off road, you will have to go to a smaller front sprocket...ARH

Weazler · 03-19-2019, 06:53 PM

I think maybe this post might have been taken the wrong way. I fully understand how the gearing works, you get top speed or low end acceleration.
I was more asking about how deeply the gearing effects this engine in particular as far as the bottom end goes. The well known 17/45 combo seems to stretch the low end gears quite a bit and adds a few mph to the top speed without sacrificing the accel much, if any, as far as I've gathered.
Please note that the 100mph figure I stated was according to an online calculator found here ---> http://woodsware.aciwebs.com/gears/
And it was in fact 100% theoretical.
I'm mostly asking from people who have made more drastic gearing changes as to how drastically it changes the low end acceleration.

Quote:

Originally Posted by Alpha Reign

With sockets you will have to choose if you want speed or torque. If you increase speed you will have a decrease in torque. You just got to find a good combo. I run a 17-40 for street riding, it does okay off road too. I do switch to a 15-40 combo when I am planning on doing harder off road sections, which works fine for me.

How is the acceleration on the low end with the 17/40 combo? Is it a drastic low end loss from the 15/40, or would you describe it as minimal?

Quote:

Originally Posted by Ariel Red Hunter

100. No. 80 plus? Yes, with a full head porting (especially on the exhaust side), a very good exhaust system, and a carb that is jetted right on the money. Peak torque is at just below 5000 rpm. Peak power is at 7500 rpm. It will pull tall gears ok, but you will have to use the gears more. If you ride it off road, you will have to go to a smaller front sprocket...ARH

Running out the gears isn't a fear of mine, but being able to safely highway commute for about 20 miles is. I don't want to abuse the engine at high rpms, but I don't want the bikes lack of speed/power to leave me in a bad spot. I don't want to be left in a sticky situation because the bike cant move out of its own way. If that makes any sense. drivers here in Ohio are not very good at paying attention to their surroundings, and acceleration can be a more reasonable option than braking in many cases. By no means do I need or want to go 100mph on a bike such as this, even 80 is a stretch. But I want to be able to accelerate past 65mph without it taking forever or killing the engine. I can like with shorter gearing and stay off the highways, but I'm just trying to get a bit more insight from those who have done it. What I've been able to find previously, is mostly vague and only mentions the positive effect of the top speed, not the negative on lower gears.

Thanks for the replies!

ChipToothy · 03-19-2019, 11:11 PM

I went to 17/40 from 17/46 last month on the Storm bike. I lost enough torque to notice a loss of power down low and am also now unable to reach the stock top speed in 5th. The motor just doesn’t have enough grunt to rev up the rpms enough to break 62 mph. I was bouncing off the rev limiter at 64 mph previously. Running a smaller rear cog definitely made a big difference in the rpms like everyone says, I like that part but the bike isn’t near as fun to ride now. In my particular case I believe 17/42 is my next experiment. My end goal is to have a bitch’n little dirt bike but hold 65 up and down the freeway all day w/o ruining the bike.

I’m also running wider, waaay heavier and taller tires than in 2018 so that may play a part in the slowing effect. One TKC 80 weighs more as both stock tires combined. I mistakenly added 30+ pounds of rotational weight to the ride but didn’t know that ahead of time and couldn’t find any other 50/50 tires in my size without spending $300+ :( . The 120 TKC once mounted on the rear wheel was so heavy I could only carry it against my leg about 10 feet at a time before needing to switch arms lol. They on the plus side are very durable and stiff so if I have a flat I doubt it will matter ha!

Weazler · 03-26-2019, 05:29 AM

Quote:

Originally Posted by ChipToothy

I went to 17/40 from 17/46 last month on the Storm bike. I lost enough torque to notice a loss of power down low and am also now unable to reach the stock top speed in 5th. The motor just doesn’t have enough grunt to rev up the rpms enough to break 62 mph. I was bouncing off the rev limiter at 64 mph previously. Running a smaller rear cog definitely made a big difference in the rpms like everyone says, I like that part but the bike isn’t near as fun to ride now. In my particular case I believe 17/42 is my next experiment. My end goal is to have a bitch’n little dirt bike but hold 65 up and down the freeway all day w/o ruining the bike.

Freeway riding without negative effects is what I would like to achieve as well once I finally make the bike purchase. Hearing your experience, and looking at some gearing specs, I would be more likely to try 16/40 than 17/42. Seems to me like it would be slightly less of a gearing reduction, and may yield better results. But I have no experience with these bikes yet, my opinion is purely speculation.

Megadan · 03-26-2019, 08:59 AM

Rider weight will play a role in how the low end feel changes. Me being a big guy, I have found the best balance point between top speed and decent torque on the Hawk to be in the 2.50 ratio range with a stock head and stock style/size carburetor with a dialed in carb tune, intake, and exhaust mods. This placed the RPM's right around the torque peak at 60mph, which made it possible to maintain speed without having the throttle fully cranked on flat ground and topping out at 70mph consistently, reaching past 70 a couple of times with my big butt in the seat.

With the ported head I actually stepped back up to a 2.70 ratio to take advantage of the better power at the upper end of the rev range now, and thus far the "happy" cruise speeds are about the same and my consistent top speed has actually improved to about 75mph - which is at 8000rpm now. I am curious to swap out the rear sprocket to try a 2.50 ratio again on this bike, but I am quite happy with it as is since I have little need or desire to spend any time on the highway faster than about 65mph anyway.

As pointed out, it is possible to go too tall and end up not only losing acceleration but also top speed by putting the motor outside of the ideal area of the torque curve and peak HP range in the taller gears and actually go slower.

Lastly, don't be too concerned about turning higher RPM's on such a small motor. The piston speeds and acceleration on engines this small mean that they can generally churn along at higher RPM with a lot less stress on the engine. The most important thing is that your carb tuning is spot on and especially not on the lean side of things. high RPM high load and lean = engine damaging combustion temps.

The easiest way to get a feel for what kind of gearing will work best for you is to do what was already suggested. Toss on a 39 or 40 tooth rear sprocket, then swap out front sprockets. a 15 front and 40 rear is essentially the same as a 17f/45r, a 16 front with the 40 rear is more or less equivalent to my favorite combo for road use, the 17f/43r, and then obviously you have a 17 front with the 40 rear for what some of these skinny guys love for highway use.

OneLeggedRider · 03-26-2019, 11:41 AM

I'm running a 12/33 in the 520 chain size, which is real close to the 16/45 in the smaller/puny lol 428 chain size. Which I think will be ideal for me. I'm a big fella and the bike will hardly ever see a highway let alone a freeway.

ChipToothy · 03-27-2019, 10:53 AM

I went back to the 17/46 after riding yesterday. 17/40 is too much of a loss after 4th gear or trying to pull a hill over 35mph with 55mph traffic up your bum so I’m going to order the 42 or 43 for certain on Friday. Even riding the dead flat highway of Spiro, OK 62mph at under 7,000 RPM is all the 40T can churn.

ChipToothy · 03-27-2019, 10:58 AM

Quote:

Originally Posted by OneLeggedRider

I'm running a 12/33 in the 520 chain size, which is real close to the 16/45 in the smaller/puny lol 428 chain size. Which I think will be ideal for me. I'm a big fella and the bike will hardly ever see a highway let alone a freeway.

I loathe the freeway/interstate/highway even in a car! In Arkansas the 239cc is great on 99% of the roads so it’s not an issue. As soon as I hit Oklahoma I swear every road has a 65 mph posted limit

55 was just fine in the 90’s.

**JerryHawk250** · 03-27-2019, 01:23 PM

Quote:

Originally Posted by ChipToothy

I went back to the 17/46 after riding yesterday. 17/40 is too much of a loss after 4th gear or trying to pull a hill over 35mph with 55mph traffic up your bum so I’m going to order the 42 or 43 for certain on Friday. Even riding the dead flat highway of Spiro, OK 62mph at under 7,000 RPM is all the 40T can churn.

All you needed to do is swap the front sprocket to a 15 tooth. This would of put you at about the same gear ratio as the 17/45. A 16 tooth with the 40 would of put about the same as the 17/43. Much easier to swap the front sprocket.

Megadan · 03-27-2019, 03:33 PM

Quote:

Originally Posted by OneLeggedRider

I'm running a 12/33 in the 520 chain size, which is real close to the 16/45 in the smaller/puny lol 428 chain size. Which I think will be ideal for me. I'm a big fella and the bike will hardly ever see a highway let alone a freeway.

If you ever need highway gearing just swap the front to a 13 and it will be in the 2.50 range just like a 17/43 setup. I went with a 13 front 35 rear - aka 2.70 or 17/45

03-18-2019, 08:10 PM	#1
Weazler Join Date: Mar 2019 Location: Columbus, OH Posts: 12	Hawk 250 power/gearing downfall? So, I've done a fair amount of looking around, on various different sources. I know the 17/45 combo is the tested and true go to for these bikes. I've heard people claim they have had luck with other combinations as well. The lowest ratio I've seen verified was 17/40, but only with claims of top speed improvement, and no mention of the effect to the low end of the power band. I cant find anyone that can verify a particular gearing ratio of 17/34 (2.0 final drive). In theory, according to online calculators, with a feather light rider, this combination could reach 100mph+!!! But my fear of this ratio is that the little single cylinder would just fall on its face trying to spin the rear wheel. Would you lose all acceleration from this and spend days trying to get up to speed? Or is this little 250 with say, a carb and exhaust actually up to the task?
	0

03-19-2019, 09:00 AM	#3
Alpha Reign Join Date: Aug 2018 Location: Ohio Posts: 131	With sockets you will have to choose if you want speed or torque. If you increase speed you will have a decrease in torque. You just got to find a good combo. I run a 17-40 for street riding, it does okay off road too. I do switch to a 15-40 combo when I am planning on doing harder off road sections, which works fine for me. __________________ Hawk 250 Lithium Battery, Mikuni Carb 110 main jet, Bark Busters with Mirrors, Extended Mixture Screw, 428 O-ring Chain, 17-15/40 sprockets, Digital Cluster, Cycra YZ250F Skid Plate, Oil Cooler
	1

03-19-2019, 11:11 PM	#8
ChipToothy Join Date: Apr 2018 Posts: 819	I went to 17/40 from 17/46 last month on the Storm bike. I lost enough torque to notice a loss of power down low and am also now unable to reach the stock top speed in 5th. The motor just doesn’t have enough grunt to rev up the rpms enough to break 62 mph. I was bouncing off the rev limiter at 64 mph previously. Running a smaller rear cog definitely made a big difference in the rpms like everyone says, I like that part but the bike isn’t near as fun to ride now. In my particular case I believe 17/42 is my next experiment. My end goal is to have a bitch’n little dirt bike but hold 65 up and down the freeway all day w/o ruining the bike. I’m also running wider, waaay heavier and taller tires than in 2018 so that may play a part in the slowing effect. One TKC 80 weighs more as both stock tires combined. I mistakenly added 30+ pounds of rotational weight to the ride but didn’t know that ahead of time and couldn’t find any other 50/50 tires in my size without spending $300+ :( . The 120 TKC once mounted on the rear wheel was so heavy I could only carry it against my leg about 10 feet at a time before needing to switch arms lol. They on the plus side are very durable and stiff so if I have a flat I doubt it will matter ha! __________________ Bashan Storm: Ebay steel exhaust wrapped, folding shift lever, seat mod, vm26 carb, air pod, dual led scrambler headlamps, windshield mod, led brake/tail light, secondary led brake light (swingarm), Ebay 295mm rear shock, back up CDI (racing unknown), oil cooler, digital gauge cluster,
	1

03-26-2019, 08:59 AM	#10
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 8,016	Rider weight will play a role in how the low end feel changes. Me being a big guy, I have found the best balance point between top speed and decent torque on the Hawk to be in the 2.50 ratio range with a stock head and stock style/size carburetor with a dialed in carb tune, intake, and exhaust mods. This placed the RPM's right around the torque peak at 60mph, which made it possible to maintain speed without having the throttle fully cranked on flat ground and topping out at 70mph consistently, reaching past 70 a couple of times with my big butt in the seat. With the ported head I actually stepped back up to a 2.70 ratio to take advantage of the better power at the upper end of the rev range now, and thus far the "happy" cruise speeds are about the same and my consistent top speed has actually improved to about 75mph - which is at 8000rpm now. I am curious to swap out the rear sprocket to try a 2.50 ratio again on this bike, but I am quite happy with it as is since I have little need or desire to spend any time on the highway faster than about 65mph anyway. As pointed out, it is possible to go too tall and end up not only losing acceleration but also top speed by putting the motor outside of the ideal area of the torque curve and peak HP range in the taller gears and actually go slower. Lastly, don't be too concerned about turning higher RPM's on such a small motor. The piston speeds and acceleration on engines this small mean that they can generally churn along at higher RPM with a lot less stress on the engine. The most important thing is that your carb tuning is spot on and especially not on the lean side of things. high RPM high load and lean = engine damaging combustion temps. The easiest way to get a feel for what kind of gearing will work best for you is to do what was already suggested. Toss on a 39 or 40 tooth rear sprocket, then swap out front sprockets. a 15 front and 40 rear is essentially the same as a 17f/45r, a 16 front with the 40 rear is more or less equivalent to my favorite combo for road use, the 17f/43r, and then obviously you have a 17 front with the 40 rear for what some of these skinny guys love for highway use. __________________ 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
	2

03-27-2019, 10:53 AM	#12
ChipToothy Join Date: Apr 2018 Posts: 819	I went back to the 17/46 after riding yesterday. 17/40 is too much of a loss after 4th gear or trying to pull a hill over 35mph with 55mph traffic up your bum so I’m going to order the 42 or 43 for certain on Friday. Even riding the dead flat highway of Spiro, OK 62mph at under 7,000 RPM is all the 40T can churn. __________________ Bashan Storm: Ebay steel exhaust wrapped, folding shift lever, seat mod, vm26 carb, air pod, dual led scrambler headlamps, windshield mod, led brake/tail light, secondary led brake light (swingarm), Ebay 295mm rear shock, back up CDI (racing unknown), oil cooler, digital gauge cluster,
	0

03-19-2019, 07:10 AM	#2
roundhouse Join Date: Sep 2017 Location: N Texas Posts: 706	I do not think that the bike could do 100mph regardless of ratios. Just too much wind resistance and not enough HP. I also think it would KILL your starts in 1st. I have 17/43 and it is good. My speedo broke so I have no idea what I am doing but I can get on the freeway for a exit or two and not be run over.
	0

03-19-2019, 12:54 PM	#4
bogieboy Join Date: May 2013 Location: finger lakes NY Posts: 2,045	i am a big guy (6'2" 280#) and on my Ninja rim conversion supermoto i am running 13-38 in #50 chain instead of #428... thats a 2.92 ratio, and i very much like it... it does get wound out on the top end cruising at 60, but it also can cruise at 60 yet.... so yeah. it gets off the line decent too....
	0

03-26-2019, 11:41 AM	#11
OneLeggedRider Join Date: Nov 2018 Location: Stockport, Oh. Posts: 1,442	I'm running a 12/33 in the 520 chain size, which is real close to the 16/45 in the smaller/puny lol 428 chain size. Which I think will be ideal for me. I'm a big fella and the bike will hardly ever see a highway let alone a freeway.
	1