Honda CBR 250 Forum banner

1 - 20 of 78 Posts

·
Registered
Joined
·
17 Posts
Discussion Starter #1
I am thinking of doing a +2 rear sprocket

right now at 75MPH in 6th I am at about 8,000RPM. I want a little more go around 70-75 MPH.
For those of you changing gearing
What are you seeing RPM/feeling wise on it?
 

·
Registered
Joined
·
455 Posts
peak horse power on the bike is at 8500. Dont think it will give you what your looking for.
 

·
Registered
Joined
·
17 Posts
Discussion Starter #3
peak horse power on the bike is at 8500. Dont think it will give you what your looking for.

I Guess I will have to stay off the freeway then.
Holding it wide open to stay at 75 to stay with traffic sounds retarded to me.

I miss my big bikes lol
 

·
Registered
Joined
·
17 Posts
Discussion Starter #5
What in the world are you hauling to have to be WOT for 75MPH?

my 195 lb ass.

traffic flys at 75-80 MPH. If i stay under it's almost death.. Well on the freeways here. So I try to stay at 75 in the Carpool lane but most the time I find it wide open to keep it at 75
 

·
Registered
Joined
·
455 Posts
Im 170. WOT for me is 94.
You would go down in back up in front for more top speed lower rPms
 

·
Registered
Joined
·
17 Posts
Discussion Starter #7
Im 170. WOT for me is 94.
You would go down in back up in front for more top speed lower rPms

the fastest I have had this is 81.. that's it.

why would I want to go Up(front) Down (rear) if the bike can't even hit full redline in 6th stock?

my GSXR600 woudl not hit redline in 6th on a track in AZ. I did -1/+2 and was able to hit redline in 6th without a problem and the bike pulled the whole time..

so what would +(x)/-(x) gearing help if the bike doesn't have the power/gear reduction to pull it's own weight?

I just noticed. Your sig. shows you having a few things done to your 250. Mine is 100% bone stock.
My wifes has a two bro's slip-on and I can tell her's is faster. it also will do 85 with me on it without a problem
 

·
Registered
Joined
·
57 Posts
.....fastest ive gotta mine to was 89-90..... downhill with barely any wind, best tuck i could manage.

but im almost full throttle at 75......with wind.

6'1" 240lb rider.....bike is sluggish at anything more then 70. traffic in my area moves fast....75-80mph.
 

·
Registered
Joined
·
879 Posts
I Guess I will have to stay off the freeway then.
Holding it wide open to stay at 75 to stay with traffic sounds retarded to me.

I miss my big bikes lol
I AGREE this bike is a dog on the freeway ecpecially with the wind in your face.
 

·
Registered
Joined
·
1,313 Posts
I changed the sprockets on my Ninja250R and it made for a much taller and more usable 1st gear, but I don't think the CBR needs it. The stock gearing is the best I've seen on any 250. I'm taking a "if it works, don't mess with it" approach to my CBR compared to going crazy with mods like I did with the Ninja. The CBR is as close to perfect as I've seen in a 250cc street bike in many respects. It doesn't cry out for mods as urgently as my Ninja did.
 

·
Registered
Joined
·
4,996 Posts
Mine will pull redline in top 171kph but takes a big effort to get there.
It indicates 162kph on a flat road in good warm still conditons.
On the track I'm getting flatout in 5th but the straight is short.

Going to try a non Oring chain to release a couple lost hp.
That combined with a 39T or 40Twill be about the best setup.
 

·
Registered
Joined
·
17 Posts
Discussion Starter #12
Mine will pull redline in top 171kph but takes a big effort to get there.
It indicates 162kph on a flat road in good warm still conditons.
On the track I'm getting flatout in 5th but the straight is short.

Going to try a non Oring chain to release a couple lost hp.
That combined with a 39T or 40Twill be about the best setup.

Yeah..

I am going the pipe 1st then +2 in the rear and see how she does.
Got 3 total bikes to do this to depending on how it is effected
 

·
Registered
Joined
·
1,040 Posts
Right out of the gate, I'd like to say gearing lower didn't do anything to the fuel economy. No loss. No gain. Here's my review of the setups I've tried...

14/38 (stock): Peak HP @ 85mph. 68mpg. Mild ride. Very little 6th gear torque.
13/38 (-1F): Peak HP @ 80mph. 68mpg. General/practical. Adequate 6th gear torque.
13/40 (-1/+2): Peak HP @ 75mph, 68mpg. Assertive ride. Useful 6th gear torque.

My personal preference is -1/+2.
 

·
Registered
Joined
·
451 Posts
Right out of the gate, I'd like to say gearing lower didn't do anything to the fuel economy. No loss. No gain. Here's my review of the setups I've tried...

14/38 (stock): Peak HP @ 85mph. 68mpg. Mild ride. Very little 6th gear torque.
13/38 (-1F): Peak HP @ 80mph. 68mpg. General/practical. Adequate 6th gear torque.
13/40 (-1/+2): Peak HP @ 75mph, 68mpg. Assertive ride. Useful 6th gear torque.

My personal preference is -1/+2.
Rusty, Do you have top speeds for these gearing setups?
 

·
Registered
Joined
·
1,040 Posts
You can plug the values into gearingcommander.com to get the values you want. Just change the "peak power" RPM to 10,500 (red line) since that's the RPM it uses in most of the calculations. For reference, 6th gear red line for -1/+2 is 93mph if I remember correctly.

Keep in mind how much wind drag affects small engine bikes. Gearing taller could slow you down if you can't tuck tight enough. I have a higher top speed with -1/+2 than I did stock, all though at a much higher RPM. I couldn't get stock past 80mph. Evidently I'm a natural wind sock. Some of the guys on this forum are awesome and hit almost 100mph. Your results may vary. I just geared mine to maximize rear-wheel torque for the speeds I use.

Best of luck. Re-gearing makes a big difference.
 

·
Registered
Joined
·
451 Posts
You can plug the values into gearingcommander.com to get the values you want. Just change the "peak power" RPM to 10,500 (red line) since that's the RPM it uses in most of the calculations. For reference, 6th gear red line for -1/+2 is 93mph if I remember correctly.

Keep in mind how much wind drag affects small engine bikes. Gearing taller could slow you down if you can't tuck tight enough. I have a higher top speed with -1/+2 than I did stock, all though at a much higher RPM. I couldn't get stock past 80mph. Evidently I'm a natural wind sock. Some of the guys on this forum are awesome and hit almost 100mph. Your results may vary. I just geared mine to maximize rear-wheel torque for the speeds I use.

Best of luck. Re-gearing makes a big difference.
With the stock gearing I top out in the mid 80s rolling on 6th. If redlining 5 and shifting to 6th I can get into the 90s, or just going down hill. Close to 100, she's a little unstable.

Since you can hit a higher top speed with -1/+2, but with a much higher RPM are you worried about long term effects to the engine?

I would have thought that gearing that tops out the horsepower at 75 instead of 85 would decrease the top speed. Or is torque needed more at top speed because of wind resistance?
 

·
Registered
Joined
·
124 Posts
Ha ha

my 195 lb ass.

traffic flys at 75-80 MPH. If i stay under it's almost death.. Well on the freeways here. So I try to stay at 75 in the Carpool lane but most the time I find it wide open to keep it at 75
Brent701 - I live in Arizona also and have put more then 4,000 FREEWAY miles on my CBR250R in the last 4 months. I weight 195 and ride on I-10 the 101 and the 202 4 times a week and have never needed to go above 75 mph. Any time I have needed more speed to pass in traffic I usually down shift into 5th. I have had my CBR250R in the 90 mph range on flat road with a bit of distance to get there. If you find your self with people trying to pass you let them by. You do not have to be the fastest person on the freeway. All you are doing is racing to a possible early grave. Use your head and not your ego.

Ask yourself if you bought this bike because of the fuel efficiency or because you wanted to go fast? A 250 is nothing compared to a 600R.
 

·
Registered
Joined
·
1,040 Posts
With the stock gearing I top out in the mid 80s rolling on 6th. If redlining 5 and shifting to 6th I can get into the 90s, or just going down hill. Close to 100, she's a little unstable.

Since you can hit a higher top speed with -1/+2, but with a much higher RPM are you worried about long term effects to the engine?

I would have thought that gearing that tops out the horsepower at 75 instead of 85 would decrease the top speed. Or is torque needed more at top speed because of wind resistance?
Part 1: If you're getting that high of a top speed, you're one of the ones who does a good job getting out of the wind's way, haha. My 6th gear roll on topped at 80mph stock. That was because of me though.

Part 2: I'm not worried about an extra 100 RPM's, no. My highest cruising speed here is 75mph at somewhere between 8.5k-8.6k.

Part 3: I wasn't making it up to peak horsepower in top gear stock via roll on. I needed the extra torque to overcome wind resistance under normal driving conditions. I wanted to ride sitting up in a regular/comfortable posture and just lay into top gear and pass cars in interstate traffic. This is a bit of a request for a 250, I know, but the new gearing does it easily and still turns 68mpg so I'm not complaining.
 
1 - 20 of 78 Posts
Top