[hudsoncustom]

So I have a 66 BSA Hornet....

I love the bike and ride it all the time around town. It is quick and has good throttle response. It likes to run all day long at 55-60, but I am looking to make it more highway worthy.

I am running stock gearing and an 18" wheel. I suppose i could go to a larger front sprocket, but would 1 or 2 teeth really make a difference?

What are you guys doing to be able to run 70-75 on your Brit bikes???

 

[VA Rebel]

So I have a 66 BSA Hornet....

I am running stock gearing and an 18" wheel. I suppose i could go to a larger front sprocket, but would 1 or 2 teeth really make a difference?

Nice bike.

Yes, a jump up a couple of teeth on the CS sprocket will lower the RPM's at highway speeds. Maybe try a 20 or 21 tooth CS sprocket. Might try the larger one first, as you will need a new chain and can shorten it if you find the larger sprocket is too tall.

 

[oktr6r]

So I have a 66 BSA Hornet....

I love the bike and ride it all the time around town. It is quick and has good throttle response. It likes to run all day long at 55-60, but I am looking to make it more highway worthy.

I am running stock gearing and an 18" wheel. I suppose i could go to a larger front sprocket, but would 1 or 2 teeth really make a difference?

What are you guys doing to be able to run 70-75 on your Brit bikes???

I ran a 20 on the Triumph and it'd cruise 70-80 all day. I'm running a 17 now, massive low end but sure sucks on the highway.

If the BSA is anything like Triumph, you may need to clearance the trap door to go to a 21. Might try a 20, seems to be a popular choice.

 

[PONY]

There is one note of caution when gearing up. The taller the gear the more power it takes to pull it. On a stock bike you probably won't want to go more that 4 teeth at the trans or 2 teeth at the engine. Gearing higher will make your bike a dog off the line and you will just run out of power long before you run out of gears.

 

[hudsoncustom]

Thanks fellas. I'll see what I can do. It must be geared pretty low, cause it sure is a rocket off the line. Plus being an off-road bike, I bet it came with lower gearing than standard models (lightnings, etc.)...

 

[lytedrive]

Thanks fellas. I'll see what I can do. It must be geared pretty low, cause it sure is a rocket off the line. Plus being an off-road bike, I bet it came with lower gearing than standard models (lightnings, etc.)...

you can go 21 no worries,

The gear ratio in most unit boxes are too low any way,

running a 16 INCH REAR TYRE REALLY causes over revving problems,

I make a primary belt drive to gear up the primary ratio by ,
10%

js

 

[wvenfield]

2 teeth most certainly will make a noticable difference. If you have the grunt you will likely enjoy riding the bike alot more.

BTW, I have the near twin to your helmet.

 

[oktr6r]

you can go 21 no worries,

The gear ratio in most unit boxes are too low any way,

running a 16 INCH REAR TYRE REALLY causes over revving problems,

I make a primary belt drive to gear up the primary ratio by ,
10%

js

Typical useless info from you, and pushing parts, just like an email list you're on. Measure the O.D. of both the 16" rear tire and the stock 18" and see how little difference there is.

 

[Brian Douglas]

running a 16 INCH REAR TYRE REALLY causes over revving problems,
js

bullshit

back up that theory please......

 

[gettingreasy]

I was just thinkin about this the other day so I measured. The 16 was a 130/90 402 Dunlop(front) and the 18 was a 4.25/85 Dunlop TT100(front or rear). The 18 has maybe 10 miles on it and the 16 has probably 3-400 miles. The circumference of the 16 is 78.75" and the 18 is 82", the radius of the 16 was 12.5" and the 18 was 13.25". I don't know if I used the correct terminology, but you guys can figure it out.
-Jesse

 

[Dragon]

I was just thinkin about this the other day so I measured. The 16 was a 130/90 402 Dunlop(front) and the 18 was a 4.25/85 Dunlop TT100(front or rear). The 18 has maybe 10 miles on it and the 16 has probably 3-400 miles. The circumference of the 16 is 78.75" and the 18 is 82", the radius of the 16 was 12.5" and the 18 was 13.25". I don't know if I used the correct terminology, but you guys can figure it out.
-Jesse

if youre going to do something besides apples/oranges (modern Front dunlop) then someone needs to get a height measurement of a full-profile 5.00 x 16 rear like the Avon sm II or the other "classic" sized tires always run on the rear... you'll find there is WAY less than .75" radius (= 1.5" height) difference.

.

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[gettingreasy]

Those were the only 2 that weren't on bikes.
-Jesse

 

[Brian Douglas]

if youre going to do something besides apples/oranges (modern Front dunlop) then someone needs to get a height measurement of a full-profile 5.00 x 16 rear like the Avon sm II or the other "classic" sized tires always run on the rear... you'll find there is WAY less than .75" radius (= 1.5" height) difference.

.

exactly

http://www.avonmotorcycle.com/us/en/Product.asp?ProdType=Classic&SubCat=34

.5 " diff between a 5.00/16 and a 400/18

on a triumph, the difference beween a 24.8" dia tire and a 25.8" dia tire at 75mph is 150rpm (4300 vs 4450)

 

[oktr6r]

if youre going to do something besides apples/oranges (modern Front dunlop) then someone needs to get a height measurement of a full-profile 5.00 x 16 rear like the Avon sm II or the other "classic" sized tires always run on the rear... you'll find there is WAY less than .75" radius (= 1.5" height) difference.

.

I have an old Pirelli 5.00 x 16" mounted on a wheel I can measure, as well as the stock wheel/tire on the '65 TR6 I just picked up. I can also toss in a measurement for a fairly new Cheng Shin Marquis 130/90H16. post measurements in a few on all of 'em.

 

[oktr6r]

I have an old Pirelli 5.00 x 16" mounted on a wheel I can measure, as well as the stock wheel/tire on the '65 TR6 I just picked up. I can also toss in a measurement for a fairly new Cheng Shin Marquis 130/90H16. post measurements in a few on all of 'em.

Best I could measure with the Pirelli not on a bike and both of the others on bikes is that all were within 1/4" of each other. The 18" was just slightly over 25", both the Pirelli and Marquis were right at 25".

 

[Brian Douglas]

So I have a 66 BSA Hornet....

I love the bike and ride it all the time around town. It is quick and has good throttle response. It likes to run all day long at 55-60, but I am looking to make it more highway worthy.

I am running stock gearing and an 18" wheel. I suppose i could go to a larger front sprocket, but would 1 or 2 teeth really make a difference?

What are you guys doing to be able to run 70-75 on your Brit bikes???

back to your question

what gearing do you have now?
the Hornet was a hopped up lighting, right? i think it came stock with offroad scrambler/tt bike gearing

so its probably geared like 17/46 or something
count your teeth (sprocket/rear wheel)

let us know

going from 17 to 20 or 21 would make a HUGE difference

 

[oktr6r]

back to your question

what gearing do you have now?
the Hornet was a hopped up lighting, right? i think it came stock with offroad scrambler/tt bike gearing

so its probably geared like 17/46 or something
count your teeth (sprocket/rear wheel)

let us know

going from 17 to 20 or 21 would make a HUGE difference

If he's running a 17 on the street, I feel his pain. That's what I use with the sidecar on my Triumph. It's rapped out pretty good at highway speeds. I ran a 20 before building the sidecar, it'd cruise 70 all day like that.