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Old 06-09-2015, 03:28 PM   #1
vorhese
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Default sprocket advice for a pre-unit bonnie

This is my current setup
crank sprocket: 24
Clutch: 43
gearbox: 19
rear: 43

I would like more take off, it's a little sluggish. I can currently cruise at 75mph in 3rd gear. I'd like it to do 70-75ish comfortably in 4th. What should I change?
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Old 06-09-2015, 03:41 PM   #2
richbob
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Default Re: sprocket advice for a pre-unit bonnie

stock is 22 and 18 or 21 and 18 depending on model
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Old 06-09-2015, 04:01 PM   #3
vorhese
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Default Re: sprocket advice for a pre-unit bonnie

So you suggest changing engine and gearbox sprockets, not just the gearbox?
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Old 06-09-2015, 04:09 PM   #4
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Default Re: sprocket advice for a pre-unit bonnie

This is cool
http://www.nightrider.com/biketech/calc_gearratios.htm

With my 24/43/19/43 gearbox setup I'm at 4.05 ratio

Stock 22/43/18/43 is 4.67 ratio

Just changing the gearbox to an 18, 24/43/18/43 makes it 4.28 ratio, bout halfway between current and stock.

Just changing the engine sprocket to stock 22, 22/43/19/43 is a ratio of 4.42. That's pretty close to stock, but probably give a little more top end.

Might be a nice compromise?
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Last edited by vorhese; 06-09-2015 at 04:16 PM.
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Old 06-09-2015, 05:36 PM   #5
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Default Re: sprocket advice for a pre-unit bonnie

4.28:1 is still very tall.
Depending on tyre size, but with 25" tyre OD that would give 121 mph @ 7000 rpm.
The average 650 unit used 4.84:1 and made around 107 mph @ 7000 rpm.
Tall gearing increases the chance of detonation and piston damage, and reduces charge rate at night ( unless you gear back to 3rd all the time).
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Old 06-09-2015, 07:07 PM   #6
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Default Re: sprocket advice for a pre-unit bonnie

Quote:
tall gearing increases the chance of detonation and piston damage, and reduces charge rate at night ( unless you gear back to 3rd all the time).
oh really?!
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Old 06-09-2015, 07:38 PM   #7
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Default Re: sprocket advice for a pre-unit bonnie

...T110s have 23T engine sprockets.
-may be you can go back to stock and put a 45 detachable in the rear.
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Old 06-09-2015, 07:42 PM   #8
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Default Re: sprocket advice for a pre-unit bonnie

I forgot to say previously how much I like your bike ,I hope you got your piston prob solved
I'm going for about 4:1 but no traffic lights-open road riding 80mph lower rpm riding,
light weight -not as much load ,I had my 71-650 pinging on hot days
i've run 10% methanol -ups octane by 4 numbers , jet up a couple of sizes
it will make your engine crisper -cools intake as well
I know it's a nuisance but if your just doing tank full runs it helps. buy 5 gallon drums
and add- don't smell the stuff - it's poison to your lungs
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Old 06-09-2015, 08:10 PM   #9
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Default Re: sprocket advice for a pre-unit bonnie

Thanks dude, I'm hoping an appropriate gear ratio will make it a whole new bike. Motor is back apart. Fixing a few aesthetic issues. and getting a new paint job.

I'm just going to go for stock 22/43/18/43
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Old 06-09-2015, 10:24 PM   #10
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Default Re: sprocket advice for a pre-unit bonnie

...man, go with the stock and put that 45; in this case is better than change the other sprocket, so add a bit of what you are looking.
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Old 06-10-2015, 12:28 AM   #11
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Default Re: sprocket advice for a pre-unit bonnie

Quote:
Originally Posted by vorhese View Post
Thanks dude, I'm hoping an appropriate gear ratio will make it a whole new bike. Motor is back apart. Fixing a few aesthetic issues. and getting a new paint job.

I'm just going to go for stock 22/43/18/43


I thought your avatar was a great paint job, what back wheel
can you run with a 43 tooth? I've only got 3x 46 cast ones
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Old 06-10-2015, 06:20 AM   #12
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Default Re: sprocket advice for a pre-unit bonnie

I have 23 engine 18 counter and 43 drum. Wouldnt change a thing for my purposes.

23/43/18/43
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Old 06-10-2015, 12:12 PM   #13
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Default Re: sprocket advice for a pre-unit bonnie

Quote:
Originally Posted by triumphrules View Post
I thought your avatar was a great paint job, what back wheel
can you run with a 43 tooth? I've only got 3x 46 cast ones
I'm running a lot of unit parts including the rear wheel and clutch. When I was buying the 43T rear, I remember there being a wait list for the UK made ones. The Taiwan ones were pretty available.

Quote:
Originally Posted by croucho View Post
I have 23 engine 18 counter and 43 drum. Wouldnt change a thing for my purposes.

23/43/18/43

That sounds like a good option too.
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Old 06-10-2015, 12:58 PM   #14
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Default Re: sprocket advice for a pre-unit bonnie

Quote:
Originally Posted by triumphrules View Post
what back wheel
can you run with a 43 tooth? I've only got 3x 46 cast ones
43T sprocket/integral cast drum was available for the 3TA. I'm not sure about all wheels, but certainly the quick-detachable one.
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