The sprocket question

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nortoneer850

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Hey all, I am going on a trip next month that will be up to 4500 miles long depending on the route we take. My partners in crime will be two friends on Harley's. What would be your advice on changing my countershaft sprocket or not? I currently have a 19t, most of the riding will be faster back roads or freeway.

Using the formula from oldbritts website at 70mph my current setup will be at 4470 rpm ( to high?? ). If I change to 21t it goes down to 4000 rpm and 22t is 3860 rpm.

So my question is, do you think 4470 is to high for consistent riding? And do you think I would see a gas mileage improvement with the bigger sprocket? Thoughts?

P.s. I have a 20t laying around hat would require no ordering of parts rpm at 70 would be 4248, would that option be best so that I don't need a new chain? Thanks
 
I would hate to hit the highway with anything smaller than a 21. Yes, it will affect the fuel and oil mileage and the comfort. Jim
 
Id say 20 would be the thing, Id go 21 if the grades werent too bad.
And that would depend on how much cargo you are carrying and how
much you weigh.
19 isnt for highway cruising.
 
nortoneer850 said:
Hey all, I am going on a trip next month that will be up to 4500 miles long depending on the route we take. My partners in crime will be two friends on Harley's. What would be your advice on changing my countershaft sprocket or not? I currently have a 19t, most of the riding will be faster back roads or freeway.

Using the formula from oldbritts website at 70mph my current setup will be at 4470 rpm ( to high?? ). If I change to 21t it goes down to 4000 rpm and 22t is 3860 rpm.

So my question is, do you think 4470 is to high for consistent riding? And do you think I would see a gas mileage improvement with the bigger sprocket? Thoughts?

P.s. I have a 20t laying around hat would require no ordering of parts rpm at 70 would be 4248, would that option be best so that I don't need a new chain? Thanks
Click to expand...

21t would be good all around with some highway and still be good around the towns. But You do have an 850 and with a bit more torque you could go with a 22 and do well. You will have to flip your own coin. I would think a 20 or 21 would be more standard on your 850. Did you change it at some point from that 20t on the shelf?
 
Same here. 19T is awesome for lower speed twisty's up in the hills. But would be kinda 'Busy' on long high speed straights such as the Interstate.
If it's just you on the bike 21T might do pretty well. But if your gonna carry 100lb of gear, stick with 20T.
 
It depends on how fast you will do the highway and for how long. A 20t is about 4000 at 65 mph which is where I ride most highways. Good throttle response and the isos are working perfectly. But if you intend to sustain 70+ mph I'd definitely go up to 21. The 22t will make around town cruising uncomfortable IMO.
 
most of the riding will be faster back roads or freeway.
Click to expand...

kind of also depends on the cargo load and how hard the HD's will be pulling the turns exits, but a 21T sounds to me like best as can use 2nd for passing gear, dicing twisties and cruise in their 3500-ish vibe range smoothly with decent pull to run up to the ton if they'd care too. Each tooth gives about 5% change in ratio and roughly 500 less rpm open road cruise. I like the long haul rpms to land between 3500-4500 zone but its a non issue to hold 5000-ish for hours. just check oil often and might want to bump up the thickness for long summer runs. Chain needs 100 links to fit 21T. Harleys and Commandos geared similar give similar mileage. Your Norton will not sound as bad ass as the big twins but likely get asked to demo it more often w/o the obnoxious big twins.
 
In the summer of 1972 I swapped out the 19 for a 21 on my new Combat 750

and rode it 5000 miles that way from Minnesota to Mexico and back

go with the 21, it should be perfect for you on the highway

oh, and I would run a good 50 weight oil, and change it every 1000 on your trip, it's gonna be damn hot all day
 
I think your choice is between 21 and 22. I'm using a 21 right now and I know I'm giving some away in the acceleration department, especially with a single Mikuni. But then 70mph is a breeze, and 80 is no problem. You don't say where you're going, but I can tell you that if you're going to be spending any time on the interstates in the flatlands, you'll get run over going 70.

You may need a new chain going from 19, but that might be a good idea anyway, tires too for that matter.
 
Freeways run 70-80 mph, even if speed limit says 65, you don't want to be flowing slower than traffic around you. Definitely begin with a new rear or may be on center cords at 4000 miles -unless ya are waving like drunk a lot like I tend to do, but not where police lurking or cell phone callers reporting. Take phone numbers of vintage vendors just in case. Harley shops have our size tires, for their fronts.
I like the long legged torque pull more than the short zoom ups on lower ratio's.
Safe Journeys and return.
 
RPMs = Revolutions Per Minute = more times your rings scrape up and down the cylinders, more times the cam lobes pass over the lifter surfaces, more times the valves open and close ect. etc. A bike with 10,000 miles on it that got there from an average rpm of 4000 is not the same as one that has 10,000 miles with average rpm of 3000. No sense turning things over so fast when you could be ambling along at a much slower rpm using less oil and gas and causing less wear and tear. Go with the 21.
 
pvisseriii said:
rpatton said:
I think your choice is between 21 and 22.
Click to expand...

I don't think they make a 21 1/2 T. :lol:
Click to expand...

Does that mean if you have to choose between Taylor Swift and Scarlett O'Hara that you're going to get half of each? :shock:
 
another one for a 21 as the minimum. the more interstate in the ride the more I would lean to a 22.
 
The Hobot said: kind of also depends on the cargo load and how hard the HD's will be pulling the turns exits,
Click to expand...

If you are on the larger side, and take everthing including your tux for formal nights, might make a difference, especially if you don't like looking at the behinds of two hogs for 4500 miles.
 
I took an 1800 mile jaunt, the 22 is the tits. I continually enjoy a leisurely 3200 RPM cruise at 65mph, and only 4,000 RPM at 80 mph. SOOOOOOOOO glad I didn't go a single tooth lower. Tractor gears are for, well, chugging along.
 
So a question here-how much difference between a 850 and 750 as far as this thread goes? Similar recomendations for each? I've ridden with Concours, and I know what his 850 is capable of. Given similar weight and engine condition factors, would my 71 750 perform like his 74 850?
Just curious
 
RennieK said:
Go with the 21.
Click to expand...
Asked Windy (aka "bill" on this site) this many years ago 'cause when I first got my Combat back from restoration it still had the 19T setup. While the 19 was blazing fast, I planned to take the bike up approx. 60 miles north of the St. Pete area on weekends to the hills and twistys of the Brooksville, FL area. IMHO the 21T offers a great solution to hwy cruising w/o sacrificing acceleration to keep up w/ my cohorts. The best of both worlds....
 
rpatton said:
pvisseriii said:
rpatton said:
I think your choice is between 21 and 22.
Click to expand...

I don't think they make a 21 1/2 T. :lol:
Click to expand...

Does that mean if you have to choose between Taylor Swift and Scarlett O'Hara that you're going to get half of each? :shock:
Click to expand...
Would that be more like between Taylor Swift and Vivien Leigh? HMMM, That might be Marylin Monroe. I'll take it!
 
I have stayed with the standard 19 tooth, but the belt drive I run has geared my 850 up, I cruise on the highways at 70/75 all the time not very often I am under that speed, and around town its just right, with the SS cam and balanced crank it works just right for me, and able to hit the throttle and just get straight power to the back wheel and in the tight mountain roads I ride all the time is just perfect for me, I also ride my Norton hard and do lots of riding well over the ton, but these days there are so many cops around that want your hard erned money :evil:

Ashley
 
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