I've finally got a running chop. Does anyone know the expected rpm for a 17/42 sprocket setup at about 60mph? I've been around v-twins for awhile and
my rpm seems high but it sounds good. Maybe I got the wrong tach.
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 mmf |
RPM?? |
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Posts: 27 (04/22/08 10:50 AM) |
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dtmmil |
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Posts: 1033 (04/22/08 3:47 PM) |
Mine with a 130-90 -17 rear , with 17/48 I am running 5200 at 70, I think 60 is about 4600. What are you running?
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Houndog750 |
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Posts: 1733 (04/22/08 8:36 PM) |
Going on 5200 at 70 with 17/48 and 17 rear 17/42 would be 4570rpm @ 70mph and 3920rpm @ 60mph.
Now I KNOW my gearing is tall! With a 16/37 and 17 rear I am running 4260rpm @ 70mph and 3650 @ 60mph. Just outside the power band at 60 in fifth. If I am figuring right (but am probably not) I am probably not even doing 5000rpm in 4th @ 70mph.
It was Honda first, all through the middle, and if I have my way, till the end as well.
Most people say what they'll do. Very few actually do what they say. |
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jpswino |
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Posts: 904 (04/22/08 8:49 PM) |
Gee Houndog, you could probably do 200mph with that gearing!?
"In the wind, with my mind on my money and my money on my mind"...now I just gotta get some.
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dtmmil |
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Posts: 1037 (04/22/08 9:10 PM) |
Hey Houndog, which bike are you running that on? What kinda mileage you gettin?
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Houndog750 |
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Posts: 1734 (04/22/08 9:20 PM) |
That is on the bagger. I more or less wanted an overdrive to keep engine temps down and increase engine life.
Jps, the fastest that bike has one is 120+. Got a little "soft" and started floating at that point, but the 18" apes and human parachute probably had it ready to start parasailing. I have to go ton up on any of my bikes or I don't consider them finished. 
There's a tradeoff. Low Rs but loss of torque. Even in 4th on the highway I am at the bottom of the power band, and with the windshield pretty close to that invisible brick wall. Romping on it I'm just shifting into 3rd about 50 to 55 if that gives you any idea. Can't say what mileage is now, but it will probably improve from between 48 to 54 MPG to something more like the chop at about 52 to 56 MPG. Both are now running 77/78 SS carbs set just a tad lean. I still have a weird "flat" spot (say around 50mph in 5th) that I have to figure out.
It was Honda first, all through the middle, and if I have my way, till the end as well.
Most people say what they'll do. Very few actually do what they say. |
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dtmmil |
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Posts: 1038 (04/22/08 9:27 PM) |
Damn! I thought I was doing good at 45mpg.
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Houndog750 |
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Posts: 1735 (04/22/08 9:48 PM) |
Well, um, uh, those numbers are when I am taking it easy.
On weeks I'm in a good mood I am sure it's a little lower. 
It was Honda first, all through the middle, and if I have my way, till the end as well.
Most people say what they'll do. Very few actually do what they say. |
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74chopper |
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Posts: 697 (04/23/08 12:13 AM) |
i was running 17/48 for a while , it sucked on the highway, great for take off and showing off though, i know got 18/48, nice all rounder, dont know exact
revs , but doesnt sound like blowing up know.
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mmf |
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Posts: 28 (04/23/08 2:02 PM) |
I miscounted. I have 17/45 sprockets with a 130/90/16 rear. I'm running over 5000 at 60. I've got mini gauges - maybe I got the wrong tach or
speedo. I tried an 18 tooth front but the chain hits the engine case. Will an 18 fit some engines? Mine's a '73.
Thanks everybody for the good info! |
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dtmmil |
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Posts: 1040 (04/23/08 3:42 PM) |
What ratios are your gauges? some say right on the face. That sounds a little high to me for your sprockets you have. The 18 you tried, was it a standard
sprocket? I think a 73 came with an 18 tooth sprocket, I could be wrong though.
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