Highway gears

[Timb4302]

I ordered a set of gears and a new chain for my bike. I went with the same 17 tooth front and went to a 38 tooth rear rather than the standard 42.

What a difference!!!!!!!!!!! Driving on the highway is so much nicer. I do not have a tach so I do not know the exact reduction of rpm's but I can say this. Going 90 now feels like 65 used to. Needless to say I am at the low end of 5th gear at 65 instead of the top end.


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[rick]

I may have just gotten a bad set last year, but I had a 39/17 set and was constantly having to adjust my chain, kept getting slack. Something you may want to watch for. Agree the lower revs was nice.


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[chi]

I was wondering how that was gonna turn out for ya, keep us posted on any changes in mpg and any problems if any as far as installation or chain slack. I was thinking about doing the same with the scoot works highway kit but I want to see how the hypercharger does, might wait until just before spring to get some pulleys I just about have things where I want them for now

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[Timb4302]

I talked to the dealer about the chain stretch thing when I bought them. He said I would have about a 500 mile break in period which I will have to adjust the chain every 50-100 miles but after this I should be good. I will keep you all posted.


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[griffjo]

Originally Posted by Timb4302

I ordered a set of gears and a new chain for my bike. I went with the same 17 tooth front and went to a 38 tooth rear rather than the standard 42.

What a difference!!!!!!!!!!! Driving on the highway is so much nicer. I do not have a tach so I do not know the exact reduction of rpm's but I can say this. Going 90 now feels like 65 used to. Needless to say I am at the low end of 5th gear at 65 instead of the top end.


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Timb4302,

How much the RPM's changed is a matter of arithmatic.

Assuming your 800's transmission gearing is the same as an '03 Classic, the change you made from 17/42 [2.471:1 ratio] to 17/38 [2.235:1 ratio] is a 9.5% reduction of RPM's.

Stock 90 MPH at ~5,170 RPM, w/new 17/38's at 90 MPH, ~4,680 RPM
Stock 65 MPH at ~3,725 RPM, w/new 17/38's at 65 MPH, ~3,370 RPM

A world of difference - You do lose some low-end torque, but, for me, the comfort factor more than makes up for that.

My 18/40's [2.222:1 ratio - from Scootworks] are close to your 17/38's [2.235:1 ratio].

I'm very pleased with all my mods to date, but I consider the highway sprockets to be my best mod by far.

[Timb4302]

I ordered mine from jawzy's which is local too me. I wanted to do a 18/38 but he explained that it is hard to fit the larger 18 front so I just went with the 17/38, overall I love it!

Thank for all the math!


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[rick]

You said were told its hard to fit the 18? Thought would be close to cover, but several have done it. Maybe one of you who have can shed some light on this? Thinking of getting a 18/40 set with my next chain.


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[Timb4302]

Please do. I know if I would have gone with a 18/38 combo I would be down to about a 2:11:1 ratio, however this would really make starting in first gear a issue I think.....


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[rick]

Even with the 17/40 I used to have on mine, starting out in 2nd wsnt really an issue for me as long as I know It was in 2nd and I didnt let the clutch out to fast. Dont know of anyone using the 18/38 setup, but think you should be ok as long as you dont ride much 2up or into the hills alot. Keep in mind te motors like to revved. If you do this, let us know how you like it. Should be great if you run at 80 or more alot.

[Timb4302]

I work and hour away on the highway, hoping to significantly cut down on the fuel bill


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