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Discussion Starter #1
I'm going to be changing my sprockets and chain on my bike soon. It's an 01' 800a. I believe it has the stock sizes. Right now the thing gets it off the lines but is screaming in 5th on the interstate at 75+. I would like to get it to where it still gets it off the line but ain't screaming so much. I don't do much highway riding. I would say my average is 45 mph. Usually don't do much over 70. Maybe I should keep the stock sizes if I want all that get up and go?
 

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I have 18/40 sprockets on my 05 classic, think has the same gearing. I dont ride it hard, so off the line is not a big deal, but I still usually beat most cars through the intersection easily. I also dont normally shift into 5th until I'm doing at least 45-50. I dont think I'll go back to the stock 17/42 sprockets if I can still find a set of 18/40s.
 

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Discussion Starter #3
Ya I believe I have the stock 17/42 because I saw 42 engraved onto my rear sprocket last night.
 

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Discussion Starter #5
I have 18/40 sprockets on my 05 classic, think has the same gearing. I dont ride it hard, so off the line is not a big deal, but I still usually beat most cars through the intersection easily. I also dont normally shift into 5th until I'm doing at least 45-50. I dont think I'll go back to the stock 17/42 sprockets if I can still find a set of 18/40s.
Just searched all of eBay and could not find any 18/40 combos. Found mainly 17/42 and some 17/40s which would Be a little better then the stock 17/42. My other option would be to keep a 42 rear and just get an 18t front which I can find. That would still be higher geAred then stock but not quite as high 18/40. But then again an 18/42 combo would be equal to a 17/40 setup probably
 

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i recommend that you do not go to a 18 tooth front , leave your front 17T, because you said that you don't want to lose your low end, and what will happen if you remove the 17 front and go 18 is you will lose 3 teeth on the rear, let me explain, a 1 tooth increase on the front is equal to a 3 teeth drop on the rear, so a 18/42 would be equal to a 17/39, and with a 39 rear you will definitely lose low end, so with a 18/42 you will lose the same low end as an 17/39, now if you go 18/40, you will basically have no low end whatsoever, because going from a 42 rear to a 40 rear you will lose 2 low end teeth and combined with the 3 teeth loss going from a 17 to 18 front, 2+3= you will lose 5 teeth torque on the low end, that's the same as keeping the from 17 and going to a 37 rear (18/40 = 17/37) so just go over these numbers before you do anything just to make sure that you are aware that with a 18/40 you will have no low end at all, sure great on the highway in 5th gear but you can kiss your low end torque good-bye, I recommend that if you want to change sprockets consider keeping the front 17 and go with a 40 rear but no lower, go 17/40 and keep the front stock, it's very difficult to remove and replace the front anyways
 

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you say a 18/42 combo would be equal to a 17/40 but actually a 18/42 is = a 17/39
 

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Discussion Starter #8
So do you think a 17/40 combo would be my happy medium? Will I lose that much down low? Will I even gain that much on the highway? Only if they made these bikes 6 speeds lol
 

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17/40 is what i have, I find it a happy medium between 1st gear get go and 5th gear 70 mph highway, down low is good, you won't lose a lot down low, on the highway the 40 tooth rear will increase your mpg and lower the rpm's a bit, what i would do is play with the rear sprocket ratio and leave the front the 17 stock, you could even try a 39 rear and go 17/39, that would be better then going to a 18/40 which is equal to a 17/37
 

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Here is a gear ratio chart might be of some help, I went to 18F and 40R and haven't regretted it yet, also re-jetted carb, scooterized intake and have a basically open custom exhaust, 1st gear doesn't wind out so quickly and I do not see any appreciable loss of torque below 50 MPH, 5 gear is way better on highway good to about 75 or 80 before it seems to flatten out on torque, will still bring bike up to 90 or better without too much extra effort
, increased gas mileage too.

Ideal target for our bikes is suggested around 2.2 similar to the Scootworks belt drive ratio


Ratios-for-Sprocket-Combinations-1.jpg
 

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Discussion Starter #12
I think I like the idea of the 17/40. Considering I only ride highway (75+) about 10% of the time I don't think an 18/40 is necessary. I do more city driving and that's where the low end get up is more important
 

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considering the 17/42 stock as a baseline
a 17/40 would be a 5% increase in speed and 5% decrease in torque
a 18/40 would be a 11.2% increase in speed and 11.2% decrease in torque
I'm playing around with that sprocket calculator
 

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I think I like the idea of the 17/40. Considering I only ride highway (75+) about 10% of the time I don't think an 18/40 is necessary. I do more city driving and that's where the low end get up is more important
mod your intake and re-jet with open exhaust, you won't notice any loss in town with 18/40 from the stock 17/42 and highway mileage will increase substantially, non-modded systems will be noticeable and suck if riding 2 up even with he 17/40 mod, I suggest doing the performance mods first then the gear mods..
 

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I changed out my front 17 sprocket for a new 17, but it sure was a bugger getting the old one off, and I hope never to replace it since it was so hard changing, the back one was much easier, if i were considering a sprocket ratio change, I would leave the front one stock 17 and just change out the rear one, and there's not much room between the chain and the guard when going to a 18 sprocket
 
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