Increase front or decrease rear sprocket

Shovel Jockey

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Upstate South Carolina mountains, (Moonshiner 28)
Looking to improve my cruising speed slightly,(lower engine rpm at speed). Which is the best way to accomplish this, raise the front one tooth or lower the rear a couple. I have the stock 17/34 setup on a 1978 XS650E standard. Does one tooth up front equal two in the rear? Are there clearance issues up front with a 18T? I switched from the 3.50X19 / 4.00X18 tires to 100/90 & 110/90 which are slightly shorter than the originals so I will have to compensate for this change as well. Thanks, Joe
 
There are clearance issues with the 18T but people do it anyway. They keep the chain tight. There's a protector sleeve around the shift shaft that I think has to be removed to provide even that clearance. If it was me, I'd go down on the rear instead.
 
I went up 1 in the front and down 4 in the rear, no clearance issues at all, and I kept my shaft guard in place.
 
18/30, works fine.

Isn't 18/30 a huge jump in gearing from 17/34? How would that work in mountainous terrain? What about low speed pulling power? My bike shows 4000rpm @ 65 mph now with a 100/90/19 - 129/90/18 and I am dropping the rear to a 110/90/18 (about 3/4 in.) I can't bring up the gearing chart posted here for some reason so I am having to ask........Thanks for all suggestions, Joe
 
Isn't 18/30 a huge jump in gearing from 17/34? How would that work in mountainous terrain? What about low speed pulling power? My bike shows 4000rpm @ 65 mph now with a 100/90/19 - 129/90/18 and I am dropping the rear to a 110/90/18 (about 3/4 in.) I can't bring up the gearing chart posted here for some reason so I am having to ask........Thanks for all suggestions, Joe

with 18/30 65 should be under 3000rpms ist will be a little tall but all the other gears will be ok
 
I run 17/31 18'' rear wheel, around 60 at 3900rpm this is just under slide lift point of the carbs so good fuel mileage when cruising, good acceleration when you twist the loud handle here's the calculator I use
http://www.rbracing-rsr.com/gearspeed.html
 

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Hi There.

I had 17/29 a while back ago on my tracker. I ran a whole lot of small gravel roads up here in the north and it worked just fine. Just need to to use the gears a bit more but much better to ride when you hit the highway.


/BigBoreSwede
 
Yes one up on the front is equal to two off the rear. I like the extra clearance of the 17 up front. I have ran the 34, 32 and 30 on the rear. I think if you do lots of high way riding then the 17/30 is a good set up. If you do lots of around town riding then the 17/34 is good. If you do a mix of both the 17/32 is a good set.
Pick one and try it. If it works, keep it, if not try another. Sprockets are not that expensive. One's that you don't like sell them.
Leo
 
My fav is 17/33 with an 18" rear wheel. You wouldn't think just one tooth would make much difference but it really does. Benefits are little if any loss of low speed "lunge" and a reduction of a few hundred RPMs at highway speeds. I feel this is the ideal gearing for this motor with an 18" rear. I have a spare wheel with a 32 on it and don't care for it as much.
 
5twins, Your 33 with the 18 inch rear is about the same as my 32 with the 16 inch rear.
I put both combos in the calculater and they came up very close to the same.
Leo
 
Yes, a 33 on an 18 is nearly the same as a 32 on a 16. As I said, I don't care for a 32 on an 18. You really feel the change and the low speed take off suffers. The bike doesn't pull 5th as well either.
 
That's what I found with the 30 rear. Ok at highway cruising but need to down shift to get much acceleration. Take off was a lot more work with the clutch.
Leo
 
If you want something to tool down the highway on, buy a Goldwing or something, lol. Frankly, I don't feel this engine was designed with that purpose in mind. Gear it up too much and you kill the bike's "fun factor".
 
Yes, I agree. The Harley handles the highway much better. The XS is a lot more fun on most of the roads I ride.
Lighter, shorter wheel base makes it much more flickable. And properly tuned doesn't vibrate any more than the Harley.
Leo
 
What leo and 5-Twins said the 18T not the way to go. Yamaha geared the bike right for the fun factor the stock motor doesn't produce that mutch power below 3500RPM pulls strong 4000 to red line. The 32T is a tall gear for a stock bike I run a 17 and 32 on my bike 750 big bore Shell #1 cam ported head 1 1/2 pipes and shorties like leo. Lots of low end power withn that combo,The 650 will handle 5000RPM all day long and not hurt it. Been there done that what will kill your motor is over jeting your motor and carbon build up in the squish area of you pistons. It will beat the mainbearings out of them I haven't done that leaner and meaner lots of good sparkplug reading info lately. My advice take it or leave it. :D
 
If you want something to tool down the highway on, buy a Goldwing or something, lol. Frankly, I don't feel this engine was designed with that purpose in mind. Gear it up too much and you kill the bike's "fun factor".

That may be ok if you just tool around town or barhop, but my xs is my only bike and I like to go to Mexico and California on it. So its fun to me to bring my bike instead of some fat pig like a 'wing. I should also mention that my engine is a 73, so it has a little more pep than my old 81 engine.
 
I prefer to change the front, you can adjust the rear wheel rather than cutting the chain,
17 33 that 5twins is running is standard gearing in europe.
 
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