17/32 gear & new tires = huge improvement

lsc86

lsc86

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Picked up a clean 1 owner '79 xs650-SP2 earlier this summer (even got the original bill of sale with it). Solid bike, around 13k miles, all stock, not hacked or altered.

Not sure if the tires were stock or not, but they were quite old and hard/greasy. Not wanting to spend a fortune on tires and tubes, shopped around and bought a matched set of Shinkos and while it was apart, figured to go ahead and put new chain & sprockets on there as well.

With the stock 17/34 gearing, she turned a lot of RPM over 60 mph and vibrated like a cheap bed in some roadside motel. With the XS being so light and torquey, I wasn't concerned with losing too much down low or around town and definitely wanted lower cruising RPM from it. 17/32 seemed to make the most sense to me on paper.

After taking a nearly 500 mile loop Sunday, I can definitely confirm that the change in gearing was absolutely the best mod for anyone that rides often at or above 55 mph for sustained periods of time. The Shinkos worked well, predictable, solid & smooth. For the relatively low miles I'll put on them, definitely a great value as well.
 
thanks for that review. I've been kicking around the idea of a 32 tooth rear sprocket since I run out of gear so quickly.

did you replace the chain too?
 
If you have an 18" rear wheel, I think you'll like a 33T better. The 32 is perfect on a 16" wheel, not so much on an 18".
 
I'm running the stock 36 (canadian special) and it's ridiculous.
How is the 32 around town? Any clutch drama off the lights? Growly in 2nd gear corners?
I was thinking of going nuts and doing a 17/30 or 31, any thoughts?
 
I'm running a 30t in the rear and an 18t up front on my '83 Heritage Special with a 16" wheel in back. Really calms down the rpms on the highway, and no drama at all with the clutch at stop signs. I can even take off in second gear if I'm easy with the clutch lever. I like the 18/30 combo but it might not be to everbody's taste.
 
I love my 18/30 on my chopper. I have no problem running through Virginia City to Reno or down i80 three times a week. Well except for things vibrating off.
 
Royboy said:
I changed out my 78' SE to a 32 on the advice of Mercury Morse at 650 Central. As 5twins said, if you have a 16" rear the 32 is perfect. Approx 4200 rpm @ 65mph and comes off the line very well.

roy
Click to expand...

I am running 17/32 with a 16 inch tire but am getting closer to 5000 rpm's at 65 mph. How do you get them so low?
 
I love my 17/32, paired with new tires balanced by Dynabeads and highway riding is a dream. Switched to an O-ring chain at the same time but no noticeable drag.
 
New 530 O-Ring chain to go along with the new sprockets. JT 17 front and a Taiwan special 32 out back (from MikesXS). Turns around 3500 rpm @ 55 mph, most times. 33 year old tach & speedo aren't necessarily always consistent, but regardless of what the actual readings are, it's like having a 6 speed overdrive now, wouldn't change a thing. Around town is fine, smooth off the line and these 650s have more than enough torque to outrun most any cager to 55.

Bike was about $2100 out the door back in 1979.
 
I never found two teeth to make a whole lot of difference. Drops the revs like 300rpm right? I had one but it was a while back. Don't remember the exact numbers but it wasn't a whole lot so I bought a 30. I put that on for higher speed road tripping and the stocker back on for day to day stuff. I considered getting an even bigger one for regular usage since I never go above 60mph but haven't tried it yet.
 
im in the middle of my first build and im was thinking about changing the stock gear ratio. most of my riding is 60+ highway stuff but plenty of around town riding as well. what would you guys recommend. id like to get more out of my ride!
 
Here is a Excel spreadsheet that will give you RPM vs MPH for all combinations of sprockets, gears and tires. This chart uses rolling distance, the distance your bike rolls with one revolution of the rear tire. The yellow cells are pull downs for the wanted values.

Revs vs MPH

The chart shows that a 17/33 combo for an 18" wheel is the same as a 17/32 for a 16" wheel, or about 4,000 RPM at 60 MPH in 5th gear.
 
Last edited:
Pete, anyone? Is there a way figure the rpm drop in 5th gear when using MikesXS overdirve 5th gear. 24 tooth Mikes od 5th gear vs 22 tooth oem 5th gear
 

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