Shimano SIS 600 lever - what's "light touch"?

What does the name "light touch" mean, as applied to the old 6-speed Shimano Index (SIS) shift levers (downtube bracket type)? Is there another similar-looking SIS lever that is not the "light touch" type? If so, how to tell the difference? (In my lever set, the left lever is friction only, and it is just marked "Shimano 600" or 6708.)

What's the right method for using the friction/SIS settings on the lever hub? It's a bit cryptic. The friction seems inadequate even after a firm clockwise twist on the bail. (Should all lubrication be avoided?)

I intend to replace the right-hand click shift lever because one of the most-useful internal click-stop tabs has broken off. The setting now tends to creep, giving surprise upshifts. Thanks for any expert feedback.

 

A lot of this is before my time, so i'm posting a reply to get thread updates.

 

Thanks.
BTW I've been using that shifter for 20 years without understanding its workings. Finally I've rebuilt the bike's badly worn drivetrain. Sheldon Brown's pages were useful for seeing the parts in the shifter but I've found nothing on reassembly or changing its settings.

 

Light Touch was nothing more than a term for marketing purposes. A lot of the early SIS shifters took a little bit of force to overcome the springs, balls, and dimples that made up their internal workings. Light Touch shifters were designed to be easier to shift and this design became standard among Shimano SIS down tube shifters. Never lube a down tube shifter that is designed to be a friction shifter, or a part time friction shifter unless you don't mind losing the friction shift option. Switching from SIS to friction and back was entirely up to the whim of the rider. Back in the day when SIS was first arriving on the scene, there were some die hards (me included) who thought that indexed shifting was a fad that would eventually die out, so Shimano had a shifter that could be used as a friction shifter until the rider felt comfortable enough to try SIS. With just a 45 degree turn of the bail, your drive train was suddenly SIS.

If you are going to disassemble the indexing handle of an SIS set of shifters, be sure to remember how it came apart. Take pictures or video of the process so that you can get it back together again and have it work. Make sure that you clean off all of the parts and resist the urge to lube any part of it. Otherwise you will be disassembling it again. Good luck.

 

Thanks, K, That's very helpful.
You're right, I'll be taking it apart again --this time no lube! (I thought it was going well enough the first time until things unexpectedly fell off the bracket during reattachment.)
I've got another lever assembly coming from England and hope the little tabbed ring in it is still all intact.
Hopefully "light touch" has enough resistance to hold the lower gears. We''ll see.

 

FWIW. If you are handy, then you can cut a DIY, replacment, FRICTION WASHER from a milk jug cap ...

 

Interesting thought, thanks, alf. (It's the little hard castellated ring that has one stop tab broken off.)