I have what is supposed to be a 1973 RT3. Is the decompression lever supposed to be mounted on top or or on the bottom of the clutch lever perch? I've seen both. It seems to fit on the perch better on the bottom and there is a space for the wires to go through. I have an old brochure and it is mounted on top in the picture. Sure wish I could have bought one of these new, that way there wouldn't be so many mysteries. Thanks in advance for any help.

It goes on the bottom. I went through this same thing on my RT1B. If I recall the RT1B diagram shows it on the top . I actually found the correct collars to do it and was corrected by the experts on this site.  Makes alot more sense on the bottom.

Cheers

I had a similar situation with my 1972 RT2, so here's what I found:-

1) RT2 had the decompression lever mounted under the perch and pages 10 and 11 of the owner's manual shows this (I have a hard copy of this manual).
2) RT3 had the decompression lever mounted on top of the perch and page 10 of the owner's manual shows this (this manual is available to view and download in the Tech Library).
3) Those who have posted here on this subject that had a RT3 new, all said that it came with the lever on top of the perch.

Unless you're going to show the bike, then ultimately it's up to you and what you find most comfortable.   

Ok I’ll add to it…my RT3 original survivor one owner (before me) has it on top. 

The lever mounts under the bars.
Pull forward to engage for starting.
Your hand will not have to leave the grip as you use your thumb on the lever to disengage for running.

Just for fun, try it both ways to see how you like operating the lever in the two different locations.

Like it in the "under" position? Continue enjoying the bike.
Like it in the "above" position? Sell the bike and continue your career in hair styling.

My 1971 RT1 is mounted underneath.

 

Alan, are you poking the bear?