Carb settings

My rule of thumb before setting carb adjustment is to do an old fashioned tune up, what used to be called "plugs and points". The object is to get spark as good as can be, timing set spot on, tappets set, air filter cleaned, etc. etc. Carb setting should be the last thing to set, never the first. This was the message from my fellow workshop mechanics when I was learning the trade and there turned out to be a lot of truth to it. Wise words indeed. Being young and brash I resisted of course..

I set the idle mixture with timing retarded and engine fully warmed after a 10 minute+ ride. Stop and immediately tune the idle mixture. Effectively find the midpoint between rich and lean. The main jet needs to be set by performance on the road. The engine should pull without misfiring from being too rich or lean.

Once I'm happy I've got these two settings close, I mark the positions of the two needles as in the pic.

Marks allow fine tuning, perhaps a click or two either way to see if there's any slight improvement. Marks also allow the original setting to be re-established (with accuracy) if need be. In addition this is handy if someone messes with your settings as some kind of sick practical joke.

Gas cap refurbishment

My 741 has a very nice original oil cap with a perfect seal. One gas cap was missing, other was partially loose in its' center. I had a pair of good fitting gas caps, not quite original but well usable. The seals were like cardboard and were quite ineffective. I hand cut new seals from thin rubberized cork sheet. Fit is good.

Update: These seals failed because they ripped. Studying a Chemical Resistant Rubber Chart it suggests Nitrile or Viton. Will visit a rubber supply shop on my next trip to town.

I found the right place and they cut seals on the spot from 1.5mm Viton. I put grease to help them slide nicely. As grease will simply wash away with petrol/gasoline I want to experiment with silicone or Teflon grease. Already I tried CPU heatsink grease and Wurth silicone spray grease. Both seemed to dissolve too easily.
8Dec update: These Viton seals worked a treat so far with part tanks of fuel.. Not a single drop of fuel leaked. I filled the tanks and I can say this is the best the caps have ever been,

I want to uncrimp the original gas cap, remove the worn/loose center then attempt to recenter it with parts from a donor cap. It will be the first time I've done this so we'll see. The cap is not usable otherwise.

3Dec2018 Update: I gutted out the original cap. Firstly I tried to roll the crimp back but cap was difficult to hold. I made a tool for the lathe toolpost which utilized a hardened steel roller. I had some but limited success. Eventually I elected to machine away the internal part till it was wafer thin. Then it crumbled away leaving the outer case perfect.

DIY Lathe tool with crimp roller.

 Original gas cap dismantled

Another view 

Updates to come..

Throttle & Advance/Retard Controls

The control twistgrips had a lot of slack in the working so push/pull movements weren't very well defined. I dismantled the twistgrips to study workings. It was discovered there was an important piece missing from cable mechanisms inside both handlebars. Schematic parts list diagram, part #14

I propose to make these bits then solder new bowden outer cable to them. The plan is to get nylon lined bowden outer and single strand inner from a local mower supply shop. About 2 years ago I made a similar cable for my Panhead so am hoping to replicate the task.

The twistgrips had a significant amount of endfloat so I added a suitable shim to each. Pic of RH advance/retard dismantled with shim in place.

8Dec2018 I haven't been able to find local stocks of this cable. It's bigger than typical lawnmower. I may elect to import from a dealer in Canada but currently a postal strike disrupts.