As you can see the BLOG hasn't been updated much. Most new pictures, projects, and info has been moved over to Facebook.
Like so many old horns, I had a 12v Lucas horn that didn't honk anymore. Horns have contact points similar to ignition points. Over the years they tend to corrode and no longer make contact.
The first thing to do is actually check if the contacts inside are working. Hook up your horn to +12v on one side and -12v on the other (or 6v if its a 6 volt horn). Touch a wrench or something metal to large screw/nut on the back. If it sticks the contact points are working and you just have to make some adjustments to get the horn working again.
So if it still doesn't work you have to open it up. Drill out the rivets from the back and crack it open. Be careful not to damage the paper gaskets when you open it. Inside you will see the contact points. Its kind of difficult to clean them in the tight area but a piece of very fine sandpaper and a spray of electrical contact cleaner will do it. You can tests the contacts with a voltmeter or just hook it up and see if it has magnetism now.
In the top picture you can see the diaphragm assembly on the left. It doesn't hurt to clean up the center post. This is the part that moves the diaphragm up and down as the core becomes magnetized and then demagnetized when the points open. You also see a fiber washer on the post. That washer comes in contact with the lower points arm and opens the points. You have to have it all adjusted correctly so that when its magnetized the diaphragm moves enough to open the points and then springs back to close the points, over and over and over. On the one in the picture I had to bend the entire points assembly down to get it positioned correctly. Someone my have adjusted it to much at one time or something. There is a screw on the back of the horn. It has square head. THIS SCREW IS LEFT HAND THREAD. This screw will adjust the point assembly up and down a bit.
To get it all adjusted correctly I would take the large screw and lock nut out of the rear housing. Use 2 screws to hold the housing and the diaphragm together and see what happens. Hopefully when you hook up power to it it blips or something. That will at least tell you the you are on the right track. It usually takes a bit of trial and error to get it all positioned right. You may have the adjust the square head screw a bit. I am sure there is a more precise way to do this but usually only takes a bit of messing with. The large screw and lock nut adjust the tone to some extent. Go in small increments. The large screw should not be in contact with the center post of the diaphragm. Once it is working again you can go ahead and rivets it all back together again. The tone might change a bit one its all mounted up solidly so you can adjust as needed.
I got a call from someone wanting to have their Triumph restored. A couple week later he brought it over. Right away I was making a list in my mind of what parts would be needed to bring it back to original. The owner goes on to say he has had the bike since 1972 and he wants it restored back to its current form, not original. Well this should be fun.
Its kind of a poor picture but you get the idea. 6" over forks, chromed sidecover and oil tank, minimal headlight mount, taller handlebars, etc.
Forks were full of water and quite rusty. I was able to find a brand new set of extended fork tubes. Everything black cot powder coated. All chrome is being re-chromed. All hardware and other various parts were re-plated. Wiring and ignition system is being updated with a Boyer Power Box and Boyer MKIV electronic ignition. It was actually a low mileage bike but the engine still got the once over with new gaskets and a refreshed top end. New parts where needed.
New valve guides.
Fabricated bracket to ensure a neat installation of Boyer electronic ignition box and coils . Bracket does not require any new holes to be drilled in the frame.
This is a recent acquisition that has a bit of a history. It was built by Doug Bingham and raced by Bob Braverman. It was featured in Cycle Guide magazine in 1972. It was road raced and it also had a few runs at Bonneville. When road raced it used a Kawasaki 500 H1 engine and for Bonneville they bumped it up to the Kawi 750 H2 engine. The best run netted 126 mph.
Below I have posted the articles from Cycle Guide. Be sure to scroll them to see all the pages.
Cool little mini bike. I have had this bike for a few years. Started fixing it up a bit and then took a 2 year break. Finished it up a couple days ago. Not restored, just a good clean up and some paint. Kept the original paint on the tank. 75cc 2 stroke so it will move right along for a little bike.
Kevin at Scrambler Cycle