Bike of the Month

January 2019

1966 Triumph T20SM

Mountain Cub

By Jim Meadows

Smokey the Wonder Cub

"Smokey" is a 1966 Triumph T20SM Mountain Cub sold new by Bill Rudd Motors on Gentry Way. However my Triumph was built by BSA. The late cubs, identified by the engine number being stamped on the left side of the crankcase below the cylinders, were built at Small Heath. The cubs built at Triumph have the number stamped on the front engine mount. To further confuse things, duplicate serial numbers were used and apparently 'Smokey' is one of those with a twin somewhere with the same number. Huh, I guess a cub single can be a twin too.

In the early 1980's I traded a plunger framed cub to Mike Hammond for 'Smokey'. He wanted to build a vintage trials bike [the plunger cubs compete in the rigid class against the rigid 350's and 500's, that doesn't seem fair]. I wanted a cub for my daughter to learn to ride on, the swing arm model I thought would be better and the mountain cub wasn't as severe a project.

Mike had the paperwork from the tow company auction where he bought the bike. It had been abandoned in an alley

I set about trying to make it run. The electrical system had been messed about with, as I recall the primary cover and alternator were off. The mountain cub was a derivative of the trials cub and used an "Energy Transfer" ignition system to save the weight and complexity of a battery system. It wasn't known for dependability when new and in the early 80's parts weren't available for the 'ET'. I don't know if they are now. It uses a different stator, coil and only a 4* advance mechanism. I put in an alternator, coil, advance plate off a Commando and a "Mity Max" battery eliminator because that's what I had. Norton parts made it go.

Daughter learned to ride, operate the clutch and shift, grew up and moved out. I started to ride the cub around town and even over to Downieville once.  Well heck, if it'll make it to Downieville [and back!] I might as well take it down to the BSA club 'All British' ride. So I did, just to show that you don't need a real 'road burner' to go 60 mph on an 80 mile ride.
 

I got to practice coordinating the front and rear brake going down a bunch of switch backs that ended at a stop sign at Highway 1, and was able to roll through the stop with out any harm. Those 5" stamped tin brake drums have their limits, but they are anti-lock so they must be safe. I adapted a 7" twin leading shoe front brake off a Honda 350 and sent it to Vintage Brake for new linings and arcing. Now a shorty lever will make the front wheel howl. Honda parts make it stop.

Since I was was riding it I ought to bring it over to the 'right side' of the law. At the 'All British' ride it's a contest to see who has the most expired license plate [last year there was a '59] but around town you don't want to get that award. I've got the paperwork of a Nevada auction from 20 years previous, what could be wrong? At the DMV when I pointed out that the year model of 1979 wasn't accurate, the plate was expired in '77 and the serial number meant it was a '66 the gal pushed my paperwork back "Take it back to the tow company they'll have to re-auction it" That didn't sound like a good idea to me.

That was before my brother Jerry found out about the Sparks court order way of getting the DMV to issue a title. I know someone who owns a tow company and she has a way of getting a title. They have to have possession of the bike, it takes 3 months and cost $300, but it worked.

By then I'd had the bike over 20 years, it goes, stops and it's legal. It was time to do something about the clouds of blue that followed it around. 'Smokey' is a nickname earned honestly and it's a 'wonder' that it never fouled a spark plug.

One winter I pulled the top end off [it's all of 9 screws] and sent the cylinder out to be nickasil plated, put in a new piston and lapped the valves. Wow, no more smoke! I was so happy I bought a new concentic carb. The monoblock didn't idle right when the bike was on the side stand, it leans over quite a ways and the float chamber being off set to the left causes it to stall, although it would idle fine if you held it upright.

I rode around town to break it in and up the hill on McCarran Blvd. [WFO!] to check the jetting. All ok!

That November, 2014 I think, I hauled it down to the 'All British' for the 4th or 5th time. A couple of miles out of town at the first bit of full throttle, and you ride a cub full throttle a lot, the engine quit. No compression. Oh _ _! I guess it was too lean at sea level. I got the 'hard luck' award, another one you don't want.

Well the bike sat around a while, this is a long term project after all. Last fall I pulled the top off again. Yep the piston was scored and the rings were stuck, there was aluminum all down the cylinder. The plated cylinder cleaned up fine and I had a new piston. A couple of gaskets and it was running again. I put on a Boyer battery eliminator, smaller and so far better than the Mity Max. I also built a better engine breather system I hope, we'll see. Gotta get some larger carb jets and I've got an electronic ignition to put on.

The late Paul Harvey told a story about being in Italy on Vacation. He and his wife, Angel, visited a foundry where they cast great bronze cathedral doors. There was a fellow filing and sanding and polishing one of those doors. Paul asked him "how do you know when it's done?" He replied "It's never done, they just come and take it away." Smokey's kinda like that, it'll likely never be done.

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