TriBSA 650

Out of the archive: in another blast from the past we look back at an article John Walton wrote in the early days of RealClassic… looking back at a bike he owned a couple of decades before then! Step into our time machine to meet a pre-unit Triumph 650 twin housed in a BSA A10 chassis…

Back in the mists of the late 1980s I had my second foray into biking. I heard of a TriBSA locally so had a look, thought ‘what a wreck’, and bought it. It was actually a nice-looking bike but was spoiled by ill-fitting, scruffy parts. Someone had done a reasonable job of fitting the engine into the frame, but the rest: oh dear.

The frame was from a 1956 BSA A10; the engine from a 1953 pre-unit Triumph 650 Thunderbird with an iron head; the gearbox and primary chaincase came from an A10. Petrol tank was a BSA, it ran dynamo and magneto ignition, an Amal Monobloc carburettor, Gold Star silencers, A10 oil tank and sidepanel. The rest? Who knows!

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I took it for run round the block, was suitably scared witless, and thought ‘yes, a good buy here.’ It was leaking oil everywhere, wobbling and had suspect brakes. A mess.

First things first. Engine and gearbox apart. Apart from a worn cylinder bore, all looked fine. It needed new pistons and a rebore out to +60, and then carefully reassembly properly. I faced all the casing joints as best I could; they were very poor really. New seals were fitted on new pushrod covers, and O-rings on the rocker spindles. It got a decoke and I reground the valves with new valve guides. It came with an alloy head which I used as it was better looking than the iron one. I thought the oil pump looked a bit suspect so bought a pattern replacement. More on that, later.

The frame and swinging arm were powdercoated. Removing the BSA silent-bloc bush from the swinging arm was a nightmare; I gave up and took it to a local engineering firm who had a fly press. No problem. When the parts came back from the powdercoaters it went back to the fly press to insert the new silent-bloc bush and then reassemble everything.

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I had the wheels rebuilt by Hagons in London. How I remember carrying the hubs and then the rebuilt wheels to and fro on the underground from White City. Next came new brake shoes and a decent A10 brake plate to replace was a botched affair with riveted-on air scoop. A local classic bike shop chastised me for asking for bonded brake shoes rather than the linings he had in stock. Apparently ‘you’re not a proper biker if you can’t reline your own shoes…’

I bought alloy mudguards and a new headlight assembly, a new old-stock petrol tank and a pattern A10 seat. The tank was from a BSA Fleetstar which meant it was small but fitted the look I wanted. The TriBSA came with a scruffy BSA Lightning humpback seat, so the A10 seat fitted better. The rear light assembly was from a Lightning and I kept that – being alloy it polished up nicely.

I had the oil tank, side panel and chain guard chromed and the tank sprayed black. A local guy sign wrote the TriBSA logo for me on the tank. Standard Triumph exhaust pipes and silencers were used. A lot changed later on!

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The TriBSA came with rearsets which I kept, they were quite comfortable with standard handlebars. The gear change was reversed because of the rearsts, giving one-down, three-up gear changing which I was used to having had Triumphs in the past. A friend gave me a nice set of chrome, open-spring rear struts which fitted perfectly.

After putting it all back together, the engine started first kick with oil returning to the oil tank, wonderful. We went for a short run and all seemed fine… until I looked underneath and oil was pouring from the crankcase breather. That meant a six mile push home! I stripped down the engine and all looked OK.

Put it all back together – again. Start up, run, oil pouring out. After a lot of heartache and time wasting, guess what? The oil pump. The pattern pump worked perfectly. Except the two crankcase mounting holes were 1/8” too high. So the gasket was slightly covering the oil outlets. That was OK when cold but when the engine got hot the oil could not return – and so it just emptied from the crankcase. Amazing.

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When I took it back to the dealer he just laughed, of course until I proved my point. He had increased his prices since I bought the pump and refunded me more than I had paid, so I had the last laugh there.

After a while I wasn’t too impressed with the sign-writing on the petrol tank. I wanted something traditional. I always liked the Matchless / AJS look so I drew up something along those lines. Another sign-writer did an excellent job using gold paint on the black tank.

I also stripped the chrome from the oil tank and sidepanel and had them painted in black with BSA logos. I thought that was better than nothing as there was nothing ‘TriBSA’ on the market then – and I didn’t want anything naff.

I think nearly every sundry part on the bike was replaced or rechromed. It had chronometric speedo and tachos. I used the standard Triumph rubber binnacles to mount these.

The dynamo was about the one thing that kept going. The magneto was difficult, the HT leads were always falling out. When it eventually packed in a replacement was perfect. The chromed front fork oil seal covers were poor so I replaced those. Do you think I could get them to screw on? Eventually I found out I had been given A7 ones instead of A10. The guy in the shop said ‘well… I thought they were all the same!’

I changed the silencers to a set of Dunstalls. They were supposed to increase power, but didn’t. They looked quite good though.

I never did keep the primary chaincase oil-tight. The BSA casing never fitted correctly to the Thunderbird crankcase. I tried various felt washers, cork ones, silicon sealant. I just had to accept I had to re-seal it every couple of months or so. In fact most of the top end, rocker box joints and rocker oil pipes never stayed oil tight for long.

I went to Scotland on it for a week’s touring and it never missed a beat. Lots of oil leaks though! The bike’s handling was brilliant. Those long sweeping Highland mountain roads are an experience never to be forgotten. Nor was the constant rain. You just cannot beat packing and un-packing wet camping gear every day! I had so much gear on the back that I had the front wheel coming up a few times. Oh, and the clutch came adrift by Loch Lomond, but that was my fault for not tightening the centre nut properly when I changed the clutch plates.

The idea of a TriBSA always seemed like a poor man’s Triton. The Norton frame was well known to be superior… but the BSA frame was much better than any Triumph from that era. A lot of these specials seem to keep either the Norton or BSA badges. Personally I don’t get this, it’s either a Triton or TriBSA. Not a Norton or BSA.

Eventually I got fed up of constantly replacing poor pattern parts. Back then the aftermarket spares were really poor. And of course everything was done by phone or snail mail. So I went down the Japanese route. And then I met my future wife and went down the Chinese route! Still there and into my third foray with bikes.

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