The BSA Rocket 3 with three lives

Over the years, we’ve featured many (many!) BSA and Triumph triples in RealClassic. Trevor Drury explains how his much-modded Rocket 3 evolved into the machine you see here…

Words and photographs by Trevor Drury

The Rocket 3 was built on 9th June 1971 and shipped the next day to California. It returned to the UK in 2007, repatriated by the previous owner who sold it to me that year in large lumps, partially assembled. He’d started the restoration; for instance the frame was powder-coated in a slightly lighter version of the controversial Dove Grey colour. I think it suits the bike better, although it’s still fun trying to keep it clean. The PO also painted the tank and sidepanels in the original colour of Etruscan Bronze. The chrome plating is all original.

Although I knew that buying a bike in big bits and half-done like this can have its problems, I was keen to get it on the road. I completed the assembly of the engine and, although there was something in the back of my mind telling me that something may not be quite right, I optimistically carried on regardless. It passed an MoT, was inspected by a nice man from the DVLA. It felt great to have a good-looking Rocket 3 on the road again.

It lasted all of 300 miles before it went pop!

It dropped a valve guide and smoked like a good ’un. This was the prompt I needed to remove the engine and do it properly. So off it went to P&M Motorcycles where Dave Whitfield made a brilliant job of making the engine better than new. I decided to go for a P&M 850cc kit, Dave Magaden electric starter, bronze clutch plate, five-speed gearbox, new P&M valves etc, nitrided balanced crank, Carrillo rods, new bearings throughout and more. You may have noticed the X75 head: it seems that Meriden were using up old stock, and a good many 1974 US spec T150s came so equipped.

While my engine was off being rebuilt I decided to play with the rest of the bike. I obtained a brand new set of T150 disc brake forks from Burton Bike Bit, and had a secondhand set of wheels sent to Brickwood, who made a lovely job polishing the hubs and building the wheels with stainless spokes and ally flanged rims. A Norman Hyde 12-inch floating disc was fitted together with a Grimeca caliper and a T150 master cylinder. A later T150/X75 rear brake plate was fitted which gives a more positive rear brake action, probably due to the longer brake arm. The next addition was an X75 chainguard which looks better and makes rear wheel removal a bit easier.

Two further modifications have transformed the handling: Falcon rear shocks which work great together with the Ceriani front fork internals – again, Dave at P&M did the work on these.

So the handling is pretty good now, although I’ve made a mistake of fitting metric size tyres which causes a bit of heavy steering. These will be changed out soon. I’ve fitted an 18-inch rear wheel which people say can upset the handling characteristics. However, my X-75 with its old original suspension handles like a trials bike on steroids compared with the R3 and the Hurricanes all come with an 18-inch rear. The Rocket 3’s big problem is its lack of ground clearance.

The gearing is currently set up with 19-tooth front and 50-tooth rear (down from 53) sprockets which seems to make it run well – it certainly pulls well combined with the 850cc kit. It’s even possible to check how fast it’s going with new pattern speedo and rev counter: no more jerky needles and you can read them well at night.

I fitted an uprated single-phase alternator with electronic rectifier/regulator unit which I feel is a must for all bikes from this era. It’s now running on a new AGM battery. Although these are more expensive to start with than standard batteries, they last for ages and won’t leak acid everywhere.

The excellent Dave Magaden starter will work with the standard size battery as it takes far less current to operate than the old Lucas starter fitted to the T160. I’ve used a left-hand handlebar switch (bought new from Tri-Cor) which does the job just fine.

To lighten the clutch action I used a new clutch lever with 7/8” centres. Combined with the T160 clutch mechanical mods this still gives plenty of lift to allow the clutch to operate well. A new seat was made by RK Leighton, although I do find it a bit tall.

I can’t own a bike and keep it standard for long, hence all the mods to my R3. However the purists may be pleased to know that all the mods are reversible and I have kept all the original parts to factory standard condition.

After riding around with the high export handlebars I decided my neck muscles could do with a break, so I obtained a set of new Triumph Speed Triple bars and risers. These work really well, better in fact than the standard UK bars with their slightly awkward bend.

When I got the Rocket 3 back on the road it was returning about 33mpg. That’s not good with only a 2.5 gallon fuel tank! I’ve now jetted it as per T160 spec (ie. weaker settings) and am now getting 40mpg. As a bonus it even goes much better: a lesson there for sure. However I still start to panic at around sixty miles and start looking for a petrol station…

A small problem which drives me mad is the slight hesitation with the carbs just as you come off idle. I’ve tried making things richer and then weaker which has made it better, but it’s still not entirely right. Also, the Tri-Spark ignition – whilst being a super piece of kit – will every now and then cut out for a micro-second. This only happens occasionally and it rarely results in the engine stopping completely…

Overall, for a 40-plus year old bike, it’s pretty good I’d say. It pulls well, you can rev it like mad if you want to. If you do, then it doesn’t hang about. I do find it a bit tiring to ride, however; nothing specific but when I get back on to an old twin they seem so much more relaxing. Maybe it’s just me getting old. You can ride the Rocket 3 sedately as well – given the way the roads are these days is a far more sensible idea – and with the 850cc kit it pulls almost as well as a T140 at low revs.

It’s my bike and I’ve done what I want to it, and I love it!