Engine Swap

[Rob Neal]

Having completed the recent restoration of my 1962 A65 I'm now looking at the huge pile of parts that came with it to see if there's another viable bike there. Ive got  a decent tank, frame, wheel hubs but the biggest concern is the state of the various rusty/knackered engine parts. From recent experience it will cost a small fortune to build back into a reliable power unit. I had at first thought of giving up on the idea of a second build and selling everything on.  However, perhaps I could use a more modern engine and build up a hybrid as the next project.  I want to stick to a 650cc air-cooled, carburettor, vertical twin if at all possible. Initially looking at a more modern (i.e. oil tight, more powerful) lump. Yamaha XS650 or early Chenai Royal Enfield interceptor units?  Concerned about the fit, particularly the height as these are overhead cam, wet sump designs which are likely to be taller than a BSA unit.  Has anyone in the club been down a similar route in the past and could offer some guidance?  Or will I be banished for thinking such heretic thoughts???  Rob

[tdc]

Every thing is possible . It is a bit like ' Speed costs money,how fast do you want to go '

[V500]

As an aside, if it has no V5C then you'll need to build it first with the BSA engine, as trying to get a mongrel registered now is a nightmare.
The BSA engine wouldn't have to actually run, but it (the bike) would need to look complete as possible.

[iansoady]

V500 is right, DVLA have been tightening up recently. Re alternative engines, I have a Suzuki DRZ400 (ex CCM) in a Starfire frame. Not built by me but well engineered and it goes very well. As it should with around 42bhp. The builder had swapped gearchange and rear brake over , which suits me, but unfortunately had given it a Triumph up for up pattern which I'm engaged in changing to up for down which I prefer and which will cause my aged brain less confusion.

I suspect a liquid cooled single isn't what you're looking for however.

This is as I bought the bike - have made many changes since.

[V500]

Is that a Morini in the background?

[iansoady]

Yes, not mine but the previous owner of the BSA/Zuki. Apparently he was selling as he had too many Morinis!

[V500]

I don't blame him. When I had mine the joke prevalent was they are called the 3 1/2 because that's how many you needed to keep one on the road.
Horrible things, although some seem to love 'em.

[iansoady]

I've always wondered why they have such a following. I've had a couple of Guzzi V50s which to my mind are a much better worked out bike - and are cheaper as well.

[ferretjuggler]

The XS650 engine is too big.
The only British frames I've ever seen one in are swing arm A10, and Norton Featherbed.
I even tried squeezing one into an Ariel Huntmaster frame, which, being big enough for an A10 engine,  you'd have thought would have been big enough for the XS.
But no, well almost,  but not without cutting some non-essential bits off the engine,  something I wasn't prepared to do.

[chaz]

the XS engines are a problem.
not running wise but accessibility

the XS650 motors are or were favourite for Wasp scrambles sidecar power units. When I had my chassis, I couldnt get a motor for love or money. The spare ones about, were being kept as spare race motors, complete bikes were being bought for the motors, the rest sold as parts.

the XS500 motors are slightly under powered and parts availability is a problem. The standard lump, uses a non standard oil filter. I worked on one for a customer, bought the last available filter £80 from Holland, none available from Japan, Aus, USA, Europe. There is an adaptor for £80 which uses normal HiFlo filters which is made in England , because the Japanese/Yamaha made part isnt regarded as very good.

One option I was told for the sidecar was the Honda NX650 Dominator motor from 1988 to 2003.

[ferretjuggler]

I once saw a "Triumph" hardtail chopper that someone had bought just for the unit 650 engine.
Having removed the Triumph lump he replaced it with a Yamaha XT500 unit.
Probably not your cup of tea,  but it seemed to fit rather well,  and it's dry sump.
Looked and sounded right, although the performance isn't going to set the world alight.
Maybe 34 Bhp if you used a SR500 engine, unless it's got a big bore kit

[Rob Neal]

Thanks everyone for the responses and advice.  Love the DRZ400 BSA, looks amazing.  I had a feeling this wasn't going to be a straight forward problem to resolve!! Thanks for the tip about the DVLA and trying to get a hybrid registered as I don't have a V5 for the frame.  If my pile of engine bits won't make a complete motor without some very serious financial outlay (I'm skint after the current project build!) and with Jap motors looking problematic I think I may need to look for a complete BSA motor and go from there.  All fun and games in the classic world, but that's why we do it isn't it?  Happy spannering.  Rob