Little BSA engine

[AussieIron]

Have this little BSA on a Scott Bonnar mower. Just got it going, and it really does a great clean cut on a lawn. I know a little bit about older engines, but can someone tell me how this "choke" lever (sliding pin), is supposed to work. Push it in and it closes off choke plate,out for open. Just curious because this carby already has choke in usual spot at air cleaner end. Probably an obvious answer, but I dont get it! The pin is where my finger is in one of the photos.

[E27N]

Air cleaner off of another BSA perhaps?

[AussieIron]

Thought of that, might be. I've never had much to do with "newer" engines.- Thanks-Neil.

[cobbadog]

Have you had it apart to see what happens when you move the pin?

Good thinking about it being possibly the wrong air filter.

Love the comment "newer engines"

[AussieIron]

Yeah, had it apart to free up the throttle slide. The rod opens and closes a rotating throttle plate. The more I think about it, maybe the air cleaner is not original. Yeah, I had a little experience with Briggs engines we used to run on our portable gold sluices and pumps, but that's about it. The older stuff is usually easier for me to work out. Just not familiar with them.
It's a slide on carby,so would easy to put a bodgie one on.

[AussieIron]

Had a closer look.The air cleaner has faint villiers transfer on it. Still, BSA and Villiers were combined at one stage I think ?, so carby may be original? Some one will know. I'll try and find I D No on engine tomorrow.

[Scotty 2]

Hello all
Yep. Air cleaner off a Villiers. Probably Mk10 or 12. The fuel tank looks Villiers as well. Have a look on the cap to see if there's a faint Villiers on the cap.
It's an interesting little Power Unit. At first I thought it to be a little 50cc unit but it isn't.
Is the carb original? I don't know why but I seem to remember BSA Power Units with that layout had a droopy bolt on manifold with an air cleaner bolted on the bottom.
A Power Unit with that particular carbi/exhaust layout is a bit unusual for BSA. A lot of the Power Units have the exhaust on the flywheel side and not the output side.
Interesting.
Cheers Scott

[AussieIron]

Scotty, yes have doubts about carb. I reckon Villiers. Also, this is on a Scott Bonnar Aussie mower, so maybe the Villiers carb suited their throttle set up better? Doesn't really matter. Nothing on fuel cap, but tank and bracket look original. Bracket is spot welded to shroud. Found engine No, it's ZARS 90B 1328. So maybe 90cc? Been looking on net, geez they made a lot of models, haven't seen mine yet! There is a Scott Bonnar site, they may know.Thanks for help. Cheers -Neil.