OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Starting issues SB 45

Hi All,

Been looking through the forum for a while now and figured out I have a SB 45 with a pulsa crab. Thanks for a great resource.

I’ve decided to get the old girl back up running again, so far I’ve replaced the diaphragm, and the gaskets between the carb and tank and carb and engine.
She won’t start, if I remove the air filter and drop in some fuel she’ll start and run fine. If she then switches off she’ll start after 3 or 4 pulls. But cold no chance, once I get her going I put the air filter back on and she carries on going.

Sounds like a choke issue? When I move the lever to start, with the air filter off I can see the piston for the choke move and leave thin slits.

Is there anything else I can check?

These are the model numbers that I found on her:

0879 01 81110303

80202

Thanks in advance
Cheers

Hello Ragnar
A warm welcome from me.

Pulsa-jets should always be serviced with new pump diaphragm and gaskets.
But always check side movement in the butter-fly valve before doing this.

It is a waste of money installing a service kit when the throttle
valve, or carby body, are worn beyond limits.

Hope this helps.
-----------------------------
Jack

Thanks Jack,

It was running ok at last use about a year ago. I'll check the butterfly valve I assume that's the bit in with the diaphram?

Cheers

Hi Ragnar (big fan of Vikings?)

Have you checked that the throttle cable is set up to fully choke the carb?
I had one that was behaving the same way and after adjusting the cable, it took the choke back a tiny bit further and she was away.
Just something to consider?

Em

Thanks EM,

Enjoy the show yes, but that's from a weekend away with some friends and the beard not looking to crack hot by the end of it..

Thanks for the tip I'll give that a go.

Cheers

Thanks for the advice guys, I removed teh carby again and used a metal rule to check if any of the surfaces are warped? (Is that how it's checked?) It seems ok.
I pulled out the diaphram again and had a look at that seems ok, how do I check how much play the butterfly valve should have?

Also adjusted the choke, took the air filter off to check. The choke might open to much now,as there's no longer a small slit when the choke is open. What's the ideal setting?

Thx