OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Reel-Type Mowers Scott Bonnar 45 - 17 inch Twin - Rookie Resto

G'day folks, I recently got bit with the SB bug and after a few weeks hunting picked up a nice SB 45 17 inch twin rail and Rover Thoroughbred 14 inch for $150 all up from Gumtree. I am going to leave the Rover as is, for now anyway, and use it whilst I do a full restore on the SB 45. The SB 45 runs well. Details which may be of interest: - Briggs and Stratton engine 2.5hp 80102 0233-01 74071803 - SB 45 mower number 45 03696 model 450520 I'm relatively handy, but haven't worked with on anything like this, so this forum has already been invaluable and I look forward to any expert guidance you care to give over the coming months. I have taken some photos and would be grateful if your expert eyes see anything I should be aware of upfront. I'm aware the spark plug isn't the right one. I note the forum advice about the inevitability of the twin rails cracking if they haven't already, should I just factor in a pre-emptive reinforcement repair as part of the restore? Other than a sharpen of the reel and bed knife, is there any parts I should replace (including engine parts) as part of the restore on the presumption they haven't been replaced at all since ~1974 and they will be worn out or at the end of their useful life? Is there any rookie errors I should be aware of in disassembling everything, which will make my life harder than it needs to be?

Hi sh2006,

Welcome aboard the Scott Bonnar train. You're certainly correct in saying the bug has bitten because it bites hard and injects a passion that's hard to revert.

You've got one of the most unique Scotty's there that was made back in around 1975 when they painted the chain cases and handle bar shields in that challenging black and also came out with a decal that to this day hasn't been reproduced as far as I know and that's the one with the red outline which was run for about a year before it was scrapped and replaced with the black and white unit.

Now considering the age of it I would check out the clutch thoroughly and see if there's any left to right movement as it's slowly rotated with the pull starter.

Let me know how that goes and we'll move on from there.

Cheers,
.

Righto BB,

I had a look and couldn't see much left to right play. When I push/pull it there seems to be less than 1mm of movement from the engine. I tried to film what it looks like with the help of a small apprentice. Disregard the fact the shaft doesn't spin when I engage the clutch, I have since re-checked and I simply didn't push the lever into place properly:

Hi,

The clutch seems to be pretty much within specs even though its the original unit.

I would say that your rails should be ok without any stress fractures as this is always caused by a flogged out clutch.

From here on in I anticipate this to be a straight forward cosmetic restoration.


Cheers,
BB.

Gurus,

I removed the clutch half from the motor tonight and noticed pitting within it. The pitting appears quite deep and runs around the entire section at that part of the clutch.

Would would have caused this pitting, how concerned should I be, and is it terminal for this part?

Cheers,

SH

Can you please supply me with photos of the Engines PTO shaft and also the transfer shaft on which the clutch cone slides back and forth.

Cheers,
BB.

So here are some pictures of the PTO and clutch shafts, rotated through 90 degrees each photo. To my rookie eye I can't see anything obvious on them that would have caused the pitting?

So today I finally got the SB fully stripped down to just the chassis. When I took the ratchet box out of one of the rear rollers, I noticed that two of the arms on it were cracked right through (see pics). Can this be repaired, or is the integrity of the ratchet box compromised and I need to purchase a new one?

Hi Sh2006,

Wow your machine has certainly copped a bit of abuse over the years, rest assured that cast iron can be successfully welded and have it's integrity back in tow. I guess it's getting someone with the ability to do it.

As far as that clutch body wear is concerned I'm a tad skeptical about it. The transfer shaft does show signs of unusual wear but really it shouldn't protrude in that far.

Personally I would replace that clutch half as its an early diecast unit of which they weren't that good compared to the cast iron units.

The is a chap in WA that is now re-sleeving them but I'm not convinced that this is the way to go as you lose the key steel on the PTO shaft and thus you really have to pin the clutch body really hard into the PTO shaft which always makes it hard for later removal as the shaft is damaged by this practice.

I'm going to have a look at a parts machine I've got and look at this shaft protrusion issue.

Cheers,
BB,

Hi Sh2006,

Well I've just had a look at one of the wrecks I have on hand and it confirms what I thought all along, the transfer shaft does not protrude into the casting as I thought and as such I just can't work out how that scoring has occurred when really that's where the PTO shaft from the engine is situated.

Regardless I would purchase another clutch body as they do have a use by date when they are in service for a length of time.

Cheers,
BB.

Thanks BB, I appreciate it.

I'm about to tear down the B&S next. It runs OK, but is there any parts it would be prudent to replace given its age ('74) whilst I have it stripped?

Cheers,

SH

Hi Sh2006,

If its running ok don't mess too much with it. I'd only change carby to tank gasket and also carby manifold to engine gasket. The rest is just thorough cleaning and prep work for painting in International Orange.


Cheers,
BB.