OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers SB45 Restoration project

Hi again,

I have just finished speaking to the guy at the service centre and his opinion is that I should put a new motor on it as well as a new cutter clutch. It seems that the mower has been used in it's current state and as such, damage has been caused to the clutch and drive shaft. The clutch and shaft can can be turned by hand about 20-30mm without the engine turning and apparently it shouldn't be like this. He says the key on the shaft is damage and that is why it can turn.

So, assuming that I would like to keep this motor, how hard is it to replace the clutch and drive shaft myself?

Also, worth noting is the fact that the service guy believes that the motor is not a 3HP built in 1981 but is actually an older 2.5HP motor. He thinks that at some point the crank case cover has been replaced with a newer unit hence the 3HP badging and model codes. The reason he believes this is that it looks like the engine has been painted black at some point as you can see the old orange colour in places where the black has scratched off. Is this likely to be the case? Is there any way to tell for sure? If it is a 2.5HP is it worth keeping or would it be better to replace with a more powerful unit?

Please let me know if you need photos to determine the state of the clutch or the real identity of the mower.

Steve

Let's start with what has gone wrong. The mower has been run with the front chassis rail broken in two across the front right engine mount, resulting in the engine thrashing about, which would maltreat the crankshaft and clutch in particular, but also the self-aligning bearing in the side plate behind the drive sprocket. If the engine side of the clutch can rotate without the crankshaft rotating, either the key is sheared or missing, or the keyway has torn out of the crankshaft or clutch. (It's also possible the crankshaft has snapped off inside the clutch.) Let's hope it's either a sheared key or the engine-side clutch-half has a torn keyway, because then there might be no damage to the engine, and the clutch half would probably be trashed anyway from the flogging it has suffered. If it is the crankshaft that has the keyway damage or is broken off, you need to replace the crankshaft with a second-hand one, or replace the engine. It is also possible the crankshaft has suffered the beginning of a fatigue failure at the step that coincides with the crankcase cover oil seal: it was being treated abominably when it was being run by the previous owner continuously with that broken rail.

The engine identification numbers are stamped on the engine's cooling air cowl. If someone has fitted a cowl from some other Briggs and Stratton engine, then the information it provides will not apply to the engine it is now on. One way to tell would be to scrape some paint off in an inconspicuous location on the crankcase. If it has orange underneath, the machine has been falsified, probably deliberately, by a previous owner, and the engine is older than the cowl. If that is the case its power output is unclear, but if it is an 8 cubic inch orange engine it would be 2.5 HP. If it is a 60102 rather than a 80202 it would be 2.0 HP. (I think that cowl fits both 60102 and 80202 engines, though I'm not completely sure it fits a 60102). Nobody has posted whether that is a 20" mower or a 17". If it is a 20", it needs 3 HP. As I recall the 17" was in production for quite a while with 2.5 HP, and the 14" originally had 2 HP, but Deejay can put us right on that.

I suggest that the first thing you need to do is the paint-scraping test to find whether the engine has been falsified with the wrong cowl and paint colour, and the second thing is to unbolt the engine, split the clutch, then remove the engine side of the clutch from the crankshaft, so you can inspect the keyway in both the crankshaft and the clutch.

Hi Steve

Where abouts in Perth are you located?

I have found High Wycomb Mowers to be very compedative on there spare parts. Plus you can get parts from outdoor king.

Jarrad

The mower is a 20" and the motor has orange paint under the black.

What you are saying is that the 3.0HP never came from the factory in orange so this must then be a 2 or 2.5HP motor, is that correct?

That being the case and because it is a 20" mower then I guess my best option is to source another motor. What are the general opinions in this regard? ie. new or secondhand, what brand and power output?

I hope to remove the motor this weekend and will post photos of the clutch assembly and drive shaft when it is removed.

Jarrad, I live in Byford (Just south of Armadale). I will keep High Wycombe in mind when I am searching for parts.

Steve

Steve, I am located in Pinjarra, just south of you. If you get stuck with the welding / repairs of the chassis let me know. Got the gear here to easily do that job.

As for the engine, have a look on Ebay. New Briggs engines are not that badly priced. I have considered this for my mower, for when my old Briggs dies. However because of the different shape to the newer engine, you need to modify the handle bars with a spacer between the bottom of the handle bars and the chassis. As the newer engine will hit the handle bars.

I would have a crack at getting the old engine up and going first, unless the output shaft as mentioned before is badly damaged.

Jarrad

Steve, the engine being of unknown but greater age than expected, has to be considered in combination with the mower being painted red. As far as I know, only the Rover 45s were red, the Scott Bonnar ones were green. We have to consider the possibility that rather than being a Rover 45 retrofitted with an engine older than the mower, we could have a Scott Bonnar mower repainted to disguise it as a Rover. That does not seem to be an unusual thing to happen. However note that most collectors seem to prefer the SB mowers to the Rovers: the main feature of the Rovers that people seem to have liked is the colour, not the build quality.

I think you need to find out whether the mower is a Rover or a disguised SB. Deejay can ask you some questions that will make it clear which it is. Beyond that, fixing the broken chassis problem is fairly difficult, because the chances are the whole frame has twisted like a corkscrew, and restoring it to perfect alignment will now be difficult. Arc welding alone will cause a fair amount of distortion - I understand the SB mowers were spot welded rather than arc welded, which made it possible for them to leave the factory with straight frames. I don't know how the Rovers were welded. The issue is that SB, and Rover, used the soleplate (the casting that holds the bedknife) as the primary alignment reference when assembling the mower. It was clamped in a large jig, the soleplate was mounted, and the frame was spot-welded while in the jig. Yours now probably (almost inevitably in fact) has one sideplate rotated relative to the other, with only the soleplate's torsional rigidity limiting how far out of alignment it is. This matters for a couple of reasons. One is that a twisted soleplate is likely to give a poor fit to the reel. The other is that unfortunately SB/Rover did not provide a way to re-align the front roller to the soleplate once the original alignment, provided by the assembly jig, has been lost. There is an alignment adjustment for the rear roller, but not the front one.

Deejay recommended that you strip the mower to the basic frame and have it aligned and repaired by a tradesman welder with proper facilities. I agree with him. The problem is to duplicate the SB assembly jig, and then arc weld the frame without distorting it. I would not like to attempt either task myself.

Hi Steve and Grumpy, I tend to believe that this machine is a 20" Rover for 2 reasons...it has a 2 piece rear roller where the SB had a 3 piece segmented unit and all SB 20" machines had an 8 blade cylinder reel; this is a 6 blader. Can we please have a pic of the ID plate that should be affixed to the rear rail and state the Model Number and Serial Number of the machine. This will confirm it as a Rover.

Re the engine, my Scotty 17" 45 had an orange 3HP Briggs fitted to it as new.
Steve's engine may be original because Rover may have inherited a stock of 3HP engines painted orange and black was their choice and well as the solid red and bright green that they used for the chassis. This engine could have been painted black at the Rover factory and the decals replaced at the same time.

The one thing that has me tossed is the deep fuel tank on this engine. In fact, twice as deep as mine. Why? I don't have a clue....maybe this engine was originally intended for a pump?? I guess it will remain a mystery.

Steve, both grumpy and I have given you advice on how to restore this machine to good serviceable condition using best workshop practice....I just hope the person at your local dealership (who will charge you big $$$) will do the same.
Please let us know how you get on.

And so the mystery deepens......

On closer inspection of the chassis it seems that this mower was originally green. Also, it looks like to cowl and motor were both orange at some point. Were they producing orange motors as late as 81?

Another interesting point is that the engine codes seem to be in a different position on the cowl than where the diagrams posted earlier say they should be.

Unfortunately, there is no ID plate. I assume it was removed when the chassis was painted red.

So what does all this mean? Maybe it is a Scott Bonnar with a newer engine cowl. But what about the 2 piece roller?

Here are some photos showing what I have found.

Well that settles it Steve, that hammertone green that you have discovered and lack of the ID plate confirms that it is a Scott Bonnar and is a late one at that....One of our members deviosi has had a lot to do with 20" Scotties and can answer questions on the rear roller set-up.
I have a funny feeling that I read one of his posts that said late model 20" Scotties had a 2 piece roller... you may like to check his profile and send him an e-mail or PM, I'm sure he will advise you.
Re: the 6 blade reel...maybe that was an option at purchase....but I know they were standard with 8 blades....orange painted reel.
That motor or at least the cowling I would say is bogus as well....Rover had taken over by 1981.
What is actually is, is now a mystery.All is not lost....you've now got a genuine late model Scotty 45.
Depending on how far you wish to go with the restore....a new Honda engine...or second hand goodie, might be the way to go.

Has it got its catcher?

It isn't surprising that the mower is an SB45 dressed up as a Rover 45, and that is no bad thing - the SBs were more collectible and are reputedly better-built. There may be cause to be irritated with the person who dressed this particular piece of mutton as lamb, because in the process he or she seems to have thrown away the mower's model identification plate and the Briggs engine's original cowl. Its collectibility is severely damaged by those events, plus there is now probably no way to work out when it was built.

The main immediate issues are getting the broken frame rail, and its downstream effects, fixed. Probably most dealers would say that there is no problem either with welding up the broken rail or arc welding in a replacement rail. If it was carefully done the resulting misalignment of the chassis might only amount to a few millimetres when measured with the usual alignment checking tool, and that might be barely visible on the mowed lawn it produced. There is some practical merit in that argument, but we are talking about a collectible mower here, and Outdoorking generally recommends good workshop practice. Good workshop practice would repair the mower to something close to its original quality when it left the Scott Bonnar factory.

So far as the engine is concerned, we don't know what it is, or whether it was the original one fitted to the mower. The only reason to think it might not be original, is the deep fuel tank. Has anyone seen a genuine SB45 with a deep fuel tank on its Briggs engine? If anyone has, this becomes a non-issue, and you can expect that it is an 80202 as advertised, but not one made in 1981. We also don't know whether the crankshaft has been damaged by the experience of running for an unknown period with a broken frame rail. My view of that is that if the crankshaft keyway isn't damaged, and the crankshaft extension (Power Take-Off in Briggs-speak) runs true, there is no point in worrying about it, it will probably last longer than I will, perhaps much longer.

Not to start an arguement, but I aggree with Grumpy. However at the end of the day it really comes down to what you want to use the mower for and how far you want to go with the restoration.

I myself have a Scott Bonnar 45 painted up in Rover Red, with a few late model Rover bits including the catcher. But at the end of the day I wanted a reliable reel mower that presents well. The purist will soon tell that it is not a Rover 45

As for repairs to your chassis, I certainly would not be Arc welding it, as the inherant distortion or risk of poor penetration could be future problems. If it was mine I would be having a go at repairing that Rail, but leave the roller and sold plate attached to chassis while welding to gain as much rigidity in the chassis whilst welding it. Clamp a scrap piece of solid material to the rail, that is the same length to hold it straight. Then I would fit a piece on the underside of the old rail. The piece should not be any thicker than twice the thickness of the rail as you will not get a strong weld and require to much heat, causing distortion. The piece will only need to be stitch welded, but allow time for the rail to cool between each weld and work from the middle out. Tou can then weld the crack on the outside and grind it back.

Overall you may get a slight twist on the chassis and you would have to way up if this is worth the risk, or how critical you will be on the finish the mower gives. I have seen new 17 inch Rover Chassis on Turf Machinery website, but dont know if you will get a 20 inch. Plus the chance of getting one 2nd hand in WA is quite slim.

My Briggs has a deep tank and was the original Orange engine on my 45.

Thanks for that Jarrad. For a use-it-but-don't-collect-it mower, which is probably all this one can ever be now that its authenticity is lost, repairing the rail can probably be done with only modest distortion using the technique you have described. The key seems to be in four points: start from the middle, weld less than 1/4" in each stitch, let it cool properly between stitches, and make each successive stitch at a point diagonally opposite from the previous one, on the plate you are welding in. When I was a kid a good tradesman welder boxed in my car chassis that way to increase its torsional rigidity. Laying it on flat concrete before and after, it only twisted about 1.5" on a diagonal across the complete chassis. However it was a long job, doing it that way. (On that vastly larger car chassis, he used 1" long stitches, and left 1" gaps between them, to minimise heat input.) In the case of the mower frame you can watch the twist after each stitch, and use feeler gauges to measure it under the corners of the frame on a flat bed plate, if you want to get the bad news progressively instead of all at once at the end.

Thank you for the information that you have a deep-tank original engine on your SB45. That seems to make it highly probable that Steve's SB45 still has its original engine, and is a fairly original mower under its disguise.

Okay, now we have it's identity sorted (well sort of!), I think I have decided what to do.

Given the mowers lack of identifying features and therefore lack of collectability I will restore the mower to a useable and presentable condition without worrying about authenticity.

As I don't know how well it will mow because of the twisted chassis I don't want to spend too much money on it so this is what I plan:

1) Strip down to chassis but leave soleplate and roller attached and repair broken rail as per Jarrad's suggestion. Jarrad, you mentioned you have the equipment and you seem to know what you're talking about so would you be keen to have a go at this for me?

2) While the engine is off, determine the condition of crankshaft and keyway etc.... and therefore determine the servicability of the engine. If it seems okay then I will give the fuel tank and carby a good clean and service and see how it runs. If not I will source a new engine, probably a 3.5HP B&S from eBay for $275.

3) When the chassis is repaired I will have the blades sharpened and then put it all back together with a new clutch assembly.

4) At this point I will see how well it cuts. If it cuts well, I will strip it back down and sand/prime and paint and then replace all sprockets, chains and whatever else needs replacing. I will then have a functional mower that should last for years. If on the other hand the cut is no good due to the twist in the chassis, I will then have to see what else can be done to sort out the twist.

What do you think? I know it's not ideal, but considering the current condition and missing ID I think this is probably the wisest think to do.

Steve

It sounds like a viable program Steve, but you can assess the amount of chassis twist with a simple gauge before you put the mechanical parts back on. If the front and rear rollers are on, and the soleplate is in position, you can measure how far out of true the frame is with a piece of half inch square steel with a screw through it. You can get details in this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=33428#Post33428

Provided the twist is small (say less than 3 mm with the alignment tester) the mower should perform adequately for almost anyone but a greenskeeper. So, you will know whether it will be satisfactory or not before you even reassemble it. Then if the frame warrants it, assemble the mower. If the crankshaft seems OK, tune the engine.

I wouldn't rush into a new Briggs engine, if the original one is sound. The new one will probably be Chinese, and the quality outcome is unclear at this point. The first few years' production seems to have been erratic, and we don't have enough recent data to estimate whether they have their act together yet. Hence the old 80202 looks like a preferable choice.

Well it looks like a good plan of attack has been reached that may have a satisfactory outcome, Steve.
Please post some pics as you go along as this would be good for the OutdoorKing archives. It may help another member with a rail fracture on their Model 45.

No probs Steve

My mobile number in in my profile. Give me a ring when you are ready.

Jarrad

Thanks Jarrad, I'll get in contact when I'm ready see what we can sort out.

Deejay, yes it does have a catcher.

Jarrad and Steve, if you can take a series of pics as you make the repair, they would make an excellent extension of this thread for the Outdoorking reel mower archive. We've had reports of broken rails on SB45s before (it is a common failure) but have never documented a repair process.

Hi grumpy, please read my post above....

Oh well, what can you expect before 8 a.m. on a Saturday? At least we both asked for exactly the same thing.

I'm hoping we can document the clamping (do you use a long lateral clamp across the side plates to close up the gap in the broken rail?), the way the reinforcing plate fits (welding room around the outside, clear of the flanges?), and several progress shots of the stitch-welding, showing the pattern of welds, and the distance between welds (usually equal amounts of weld and space, but let's see Jarrad's approach). Then some pics of the alignment check with the gauge would be good. If it were me I think I'd do the welding with the front and rear rollers in place, and I'd check the alignment after the first pair of stitches, then every few stitches afterward. If the process is done correctly you should find it is pulling itself back straight whenever the pattern of completed stitches is symmetrical. If I'm doing it, on the other hand, it's out with the angle grinder after the first couple of stitches because it isn't precisely correct.