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

G'day All,

Acquired a 17" SB45 that I would like to give a bit of TLC. Unfortunately, I have no idea exactly how to go about this, so I' asking for your help!

Please check out the photos below, as Im not even sure of the model or engine type.

Any thoughts or information you can provide would be very much appreciated.

Cheers

Looks to be in reasonable condition. The chassis would clean up nice with a fresh coat of paints. In my opinion the SB45 are a great mower and I have learned heaps about them in the last 12 months while re-building mine slowly.

The engine looks to be off a Finsbury water pump, but dont let that worry you.

I would cable tie that clutch cable away from the mower as a precaution.

What are your intentions, does it run at the moment. There is a good video on this site of hew to remove the reel and bedknife so you can send them off to be sharpened, but are they OK at the moment?

Hi Salty, welcome to Outdoorking. If you give us the long string of numbers stamped on the cooling air cowl of that Briggs and Stratton engine, we can tell you what model it is and when it was made. As Jarrad said, it does not appear to be the original engine for that mower, but many - in fact I think most - Scott Bonnar 45 mowers had Briggs and Stratton engines, and we should be able to tell you if you have a correct type that was used as original equipment. Our SB guru, Deejay, may be able to estimate very approximately when your mower was made, and we can tell you when your engine was made too.

As far as I can tell from the pictures your mower seems to be in sound general condition. Please tell us whether the two clutches work, and whether the engine runs properly. If there are faults, we can talk about how to overcome them.

Hi Salty, and a warm welcome to the forum. It's great to have another Scott Bonnar owner on board.
Now to your machine...you seem to have a "bitsa"...that is a machine made up from parts from other machines. No probs here....we can restore it to original specs easily. All parts are available.
Lets go through it....
The chassis appears to be a late (1970's) model 17" Model 45 in reasonable condition as Jarrad has pointed out.
The Briggs should be a 3HP and does not appear to be the original engine. They were orange in colour.

Here are my observations:
1. the catcher is genuine and in great condition but from an early model 45 (the early SB logo is the give-away)
The correct one should be the same as this:

A complete set of decals are available on eBay.

2. The 3 screws that join the 2 halves of the cutter clutch (next to the engine) are not the countersunk type as the are supposed to be, also the are the wrong length...this may upset the balance and cause vibration. the nuts should also be nylocks.

3.You are missing both the catcher rubber support blocks on both chassis rails.

4. You are missing the red plastic button (dust cover) that is located in the centre of the front roller height adjuster.

5. You are missing one of the black plastic knobs for the grass deflector adjustment.

6. The cylinder reel appears to be in good nick but will benefit from a spin-grind; as will the bottom blade. (We will go into that more later.)

We need to see a pic of the inside of the chain case to see the condition of the chains and sprockets....

It is also missing its original Scotty ID Plate...this is unusual....

We can help you with advice for the resto as you go along....with a paint job and some TLC, she will look grand and give you hours of mowing pleasure.

hey all,

Thanks for the informative and prompt replies.

jared - it may run, but I can't get it to. As for the cable, well I intend to pull the whole thing apart and clean it up first, but I will tie it out of the way when it goes back together. Do you have a link? for where that vid you mentioned is?

grumpy - See following post for engine details. As mentioned, I can't get it to run, so I'm not sure if the clutches work properly....sorry.

Deejay - please check out the photos below of the condition of the chains and sprockets as requested.

So, what to do first.....As much as I would like to 'fully' restore it, I don't have my heart set on keeping the current engine. I think I would prefer to replace the existing one with either: a new one, or one that would have been on it originally. If anything, perhaps I'm leaning towards a 'new' engine for reliability/parts etc., but am happy to be swayed either way.

I'm thinking that I probably need to pull the whole thing apart and have each individual component cleaned up (sand-blasted?) and painted?

Thoughts?

Correction to my last post - I found the engine numbers:

Model 80232
Type 0913-01
Code 79022203

So, the Briggs and Stratton engine is 130 cc, an example of their first design generation, with a horizontal crankshaft, a Pulsa-Jet carburetor, a flange-mounting built-in reduction gear, ball main bearings, and a rewind starter. It obviously does not have a reduction gear now, so that has presumably been removed. That engine is almost identical to the correct engine for your mower, which was an 80202: it had plain main bearings and no reduction gear. Both 80232 and 80202 are 3 hp. That was the best original engine ever fitted to the SB45 as far as I am aware. Your engine was made on 22 February, 1979, which means it is probably much the same age as your mower. If you get rid of the Finsbury tag and paint it orange, it will be pretty much indistinguishable from the original engine.

I suggest you undertake a diagnostic program to find out why it doesn't start, use it a bit, then decide whether you like it.

Before you try to start the engine, check the oil level in the sump. It should be full up to the top of the filler plug's thread. The engine has a manual choke, and will not start unless you use it. I hope you haven't been using it up until now, or you have probably flooded it and made it more difficult to start. The standard starting technique is to set the speed control for maximum, close the choke (pull it straight out, as far as possible, which is about 1/4" or so), pull the starter cord about twice, and if nothing is wrong, it will chug a couple of times and stop. You then push the choke right in (which unchokes it completely) and pull the starter again. If nothing is wrong it will then start, almost certainly on that first pull, and run sweetly until it runs out of fuel or you move the speed control to the stop position.

If you do that and it doesn't start, report back on what it actually did, and we can go on from there.

Hi again Salty...the video that Jarrad means is the one that Joe Carroll and myself put together to show the removal of the cylinder reel and soleplate complete with the bed-knife blade before going to the engineer for sharpening. Click HERE
We have also just completed another vid for the replacement and clearance adjustment which is contained at the top of this forum (both posts are sticky).

Thanks for the pics...unfortunately they don't show the exact area we need to look at....my fault ..I didn't explain what I wanted...can you please take some of the sprocket where it isn't covered by the chain...I need to see the condition of the teeth (ie.) whether they are pointed or not.
I did see in the pics that the grass deflector has been repaired by the previous tenant... we may be able to source a second hand one for you.
As to where to start...I think that you should consider how far you wish to go with the restoration and how many $$ you wish to spend.
If your machine was mine I would:

1. Remove the 3 bolts that secure the cutter clutch...remove the throttle assembly from the upper handle-bar then the 4 bolts that secure the engine to the chassis and remove the engine and set aside.

2. Using the video as a guide ...remove the reel and soleplate complete with the bed-knife.

3. Decide on a colour scheme for the engine, chassis and cylinder reel. Obtain a set of decals and stickers for the Briggs 3HP and the late model Scotty decals including the handlebar center cover.

4. Take the cylinder reel to the sand or grit blasters and then prime and paint it (or powder-coat it, if you wish....then take it, with the soleplate complete to the engineer for sharpening...(there is a topic on this subject in this forum) Also at this time purchase some new reel bearings.(this will ensure correct clearance when you replace and adjust)

5. Decide whether to strip the chassis completely to sand blast it, or to sand, prime and paint as is; masking off where necessary, including refinishing the chain case cover, grass catcher and handlebar center cover.

6. Grumpy, our resident Briggs guru, will help you decide how to approach the engine in detail then repaint in your chosen colour.

7. Clean and polish all the bright-work.

8. the clutch and throttle cables are secured by clips...obtained from a bicycle shop.

grumpy - thanks for the info. I tried to start it using your described method, but no luck. It didn't even really sound like it wanted to start....maybe an electical issue. Not that it matters at this stage though, as I intend to give it a a full going over. What is the best way to go about reconditioning it? Are parts easy to come across?

Deejay - check out the photos of the sprockets below, how do they look? I like the sound of your recommended course of action. So I intend to do just that. I'll deal with the chasis and the reel first, and the engine last. I'll post the progress as I go so that it may be of assistance to anyone doing something similar in the future. I think I would like to replace the grass deflector - otherwise it will just annoy me looking at it in the future. How/Where do I get parts from?

I did read the other thread regarding colours but I couldn't find the septone brunswick green on their website....is it still available? Is there a better colour?

Enjoyed the vids on youtube as well...very informative and well done.

Regards

Salty

There are basically three elements involved in getting a piston engine to run: spark, fuel, and compression. You need to check all three.

First, to check spark, you remove the spark plug, attach the plug lead to it, and lay or clamp it onto an unpainted metal part of the engine. Usually a cylinder head cooling fin is good. Set the speed control in the starting position, and pull the starter cord while watching the spark plug electrodes. Expect to see a blue spark between them, once each second revolution of the engine. If there is no spark, there will be no action from the engine. Tell us about it and we'll discuss how to find and fix that fault.

Second, if you have spark, put just one spoonful of petrol into the engine through the spark plug hole, then install and connect the spark plug, set the speed control for start, do not operate the choke (leave it pushed in, which is open) and pull the starter a couple of times. Expect the engine to start and run for a couple of seconds then stop. If it does, your spark and compression are not the issue, the problem is no fuel is getting into your intake pipe from the carburetor. Report this to us, and we'll talk about carburetor diagnostics.

Third, if the engine has spark, but won't run when you provide it with fuel, you'll have to check the compression. This is usually done with that Briggs engine by disconnecting the spark plug wire, and turning the clutch housing backwards by hand. You should find at one point it becomes harder to turn. Rotate it forward a half turn, then spin it backwards with your fingers, so it bumps against that point of resistance. It should bounce off that compression pressure, and rotate forward. If it does that, chances are it has enough compression to start and run.

Please report the results of these tests, and we'll try to figure out what the results mean, and what to do next.

Incidentally, both of your outer chain's sprockets are worn, the smaller one fairly badly worn, so the chain is probably worn out (that is what causes the sprocket wear).

Hi again Salty, Re: the sprockets, I agree with grumpy, the front sprocket needs replacing, you may like to check the upper one on the cutter clutch shaft as usually if the cutter sprocket is worn both should be replaced as well as the chain.
All parts are available from the OutdoorKing online store, if they are not listed; send Bruce a PM and he will source them for you.

Re: Septone...I do know some colours are no longer available....try Bunnings, they have a range of hammer finishes or maybe try an automotive paint supplier or Supercheap Auto.
Auto One may be able to help you as well. Unfortunately the original Scotty hammertone formula has gone into the ether....
Thanks for your kind comments on the videos...I am glad they may be of help.

Well success! Did as directed Grumpy, and after finding a spark, did the next step and it started after about 4 pulls. I stopped it after about 20 secs. I then tried to restart it (no choke) but no luck.

I then repeated the step of adding fuel straight into the cylinder, started it up (about 5 pulls) and just let it run, which it was quite happy to do.

The clutch does not seem to disengage the cutting reel to well though. At low speeds it sometimes stops spinning, but at higher revs it engages the reel regardless of the clutch position.

I didn't give it a full work out, but the roller clutch does work, a bit faster than I would care to mow at though. Anyway, I think from here I'll start to pull it down, sandblast and paint the frame, replace what needs replacing, and have the reel sharpened etc.

Ill post updates as things progress.

Salty

Thanks for the report, Salty. Please remember, do not prime the cylinder as a regular method of starting that engine - it will ruin it over time. It appears the starting problem is your choking technique. We can talk about that if you like, or you may want to pull the rest of the machine to pieces right away. It does sound as if your engine will be quite functional with a simple tune-up.

It sounds as if your cutter clutch is not freeing properly, which may mean it needs to be adjusted. Alternatively it may have an internal fault, such as the cork facing inside the clutch has been damaged. This is not difficult to fix.

Hi all,

I new to the forum, just stumbled across it while looking for info regarding restoring a mower that I have acquired.

The mower I have looks very similar to Salty's but is branded as a Rover 45.
I don't have pics at the moment but I think it could be identical apart from the colour (mine is red) and badging. Even the motor looks the same (except mine is black).

My engine numbers are:
Model: 80202
Type: 0879-01
Code: 81110

Again, mine is not running at the moment. It has spark and will run for a few seconds if I put some petrol directly into the carby. I have not tried puting petrol into the spark plug hole. Is this likely have a different result than putting it into the carby?

The other obvious repair that I need to do is fix the front engine mount bracket as it has snapped in the middle. Is this a common repair? Should I just weld it back together or replace it or something else?

Also, I know that when it was last used (about 8 years ago) it wasn't cutting straight. ie. it was cutting lower on one side than the other. Would this be fixed by having the reel and bedknife sharpened?

Any information you can provide would be greatly appreciated as this is the first time that I have worked on anything like this.

Steve

Hi Steve and a warm welcome to the forum. Its always great to have another Model 45 owner on board.

Grumpy (our resident Briggs and Stratton guru) will give you advice on your engine probs and can date the engine for you.
Your machine is virtually the same as the Scott Bonnar Model 45 (late model) and all spare parts are still available.
If you can take some pics of the machine from different angles and a couple of the chain case (cover removed) and of the exposed areas of the sprockets (ie. not covered by the chain, so as we can see the condition of the sprockets. Also a pic of the cylinder reel and the bottom knife blade (also called 'the bedknife') so as we can assess the condition.

You mention that it is cutting lower on one side; this could be an alignment problem...see the post that we have just been discussing...Click HERE

Re: the cracked chassis rail...it needs to be welded or preferably replaced...it is just steel 'C' channel and could easily prefabricated and welded back into position. You would need to remove the engine to do so, and we can step you through the procedure when the time comes.

When we see the pics of the cylinder reel and bedknife we will tell you if it needs sharpening...there is a video in the Scott Bonnar topic on how to remove/replace the reel.
Once again, Steve,

Hi Steve, I think there are 3 digits missing from the code you have posted. If you supply the complete code we should be able to tell you your engine's date of manufacture. It is an 8 cubic inch (130 cc) first design generation engine with a horizontal crankshaft, a Pulsa-Jet carburetor, plain main bearings, and a recoil starter.

The fact that it will start if primed but not otherwise, means that the carburetor is not functioning. Fixing this will involve removing the carburetor and fuel tank, still connected together, from the engine, then separating them, cleaning both, and reinstalling.

Here are the B&S instructions for doing the job:
http://recoveryvehicles.tpub.com/TM-5-4240-501-14P/css/TM-5-4240-501-14P_108.htm

However I suggest that you do not undertake a full overhaul of the carburetor at this stage. There are a couple of things that are particularly likely to be the problem, and they are relatively easily checked. If you begin by looking into the fuel tank, you may find there is a lot of garbage on the bottom of it: old grass, and other things that have found their way into the tank during refuelling operations. If you separate the tank from the carburetor, you can then clean out the tank, and inspect the fuel filter screen at the bottom of the longer of the two tubes extending down from the bottom of the carburetor. You may find the fine mesh is crudded up and blocked. Follow the manual's instructions for removing the tube (not the mesh - it has to be cleaned in situ) and cleaning the mesh. (Figure 47). Then clean the metering holes and inspect the needle valve (Figure 50), and check the fuel pump diaphragm (Figure 51). If the diaphragm passes inspection, put the carburetor back together, reattach it to the fuel tank, and put the assembly back on the engine.

By removing the needle valve (to get access to the metering holes) you have lost the mixture adjustment, so when you reinstall it in the carburetor use the "standard" adjustment of 1.5 turns anticlockwise from fully clockwise. Be very gentle when you turn it fully clockwise - just turn it until you feel the presence of the seat, don't "tighten it up". Carburetor tuning instructions are on page 111 (you started on page 108; just keep using the "next" button at the top of the page).

Please come back to us with any questions you have. Feel free to clean out more of the carburetor if you are confident to follow the instructions in the on-line manual - I do not know what experience you have in this kind of work, so I've just covered the most likely sources of your blockage.

Thanks for the quick responses guys!
It appears that I had missed a few numbers from the engine ID the correct number are:

Model: 80202
Type: 0879 01
Code: 81110403

I have included some pics below, please let me know what you think.
It appears to be missing the little plastic part at the end of clutch assembly (on the frame side not engine side) which is strange.

My main concern at this stage is getting the engine running so I think that I will try and remove and clean the carby and fuel tank before anything else. I assume that I will need some gaskets to do this, is that correct?

As I said, I have had it run for a few seconds by putting petrol directly into the carby. Unfortunately I have just realised that there is no oil in the motor so I hope I haven't done any damage by doing this.

Considering there is no oil in the motor and no fuel in the tank, what should it sound like when I pull the starter? I pulled the starter a couple of times tonight and there seems to be a loud metal knocking noise of some sort. I also noticed that the reel turns a bit when I hear this knocking noise. Any ideas?

I also noticed that the blades on the reel are backwards compared to Salty's, is this an issue or doesn't it matter.

Thanks again,
Steve

First, your engine was made on 4 November, 1981. If it was the original engine, your mower would have been made about 6 to 12 months later.

When you clean your tank and carburetor, you may need a new intake pipe flange gasket for where it connects to the engine block, but you may find the old one is undamaged. Similarly you may find you need a new diaphragm for the fuel pump, or you may not. It may be best to wait and see whether you need any parts.

I hope you only ran the engine for a few seconds without oil. If so you may not have done any harm, since there would have been oil film still on the bearings and piston rings. However, don't do it again. Engines with aluminium cylinder bores and aluminium connecting rods with no separate big-end bearing, do not take kindly to that sort of thing.

You should expect a few odd clunks from the engine when you pull it over with the starter. There is a bit of a clack from each tappet, for example. I'd have to hear it to comment on whether there is anything inside the engine to worry about, but there probably isn't. I'll leave it to Deejay to comment on the mower parts and the clutch.

FYI, your three smallest sprockets all look as if their best years are behind them, especially the two on the chain closer to the side-plate. It appears you will need to replace both of those, plus their chain.

Hi again Steve, and thank you for posting the pics.

From the pics I have made the following observations:
1. Your machine is a 20" Rover 45 most likely manufactured in early 1982
2. I agree with grumpy that the cutter sprocket and engine shaft sprocket need replacing as well as the primary chain.
3. The nut on the engine shaft sprocket is missing.
4. The primary plastic clutch pad is missing and must be replaced or damage will result.
5. The cylinder reel has not been sharpened in a while and has plenty of life left in it.
It will require sharpening as well as the bed-knife blade.
6. It is missing the catcher support rubber on the left hand side (looking from the front).
7. The front rail is seriously cracked and must be replaced before the engine is run. This will be causing the clutch to run out of alignment and could coause serious damage to the clutch components.

Steve, the engine problems can be addressed when the frame probs have been fixed.
Here is the plan of attack that I would use if it were my machine...

Unfortunately, the crack in the front rail will require it to be removed from the machine, a new rail fabricated and welded in plus the clutch support panel welded in place. To do this and maintain chassis alignment....this work will have to be completed by a tradesman welder that has the expertise and equipment to stop the frame from twisting or warping, thus throwing out the alignment. To do this, the chassis needs to be stripped.

1. Remove the 3 bolts that secure the cutter clutch...remove the throttle assembly from the upper handle-bar then the 4 bolts that secure the engine to the chassis and remove the engine and set aside.

2. Remove the cutter clutch, clutch cone, spring, thrust bearing and Woodruf key.

3. Remove the engine shaft sprocket, bearing housing, bearing and engine shaft and Woodruf key.

4. Using the video (a sticky post in this forum) as a guide ...remove the reel leaving the soleplate complete with the bed-knife. This will help maintain frame integrity.

5. Remove the drive clutch cable, roller clutch and rear rollers.
Leave the front roller and assembly in place for frame integrity.

This seems a lot of work...but not necessarily a bad thing....this will allow you thoroughly inspect the clutch linings of both the cutter clutch and rear roller and replace if necessary.
It will also allow you to inspect the pawls in the rear rollers for wear...as well as the bearings for serviceability. The cylinder reel bearings should be replaced in any case. This will assist in reel to bedknife clearance after sharpening.
Purchase any spare parts you need.

After the rail is replaced, remove the soleplate complete with the bedknife attached and then sand blast the cylinder reel and then prime and paint in the preferred colour...(I had mine powder-coated 'Signal Red').
Now send both the reel and soleplate complete to the engineer for spin-grinding.

While the chassis is bare, it would now be a good time to clean it thoroughly and repaint in your preferred colour scheme, plus clutch parts and engine shaft. Mask off where necessary.

Replace all parts including the engine and grumpy will guide you from there to get it running sweetly. Use the video to replace and adjust the reel clearance.

You now have a fully restored machine that will give you hours of mowing pleasure.

Thanks for your feedback guys.

Deejay, your plan of attack sounds like the way to go.

This morning I decided to drop the mower off at a reputable service centre near me. They will be the ones doing the sharpening when I get to that point. I have asked them to have a look at the mower and give me a list of everything that needs repairing/replacing. They are going to do this for me for $30, I think that is money well spent. When I get it back I will post the list of repair items and get further advice about which things I can tackle myself. (Hopefully everything except the welding).

I asked them about the broken chassis rail and how they would fix that. Their response whas that they usually reweld where it is broken and then weld a strengthening bar inside the C channel. Does this sound like an acceptable way to repair this problem or would you only recommend removal and replacement of the broken rail?

Steve