OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Reel-Type Mowers SB33

The Gumtree addiction has resulted in another purchase. A Scott Bonnar 33 that is pretty original in all respects except for an updated engine. The previous owner bought a new 3hp Briggs and put it on. It is an '05 model that started easy and ran well. I don't know about the rest of the mower yet because I have to get it into the shed and check it over. So far it seems that it was worth the $50 purchase price.

Finally got the chance to look over the mower in a bit more detail. The engine was running a little rough so I checked oil (ok), plug (ok after a clean) and air filter (very blocked but now fully cleaned). What a difference, she starts first pull, idles smoothly and runs smoothly too. I will put in a new air filter but I've sorted out cause of rough running.
Here are a few pics of the drive belt and chains, chain and sprockets look alright but belt will need replacing as it is a little frayed.

It sounds as if the air filter was the culprit. When you acquire a mower, servicing the engine should always be the first order of business. Second job is to service the blades. With a reel mower, third job is to carefully check it all over for loose bits - otherwise they fall off and you run over them, ruining the reel in the process. Just ask Deejay how that goes.

Hi Diablo, and my on a great score there for $50!
The Model 33 was first introduced in 1960 and was manufactured in the Thebarton factory in South Australia.
From what I can see, the machine looks in great condition for its age and the sprockets in good serviceable condition.
I would like to see some pics of the cylinder reel and bedknife blade, to assess their condition for you.

Sorry for my delayed reply Deejay, I've been caught up with work and a few other priorities around the house. I don't have any pics of the reel and bedknife yet but they are certainly in need of attention.

I had done no further work on the mower since the last post until today. I removed the front roller so I could replace the worn out alloy end caps.

The end caps are too far gone so I have picked up plastic replacements. They will certainly make the cut a bit more even when installed.
Next on the list is a carby clean and diaphragm replacement to get the engine starting/running better.
After that it will be replacement of the cutter bearings along with a reel/blade sharpen.

Hi Diablo, it is good to see you back with a good plan for the machine. Our global mod Grumpy is our resident guru on Briggs engines and can assist you with any questions on the engine.
I can help you when you start sorting the cylinder reel.

Hi Diablo, if you post the Model, Type and Code for that engine we can find it in the Briggs literature, which may make it easier to work on and discuss. Please put in a proper air cleaner element before you use it.

Thanks for the offers of help and advice. I had already picked up the parts from my local mower shop the other day and cleaned the carby today. With the clean and fitting of new diaphragm, air filter and spark plug the engine is starting and running much better than before.
The engine details are: 91212 1025 E1 971205FA

The Model tells us it is 9 cubic inches (148 cc), of the second design generation, with a horizontal crankshaft, a Pulsa-Jet carburetor (hence it has a fuel pump, with a diaphragm: the Vacu-Jet version had neither), plain main bearings, and a rewind starter.

I can't find any information on Type 1025, but since you have the parts you need that should not be a problem at present.

The Code tells us your engine was made on 5 December 1997, which as you have observed, is quite a bit more recent than the production of the SB33.

Does the engine blow smoke, either on start-up or when running under load? Does it use oil? You have said that after each repair the engine runs "better", but not that it runs "well". Those Briggs engines normally run quite well - nothing comparable with a Honda or chonda, but it should be very easy to start hot or cold, and it should be quiet and reliable.

The front roller has had the end caps replaced and I also had to make a new shaft because the old one was too worn where the bushes had given out. The only problem is the roller is too tight to move freely. I assume the shaft is supposed to be locked in position when bolted to the frame. Allowing the end caps to support the roller and also rotate around the shaft on the centre hub which acts as a bush. If so the the clearance between the shaft and internal bore of the end cap must be too tight.

Hi Diablo, yes mate, I would have to agree with you there.
Did you check the clearance of the end-cap on your new shaft before you fitted it all together?
I would also consider drilling a small hole on an angle through just the plastic end-cap as close to vertical part of the cap so as to enable oiling with an oil can...this will help the roller to spin freely and also help prevent wear on the shaft.
You could also try loosening the nuts on the shaft a little to see if the roller spins freely.
Please let us know ow you get on.