OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers First Timer - with an old SB 45 (i think)

Hi Gents,

I got tired of being charged $45 from my lawn mower guy to mow 70sqm of lawn so I acquired a old Scott Bonnar the other night. The motor runs as I got the guy to start her up etc, however the blades need a good sharpening and alignment.

My plan was to just sharpen her up and possibly de-grease the engine where I can easily remove the parts, change the filter and leave her be, however after coming across this forum I've got a few other ideas (restoration/paint) that I would love to do.

I have never used a cylinder mower before, so its all new to me.

I also have no idea what model exactly this is, as the serial plate has worn off and I cannot read any numbers. Any ideas or help on how to go about things would be much appreciated!!

Hi waxdass, and a warm welcome to the forum.
It's always great to welcome another Scott Bonnar Model 45 owner as we all like to learn new things and tinker here.

Your machine is a 17" Series 2 (twin rail engine deck) Model 45, manufactured in Thebarton, South Australia. If it has the original engine fitted, if you could post the Model, Type and Code numbers stamped into the metal air cowling of the Briggs engine we can give you its date of manufacture, which in turn can give us an approximate date of manufacture of your machine.
The numbers can be usually found close to the intake manifold of the carby and run vertically...please post all the numbers.

The cylinder reel looks like it has had a hard life. the bent blades will have to either be replaced or straightened or perhaps the entire reel replaced...the machinist/engineer that does the spin-grind for you will advise you on the best way to go there.

You will need to remove the cylinder reel and the soleplate complete with the bottom blade (bedknife) attached, and both taken to the engineer.
See the video HERE for help in the removal.
Please post any further questions you may have here to this thread.

Once again waxdass, to Outdoorking.

Sure thing, I plan to start stripping it down very soon and see what I can find.

Your right about the cylinder reel, however I'm hoping once I take if off with the bed knife and bring it to my local Mower shop - they will be able to bend the blades out and not cost me too much.

So this 2-stroke motor, what oil is recommended to add to the fuel?

Hi waxdass, NO mate, that is a 3HP, 4 stroke engine....use straight unleaded petrol....absolutely NO oil in the petrol. The oil goes into the engine via the oil filler hole on the front of the engine.
Place the machine on a level surface, unscrew the oil plug and check the oil level.

Ahah whoops! Cheers for that info!

Here is a picture I took of the code stamped on the side of the motor near the air filter.

Hi again waxdass,
Well that clears that up....that 3HP Briggs engine is not the original for that machine....the previous engine would have been orange in colour and been manufactured before the company take-over in 1980 by Rover to form Rover-Scott Bonnar.
Your Briggs engine was manufactured in the USA (Rolla, MO) on the 18th July 1985 and is a model 80202.

thanks mate, good to know.

So what initial steps can I take with this motor? I don't exactly want to strip it apart when I know it runs. Are there any minor things worth doing/replacing? Obviously its getting sharpened once i take apart the cylinder reel...

I will probably Brakleen everything I can on the motor side of things, get it ready for a new coat of paint once its all tidy.

Hi waxdass,
For questions on your Briggs engine, I will hand you over to our resident Briggs guru, Grumpy, who hopefully will chime in here and give you some advice.
I will help you with any chassis/frame/reel questions you may have.

Hi waxdass. Please do not put brake cleaner on that engine. If you get it on plastic parts it may eat them, and some of those parts are quite difficult to replace.

Here are the Operating and Maintenance Instructions for the engine:
http://bsintek.basco.com/BriggsDocumentDisplay/flivAJX-nfBhU7y.pdf

Here is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6nkAJVJ1DajI.pdf

I suggest you begin by reading the operating instructions carefully, then ask any questions you may have. After that we can run through some simple checks you should always make when you acquire an engine, to ensure it is in good order and good tune.

Cheers Deejay & Grumpy,

I started her up again this morning, but the motor died on me after about 10 seconds, and didn't want to start again. I also managed to tear the starter rope, putting it back together was a very tedious task with that wound-up spring inside.

I have bought some WD-40 de-greaser instead for the initial cleanup.
I followed your youtube video to disassemble the cylinder reel and bedknife. Very quick and easy. Thanks for that.

More pics of my progress to come.

Your engine has a Pulsa-Jet carburetor, with a built-in fuel pump, and a small "well" which the pump is supposed to keep full of fuel. It sounds as if it is not doing so, which means the carburetor will have to be removed, dismantled, cleaned, and probably have the pump diaphragm replaced. This is not a difficult process but does have to be carried out carefully.

Hi waxdass,
Thanks for the update, I will look forward to seeing the pics of your progress.

That cylinder will come up fine once the blades are knocked back into shape and given a grind. It looks like it has a lot of meat left on it.
Depending on how worn the bottom blade is, it may be able to be reground flat. If too worn though, it needs to be replaced. A new bottom blade also should be ground flat, so make sure you check that this has been done when you get it back.

I've already sent them to my local mower shop. Cost me $66 in total. They said that the bent blades shouldn't be a problem getting back to shape which is good.

Hi waxdass,
Well that is good news. Can you please post some pics of the reel and bedknife before you re-install.
Thanks mate,

Well I took the motor to another local who specializes in small motor servicing, bad news is that he spotted the carburetor is cracked at the flange end. He told me that its not worth the cost of replacement and labour- i may as well find another motor.
He also mentioned the lack of oil in the motor, so its most probably been eating oil as well.

So now, im on the lookout for a 2nd hand Honda GX or any other recommendations?, and a 5/8 to 3/4 adapter (my mower guy was selling them for $85 ea.) No sure if this is a good price or not. I dont want to spend more than $160.

Anyway a few pics of the busted motor cleaned up:

The flange that you report as cracked, is part of the carburetor casting. The complete carburetor is part number 398711. The carburetor should be replaceable with a second-hand one for less than $20. On the other hand if the engine has been run without oil, it is better not to spend money on it, but to replace it either with a second-hand engine, or perhaps a new one. However the only new engine you are likely to find in your price range would be a chonda. I suggest you begin by checking the availability of second-hand 80202 carburetors in the Outdoorking Wanted forum.

I have found a few 2nd hand Honda GX200's locally, I may pick one up for around $180.
I'm not going to bother fiddling with the briggs motor.

Well what an interesting day,

I got news regarding the blade sharpening, that the sole-plate is fubar'd, and that they could sharpen however it might run unbalanced.

I also managed to pick up a good working Honda GX-160 for $150.

Hi again waxdass,
I really need to know more about your soleplate that you say is buggered; just so we're on the same page...the soleplate is made from cast iron and has the bedknife (bottom blade) attached to it, with countersunk screws.

If that has been broken or cracked, we are in real trouble... because they are no longer made...and a second hand one like hens teeth!
You cannot run a cylinder mower unbalanced.
We do need more info on exactly what is wrong....