OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers My Scott Bonnar 45

Hi all,

I have been viewing this forum for a while now and found the information given from members really good.

I have had my Rover Scott Bonnar new since about 1983 and have just started to use it again. Due to the previous state on my lawn it has been in the shed for a few years, but I have recently replaced my lawn at home and started to use the good old SB again.

The old girl needs a bit of TLC and a couple of replacements but it has been an excellent machine since day one.

The details of the mower are as follows:

Rover Scott Bonnar Model 45058. It has the 3HP Briggs and Stratton motor which is a model 80202, Type 1735-01, Code 82111901.

Here are some photos I took this morning.





The blades have a few dents in them, but I think they should be OK. I also need to replace the air filter and get a new clamp for the deflector plate, but apart from these the mower is working well.

I would like to inspect the chain and sprockets, however, the bolts holding the cover to the body will not budge. I have tried the old trick of hitting the head of the bolt with a hammer, but no luck. Any suggestions as to how I can loosen the bolts would be appreciated.

I have noticed that after a few minutes of use, the engine seems to over rev without any input into the throttle control. Can anyone advise me on what I need to do to fix this problem?

Hi Ian55,

Nice to see your model 45 that seems to be one of the very last that was manufactured at the Adelaide based Thebarton plant before operations moved to Brisbane.

Your machine was made in early 1983 as the engine was assembled in the USA on the 19th of November 1982, thus that engine would've been fitted around 3 months later to a newly made chassis.

As far as removing that glorified gutter bolt that secures the chaincase to the mower I would give it a bit of penetrene and then use a screwdriver as if you are undoing the bolt head and gently tap the end of the screwdriver with a hammer while pushing hard against the screw with an undoing twisting action at the same time. Try not to allow the screwdriver to slip and flare out the slot in the head.

This should work as it has for me everytime.

Cheers,
BB

Hi bonnar_bloke,

Thanks for your information re the mower and also how to get the bolts loosened.

I will give your advice a go at the weekend and let you know how I go.

If I get it off I will take some more photos and post them to get some advice from the members to see if I need to replace anything.

Cheers
Ian

Well.... I finally got the stuck bolts to move and remove the chain cover over the weekend. I did take some photos of the chains and sprokets on the phone, but it appears I need to do it again, as they are all blurry.

The first thing I noticed when I removed the cover was the chain driving the main rollers has become loose and almost coming off the bottom sprocket.

I dont know much about this part of the mower, so I will get some more photos taken and post next weekend to get some expert advice.

Thanks in advance and cheers
Ian

Hi Ian,

Nothing we can't walk you through, look forward to the photos.

Cheers,
M

I was able to get some photos today of the chains and sprockets which are not blurry

As you will notice, the chain for the roller appears to be loose. Has there been any damage done to the sprocket? Do I need a new chain or will I be able to tighten it up?

Any advice on the overall state of the chains and sprockets would be appreciated as well.

Hi Ian55,

Overall things aren't that bad, I will say that the cutter sprocket is well on it's way to requiring replacement but believe me we've seen much worse here on the ODK forum.

As far as the rear roller chain being lose is concerned, that can be easily sorted out by adjusting the flat steel bar with the slots in it which mounts the land roll clutch to the chassis side plate. There are two planes of adjustment, up and down and also left and right. The vertical height is adjusted by the lower nut and bolt that is visible at the lower area of the land roll clutch sprocket while the lateral adjustment is done with the other nut and bolt at the upper area of that flat bar. It will take a bit of trial and error for the non experienced but after you loosen the bolts you'll soon get the idea of how it has to be done using the combination of both adjustments.

Eventually you'll have to replace the cutter sprocket, chain and also the top sprocket on the transfer shaft. But for now I can still see you getting a fair bit more usage out of it if it is correctly adjusted and not too tightly.

Cheers,
BB

Thanks BB.

I am pleased to know that the running gear appears reasonably OK, with the possibility that I will have to replace a couple of sprockets and chain later on. I will keep an eye on these and replace them before they cause any damage.

Thanks also for the instructions on how to tighten the loose chain. I will attempt this fix at the weekend and let you know how I go.

Cheers
Ian

Once again thanks to BB for his advice.

I was able to adjust the roller chain and gave all the chains and sprockets a fresh application of oil.

Whilst I was at it I also adjusted the blades as I saw that they were not touching the bottom blade properly.

After I had done all this I gave the lawn a mow with the machine and it worked a treat.

Cheers
Ian