OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Scott Bonnar Main Roller Cog Removal

Hi everyone,

I'm pulling apart a Scott Bonnar 45, most of it stripped down however I'm having trouble with the main cog on the rear roller, all the other cogs slipped off easily however I can not get this one to budge. I don't have a cog puller. Has anyone any suggestions or methods used if they have encountered the same problem or could point me to a post where this has been answered before.

Cheers for your help in advance.

Hi Ozziesim, a little bit of a penetrating oil left overnight might help but I think you'll need to invest in a puller otherwise. Some of the sprockets can be a little hard to budge at times.

Thanks, I think you are right, I don't know much about the pullers, I measured the diameter of the cog which was about 120mm, I am looking at a puller that does up to 150 mm, would that be good enough to do the job or is there anything else I need to consider?

Hi Ozziesim,

Yes mate, a 3 leg puller that fits the circumference of the large sprocket will do the job. Rolla has set you on path to success though, a little penetrating oil first left overnight and then the gear puller will do the trick and not damage any of the components.

Would you please be good enough to post some pics as you go along with your restoration, it will be great for the ODK archives and maybe help other members in the future.

Sure will do, thanks for all your help

Ok so I thought I would just share the removal of the main roller cog in the event that someone else has the same problem.

A little about my restoration, I have picked up 2 Scott Bonnar 45's for $100, what I thought were 17 inch actually turned out to be 2 20" machines, they had been sitting out in the weather for a few years and were not running.



Usually the cog should slide off quite easy as did most of the cogs on my restoration project however the main roller cog would not budge an inch. I did a rough measurement of the cog and found it to be approx 120mm.
I purchased a 150 mm cog puller for $24.00 delivered which worked well.


I left the nut on in the event the cog gave way in a hurry, there was quite a bit of force and didn't want every thing to shoot off and cause the cog to drop and get damaged.
I found that it was hard to get the puller legs between the back of the cog and the frame so I used the puller to pull the cog slightly, then loosened and re set the legs.



Then it was a matter of continuing to screw the shaft on the puller till the cog came free, making sure the shaft in front of the cog was well oiled to help it slip off easier, much better method than using a screwdriver or crow bar and the puller was well worth the investment.

Thanks for the report, Ozziesim. The right tool usually makes a big difference.

Just one finicky point: a cog is a tooth on a gear. The tool you bought is a gear puller. The object you removed with it is a chain sprocket.

Oh ok thanks for the correction, learn something every day.

Cheers

Hi Ozziesim,

Do you normally buy lottery tickets as if you don't I'd start doing it, as 2 x 20 inch machines and especially one being a solid deck for $100 is a bit like winning the lottery in my opinion. If you don't mind me asking how did you source them or better still become aware of their availability ?

Cheers,
BB