OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Rover 45 Maximum Height Modification?

Hi All,
A new member so learning the ropes.
I have just purchased a 20� Rover 45, Model 45158 with 3.5HP Briggs and Stratton Model 91202 Motor. It seems to be a fairly late model and appears to be in generally in good condition with a 10 blade reel which I will arrange to get sharpened.
The B&S Code number is 02120636A so I assume the motor was manufactured in 2002 although it has a sticker saying it complies with the CA 2006 emission standards. Not sure how it would have got that sticker in 2002 so maybe I have misinterpreted the code.
I have established it definitely needs a new carburettor diaphragm, perhaps because there is now ethanol in 91 Octane fuel and maybe the diaphragms don�t last as long. Are the B&S OEM diaphragms more reliable than the aftermarket versions?
I am hoping to use it to mow Sapphire Buffalo and wondering if anybody has a recommended modification to raise the mowing height above the standard maximum height. I would hope to get say 35-50mm range. At this stage I am looking at welding a small plate to the bottom edge of height adjusting lever arm so I can drill an additional hole in this plate on the same pivot radius as the original hole and re-locate the peg at the bottom of the adjusting rod into this new hole. This would enable the front roller to move lower down thus raising the mowing height. It would still be possible to move back to the original hole if needed.
I also wonder if it is possible to change the gearing to reduce the mowing speed. It certainly speeds along which might be good for large areas but not so good for smaller spaces.

Hi Rover45158, and a warm welcome to the forum.
Its great to have another Rover reel mower owner onboard, and one that has such close affiliations with the Scott Bonnar Model 45.

Height adjustment range has been factory set to take into consideration the different types of grasses encountered; as has, the number of blades in the reel.
The 10 blade reel is for use primarily on blue couch (or fine leaf grasses) and your machine; 20" (when manufactured by Scott Bonnar) was originally fitted with an 8 blade reel.

For comparison the 17" Scotty had a 6 blade reel. The height range may be able to be increased a little, but is discouraged by a lot of owners...it is up to you...Modifications to original specifications are called here "Tenants Improvements" and can be either successful or a disaster, because once modified..your machine is no longer original. In other words, it is your decision alone....
Have a read of this thread from 2009... it may help you.
Click HERE

Re: the engine number, can you please post the complete string of numbers stamped into the air cowling of the Briggs...it should be in 3 blocks....we will then give you the exact date of manufacture of the engine.

The mowing speed (and the sprocket ratios) have been carefully worked out by the Scott Bonnar design engineers at the time of release of the Model 45 range (1968) and is a matter of operator technique.

Set the throttle (once the engine has warmed up to operating temperature) to about half / 3/4 throttle, engage the cutter clutch, and just squeeze the clutch handle on the left hand handle bar just enough to walk at the pace you desire...the design of the roller clutch, allows it to slip, without any ill effects. If you wish to go quicker...squeeze it harder...Easy-peasy!!

Regarding the fuel issue, please don't use ethanol on your machine....use premium ULP which does not contain ethanol...your carby will love you for it, because there will be no gasket erosion or crap left behind when you store the machine for a short while.

Please let us know how you get on.
Once again, to the OutdoorKing forum.

Hi Deejay,

Thanks for all the info,

I have mixed up the sizing and my mower is a 17" model and not 20" as I originally posted. The Mower is currently off being sharpened so I will check other details when I pick it up. Having dismantled the tank and carburettor the inside of the tank is pretty clean but the diaphragm is definitely the worse for wear so your comments about ethanol are helpful. The replacement diapragm will run on 95 Octane. Are there any other carby components I should replace that might also have been ethanol affected?

I will see how I get on with the height adjustment. I have welded a small plate to the front roller pivot arm but this will be the only modification required and easy to return to original condition at a later time. I certainly don't intend to change the slot in the chassis or any of the adjusting arm mechanism. If I can position the second hole correctly the minimum cutting height for this new hole will hopefully overlap with the maximum cutting height for the original hole. I will try to post a picture once I have tested it for a while and see how the cut is affected.

I expect I may have to mow more often than might be the case with a 6 blade model but I expect the cost of a new cylinder might be somewhat more than I paid for the mower. Certainly having a wider range of cutting height might help as I can take a lighter cut on the first pass.

I was uncertain about whether the clutch needed to be fully engaged so being able to slip the clutch will mean I can cease training for sub 10 second 100 metres.

Thanks Again.

Hi Rover, as far as I know, there are no other parts in the carby that will be affected by the ethanol.
Can you please post some pics of the modification you have done?
Thanks mate,