OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Reel-Type Mowers Yardstar STA-17 (Scott Bonnar 45 copy) drive shaft replacement

Hi guys, I have been reading your forum for months, and have gained LOTS of valuable information. Thanks so much to everyone for your posts and your pictures. They are amazing. I have a Yardstar STA-17 mower. It is a Bunnings mower that I bought new about 6 years ago. It has been pretty good, it has a "Chonda" motor (labelled a Komodo 160F), and it is essentially a Scott Bonnar 45 chassis. I know most of you will say, "You should have bought a name-brand mower", but it was my first reel mower and at the time I bought it I didn't know the difference. Yeah, if I had my time over again I would have bought a Rover 45, but I have this one and that's that. Anyhow.. The plastic thrust washer had worn totally away over the years, so I pulled the motor off, opened the cutter clutch and removed the clutch half on the chain case side and replaced the thrust pad washer. All good and working fine now (thanks to the video posted by deejay that showed how to remove the motor from a Scott Bonnar 45 and separate the clutch), however I feel my drive shaft and woodruff key is in pretty bad shape. I have some pictures, I think I have attached them. I bought a new drive shaft, new clutch bearing for the motor side of the clutch half, new self-aligning bearing for the chain case side, new woodruff keys for the clutch and the drive sprocket, and also a gear puller to remove the drive sprocket. My question is, how do I install the drive shaft into the chain case side bearing? Do I need some sort of press? I have read that people put the "drive shaft in the freezer and the bearing in the oven" before assembly... is that required? I'm a bit lost... Let me know... oh, and GREAT FORUM. Also, pity I didn't just buy a second hand Scott Bonnar 45 but I have this Yardstar and I wanna keep it running if I can.

Hi Muz,

Firstly welcome to the forum, great to have a Scott Bonnar Clone on here as it's a great comparison between the originator and the imitator.

This is a perfect example of Chinese steel quality compared to Australian made steel. Really this shaft should not fail at such a young age as it has. I guess this is why reel mower purchasers have hunted down genuine Scotty's opposed to buying a imported unit. But as I always say "it is what it is".

Now as far as the job at hand is concerned,

You are going to have to get the original bearing out of the housing as you are wanting to use the original housing again, so, I would remove the drive gear from the end of the shaft and then remove the two mounting bolts and remove the housing and shaft together as one assembly.

As your machine is rather newish the gear should slide off fairly easily. The only issue I can see is getting the nut undone as you've already removed the engine. So you will have to use a set of vice grips and lock them on to the shaft so it can't slip. As you are not going to reuse that shaft don't worry to much about putting marks into it with the grips.

From there you'll have to use a vice and open it precisely enough so as to rest the edge of the mounting surface of the housing over the top of the edge of the jaws of the open vice on the housings outer extremities, but just enough clearance so as not to restrict the bearings movement downwards as we want, thus the engine end of the shaft should be vertical now pointing towards the roof . As you are no longer going to be using that bearing and shaft again you can use a soft blow hammer and tap on the end of the shaft which should push the bearing out of it's housing downwards between the open jaws of the vice. As this machine is relatively new the bearing should come out rather easily. It's somewhat harder doing this if it's in an old Scotty that's been sitting out in the weather for many years and corrosion has taken a stranglehold, but that's not the case here.

Now as far as reassembly is concerned all you have to do is reassemble the new bearing into the housing remembering that you must not apply any pressure to the inner race alone, only the outer edge of the bearing. You can use a vice here as a press to push the new bearing into the housing but I would use two nice clean and perfectly flat pieces of MDF sheet timber to protect the surfaces of both the bearing and also the housing surfaces. **Please note, if it's the the same as a Scotty the bearing will be pushed in past the mounting surface of the bearing housing, thus you'll have to find a general half inch drive socket of the same size as the outer race of the bearing so as to push the bearing in fully sub-surface, remembering not to place any force on the inner race. Before you do all of this work you can put the new shaft into the freezer making sure it's in there for a good half hour prior to requiring it and when you're ready you should be able to slip the bearing straight over the end of the shaft by hand and allow the shaft to normalise. This should be able to be done without pushing the bearing backwards out of the housing. Maybe it's best that you take the housing with the bearing in it to the freezer and do this small part of the process right as you take the shaft out of the freezer. Once it has normalised then just install the full assembly back into the mower.

I'm only explaining the freezer process here as you probably have rather limited tooling. I personally would use a different method of installation but I have much more engineering tools at my disposal I guess.

Procedure is now just the reversal of the disassembly process.


Hope this helps.

Cheers,
BB.

I wonder if you could gradually replace all parts that fail with genuine Scott Bonnar replacement parts, or even second hand from the 70s?

Hi MF,

I had thought of that myself but I guess the only way to find out is to get two machines side by side and thus compare apples with apples as they say. As there always is with Asian copies there are some minute differences that get in ones way of doing that.

Also the other point is all these replacement parts that appear on eBay and the likes that are being sourced from many different suppliers are all originating from China I'd say and their steel quality is questionable as well. A few bits and pieces though are being made here in Adelaide I've noticed on a small scale basis in a backyard operation up in Blackwood.

As far as taking items from 1970's machines as you suggest is probably a tad fruitless as you're better restoring that original machine in the first instance and end up with a better standard of product. For every part you remove from an original SB chassis you'll render it useless and that's pointless from where I sit.


Cheers,
BB.

I agree, all energies should be toward keeping SBs on the road from a limited resource of spares, especially since Scotty restos are a growing cottage industry.
I just thought the framework may be comparable enough to improve with SB bits.

Were SB reel mowers exported like Victa ?

Hi MF,

Yes they were to a few countries overseas, notably South Africa where they actually had an office there, so eventually when we get low on them here we can bring some back from SA just like they've done with older bodied Monaros.

Cheers,
BB

Anyone prepared to go hunting there ( instead of Lions!) stands to profit very handsomely indeed from a bulk lot of parts and complete machines!

Hi MF,

I think there's got to be a helluva lot more money to be made to make it viable to do that. Most of them would be pretty beaten up by now, just look at any of the Export Monaros (SS Chevrolet) that have found their way back to Australia. Trashed rust buckets

Cheers,
BB.

I'd love to find a 1973 -75 Valiant we exported with the Slant six instead of the Hemi!!
EDIT how did we get from Scott Bonnar copies to export Valiants from S.A to S.A again?

Monaro and South Africa seemed to be the link words