OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Reel-Type Mowers Misalignment issues when replacing Kirby-powered Scott Bonnar 45’s

I have had a quick search and have not seen this topic covered as yet. Recently, a gentleman in WA has made up a full jig setup to totally replace the rails on twin rail machines. While doing this, he has reported that the Kirby mowers have a higher crank output than Briggs-powered 45’s.

The difference is 3/32” which is suggested to be too great of a difference for the self aligning bearings to correct. He has suggested that if re-powering a Kirby machine with a Briggs, a 3/32” shim should be placed underneath the engine.

I found this quite interesting. These photos were supplied by him on Facebook and demonstrate the height difference well. the first photo is of a Briggs and shows that the output jig does not align with the hole in the chassis. The next photo shows perfect alignment with fitted to a Kirby.

Funnily enough, I have not rebuilt a machine with a Kirby on it, but this is certainly something to consider if users are planning to put a new Briggs on their rebuild.

Em

Hi Em,

Honestly I've never found this to be an issue in my 40 odd years of servicing Model 45's. The self aligning bearing should be able to take that on board and easily deal with it.

I'm wondering if this chap is dealing with a machine that has got sagging rails as that's quite common.

So what this chap is saying is that the Kirby engines had a "higher than industry standard centre of shaft from deck position" opposed to every other engine manufacturer on the planet ? and that they put a hole in the side plate in one position to suit a particular manufacturer while they were also using an engine from another supplier at the same time and placing it off centre to the transmission shaft hole ?

Must admit this Sounds totally absurd, but anyway....................

I am going to grab an example from both manufacturers which I have on hand and measure the height of shaft from the mounting deck position, after that I will report back to bring forward my findings.

Cheers,
BB.

You make some very good points as per usual, BB. The voice of reason. It really doesn’t make sense...

I’ll be interested to hear how you go.

I have wondered about this. In my mind it never made sense to have two pieces of tooling for this.

Interested what you find BB.

Hi All,

All I can say is that these Facebook people are abusing too many substances.

There is "Absolutely Nothing different" between the two engines and I've posted a comparison photo up here just to show all the doubting Thomas' that require proof.

The Briggs engine is on the left with the rusty PTO shaft and the Kirby Lauson on the right. They are sitting on a fairly even surface I'd say with no more than a few thou of variance possibly which is of no consequence whatsoever.

Cheers,
BB.

Probably a good reason why is because the issue doesn't actually exist Em

Wow, hard to argue with that photo you’ve provided, BB! Consider the myth busted 😊

Hi all,

How much of an issue are the sagging rails? I’ve just pulled my 17” model 45 down and the rails are in pretty bad shape. I would say there have been a few dodgy repair attempts in the past. I would estimate there is about an 8mm drop under the middle engine mount in relation to the 2 sides. It looks like a crack has been welded up without the rail being straightened. Just contemplating a donor machine or getting in touch with a tool maker I know to try and cut the rails, press straight, reinforce etc. It didn’t run too bad, but did shake around a bit. It has a Briggs 80202 (which I plan to replace with a Honda gx100 or chonda equivalent ohv motor. Clutch half looks to have been replaced and seems sound.

Cheers,

John

Hi Em,

I’m in Perth and pretty keen to get in touch with this fella to see if I can get hold of any information about his process, it might be feasible for me. Any chance you could pass on his details as I’m not on Facebook? PM is fine if this is the appropriate way to go about it.

Cheers,

John

Hi John,

If I may say, photos are the key here. They give us all a perspective on the overall issue and thus we could then give you the best advice that it seems you are looking for.

Cheers,
BB

Hi Bonnar Bloke,

Please see the attached images. You will have to excuse the crude straight edge and photos. Hopefully this makes the issue a little clearer. The back rail is similar although not as bad.
While considering my options, I had a look at an early series 2 machine yesterday, and although the rails looked in good condition, the rear rail appeared to have sagged slightly too.

Cheers,

John

Hi John,

I'd safely say that these are pretty well finished and either you fabricate new ones or simply toss that chassis into the scrap bin and find a better one to work with. These machines are not rare and there's still bucket loads of them out there to be had.

Maybe it's best that this one becomes spare parts for another as that's what's happening with many bad ones due to the ridiculous prices of all the consumable components required.

Sadly as these rails get worked and reworked again and again using heat the steel becomes rather soft and it's pointless mucking around with it any further

If this other guy in Perth is able to fabricate new rails and stitch them into your side plates then that will be the best option I'd say.

All in all this chassis as it stands is now considered as compromised.

Cheers,
BB.

Hi BB,

I feared that may be the case. Thanks for having a look. I’ll see what donor machines are around or look at getting new rails fabricated.

Cheers,

John