OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers 17 inch SB 45 Solid Deck with Kirby HK25

Hi Guys and probably more so Grumpy on this topic.

I have been lucky enough to have had an original 17 inch Scotty solid deck given to me by a wonderful ODK member. I have gotten the engine running but sadly the oil in it has gone a very sludgey light grey / whiteish which indicates to me that moisture has been involved. It is a fantastic original unit that has a Kirby Lauson fitted to it and I'm the first person to say yuk about the Kirby but it is running and rather well I might add.

I have drained the engine of its oil and am wanting to flush it out prior to putting new SAE 30 oil in. My question is and I am sure I've read it here on the forum before and that is should I simply put a litre or so of diesel into the crankcase and run it for a few minutes then empty the sump and do the same again and after that drain it for about half an hour, then put new 30 weight oil in. Is this a good recommendation ?

I know that most of you guys know that I'm not a fan of the Kirby power plant but as it is running and the machine is quite a good survivor I thought I might leave it on there until it totally fails and only then replace it with a Honda etc. Being an undamaged Solid Deck it will stay with me as good 45 SD Scotty's are getting thinner on the ground day by day.



Cheers,
BB

Hi BB, YOU MUST NEVER START OR RUN AN ENGINE WITH ONLY DIESEL FUEL IN THE CRANKCASE. Diesel has only very slight lubricating properties. I think you have read a recommendation on the use of "flushing oil" which typically consists of a mixture of engine oil and either diesel or kerosene. The maximum proportion of diesel to be used is one third of the total amount of flushing oil you prepare. A low-stressed low speed engine can be run for a short period unloaded, at up to say 2,000 rpm, with the sump filled with flushing oil, as a way to remove the residue of badly sludged or contaminated oil (which has already been drained thoroughly, of course). This used to be fairly standard practice back in the days when cars (primarily British cars) had no oil filter and plenty of blow-by past the piston rings. After running for a maximum of 5 minutes, preferably less, with the flushing oil in the sump the engine must be stopped, the sump drained throroughly, then filled with the recommended engine oil. Do not do this process with a modern car engine, or with any kind of crankcase induction two stroke engine.

I personally regard the use of flushing oil in badly sludged 4 stroke mower engines to be a viable alternative to dismantling the engine, in most cases. If your Kirby Lauson has had water in the sump for a substantial period, though, I'm not confident that this will be sufficient to save the day: some parts may be rusted. The approach I would probably use in that case, if the contaminated lubricant all came out clean with no visible rust, would be to put a suitable amount of soluble oil in the sump, and spin the engine with the spark plug removed, using an electric drill. Then drain the soluble oil and see if it has become milky, indicating that it has become emulsified with water. If it has, repeat the procedure with more new clean soluble oil. When the soluble oil comes out looking the same as when it went in, it is time to put in the flushing oil, and again spin the engine for a time with an electric drill, in order to spread the flushing oil around and get it into the big end bearing in particular. Then you can leave the flushing oil in there, and start the engine for the normal brief, unloaded run on flushing oil, before draining it and replacing it with the correct engine oil.

It all sounds a bit tedious I know, but while I may dislike Kirby Lauson engines for mowing the lawn, they are becoming classics and a good, complete one deserves some basic respect in my opinion.

Hi Grumpy,

Thanks ever so much for your response post.

If I may ask where is soluble oil available from ?

and honestly I was really wondering about the diesel thing as it didn't sound correct, thus me asking before I proceeded. If this was a high Km Kirby I would've simply hoiked it off to the local scrap yard as I have done previously with a few but this one seems too good to toss out and it ran very strongly for the short 10 seconds that I had it going.

BTW there was absolutely no signs of rust when I drained the old oil, more than likely it was still the original oil from new mower purchase as the mower wasn't used much at all as the original previous owner didn't like it much at all and just left it in the shed for all these years.

Once again thanks Grumpy.

Cheers,
BB

Soluble oil is essentially an industrial item BB. I would personally try Repco first, but like others of their ilk they are not all that cheap a source, so I'd look elsewhere as well. We have one or two old threads where engines have been submerged in floods and I've recommended the use of soluble oil. You'll find some references to sourcing the stuff in them:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=53894#Post53894
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=44708#Post44708
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=45404#Post45404

Hi Grumpy,

The oil flushing went well as I got hold of 3 litres of soluble oil from a mate who had a 20 litre drum of it and it didn't take much at all as I left the motor overnight with the bottom plug out and leaning over so ever little bit came out and then ran 2 lots of SO through it. Second lot came out as good as it went in. After a good draining I've filled it up with SAE 30 and it sounds and runs great.

Cheers,
BB

Thanks for reporting back, BB. Was the first batch of SO milky when it came out? If so, it confirms your diagnosis of water in the sump, and validates the action you took. It sounds as if you took the right action at the right time, so hopefully no harm came to that engine. If you keep it full of clean oil, it is likely to last an awfully long time - they seem to be very durable mechanically.

Hi Grumpy,

I think that because I left it overnight to drain out very thoroughly through the lowest point drain plug that the first lot came out with a very small amount of contamination. The second lot came out pretty much as I put it in thus it's very clean. After putting the new SAE 30 oil in and running it for around 15 minutes I checked the new oil and it was still the same as how I put it in, thus your method has worked perfectly.

As far as sourcing the product is concerned I haven't set any new bench marks there for other ODK members as I scored it from a mate that bought it in a lot of oils from a machine shop that closed down and he's been using it on his Warren Brown valve facer, but has since changed over to honing fluid which came in another auction lot, thus the SO is now pretty well obsolete but that's worked out well for me I guess.

Once again thanks Grumpy.

Cheers,
BB.

So you are now well placed to turn up in the aftermath of floods, and buy up the machinery that's full of water. Actually the same problem seems rather common with old tractors that have been left out in a paddock for 30-50 years.

Thanks for rounding off the thread, BB. I'll close it.