Now hear’s a thing

[roatavator]

I have six SIMARs. I mix up fuel for all of them with the same fuel/oil mix. The 56 tiller and the 30,35,50 and A5 tillers all run nicely with very little smoke from the oil being consumed. However, the 56 plough smokes like crazy. I religiously open the oil drain taps on every machine after use. I don’t mind a bit of smoke but the extent of the fug produced by the plough can sometimes be a cause of embarrassment as the ploughman on the plot adjacent can often not be seen (although his presence is confirmed by loud coughing). And that’s before I get my pipe on the go (aids concentration whilst ploughing, you know).
But why does the plough smoke so much more than the others?

[charlie]

Very odd. If it was a 4 stroke then worn rings/bore or valve stem seals would be obvious suspects, but a 2 stroke has no valves and contents of sump (crankcase) go through combustion chamber anyway so rings should not cause smoke.
Is air filter restricted? Not sure if that would cause smoke.

[roatavator]

Hi Dave
No, air filter is fine. I suppose mixture could be running a bit rich but then you might expect mix of black and blue smoke, whereas this is a lovely shade of blue. Neither does it seem to use any more fuel per hour than my other 56. Coincidentally, the volume of oil draining from the oil tap is always greater than my other machines.
One of life’s many mysteries, providentially the smoke does tend to mask the poor quality of my ploughing when the judge is looking on, so maybe I’ll just carry on!

[trusty220]

It does sound like the mixture is too rich. With a four stroke this would tend to produce black smoke (soot) but I haven’t come across a two stroke being run for too long on a rich mixture because they tend to oil the plug up. The extra oil being drained off afterwards would also point to too much mixture going through.

What colour is the plug? This would give you the best clue as to what’s going on.

[roatavator]

Yes, the plug is dark and a bit sooty. However, the machine actually runs great, like all two strokes it’s not so keen on starting when hot so at a ploughing match I start it up and leave it running until the plot is finished and the machine back on the truck. This is often 2/3 hours during which time it sits and idles very slowly and happily whilst waiting between judging points and picks up straight away when I need it to work. It’s probably the best runner of all my SIMARs so I’ll probably leave things as they are!

[charlie]

There is a film clip in the British Pathe online archive showing a SIMAR 10 working (scroll to 4:10 for film of SIMAR), 1925 and that has a faint cloud of smoke coming from exhaust.

[stuart]

Has it a larger main jet in the carburettor or is the throttle needle in a higher position in the throttle valve ?.Both would make the engine run richer.

[roatavator]

“Faint” Charlie? That’s a lot worse than mine! I don’t feel so bad now.
Not sure about the carb, Stuart, I’ve not looked. However I’ve just realised I’ve got a short video from when I picked it up from Andy’s some time back and it wasn’t smoking then. Obviously it’s now on my fuel mix, but that same mix doesn’t make the others smoke.

[charlie]

I have a feeling the ground in the film clip may be Wembley.
Carb does not have a needle, at least the one on my Rototiller doesn’t. I use 6% oil/petrol mix using some Castrol XL which came with one of the Rototillers, along with a genuine SIMAR measuring can, and get little smoke from the 56, although it does tend to 4 stroke at times.

[roatavator]

Presumably stadium was being cultivated as part of war effort, Charlie, or is that a mad suggestion?
I use SAE40 as recommended in the Mechanised Gardening leaflet, I’ve got a couple of the measuring cans and always use those when mixing up.

[vhgmcbuddy]

hi i think a lot of your problem is oil leaking from gearbox to engine check oil level on gearbox

[roatavator]

Hi Tom. Funnily enough I just came to the same conclusion today whilst out ploughing. The oil from the drain tap is definitely thicker than the 40 grade I put in the fuel.
I’ll just live with it. No point going to the trouble of doing the seal since it also leaks from the wheels as well. She actually runs a treat so I’m not bothered. Best location I’ve been to today for a match. Elevated field overlooking Blakeney Point in the distance. Some people said they could see seals, but all I saw were bent furrows!

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[vhgmcbuddy]

ye most of my simars are the same but not worth the trouble least they getting enough oil how i wouldnt say bent furrows by you

[roatavator]

Yes Tom, mine too mostly leak from the seals. The 56 tiller used to leak quite badly but in recent years when it’s seen more regular use it’s stopped leaking so badly, I guess the seals had probably got dry.
Bent furrows were mine! But in my defence I was turning up huge stones. The plough itself is a lovely piece of kit and on decent ground does a lovely job.

[andyfrost]

Peter , only my personal opinion , but I always laid it down to the fact that ploughing with it never “loaded” the engine up enough , i never once had it really pulling hard enough to even the engine out.
Also I would have thought that crankcase compression would not allow oil from the gearbox to pass into the engine once running.
At the end of the day , it’snot something I would lose any sleep over.

Andy.

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