Square 4 Mark 2 Recommissioning

[Andygill]

Hello
I recently acquired a 1958 Square 4. It starts and runs but needs service etc, it hasn't been used for a while.

Would anyone know where I could get a full service and recommissioned. A few issues and would like a double seat fitted. Not looking for full refurb or contours, just up running so I can enjoy it.

I am based in London but will travel just need someone with capacity and who's good.

Thanks in advance.

[simon.holyfield]

I may as well be the first to ask you... What do you know of its history, particularly relating to the engine?

Unfortunately, its all too easy to destroy a SQ4 engine if the oil ways are blocked up.

[paul.jameson]

As Simon says, knowing the history is key. Specifically, you must find out whether the crankshaft sludge traps are clean. If they are not clean then your engine will explode in under 500 miles. The only way to know for certain is to look at them but this involves a total strip down of the engine. Hence we usually ask a series of questions so that we can begin to assess the risks:

When was it last run?
Do we know if the engine has recently been rebuilt and if so, who did it?
Is there an external oil filter fitted in the oil return line?
If you remove the timing cover, is the engine sparkling clean inside or is there evidence of black gunge?

The fundamental problem is that the 4 sludge traps are tiny so fill up easily and then block the oil flow to the big end. This seizes, the con-rod snaps and destroys the crankcases and cylinder on its way out of the engine. If the engine has been run on straight oil in the 1960s and not used since, any modern oil (which will have detergents in it) will wash the deposits off the inside of the engine and they will end up with the sludge traps. The 500 miles comes from the experiences of Square Four specialists the Healey brothers in the 1970s. Sadly, there are those who do not listen to the warnings even today. They end up with a blown up engine and no possibility of replacement parts because this has happened so often.

[Andygill]

I know nothing of the history so I would imagine it's s bottom end strip at least. It was a well cared for bike in its time but now in need of a bit of work. If I start it oil spews out of the oil storage tank through the overflow on to the chain l/ wheel . Who could and would be available to get this back on the road do you think?

[KevinOToole]

I've only owned a Sq4 for four years but this is my advice... Strip the engine, fit new club conrods, a Morgo pump and an oil filter kit. I had trouble with the oil pump pick up pipe filter, so redesigned it. I think it's worth fitting the alternator conversion from https://ironhorsespares.co.uk/
I'm just about to fit my third new rear tyre, so I can confirm it's a lovely bike to ride!

[keith wainwright]

Hi Andy yes Paul is spot on. It's an engine complete stripdown, check those crankshaft oilway's and purchase a long series 3/16 dia drill. Run the drill through the oilway's and clean well. If budget will go to it, fit an oil filter kit together with a Morgo pump and club magnetic sump drain plate. Run the engine on modern multigrade 20w/50. The modern oils have a detergent added to keep the rubbish in suspension and then collected via the filter. Filter needs to go on the return flow pipe to tank. Hope the above helps and the bonus is, it's a nice feeling riding the bike with all the above carried out. Keith

[simon.holyfield]

Do you fit new rods Keith?

[keith wainwright]

Checks the con rods for any sign of damage if OK fit new Sims lock nuts 5/16 BSF and go for it. I would fit new shells just to be on the safe side. The only reason rods go is because the crankshaft oilway traps become blocked. You won't have problems with modern multigrade oils and oil filter. To Belt and brace it install a Morgo pump. Keith

[simon.holyfield]

Checks the con rods for any sign of damage if OK fit new Sims lock nuts 5/16 BSF and go for it. I would fit new shells just to be on the safe side. The only reason rods go is because the crankshaft oilway traps become blocked. You won't have problems with modern multigrade oils and oil filter. To Belt and brace it install a Morgo pump. Keith

That's boosted my confidence no end. It's just what I did years ago and I've worried constantly about whether I should have fitted new rods!

[david.anderson]

Conrod failures are not just due to blocked oilways. Unlike steel, aluminium rods (and titanium rods) have a duty cycle, ie they will only last so many engine cycles. Steel rods do not have a duty cycle and will only fail if overstressed. Generally in a normal street engine 100,000 miles is regarded as the absolute limit for an aluminium rod.
The square 4 is not a normal engine in that the gudgeon/little end is not centre of the piston. That creates additional stress on the conrod. The square 4 rods are also known to have a stress riser in the design. But how does a conrod normally fail. It is not on the compression stroke as most would expect, but rather on the exhaust stroke, due to the eccentric load created by the exhaust stroke which creates a tensile load on one side of the rod. The square 4 rod also experiences the eccentric tensile loading on the compression stroke due to the out of centre gudgeon.
So what is the safe mileage for an original square 4 rod. How many miles has your 4 actually done, and how many times has it been over revved by a previous owner (Australian mk2s are very suspect as most mk2s imported here were for police use). I do not know what the safe mileage is but it is probably much less than 100,000 miles. My 4 , when I purchased it had the no 1 rod hanging out the crankcase, so I know how costly it is to rebuild a blown up 4. In my opinion it is a gamble not to fit the club rods. I have never been lucky gambling.
David