Sq4 MkI- new life

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Gui.dorey
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Re: Sq4 MkI- new life

Post by Gui.dorey »

Allan, I didn’t have a filter installed. And I had emptied the sump before those videos, so it is coming from around the plain bearings.
1951 Ariel Square Four MKI
1954 Ariel NH Red Hunter
1929 BSA Sloper
1946 BSA B31 (project)
1954 BSA C11G
1960 Harley Sportster XLH
1951 Harley WL 45
allan.walker
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Re: Sq4 MkI- new life

Post by allan.walker »

Thanks, Gui.
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Re: Sq4 MkI- new life

Post by paul.jameson »

Looking at those videos, the second one says to me that there is a problem on the rear crank timing side main bearing. At tickover speeds, that is an awful lot of oil coming out. So, have you got the proper plain washer fitted between the crank and the timing sprocket? Is the end float on the crank within the recommended 0.002" to 0.004"? (Note that this is not quoted in the Square Four chapter of Waller but it is quoted in the KH chapter and the KH does of course use the same bearings.) You say that you turned the timing side bushes yourself. Do I assume that they are phosphor bronze from that and, if so, could it be that your original surface finish on the inside of the bush was poor? Could it have worn during the running in period to give an excessive clearance? If, on the other hand, the bushes were whitemetalled, did you just turn them in the lathe or did you finish with a reamer? I turn in the lathe to about 7 or 8 thou oversize, then fit them to the cases, then finish with the reamer in line as described in another thread. With the lathe alone, I am incapable of getting a surface finish anywhere near as good as that achieved with the reamer so I would expect very rapid wear on my bushes if I didn't finish with the reamer.
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paul.jameson
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Re: Sq4 MkI- new life

Post by paul.jameson »

A further thought. It must be difficult for the pressure relief valve to have a problem with debris on the seat since the oil pump will push oil past the ball and tend to wash any debris off ball and seat pretty quickly.
Paul Jameson
35 LG (project), 37 RH500, 52 ex ISDT KHA, 54 KH(A), 75 Healey 1000/4.
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist (but not Machine Registrar), Gauges and Clocks Spares Organiser.
Gui.dorey
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Re: Sq4 MkI- new life

Post by Gui.dorey »

Paul,
the plain washer is there and the end float was set according to specs.
The bushes are white metalled, and I only turned them on the lathe, but did not finish with a reamer.

The question is, could the clearance be so large as to be the source of my troubles - i. e. letting so much oil escape that the oil pressure drops to 0, preventing enough oil to reach Nr 3 big end and filling the sump with oil every time the engine runs? Does that sound like a plausible string of events?

I expect a similar situation would arise in a well worn engine, where the plain bearings are well worn. Has anybody heard of such an effect?
1951 Ariel Square Four MKI
1954 Ariel NH Red Hunter
1929 BSA Sloper
1946 BSA B31 (project)
1954 BSA C11G
1960 Harley Sportster XLH
1951 Harley WL 45
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simon.holyfield
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Re: Sq4 MkI- new life

Post by simon.holyfield »

Gui.dorey wrote: Sun Feb 26, 2023 1:58 pmThe question is, could the clearance be so large as to be the source of my troubles - i. e. letting so much oil escape that the oil pressure drops to 0, preventing enough oil to reach Nr 3 big end and filling the sump with oil every time the engine runs? Does that sound like a plausible string of events?
That's exactly my line of thought.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
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Re: Sq4 MkI- new life

Post by allan.walker »

simon.holyfield wrote: Sun Feb 26, 2023 4:11 pm

That's exactly my line of thought.
It does seem very likely that all the oil pressure is being dissipated at the rear crank bush.

But....isn't the capacity of the return side of oil.pumps supposed to be greater than that of the feed??
If that is the case, why does the sump fill up with oil?
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paul.jameson
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Re: Sq4 MkI- new life

Post by paul.jameson »

I am with Simon on this one so, very regrettably, my recommendation must be to take the engine back down and measure the clearances.

There is a parallel I can think of. A prominent club member once built a KH for his wife. This threw a rod in under 1000 miles although I can't remember whether it was after 500 or 800 miles. So he built another engine and exactly the same thing happened. The cause was that he had not fitted an oil pressure relief valve at all, in either engine. Both engines had arrived without the valves so he didn't know that one should be fitted.

So if your clearances are big enough, we can be confident that a rod will be thrown and on a Square Four, this is usually No 3, like yours.

As a first step, I would take off the timing cover and take out the sparking plugs. Set the rear crank so that one set of the flats on the crankshaft end nut are horizontal. Using something like a car axle stand as the fulcrum, try to lever the crank upwards. I think you will see or feel movement (or both). It might even be possible to get an idea of the magnitude of such movement using a dial gauge.

However, even if you can't detect any movement with this test, I would strip and check the clearances in any case.

As a consolation (and it won't be) a notable Square Four re-conditioner once completed building the engine only to find the scavenge pipe still sitting on the bench.......
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Re: Sq4 MkI- new life

Post by john.bebb »

Hi Gui - hope all goes well this time!!!
Mine is also currently in bits - but only for the top end & new rims painted to match the tank..
probably put some heated grips opn whilst it's apart... (yeah - I'm getting old).
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Re: Sq4 MkI- new life

Post by simon.holyfield »

allan.walker wrote: Sun Feb 26, 2023 4:40 pm
simon.holyfield wrote: Sun Feb 26, 2023 4:11 pm That's exactly my line of thought.
But....isn't the capacity of the return side of oil.pumps supposed to be greater than that of the feed??
If that is the case, why does the sump fill up with oil?
A fair question... Assuming that the suction side is in good shape, and Gui says it was, I don't have an answer at the moment.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
https://ariel-square-four.blogspot.com
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