Flushing a crankcase out

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Flushing a crankcase out

Postby Group Leader » Mon Sep 14, 2020 11:44 am

Elsewhere you may have learnt of my tail of woe with regard to my little Beeza. To cut a long story short, the barrel is being re-bored, new piston rings etc but the bottom end is remaining intact (hopefully!).

I've fished out of the crankcase all the bits of piston ring debris that I can see but want to give the whole bottom end a good flush out and then a blast out with an airline. The Beeza has the benefit of an oil filter mesh and the pump at the bottom of the sump which can be accessed by removing a plate on the bottom of the crankcase. Removal of the plate and filter rather conveniently allows the sump to be completely drained without having to turn the bike upside down or anything similarly drastic!

What should I use to flush/clean out the crankcase. A friend has suggested petrol but that sounds rather too lively to be splashing a quart or so about so I was thinking paraffin but the period handbook I have (which isn't brilliant it has to be said) states in a number of places to never use paraffin! Why would that be? And what would you suggest?

Obviously I'll have to be quite careful to make sure all of the solvent (whatever is used) has been replaced with nice fresh oil (in the mains, big end etc) before reassembly and starting.

Any suggestions?

TIA

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:

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Re: Flushing a crankcase out

Postby Reynard24 » Mon Sep 14, 2020 12:15 pm

I seem to remember reading somewhere that paraffin never dries and leaves a residue on the engine components and therefore using it to flush an engine would contaminate the new oil causing it to breakdown quickly.
I've never flushed a crankcase with bottom end still in situ but I do use petrol for other flushing/cleaning jobs.

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Re: Flushing a crankcase out

Postby Group Leader » Mon Sep 14, 2020 12:22 pm

Oh thanks for that information, that makes sense as to why you shouldn't use paraffin! :beer:

Alan
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Re: Flushing a crankcase out

Postby Mick D » Mon Sep 14, 2020 12:27 pm

Hi

You are going to split the cases aren't you?

During my restorations I usually start with 'Gunk' followed by blasting with a water fed air gun. Stubborn stains get a dose of IPA/brass brush followed by another blast with the water gun and then dried by air blast and heat lamp / hot air gun.
Galleries are checked with drills or wire and then cleaned and blown through.

Regards Mick

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Re: Flushing a crankcase out

Postby Rob Harknett » Mon Sep 14, 2020 1:51 pm

Back in the 50's we had flushing fluid. So when changing oil, you filled the tank with flushing fluid ran tghe engine to clean out sludge.
BUT, you are taking damaged metal. So the engine really needs to be striped.

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Re: Flushing a crankcase out

Postby Group Leader » Mon Sep 14, 2020 2:35 pm

Mick D wrote:Hi

You are going to split the cases aren't you?



No, not if I can help it. It's heavy maintenance Mick not a restoration ......

Alan
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Re: Flushing a crankcase out

Postby Mick D » Mon Sep 14, 2020 3:27 pm

Group Leader wrote:It's heavy maintenance Mick not a restoration


No Noo Alan

You're talking 'overhaul' - not somewhere I'd take short cuts ;)

Regards Mick

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Re: Flushing a crankcase out

Postby Tolly » Mon Sep 14, 2020 6:08 pm

I personally would flush out with diesel as this is non flammable and acts as a lubricant.
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Re: Flushing a crankcase out

Postby 1608 » Mon Sep 14, 2020 7:24 pm

I believe flushing an old engine is asking for trouble. I ruined a ford zephyr engine with flushing fluid. Bite the bullet and strip the engine. If you think about it, flushing will just loosen all the accumulated crap.

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Re: Flushing a crankcase out

Postby clive » Tue Sep 15, 2020 5:17 pm

I got away with flushing a crankcase using petrol after I holed a piston. Not sure I would recommend it though, back when I needed the bike to get to work the next day.
clive
if it ain't broke don't fix

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