Author Topic: Change in oil colour  (Read 859 times)

Offline Pecon

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Change in oil colour
« on: 23.10. 2012 16:10 »
  Just got the bike back on the road after a bottom end rebuild. I ran it for about 80 miles when I discovered that I had a crack in the oil tank. When I drained the oil (Castrol 30) I noticed that it had started to change colour from gold to a dirty grey. I checked the sump plug and found that the magnet was covered with a thick grey grease like substance which when I ran my fingers through it just felt soft with no apparent metal particles. Both the sump and tank filters were clear.

 I contacted SRM who did the rebuild and their opinion was that the substance around the magnet was a fine cast iron from the cylinder bore which was normal, which sounds plausible but why the change in colour?. I sent off a query to Castrol and they said that perhaps a graphite or moly paste might have been used for initial lubrication. 

 SRM also fitted a Super Rocket Camshaft and I was wondering if this would require any changes to tappet clearances?. I did an initial setup at 10 thou but will soon be rechecking after I tighten the head when I put up a few more miles.

Peter

Online morris

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Re: Change in oil colour
« Reply #1 on: 23.10. 2012 19:49 »
Hi Peter,

I have exactly the same experience. Only, my bike has at least run for about 10000 miles since its rebuild.
When I acquired it about 6 months ago, I changed the oil, and changed it again after 200 miles.
I also noticed the oil was greyish of colour, and on the magnetic sump plug I found a grey fluff which, when I rubbed it between my fingers was like an extremely fine paste.
In my opinion, this can/will do little harm, but if anybody could give a scientific explanation, I will be glad to hear.

regards,
Patrick

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'52 BSA A 10 Plunger
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Offline shabashow

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Re: Change in oil colour
« Reply #2 on: 23.10. 2012 21:00 »
The answer's in the thick paste you found on the magnetic sump plug. That is very fine particles of iron which is worn off the various moving parts as they bed in. The very fine nature of the particles will reflect light back to you. The oil will blacken, also, due to combustion products, the effect of heat and friction. Black with the fine particles in susupension will appear black. Once the engine's components all bed down, and the inital (highish) wear rate settles down, your oil should tune from gold to black between normal changes. The amount of fluff on the plug will also diminish over time. My bike's done around 8000 miles since its rebuild and there is virtually no fluf on the plug, and the oil is black when I change it. Initially, I had the same symptons as you've described.

Offline Pecon

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Re: Change in oil colour
« Reply #3 on: 23.10. 2012 21:48 »
Thanks guys, it's a relief to hear that this is a common experience. I was expecting the oil to darken with use but the very low mileage at which it occured was a concern. I've refilled it with fresh oil and will give it a couple of hundred miles and change for a 50W as recommended then.

Can anybody comment on the tappet clearance issue?.


Peter

Online trevinoz

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Re: Change in oil colour
« Reply #4 on: 23.10. 2012 23:40 »
You say that you have a Super Rocket cam but which one?
The tappet settings are 0.008" & 0.010" but apparently the 357 cam is set to 0.010" & 0.012" for maximum power output, according to Eddie Dow.

Trev.

Offline muskrat

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Re: Change in oil colour
« Reply #5 on: 24.10. 2012 09:53 »
 I think it's because people who fit a 357 usually fang them a bit harder and produce more heat requiring more clearance. Works for me. *smile*
Cheers
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Offline shabashow

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Re: Change in oil colour
« Reply #6 on: 26.10. 2012 18:52 »
Black with the fine particles in susupension will appear black.
Spot the mistake (apart from the spelling).
This shoiuld have read Black with fine particles in suspension will appear GREY.
Doh!

Offline wardleybob

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Re: Change in oil colour
« Reply #7 on: 28.10. 2012 18:18 »
when I rebuilt my engines I always yous graphite grease It stops wear on first start up no matter how 
long they stand