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Rubber particles in oil

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Rubber particles in oil

Posted by fred_goode at April 10. 2017

Just drained the sump of my 1970 Commando after a 2 month layup (wet sumped of course) and found a number of 0.5 to 1 mm rubber particles in the oil pan. Prior to layup I had removed and replaced the timing cover to replace a leaking blanking plate gasket and ridden the bike for about 15 minutes. Anyone have any ideas as to the origins of the rubber or does it look like I may have to pull the timing cover to check the oil pump seal, and crankshaft and points oil seals. Thanks Fred

Re: Rubber particles in oil

Posted by david_evans at April 10. 2017

It would be difficult for rubber to get from the timing chest to the sump but not impossible. on a standard 1970 commando the hole into the crankcase from the timing chest is up nearly level with the intermediate gear. If your pump nose seal was displaced/damaged. plenty of oil would flood the timing case and the bits of seal could go though the hole into the crankcase. I drilled a hole through below and to the left of the oil pump.  I think a lot of oil sits in the timing chest doing not much. Symptoms, Run the bike, the crankcase should be scavenged almost clear of oil, remove the crankcase drain plug, a teacup full of oil drops out, where did that come from?, The timing chest via the RH main bearing.

Re: Rubber particles in oil

Posted by john_holmes at April 10. 2017

Could be the oil feed hose is decaying internally, or the hose after the oil filter on its way back to the tank or the breather hose. Trouble is how do you determine where it came from until you find the culprit.

Re: Rubber particles in oil

Posted by jonathan_newton at April 10. 2017

"Prior to layup I had removed and replaced the timing cover to replace a leaking blanking plate gasket..."

You sure its Rubber?  Not gasket sealant overspill that has rolled around a while.... or castor oil additive congealed?  What ever it is, it's not traveled  far or it would have been filtered.

Set it light, if its rubber it will stink and produce a black acrid smoke. if it fails to burn its probably liquid gasket/ sealant.

If it is rubber, refer to JH's answer above :) 

J

Re: Rubber particles in oil

Posted by fred_goode at April 11. 2017

Previously jonathan_newton wrote:

"Prior to layup I had removed and replaced the timing cover to replace a leaking blanking plate gasket..."

You sure its Rubber?  Not gasket sealant overspill that has rolled around a while.... or castor oil additive congealed?  What ever it is, it's not traveled  far or it would have been filtered.

Set it light, if its rubber it will stink and produce a black acrid smoke. if it fails to burn its probably liquid gasket/ sealant.

If it is rubber, refer to JH's answer above :)

J

Re: Rubber particles in oil

Posted by fred_goode at April 11. 2017

Great suggestions thank you. I will try them out over the Easter break. Hoping it will be John's idea as all the hoses have been replaced except for the breather hose which is 46 years old and was pulled off and on and twisted and bent several times in the last few weeks So it may be breaking down internally. I should also add that the engine has had the breathing modification to move from the timed breather to an elbow at the timing case blanking plate including the drilling of the crankcases.

Re: Rubber particles in oil

Posted by fred_goode at April 17. 2017

Hoses were all fine so l bit the bullet and pulled the timing cover. Found the remains of the oil pump conical seal in he bottom of the cover - should have taken more care when I replaced the cover last time. Replaced the seal and the bike runs fine. I've found over the years that Commando issues usually have 3 or more possible causes and that the correct fix is usually the most difficult and time consuming one. Still love them though!

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