White spirit flush and oil strainer

Non bike specific questions

White spirit flush and oil strainer

Postby GrahamW » Thu Nov 02, 2017 3:44 pm

Hi I just had a look at my oil strainer and it needs replacing as the gause is coming away from the housing resulting in holes where unfiltered oil can get through. I am having a worry as I put the crank cases back together and put the clutch back together just over 3 years ago but then moved house so it all went to the back of my mind. I cant really remember what I did but I have a hazy memory of checking the oil pump while the cases were split and it looking ok I think I tripled checked most things before gluing it back up. I think I just gave the strainer a cursorary glance to check for debris at the time.

oil strainer.jpg

I am going to order a new strainer the screws were a bit mangled where somebody had a go at removing it before I think so had to use mole grips to undo the old screws, but have a couple of stainless button head screws the same size so can use them with the old washers and refit the new one.

While searching the forum for oil strainer I came across this thread:


Now filling the engine with 5l of white spirit sounds like a great way to give it a good clean and I think mine really does need cleaning now.

Bob can you extrapolate on how you do that flush, putting the white spirit in instead of oil and then draining from the sump I understand but do you run the engine with the white spirit in or do you just cold crank it? Should I have an oil filter in while doing that? Sorry for all the questions it's just I have focused myself on getting this bike going now and why to try and do a good job of it. ;)
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Re: White spirit flush and oil strainer

Postby nug » Fri Nov 03, 2017 12:08 am

I would not put any neat solvent or spirit in a motor. The Big motor is fairly resilient having a roller bearing crank but you would never assemble a motor without lube on it and by doing a neat flush you are going to strip any oil from critical running surfaces. Just use a branded flush at running temperature. They tell you to idle for 10-20 mins then drop the oil. There is a reason for this. Better still, just do a couple of oil and filter changes in a short period.
I recently got called nasty names on youtube after telling a guy that he shouldn't fill his engine with kerosene and turn it over on the key to flush all the oil ways through. This guy has been doing it each time he did an oil change and constantly gets grit? and metal in his sump (his words). He is destroying his bearings! He is basically having a dry start up each time he does this and that is wrecking his motor. Most of the damage and wear in motors is done at startup when cold and this is with oil in it! It is also bad for seals. The Big bottom end might survive this treatment a couple of times but the cam and followers will take a hammering and it is something I would never do.
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