Oil cross contamination

[Fleetway]

At the risk of howls of " Oh no not again" and incurring the wrath of Baza, I know the benefits of this or that oil has been discussed at length, the subject of contamination when changing from one to the other has not, apart from one post I found from Banquo. When synthetics first arrived the use of flushing oil was recommended when changing, I have just bought a bike which has synthetics, and I want to change it back to HD oils, can anyone tell me of their methods of changing, or of any problems?

[Tony Cross]

My question would be why do that? An inferior spec at a higher price. A triumph of marketing over technology.

[banquo]

Which is a good question....
Assuming you do want to do it though, drain oil, remove filter, remove plugs, and spin motor until dirty oil stops coming out. Refill tank with oil, and spin again until clean oil comes out. Refit filter, refill tank with oil to correct level, and you're done. If paranoid, run it for 100 miles or so, and do it all over again. Flushing oil is designed mainly to remove gummy deposits inside engine, rather than to prevent cross contamination. Unless the motor's ancient, probably of no benefit.
Tips: Run starter for only about 10 seconds or so, and allow to cool in between spins. It's not designed to run continuously. Also, if your battery is anything less than perfect, remove leads, and connect them to a car battery with some jump leads instead, to save draining the bike's battery.
Some people are brave enough to fill the oil tank, and start the motor, running until clean oil comes out, and topping up as they go along.
I'm not that brave....

[Fleetway]

Thanks for the replies, as for why, I guess because I've always used mineral oils, mainly GTX before I had a Harley, at the moment I've no idea whats in the transmission, but I know it's Revtech in the engine.

[Chris L]

Originally Posted by Tony Cross

My question would be why do that? An inferior spec at a higher price. A triumph of marketing over technology.

Inferior spec yes...but its not more expensive...H-D 360 half the price of Syn 3...having said that Ive got an Evo, if it was a TC id use Synthetic.

[Tony Cross]

Last week I bought 5Lts of full Synthetic for £25. No real difference to MoCo oil which is mineral. We get charged for the name. God knows what the MoCo charge for full synthetic as specified for the the big twins. Shop around, it can pay off.

[Scotty]

Originally Posted by Fleetway

I've always used mineral oils, mainly GTX before

Must be an old dude then...

I used to have a tyrannosaurus rex that i ran on GTX!

[Fleetway]

Pensioner, 65 this year