Hi
I have dis-assembled an OS 91 FS II pump engine for cleaning. How to know when the bearings need to be changed? When I spin the bearing it does so noiselessly but after the bearing has been soaked in thinner for about 2 hours, it makes lot of sound and does not spin smoothly. But after a few hours and some lubrication, it came back to normal. It this OK?

What kind of oil should be used to re-assemble the engine? I can not use the after-run oil as the engine has a pump. Can I use the SAE 15W/40 car engine oil? We do not get Klotz or Marvel oil in India.

Thanks

Vikas

Car engine oil is OK, maybe a little thick. I use only Automatic Transmission fluid for all of my engines. It does the job and is a lot cheaper and more readily available than after run oil.

Ed S

It's normal the bearings make a little noise when there is no lubrication at all in them anymore. I replaced a bearing in my Irvine .53 today. It made noise even when very greasy. There was some rust on the big rear bearing. Replaced it and the engine turned over smooth and noiseless again.

Would standard cycle oil (medium-thickness general purpose oil) be suited for use as an after-run oil?

any type of multi-purpose (thin) machine oil works best. It will settle down thruogh the engine a lot better than a thicker oil, and when its time to run it again it will burn out cleaner. Sewing machine oil also works great.

The absolute best easily available oil for assembly or after run is plain old Dexron automatic transmission fluid.

It has a moisture displacing quality, so it actually works its way between any water droplets and the underlying metal.

It is a mild detergent, so it cleans the gunk out.

Finally, it is highly resistant to degradation from exposure to the atmosphere, so once it';s in the engine it will last indefinitely.

A good grade air tool oil might be better, but it's harder to find. Every grocery store has ATF Dexron.

Bill.

" Every grocery store has ATF Dexron"

In INDIA???!?

Gary:

Good point. Maybe not in the Netherlands, the UK, or Canada either.

I try to avoid it, but I'm afraid I think "Nationally" far more easily than "Globally."

Bill.

As far as the cycle oil or sewing machine oil is concerned, they work very well on non pumped engines. These oils contain kerosene and can not be used in pumped engines as they damage the pump diaphragm.

Hence, will the car engine oil or ATF will have any effect on the pump diaphragm? Do they contain any kind of chemical that may react with silicon?

Thanks

Vikas