I have a 1997 Harley Softail Custom with 45,000 miles on an EVO. I have been asking around about switching to synthetic oil and have received mixed answers. Some saying too many miles on the bike, don't switch, it will leak out the gaskets. Others saying it won't bea problem.
My questions are:

Should I switch with that many miles? Has anyone done it without leaks?
If so, which oil? Amsoil or Mobil 1 or ...?
Should I flush the system 1st with engine flush?
Also, Should I also change the tranny & primary fluids?

Any help would be greatful.

Stcryder

 

Personally, I would not hesitate switching. In my opinion the benefits far out way the risks Sometimes you get leaks and sometimes you don't. Depends on how the bike was maintained. If the previous owner changed oil regular and used a quality petroleum oil then there should be no problem. Occasionally synthetic oil will find a bad seal if one is caked up and dried out from "petrogunk" . Should that happen, change the seal and put the synthetic back in. Synthetic Oil has the same seal conditioners in it that Petroleum does and by law, it has to be seal compatible.

The proper way to flush an engine is to dilute the oil with engine flush and run at idle for 30 minutes. That is ok for water cooled motors but PLEASE do not flush an air cooled engine. Good way to burn it up. As for which oil, I prefer AMSOIL but Mobil 1 V Twin and Redline are also good oils. A matter of choice.

You can run 20W50 in all three holes but most folks prefer to run a gear lube in the tranny. A 75/90, 75/110 or 75/140 are all good choices. AMSOIL has all three weights, not sure about the other brands.

Bear

 

Agree with everything Bear said. Sounds like we may have gone to the same school??

 

I heard the same thing about my 96 Evo with about the same mileage. Changed to Syn3 in the engine and no leaks. I put Formula+ in the tranny and primary. I did this just for the hell of it. I really do not think there is any advantage to running synthetic oil if you change your dino oil regularly. I know most on this forum disagree but I'm sticking with my opinion. I do have syn3 in all three holes on my 07.

 

I recently made the swith on my '91 Sportster.

I did develop a few leaks, but it's not necessarily a bad thing. The "leaks" are just the synthetic oil creeping into everywhere it can and that's a good thing. It just happens that it wicks through areas dyno oil doesn't. So it improves lubrication while leaking a few drops here and there. I think it's worth it.

 

I think I'd stay w/ what your using, really not worth the possible down side's of a change. I think you'll be chasing a few leaks, and noises. It looks like you only ride around
4-5k miles a year so is it really worth it?? Oh. I'd never use H/D's syn. not worth it.. I use Mobil 1 15/50 syn. and my bike loves it. Steve