Changing oil on '82 Maxim 400

I do not have a manual and the view opening on the crankcase has been clouded over so i can't see the level of oil. So, a few things:
- What is the best way to "flush" the oil? Wondering if there is a technique for cleaning after letting the old oil drain out?
- What oil is recommended?
- How much oil should I add to proper fill?

Obviously new at this....any help is appreciated.

Thanks,
Josh

 

I would just put new oil in, don't worry about flushing. Wipe off the magnetic drain plug if you have it, clean all the parts pertaining to the oil filter thoroughly before reinstalling with a new filter. Probably let it run for 5-10 minutes to warm up first, then drain it and move it back and forth, left and right if your concerned about getting as much dirty oil out (also helps to leave it drain for an hour or two). Other than that modern oils have very good detergents in them that if changed regularly should work effectively. As for the amount of oil my guess would be 2.3 liters based on a quick google search.

 

10w-40 motorcycle oil will be fine (look for JASO MA certification). The sump capacity should be cast into the clutch cover near the oil fill, but I reccomend that you source a new gasket for the clutch cover and pull the cover to clean the sight glass, or you will never know if the bike is losing oil as you ride (a litttle drip might go unnoticed otherwise, and will add up to quite a lot of oil loss). You don't need to flush the old oil, just warm the bike a bit, pull the sump plug, and let it drain. You should also change the filter.