Running-in seems fairly basic. The engines were designed to use 50wt oil, so I feel it would be best to use that (although others may have different ideas about that). They can use any oil from 30 to 50wt, of course, without harm, I am told. In winter a 30wt might be a good option.
The idea of running-in is to not drive the bike hard, so the piston rings can settle in, and other parts can get used to being in motion again. Change the oil after 100 miles. After that every 500 miles until you're at 1000+. By this point you should be ready to use the bike however you wish. The claimed top speed for the WM20 is 58 mph, so keeping it at around 30mph should be good for this early period. Don't ride for long extended periods with just one throttle setting. Vary your speed, even if only a little. One gentleman suggested that riding in the rain was a good way to ensure the engine was cooled well during the early miles. He'd had many bikes and I took his advice (because it was raining!)
Others may have other views. I'm just saying what I did with my bike.
I'm sure you'll enjoy the bike just as much on a country lane at 25 to 30mph as when you're flat out. It's a lovely bike to ride!
You have a roller bearing crank that will polish fairly quickly. Obviously the first 100 miles is best made up of a number of heat cycles and a head re-toque.
The only real worry is the bore. Presumably re-bored ? With which piston and to what clearance ? There is a school of thought which says that rings seal best if quickly run-in. I wouldn't risk it with an OE piston bored to modern clearances though.
Don't lug it and don't thrash it, work it harder up until 1000 miles or so is what I've always done with older engines.
Breaking in a new engine takes a lot of patience, but it is completely worth it for the long-term reliability and overall performance. You really have to track your hours and miles closely, much like managing a strict https://parkercountycourt.org so you don't miss any critical maintenance milestones during the process. Just keep varying the RPMs, avoid sustained heavy loads, and change the oil after those first few hours. Good luck with the rest of the build, it looks like it is going to be an awesome setup once it is fully sorted out!
Piston, rings, cylinder, small end bush, valves and guides, outrigger plate bush and any other bushes you may have replaced in the engine..Ditto inside the gearbox....Ian
I was reading an original rider handbook recently and it mentioned a couple of table spoons of engine oil in every fill of the petrol tank for the first 500 miles iirc
Re: New engine - running in process (Edited by Author)
If you want to put oil in the petrol, use two stroke oil the same as you would use in a petrol grass trimmer. It won't smoke of foul the plug like motor oil. It also will lubricate the carb slide and keep it from wearing out so fast.
I started doing this after spending a lot of money on a new 276 carb. As Draganfly wants £444.96 for one these days, I don't want to do this again.
Thirty years later the carb slide still looks as new. You only need a small amount of oil in the fuel.
