I doubt it's going to be a long way off, if you're running in, you aren't going to be running it for a protracted period on wide open throttle. It's heat build-up that will cause a seizure/burning/nastiness. Put in something close to what you estimate to being right, warm up the oil, take it for a short run, check the plug. If it looks to be running lean, up the jet. Rinse and repeat.
There's a lot of myth, or I don't really know what floating out there in the ether/peoples heads about "running in". You are wearing the piston rings against the honing marks on the bore so they make a seal. This will generate more heat than in normal running. As such you need to be mindful that heat doesn't make the piston expand so much and so quickly that it jams in the bore. That's all there is, as far as i can see, anything else people might have in their heads is just voodoo. Your bearings are as round and smooth as they are ever going to be, your oil pumps are as sealed as they are ever going to get, your valves are clean and sealed, if your floating bush ever touches anything but oil again you are in trouble. The only bit of your engine that needs to learn to do what it needs to are the piston rings.
So being a little bit off in your carburettion may increase that heat. Going for a 20 mile run at full road speed with an uncertain carb setup on a freshly rebuilt engine would probably be a bad idea. Warming your engine up on the idle circuit then having a half mile pull and stopping to check the plugs is unlikely to result in a disastrous heat build-up. The more normal your plug chops, the longer you can confidently make those pulls.
Puting my money where my mouth is, I jumped on my 612 with a new piston and rings and a roughly ballpark TM32 carb using baseline settings from people running them on 535 bikes and did some runs and plug chops. I was way out on all the settings even getting some detonation under load but I was careful, did short runs and listened to the engine and walked my way into the correct settings. I started on some 1/4 throttle runs and got the pilot jet dialled in. Then I did some 1/2 throttle and got the correct needle jet. 3/4 to full took a bit of getting and I went through various combinations of needle size, needle position and main jet before I was happy. Nobody died.
I'd suggest you do similar. Go out for a few short 1/4 throttle runs and check the slow running is where it should be. Then go for some 1/2 throttle runs and check that. They'll probably be right, or near enough. Then work your way up to the main jet. It'll probably be damned near run-in by the time you've got it and multiple heat cycles with steadily increasing engine pressures and rev speeds isn't a bad way to do it.
Topic: Black sparg plug, heavy oil use, new build up engine (Read 10590 times)