I have found that the idle on these engines will not settle in the way you want until after about a gallon of running. Then it will be very stable to where you can fine tune it nice and low without stalls.
Also this engine is very easy to have the low needle too lean because it will mask it very well. It will idle ok and bottom end will seem ok but that is because you top end is too rich... but the engine will run hot... Once you get used to tuning them it becomes easy but every brand tunes a bit different.
But all in all I am VERY happy with the power these produce! My truggy has never been happier :-)
Originally Posted by
ShortCourseOnly
Thanks Alan. This matches my experience so far. The pinch is pretty tight from my little experience with smaller engines. I'm glad to hear that this should smooth out.
I am in the initial tuning phase of brake-in and less than a 1/2 gallon through the engine so far. I am running 30% MK (Brazilian blend) fuel with an OS P4 plug, 2035 Pipe and the two small head shims that came installed on the engine. The local rep in Brazil has helped me a lot with the details of tuning this engine and has been running them for the past 3+ years. Currently my engine is running fairly well but I think it is on little rich HSN and a little lean on LSN. I am getting good smoke and crisp response in all throttle positions and the idle seems OK only. I was tuning idle yesterday expecting a high speed for a few seconds and then settle to a lower speed indicating rich. I would run at higher RPM to clear out the crankcase before entering idle. What was strange was after I dialed it in stable with little droop and smooth low idle I would get a higher speed surge for a short time. I would run high and enter idle smooth and after a few seconds the idle would increase for a second or two and then settle again. I am thinking that my HSN is rich loading up the crankcase such that the idle is good to start and then leans out until stabilizing. I need to run it more this weekend to adjust the tune further. My HSN is at 3 3/4 and my LSN is 1 3/4 right now.
Head Shims:
My local rep stated that 0.55mm is what he found as the best thickness for 30% fuel running the OS P3 plug. I am getting a dail caliper to measure the shims provided with the engine to select shims to get close to this. Has anyone else measure head shims to determine their best selection for a OS P4 plug? I only have P4, RT4, RT3 and colder plugs right now.
I hope to finialize break-in this weekend and burn through most of the MK fuel I have. I hope to switch to Byron or O'donell 30% Race blend fuel.