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I guess I am basically asking if the engine is being dyno tuned (through out the entire RPM range and gears) before you take the bike home, then can you safely ride it like you stole it as soon as you get on it?
I'm certainly no expert, but there are a lot of guys that disagree with HD's break-in procedure (and lots that do agree with it). Those that disagree feel the best way to brake in a Harley IS to ride it like you stole it.
The rings and cylinder walls of a brand new engine need ample time to allow complete seating. During that time the friction encountered will generate a lot of heat. The higher the RPM's the hotter it will get. Too much can do mild to moderate scoring of the walls and case harden the ring edges as they expand too much too rapidly. That's what varying the break-in speed will avoid. Seating will happen gradually. It may not take the full 500 miles to do so. But then what's the rush. I wouldn't dyno an engine until it had 1000 miles on it just to be safe. That'll give all moving parts time to get use to each other. JMHO
The rings and cylinder walls of a brand new engine need ample time to allow complete seating. During that time the friction encountered will generate a lot of heat. The higher the RPM's the hotter it will get. Too much can do mild to moderate scoring of the walls and case harden the ring edges as they expand too much too rapidly. That's what varying the break-in speed will avoid. Seating will happen gradually. It may not take the full 500 miles to do so. But then what's the rush. I wouldn't dyno an engine until it had 1000 miles on it just to be safe. That'll give all moving parts time to get use to each other. JMHO
I agree with this post entirely. I would like to add that lugging the motor, while always a bad thing for an air-cooled v-twin, is especially bad in the first 1000 miles. It leads to especially high cylinder head pressures and extreme heat. During the first 100 miles, operate the motor conservatively in the 2500-3000 rpm range. For the next 500 miles, I suggest conservative engine demand in the 2500 to 3500 rpm range. Oil and Filter change at 1000 miles of course to analyze if it made any significant amount of metal.
Just a quick question for those that are experienced with engines and building them. When is the most important time of the engine break in period?
I ask because if you get a new bigger engine they dyno tune the engine and hit the higher RPMS, so would this not hurt the engine from the start, or is it a long term break in that matters and short bursts up through the gears doesn't do damage?
I know the break in process Harley suggests, but just wanted to know about this.
Depends who supplies the 'new' bigger engine. In my case, when I had an S&S engine installed by an S&S shop, they went through a process of several runs of differing lengths, including some oil changes, progressively increasing run time and revs. I wasn't there, but it must have taken them some time. The first dyno tune didn't take the engine to peak rpms, I went back for that some time later.
My motor was rebuilt last Sept. by an independent shop. The builder did the initial break-in runs under controlled conditions on the dyno. Must have taken a while because there were over a 100 km on the motor when they let me have it with a fresh oil change. I was told to avoid long periods of the same RPM / highway speed but to vary it and stay below 3,500 RPM for the next 1,000 Kms. They also most strongly said do not lug the motor under at all. So I ran the machine at various speeds within the RPM guidelines for the next 1,000 Km and had another oil change (which was clean). I ran the bike another 1,000 kms but brought the speed up to 5,000 RPM and then backed off to 3,500 RPM and had the oil changed again (still clean). Bike is running pretty good but now to bed for winter. The oil I used to break in was dyno (mineral) oil as I believe that helps seat the rings and settle things down better. I'll run the next 5,000 Km with the mineral oil and then might go to synthetic.
Toying with the idea of another final dyno run???
Big old radial aircraft engines would break in the first 100 or so hours with mineral oil before going to a detergent based oil to get the rings seated and everything settled down so my thinking is the same. Some of these engines had a lot of oil; if I remember correctly the DC6 had 37 gal of oil per engine.
So, here is what we have in the shop and 90% complete: 2019 RKS orig. 114 then 117 stage 3 Harley, now going to 128 below, 7000 miles, Twister Cherry S&S 128 cu in Power Package https://www.sscycle.com/products/pow...m8-114-models/ 550 cam , 4.250 bore, forged pistons, 11:1 comp., oil pump plate, S&S tappets, S&S cone springs. S&S Head bolts Harley 64mm Throttle body SE Fuel injectors 5.5g/sec., Power Vision tuner, Fuel Moto Jackpot 2:1:2 header, S&S Grand National slip ons, Harley Extreme Intake, Harley Clutch upgrade to 10 plates and 1200N springs,
The below is not my performance curve. It is from Fuel Moto's website. It is the closest build to the one I am trying to build. The only difference is I am going with the Bigger 64mm throttle body. I am hoping for a little more horsepower. I should be able to breakin over the next few weeks, then final tune and I will post the results.
Well, by following the suggestion of Fuelmoto and installing the SE 64mm throttle body, we got a little more top end!
Last edited by #Ride; Feb 10, 2020 at 09:38 PM.
Reason: spell check
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Final Dyno results
