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.

 

Builders do break in on the dyno before any high rpm runs.

 

Some better tuners can break in your bike on the dyno but they still don't do high RPM runs until it's broken in.

 

So if Harley suggest no high RPMS and taking it easy for the first 500 to 1k miles, then how is the engine broken in properly by the tuner on a new engine? Is it really only the first 10 to 20 that matters? I mean a tuner isn't going to put 500 miles or 1k miles on the engine before he tunes it after install.


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've wondered about this myself, Nate....

 

The factory does run them up on the dyno and the rings are pretty much seated if not completely seated already. That 500 mile break in requirement is more for giving new riders time to learn their bike before running it hard and ending up with some broken bones or worse. Another thing is that it's not just the engine that needs breaking in but the whole driveline too. Most engine builders will tell you to break it in as you would normally ride it or even harder than you would normally ride it.

 

If someone tuned it, absolutely. When I got my bike back from the dyno, they ran it over 100 miles tuning it. You would just do a bunch of runs at the proper RPM to break it in before going full blast on the dyno. You can control the conditions better on the dyno so you can get away with doing it right and taking far less miles to seat the rings and clean out the metal shavings left over from machining. I'd hope they would change the oil after breakin and before the real fun begins.

 

Stock heads and TB is the main reason for the low power. Everything else is huge, but starving for more air and gas mix. Personally, out of a 128 I wouldn’t want any less than 130hp/tq minimum. Skipping on the air coming into the bike will definitely show in the numbers.

...wanted to add that I on my previous dyna I built an S&S 106 w/ head work and stock TB/injectors and on dyno it did 113hp and 120tq

 

I think I will find out some of the answers in the next week when my wrecked motor gets rebuilt.

From the S&S site:

For the balance of the first 1000 miles the engine can be run in a normal but conservative manner. You can be more liberal with the rpm range and the motorcycle can be operated at normal highway speeds. Avoid overheating or putting any hard strain on the engine; no drag racing, dyno runs, excessive speed, trailer towing or side car operation.

 

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.

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