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Break In RPMs

1179 Views 6 Replies 4 Participants Last post by  claydbal, 
K
Before someone asks, I haven't read the recommended break in speeds in the owners manual. I have my own ideas based on experience. I wanted to limit the rpm to not much higher than 2000 while not lugging it either for the first 75 miles. So, with no tach I calculated the RPMs and thought I would share with others who may also be wondering.

The RPM formula is....

RPM = (MPH X RATIO X 336) / 25.75" REAR TIRE DIAMETER

Example..(30 mph x 5.09 3rd ratio x 336) = 51,307 / 25.75 = 1,993 rpm

(40 mph x 4.17 4th ratio x 336) = 56,045 / 25.75 = 2,176 rpm

(45 mph x 3.46 5th ratio x 336) = 52,315 / 25.75 = 2,032 rpm

45 in 5th is right on verge of lugging it unless you are going down hill because of the lower torque multiplication as the ratios decrease.

Now when the motor is broken in and the rpm and forward momentum is up, along with more stored flywheel energy available, different story!

75 mph in 6th is 2,897 rpm

All the ratios are listed in the owners manual if you want to play with them
:cheers:
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2,000 rpm's is lugging a TC HD motor.......Ward
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bigblock455 said:
2,000 rpm's is lugging a TC HD motor.......Ward
Click to expand...

Are you saying you should cruise 30 in 2nd if you ride a Twin Cam, or that you are lugging the motor as you take off in first from 1000 RPM?

The appropriate RPM as it relates to not lugging your motor always depends on the available torque multiplication as determined by the overall gear ratio. Other factors also apply, but none are as important as the gear ratio is. :cheers:
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No, I'm saying that in my book when moving under 2,000 rpm is lugging it. I think motors once heat cycled should be broken in as your going to ride them within reason. Oil change after first 100 miles, then 500, then 1,000 and every 2500 to 3000 after that. 5th gear needs to ba applied carefully between 2500-3000 and a little after. More damage is done, in my opinion, by under reving than over reving TC motors...................Ward
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Check this site out. Some interesting reading. Of course ask 12 people how to properly break in a new engine and you will probably get 12 different answers.
http://www.mototuneusa.com/break_in_secrets.htm
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The mototune guy has been around for a while, and although he's not always wrong I don't have any respect for most of his theories.

If Ron Dickey was one of the 12 I think I would go with him, and not just because he has forgotten more about making power than most will ever know, but rather because he admits to still learning and not knowing everything. In other words he's a thinking man. What he found to be true about ring seal and break-in is well documented, but something rarely talked about.

http://www.axtellsales.com/RonsDocs/Ring Seal.pdf

http://home.ama-cycle.org/forms/museum/hof/hofbiopage.asp?id=117


Some interesting reading. Of course ask 12 people how to properly break in a new engine and you will probably get 12 different answers.
http://www.mototuneusa.com/break_in_secrets.htm
Click to expand...
http://www.mototuneusa.com/break_in_secrets.htm
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C
drive it like you stole it and trade when the warranty is up.
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