Blowby Article

[SamC]

I just stumbled onto this thread (slow reader) and I notice something nobody's touched on; relaxing the stresses in the castings, forgings, etc. Freshly-made pieces have locked-in stresses that will eventually normalize. If they're heated too quickly and too much, the stresses will deform the piece. Mototune totally ignores this. Fresh parts will turn into pretzels if they're treated like he says.

Years ago, Gordon Jennings noted that when he was messing with piston shapes on two-strokes by welding on the domes, a used piston would stand it OK but a new one would generally deform into uselessness. The difference was that the used pieces weren't internally stressed, so they didn't deform when heated by the welding.

I'm not a professional engine builder, I'm in the once-in-a-while category. I used to be a machinist and I'm familiar with normalizing parts. Seeing something like the "beat it hard and it'll be fast" school of break-in makes me glad he's not building my engine.

[shotgun46]

so tell me what is heat cycle your motor ?????

[Albie1200]

Very interesting information here.

My Dad is getting ready to get a 07 wide glide or softtail custom. What should I tell him to do for the break-in? He lives about 15 miles from the dealer that he would buy from. Not a huge distance, but enough to bring the motor to full operating tempature. Should we go down first thing in the morning with the intention of spending a good part of the day going through the first steps in the S&S proceedure that Stevo recommends?

It would look kinda funny sitting there after the purchase(not to mention a patience tester) starting it for a few minutes and shutting it down to cool completly. If it will produce the most power and least oil comsuption I will push him to try it, as I think it is worth it.

Question is: Do you guys with the best experience think it is worth it? or do you have any other ideas?

[stevo]

That's how I do it when I rebuild a motor...



I only ran it for a few seconds... then a minute or so ... then rode around the block and bedded the rings in when I was at the dealership...

The S&S break in is the ideal way.... and babying the motor is the opposite end of the spectrum...

Basicly run it medium/hard for short busts as heat is the enemy... then let those bursts get longer

ya don't want things to expand and distort that much that ya break the oil film....

and ya gotta take the high points off left from machining..

[Albie1200]

Thanks Stevo!!

[blazer95]

What about an 2001 XL1200c that is spitting oil out the air breathe, bought it with 3,112 miles now has 10,000 miles ???

[sportymike02]

Originally Posted by blazer95

What about an 2001 XL1200c that is spitting oil out the air breathe, bought it with 3,112 miles now has 10,000 miles ???

on a sporty?? no way!

unless its more than a few drops, thats normal. you can install a breather or get used to it. welcome to the oily right leg club of sportster owners!

J&P Cycles part# 4000330 $30 or if you are handy you can make your own
keep the sun in your face & the shiny side up

[blazer95]

thanks i will have to get used to then i still love my sporty

[Mattbastard]

This is all great information for when I re-assemble my converted engine this spring.

[robert]

I just learned more from this thread in ten minutes than I'll learn the rest of the day! Hey, now I can go back to bed.