Topic: engine break in procedure?

[orkid1989]

alright i was wondering what is the best procedure for breaking in an engine? i have a 71 cb750 and im putting 849cc pistons, heavy duty cam chain, new cam tensioners, heavy duty valve springs, and a cam (the best one cyclex has). last thing i want to do is build the motor and mess it up by not breaking it in properly. ive heard of riding it hard to break it in (sounds like it will damage the motor to me) and the taking it easy method. any suggestions?

[phil71]

this isn't scientific, but i usually take it for a few quick warm up/cool down cycles right out of the gate, varying speed as much as possible, but not really getting much above 5k rpm. after an hour, i drop the first oil and look it over... that will give you an idea if anything's interfering, and it'll clear out the assembly lube. THEN go beat the snot out of it.

[orkid1989]

this isn't scientific, but i usually take it for a few quick warm up/cool down cycles right out of the gate, varying speed as much as possible, but not really getting much above 5k rpm. after an hour, i drop the first oil and look it over... that will give you an idea if anything's interfering, and it'll clear out the assembly lube. THEN go beat the snot out of it.

o so kinda run it hard bellow 5k and change the oil. also what oil should i put in there? i was thinking about using marvel mystery oil as well but not sure yet

[phil71]

Ugh, that question can get you a ton of responses in this place.. marvel mystery oil is an additive, not a crankcase oil. Its used, oftentimes to soak up moisture and free rust in old engines. I'd say don't use it yet.
   Original spec on these bikes call for 10w/40 OR 20w/50 multi viscosity. They don't specify what conditions, but I'll hazard a guess it's cold weather/warm weather (heavier in hot weather).
Since your engine's new, i'd go with a lighter conventional motor oil for now, maybe going thicker when the summer really gets cooking.
  Also, your engine is now pretty far from stock.. so who knows. Without specific instructions from the manufacturer of the kit, and cam, I'd just go with the OEM spec .
  I have a bike with 10k miles and the transmission definitely likes the heavier oil better, but you've got a lot of go-fast stuff.. and for all i know you have back-cut gears that would be less finicky than the stock .
   

[dave500]

dont let it idle,in fact turn up the idle a little,loading the engine for short 3 or 4 seconds almost to the point of lugging will bed the rings in quickly and well,pressure goes down the gap and actually gets behind the ring and forces it against the bore,avoid heavy downshifts and over revving,you will find the oil has a mettalic sheen in it,this is normal,i have small magnets stuck to the outer face of the oil filter and they pick up fur well,if your keen to tinker after a couple of oil changes drop the pan and have a gander at whats gathered and wipe it out,some aircraft piston engines get dissembled after break in and cleaned out then put back together, ford used to do lincolns engines like that.

[Kong]

Ride it easy for the first 500 miles, then change the oil and filter and then ride it as you normally would. 

A new engine has a lot of parts that, save for an oil film, are in direct contact with one another.  That would include bearings and journals, cams and followers, cylinder walls and rings/piston skirts, and of course gears, gears, and more gears.  There is always - always - some initial wear of these parts as they "lap" themselves to each other and that wear puts contaminants (metal) in the oil.  The larger of them is of course captured by the filter but many more microscopic particles are not.  You need to get that stuff out of there.  That is the reason for the first oil change early on.  The reason you take it easy on the engine is, among other things, that you do not want to overheat the engine at all; once the parts have worn in and the final clearances have established themselves, after the contaminated oil has been replaced, then you can crank it up without fear of doing damage.

[orkid1989]

o ok well what i mean is their any addative that u have to add to the oil or anything? before the motor was built a was using lucas 10w40 in it.

[Old Scrambler]

No additives............Lucas is fine............take a look on the Hi-Po page for ideas of how performance motors are 'run-in'.

[Doctor_D]

Gas pressure is what presses the rings into the cylinder walls and get's them to seat.  Taking it easy is an outdated and incorrect approach.  It's also a great way to glaze the bores.

Assemble and run in with clean, dry cylinder bores.  Use non-detergent 30wt for the first heat cycle (up to operating temp, vary revs).  Shut it down, drain the oil, change the filter, drop the sump and look for metal in the sump and filter element. You'll always have some fine metal from your first run, but that's all you should expect to see.

Install new filter, and non-synthetic multi-grade oil. Allow to cool completely, adjust valves.  Bring to operating temp, adjust mixture and timing, and go out and ride it fairly hard. Up hill, third gear roll-ons will give you the kind of cylinder pressures necessary for good ring seating. I have access to a dyno, and I break my engines in with full power pulls - and have never had a problem. If something was going to break under load, it wouldn't fare any better if I coddled it for a month first.  Change the oil again after a half-hour of riding, inspect for evidence of wear or failure.

I'm fine with using Synthetic motorcycle oil after a 12-18 full pulls on the dyno or a few weeks of regular riding.  Though many factory cars and bikes are run to their limits right off the assembly line with synthetic oil, I am still wary of breaking in an engine with it.  I guess I cling to a couple of outdated  beliefs myself.

[orkid1989]

so why conventional over synthetic? i always thought that the synthetic oil was the best. ill use whatever is better for my bike especially seeing as im rebuilding it and no reason to do it half assed after putting all this money into it.

[Retro Rocket]

Ride it easy for the first 500 miles, then change the oil and filter and then ride it as you normally would. 

Thats a bit of an old school approach. Every new engine i have had has responded better to using the engine throughout its entire rev range quite hard. Initially, keep the engine around 5 grand {revs} up and down the gears and load it up a bit {for 50 or so miles} then don't be shy to work the engine quite hard. There is a thread in the high performance section with a brand new 836 engine and it is being run in at the drag strip and it is running perfect. Just don't over rev it whilst it is still young.....I have found this method to produce a better running engine and an engine that likes to rev. I had a GPX750 race bike that was run in like this {at the track} and it absolutely flew......You may be better served posting this in the High performance section where all the top notch engine builders reside.....

[Doctor_D]

so why conventional over synthetic?

Folks have argued that synthetic was too slippery and that rings wouldn't seat.  Like I said, many new engines are broken in on synthetic oil with no issues.  Glazed bores may have had more to do with not running it hard enough during break-in.

How some synthetic oils effect wet-clutches is a whole 'nother issue though.