Topic: Post rebuild engine questions....

[mattcb350f]

My 350F engine is back together and runs well 

got a couple of questions about what to do next.

1) It has a web cam in it and the spec sheet said set the valve clearance to .004". I set it at that so should I keep it that way. Did a search and that's what I found; to use a larger clearance, just wondering if that's just for the 750's or all SOHC/4's.

2) What kind of break in procedure should I use and for how long. All new bearings, rings and rebuilt head and new cam. I've been varying the RPM's and not going past half throttle, but am I being too gentle?

 Thanks, Matt.

[754]

I usually dump the oil after 50 or 150 miles & look at it..

 Many say it is not needed but I would rather se what is coming out(and removeit) and get a heads up on wether or not something is rubbing or letting go due to incorrect clearance, or something falling in , etc..

Stick to the cam makers settings.. unless you know more than the maker.. if so let us know to..

[mattcb350f]

I usually dump the oil after 50 or 150 miles & look at it..

 Many say it is not needed but I would rather se what is coming out(and removeit) and get a heads up on wether or not something is rubbing or letting go due to incorrect clearance, or something falling in , etc..

Stick to the cam makers settings.. unless you know more than the maker.. if so let us know to..

Thanks 754, makes sense to me.

This is from TwoTired on another thread:

The bike needs to be making power (needs a load) for the rings to seat well onto the cylinder walls.

Ideally, you want everything wear in at the cylinder temps you expect to normally run with.  This is because all the parts have their own coefficients of expansion and you want them to fit together best when all are at operating temperature.  If this is done when the engine is cool, the parts will fit together best only when the engine is cool.  Then when you run it hot it has to wear in all over again as the piston to cylinder fit is tightest when hot.

This is one of the drawbacks of air cooled motors for long term longevity.  But, you have to live with it.

The other bit to be concerned with, is that the pressures of combustion leak down the piston sides and are supposed to end up behind the compression ring, pushing it against the cylinder wall.  These pressures aid in ring seating/breaking in.  The cylinder pressures are the lowest during idling and no load, and highest during full power acceleration.

The Honda owners manual has a break in procedure that applies for the first 600 miles.  Do not exceed 5000 RPM.  Next 400 miles 7000 RPM.  All this with constant varying speeds.

If you only did a top overhaul, however, you are only concerned with ring to cylinder break in, not main, rod, cam bearing, and cam lobe break in like the Honda procedure entails.
Were it me, with only a top overhaul.  I would find a test track and flog the bike uphill in bursts, being careful not to overheat the cylinders (which will run cooler after the wear-in is accomplished).

Good luck!

All in all, I guess with my engine being entirely rebuilt than I should stick with Honda's recomendation for break in.

 Matt.

[paulages]

i believe there have been several threads on here about break-in procedure. most people seem to agree with following honda's guidelines (which is probably wise), but there is a fairly good argument made for breaking it in hard, which essentially follows the logic TT laid out describing compression and how the rings actually seat. my concern would be running it too hard without knowing that everything else is doing well.

[mattcb350f]

i believe there have been several threads on here about break-in procedure. most people seem to agree with following honda's guidelines (which is probably wise), but there is a fairly good argument made for breaking it in hard, which essentially follows the logic TT laid out describing compression and how the rings actually seat. my concern would be running it too hard without knowing that everything else is doing well.

Thanks Paul. I really have to do more searching before I post  I added a tag to this one which pretty much mimics the rest.

I know from breaking in aircraft engines they need to be run hard or they run the risk of glazing the cylinders. I hated doing this on a flat six in a Cessna 180; running it at full power much longer than needed for the first 25 hrs. Made it go fast, but It just felt wrong to my mechanical senses.

Anyway, back to bikes. The general consensus seems to be that it's a trade off between enough load to seat the rings while keeping the RPM's low to allow the rest of the engine which needs the lighter load through low RPM to break in.

 Matt.