rrengineer.mike at att.net
Mon Aug 29 19:20:30 MDT 2016
OK, so now you have me worried about my Harley Davidson next time I freshen up the top end. It is an air cooled flat tappet cam engine. I don't remember when I brought it home new in 2002, the owner's manual saying run flat out to seat the rings.Mike MacLean
On Monday, August 29, 2016 6:14 PM, Bob Spidell <bspidell at comcast.net> wrote:
The break-in procedures for air-cooled motorcycles is very similar to that for (air-cooled) aircraft piston engines. Because the clearances are greater in air-cooled engines--to allow for greater and varying metals expansion rates--the emphasis is on bedding-in the rings (although these engines also have flat-tapped, OHV valve trains). That should be somewhat less of a concern--but still a concern--in our water cooled engines, where cam/tappet break-in appears to be critical.
A point not mentioned in the motorcycle procedure is that breaking in an engine at high altitude might be problematic, since you won't get the same BMEP at, say, 5,000 feet that you would at sea level (non-turboed and non-supercharged engines, of course). For an aircraft engine you are advised to run at 1) low altitude, 2) full power (WOT or close to it) and 3) full rich for the first few hours (up to 50). The rich mixture is to used to wash oil off the cylinder walls to promote break-in and prevent oil glazing (I've heard of desperate airplane owners--who may have spent $50K or more on an engine rebuild--dumping Bon Ami into cylinders in the hope it will break the glaze). Since an SU carb's mixture can be set across the RPM range it might be a good idea to run them extra rich for the first 500 miles or so.
I always drove gently for first 100 miles changing rpms and speed, changed oil, then continued to drive and change oil again at 500 miles. Varying speed and RPM. Not sure why we did this, something about seating the piston rings. Clearly many ways to run in a new engine
Ira ErbsPortland,OR _______ _______
(______ \____1959 BN4____/ _______)
(_________________________) BT7 engine and disk brakes
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On Sun, Aug 28, 2016 at 10:11 PM, Michael MacLean <rrengineer.mike at att.net> wrote:
A friend who recently past away in January that had been rebuilding Healey motors for over forty years told me he just gets them started and idles them for a while and then runs them gently for a 100 miles or so, changes the oil and then it's your choice how careful of a break in you want to do. He said he never had a problem with them or the cams during break in. Go figure. I also have an article that says as soon as you get the motor started, run it at high rpm to seat the rings properly. They are talking about a motorcycle, so I am not sure if applies in our case, but an interesting read.New Engine Break-in Procedure
| | | | | | | |
| New Engine Break-in ProcedureWhen a cylinder is new or overhauled the surface of it's walls are honed with abrasive stones to produce a rough surface that will help wear the piston rings ... |
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