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ambler

Engine rebuild questions

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ambler
I'm putting the engines back together and I thought I would post my questions in this block. 1.) Machinist placed single sided sealed main bearings in crank (seal facing knee) and in the bearing support (seal faces chamber body). Concern is that will oil penetrate to open face for bearings. He believes that these bearings are better than original. Is their grease in the main race? 2.) Camshaft bearing I forget which way it faces. I believe it faces inward. Didn't put shim in it feels loose. 3.) How do I break in the engines. Someone told me oil change every 5 hours. Do I run them at constant rpms. I'll post pics of my questions, when I get home.

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Salthart
Wet all the parts down with ATF fluid before you close the engines up. Or put a couple of quarts of ATF in one and spin it for a few minutes ( Don't start it ! ) Drain out the ATF and fill with oil. You will find that the rings seat quickly. Though I have a few ideas as to why, I really can't say for sure. But its what the racers ( Auto ) around here have done for years and it has worked well for me too....... Camshaft play is not near as big a deal as say crankshaft and the engine oil will take up some slack. Just make sure the cam gear isn't getting out of line enough to damage another part or touching the block. LOL Word to the wise.. Don't put Slick-50 in a fresh rebuilt or new engine ! ( Will take forever for the rings to seat ) Made that mistake when i built one for a friend. He wanted the stuff in it..LOL For the next month he would be mowing ( 16 briggs single ) and the dip stick would blow out ! Cured it by spraying water into the carb at full throttle... Still don't use the stuff but have to admit it did something...LOL

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ambler

This shows magneto side with camshaft bearing and pic of the other bearing as well.

This shows I hope timing marks of cam and crank gears. I believe it slipped one notch in setting the shot up.

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ambler
Its a 16 horse briggs. Thats interesting about ATF first. No slick fifty in this baby, I was going to run 10-30 synthetic after the breakin period. I hear it takes 40 hrs to break in and to change oil every 5 hours until that point. 8 changes 16 quarts. How do you run it in constant rpms? Under load? Does anyone of the experts want to shed some light in this matter? Look at that single side sealed bearing, should that be replaced? I believe he got them through mogul. I could look for a bearing number tomorrow.

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HubbardRA
Vary the speed as much as possible. Acceleration is good for seating the rings. I would not run at sustained wide-open-throttle until is is well broken in. I would use it for light work with lots of variation in speed of engine. Constant speed produces the most vibrations when not loaded heavily. Vibration is the main cause of bearing failures, especially in new engines. My two cents!

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slb04786
I am in the process of rebuilding B&S 16 L-head too. I am wondering about the cover that goes on the driveshaft end of the engine. It has a gear on it with what appears to be a counter weight on it. How is the counter weight lined up in reassembly? I see a small screw on the bottom of the cover that you could remove to either line up or put a longer screw in to hold the counter weight for assmbly. I have the service book on order from a B&S dealer. Just wondering while I'm waiting for the book. Stan

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ambler
Thats the synchro balance. Get the Briggs Lhead book post chapter 12. On page 2, I believe cylinder goes top dead center, there's a hole in the external gear on the camshaft. pin through hole in gear and into hole in crankshaft bearing support. This is done with little gear on as well The you install time counterweight with a locating rod through the screw hole you referred to and through a machined hole in the counter weight.

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ambler
Thanks Rod, Then I shouldn't run them in at the bench at constant non full load rpms. what about the frequent oil changes? Any thoughts on the main bearing I showed with the cover facing the cranckcase?

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HubbardRA
Ambler, Can't help you on the bearing. Been a long time and I can't remember which way the bearings face. I do know that there should be very little end play in the camshaft and crankshaft when fully assembled.

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Salthart
Ambler, Not to take away anything said by Rod or anyone else. This is not an "I'm wrong, he's right" thing.. Its more like to many cooks..LOL What Rod has said has worked for a great many people for a great many years. My way has worked for a good many for 20 or so years. Main thing is, if you start with one, follow through with it. Don't mix them... When using the ATF, It needs to be a fresh build. Wet all moving parts, coat the bore, install the head and the oil sump and the starter and spin the engine about 20 seconds with no spark plug installed. Fill with the oil of your choice. ( 50 valvoline for me but I don't run in cold weather )Install the spark plug and start the engine. Run at 2500 rpm for 20 minutes. Watching and listening for any signs of trouble. Shut down and change the oil. And your done... I understand this is far removed from the "old school" ways of doing things and believe me, I won't blame you if you try another way. I just know it works for me...... I am somewhat suprised than no one else has mentioned this method...........

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ambler
I am listening to everyones experience, sooner or latter I must run them in. Pat Rarick comments by PM when I queried him. There does appear to be a germ of commonality here. The bearing only has a single seal. I'm going back to the machinist, I do recall him stating that these bearings were rated for much more severe conditions than this application. Hell neither Briggs nor Kohler make their own bearings. I can always remove the shield if it makes me nervous. I'm a little nervous now thus the questions. Ambler, Don't know what to tell you about the bearings. Been watching your post to see what others had to say. Sealed bearings are loaded with grease. My personal opinion is that that sealed bearings should not be used here. They MIGHT be fine, but I would be uncomfortable using them. This is how I view the situation: How long and how many hours did the original, unsealed bearings last? Can you really improve on that? Unsealed, OEM bearings may be a little more expensive than aftermarket bearings, but for the time and labor involved in replacing them, is it worth it to change something that has previously provided good service? As to the camshaft bearing, I'm a little confused as to what you mean. Don't have a 16 horse in front of me right now, but I believe that it can only go in one way. On one side, there should be a tapered "snout". The other side should be flat. The tapered "snout" goes outward. In any case, you should be able to see the thrust area against where the camshaft ran. The bearing should also show where the bolts were previously tightened against it. The end play on the camshaft should be from .002" to .008". If more than .008, a "service bearing kit" is needed. This is a kit that includes a new bearing and shims to adjust the end play. The Briggs number is 299706. To break it in, I run the engine at different speeds under a varying load. If mowing, I run at a slow ground speed and vary the throttle from 3/4 to full throttle. Change to a high ground speed and vary the throttle in the same way. I don't want to make it lug, but I DO want to hear the governer work every once in a while. I also let it idle for about five or ten minutes before shutting it down. As to the first oil change(s), I feel that oil is cheap compared to rebuilding or replacing an engine. As new parts break in, there is a lot of metal wearing off. This needs to be drained off before it causes damage. Everything is not as perfect in a rebuild as it is in a new engine. There are more imperfections from previous wear that must wear in (break in). I make the first oil change after the first actual use of the tractor, even if it's only half an hour, but no more than five hours. I change again after the next five hours, the next ten hours, then every twenty-five hours. When changing the oil, pull the plug as soon as the engine is shut down. The impurities are still suspended in the oil and the oil is warm so it will drain more completely. If you wait until the engine is cold, the oil will be heavier. A thicker coat of oil will remain in the pan. Since the impurities will settle to the bottom, that thicker coat of oil will have a strong concentration of impurities which will quickly be mixed into your new oil when you run the engine. Never heard of using ATF. Don't know if there would be a benefit, but there won't be a problem. I use ATF to clean operating engines, both automotive and air cooled. I drain the oil and refill with ATF. Start the the engine and let it idle for ten to fifteen minutes. Drain and you wouldn't believe the gunk that is cleaned out. An old mechanic here in town replaces one quart of oil with ATF every time he changes oil on his car, to keep his engine clean. Hope this helps. Any other questions, just ask. Good luck!!

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