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Briggs Vanguard Crankcase woes


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TomMaryland
Posted
Hi all, I have my second crankcase for a 92 Briggs Vanguard 16 twin ready to go. The plain bearing (just a bore thru alum crankcase) is about the worst design I've ever seen. I don't run low on oil, change every year, etc., etc. OK, now that I've ranted, I feel better, but not much. Has anyone changed these engines out for either a crankcase with a roller bearing in them? Or maybe a nicer engine? I'm going to put the new crankcase on with new seals, etc., but I know this problem will crop up again. Thanks for any input.
Posted
I'm not sure what you are asking - is it the crankshaft that's worn and needs replacement or is it the bearing in the front cover where the crankshaft comes out or something else? I've got a fairly new 23 hp Vanguard so have not had problems with it yet. Hopefully won't, but would like to understand what I might be trying to avoid.
maxtorman1234
Posted
hmm, those aluminum bearing contraptions are pretty weak, no wonder i mentioned it in the 23d topic.
Posted
Sometimes on plain bearings it helps to put a small oil groove in them. But, you need to know what you are doing or you can speed up its demise. Full synthetic oil might also help. You might also make sure the oil pump (or whatever system they use) is working properly and the bearing is getting the oil it is supposed to. Normally Briggs plain bearings are not a problem but I'm not familiar with their vee twins.
Posted
You you have any severe angles such as ditching. This causes some lack of lubrication to crank throws and smooth bore bearings with splash lubrication. Even the toilet poppers don't like severe angles.
Posted
Are you talking horizontal shaft, or vertical shaft? What was the engine on? On the horizontal Vanguard, I believe it should be a replaceable sleeve type bearing, unless you are talking about the sump cover on a vertical shaft. I once researched the idea of machining the block to accept a needle bearing on the mag side, but finally realized that you have to stay with the sleeve type bearing in order for the pressurized lubrication system to supply oil to the connecting rods. Pat
TomMaryland
Posted
Peter, It's a problem with the cankcase and the plain bearing wearing out where the crank goes through it. I went round and round with Simplicity on this about 6-7 years ago, and they were very helpful (including a free rebuild after I sent them the crankcase). It bearing surface wears in the direction of the load, the deck and drive pulleys, to the extent that the oil seal cant hold any longer. If it wears enough, it an probably change the stroke just a tad as well. Graham, I didn't find anything in the previos posts or archives on this, but that may just be old farts disease! Bob, I have a gently sloping front yard, and a drain ditch on it (two passes). Would that be enough to do it? This is on a 92 Broadmoor, vertical V twin, and the shop manual calls out 3 different crankcases. The plain bearing one, a bronze bushing one, and a roller bearing one. Could I find a roller bearing one and swap it out? Or would the pressure drop like Pat mentioned? Thanks guys, for the advice!
Posted
Hi, We have many of these engines out and the only failures I have seen have been caused by a defective electric clutch. If the coil in the clutch shorts to the housing it is in, it will take out the main bearings. Depending on how close to the ground end the short is, has an effect on how long it takes. A short at mid coil, can take out the main bearings in 3 or 4 hours of running. To check for this, check for resistance from the coil leads to the clutch frame. Next connect the clutch to a battery for from 1/2 hour to an hour and recheck. It is not uncommon for the clutch to check OK cold and short to the case when the wires expand when hot. This clutch problem was very prevelant 5 to 10 years ago. The clutch company has fixed the cause about 6 or 7 years ago. Problem was usually associated with the Warner clutch. I have never seen an Ogura clutch short. If you have a clutch caused failure, the crankshaft will usually have a dull gray finsih on the journal, instead of a shiny surface. If there is any interest, I can expand on this problem. If you are failing these bearings, I'm betting you have a clutch problem. Have never seen one fail in a tractor that wasn't clutch caused. Al Eden
TomMaryland
Posted
That's interesting, Al. I have the original Warner clutch in it. Can you elaborate on the failure? Does it break down the oil viscosity, or what? I didn't notice a gray finish on the crank, but I was only looking for wear, score marks, etc. As of last night I have it all buttoned up, but not bolted in yet. The clutch is still off the tractor as well.
Posted
Hi, Several years back there was an epidemic of clutch failures. Many of these destroyed engines. I have a Vanguard with less than 50 hours on it that has about 1/8 inch of play in the bottom main. The cause of most of these was a failing clutch. Simplicity had to buy a number of diesel engines with very low hours on due to a grounding problem where the battery ground was on the frame and the engine sets on rubber mounts and the ground path for the charging system was through the drive shaft and the crankshaft. Proper grounding fixed the problem. Electric current through the crankshaft is a doomsday situation. It acts like an EDM (electrostatic milling machine) This the process which was developed to machine difficult to machine materials like titanium for the aircraft and space industry. EDMs machine by "sparking" away the metal. I have had a broken tap taken out of a magnum block with an EDM machine. The process just keeps eroding the material away with a tiny spark repeated over and over again and again. It is a slow process and has the advantage of not creating large amounts of heat. The same thing happens in an engine when current flows through the crankshaft. There is sparking and erosion of the crankshaft and the bearing surfaces. The aluminum being the greater donor. The connecting rods also are damaged, but to a lessor degree due to the higher resistance path through the rods, wrist pins, pistons and rings to the block. The crankshaft usually looks like it is satin finished and kind of dull gray. Now the clutch. An electric clutch is composed of 3 major parts. The field assembly, the rotor and the driven plate and output pulley assy. The coil is wound with varnish insulated copper wire in a circle about 4 inches in diameter. This coil is them laid in a U shaped circular trough. The leads are brought out the back and the coil is "potted" in to the trough. This provides the magnetic field to energize the clutch. In earlier clutches the field coil was bolted directly to the engine block. If the coil shorted to the field housing "trough" the path was right to the block and to the battery ground cable. No real problem. Next step The floating clutch. This clutch has a ball bearing in the field housing and floats on the crankshaft. Usually there is a small "finger" to keep it from wanting to rotate with the shaft. Nest the rotor is keyed to the crankshaft and slides back close to the field coil, it also extends back along the sides of the field coil to have more of the magnetic field energy induced into it. When the clutch it turned on magnetizes the rotor so it has a very strong pull. Ahead of the rotor is the driven plate and pulley. This also has a ball bearing in it. Behind the pulley is a flange with about 6 spring steel flat straps that go from the flange to the driven plate. These strips flex when the rotor is magnetized and let the driven plate "suck up" against the rotor to turn the pulley. On most of the clutches except the Warner Mag Stop units, there is a triangle shaped ring that the driven plate snaps out against when the field is switched off. There are 3 springs on the bolts pushing the brake plate away from the driven plate. The 3 nuts of the front side of the plate are the adjusters to limit the gap between the rotor and driven plate to the prescribed amount. Usually .010 to .015 inch. If the gap is too wide, the magnetism is too weak to over come the spring straps and flex them and pull the driven plate in and the clutch won't engage. When the clutch gets hot 2 things happen. 1 The wire tends to want to expand. 2 the resistance of the wire increase. As the resistance goes up the current flow is reduced proportionately. This results in reduced magnetic energy and the clutch that has too wide of a gap, but not so wide it won't turn cold, won't energize hot. This why most clutch fail to work hot are able to be fixed by correctly adjusting the clutch clearance. Next when the wires are laid in the trough and potting material is poured in to hold them some of the wires may be touching the trough on the outside and when the wires get hot they tend to expand and push against the outside of the trough. Sometimes between the heating and cooling the insulating varnish can wear through and that turn of the wire can short to the trough. The floating clutch always has 2 wires. One that brings the 12 volts in and the other going to ground, often through a couple of safety switches. If the wire shorts to the housing (trough) electricity always looks for the shortest path to ground. Part of the ground current will flow through the ground circuit, and the majority will flow through the field bearing and through the crankshaft to the block. As the crankshaft is turning, it is continuously sparking away. (Very tiny sparks) It is eating the life out of the engine. Clutches should always be tested for shorts from the coil to the housing cold and then be connected to a battery for .5 to 1.0 hrs to heat them up and retest them. Often they are fine cold and short out hot. Most clutches draw from 1.8 for low torque units to about 3.5 amps for hi torque units. A 0-10 amp meter out of an old tractor with some leads and terminals to connect it in series with the 12v in wire to the clutch makes a good cheap monitor. This can be used right on the tractor. When the clutch coil shorts, you should see and increase in the current. Another clue. If the PTO switch burns out on a tractor. The clutch current should ALWAYS be checked before it is replaced. These switches are rated at 8 amps and have a 100% safety factor. A failure should cause one to BEWARE. When we saw so many clutch failures we were seeing clutches with 50 to 100 hours having bearings go out. I talked to Mike at Simplicity (deceased now) and he thought it could be a lube problem. He thought popping the seals out and adding some hi temp grease might help. It didn't. Later I talked to a source in the clutch industry that I cannot reveal that told me the problem was finally traced to a process change. The vendor went from a retaining ring to putting the bearings in and "staking" them with a 3 point stake. When the stake tool shoved and rolled the crimp to the bearing, it actually distorted the bearing a couple of thousandths. The balls were like they were rolling in a triangle, or rather the reverse of a triangle. This generated more heat and caused the coils to run hotter, causing more thermal movement. So the final solution was to change to a 12 point stake on the bearings to retain them and the problem has gone away. We have not seen nearly as many clutch failures in the last 5 years as before. We had a Grasshopper with a Kubota diesel in a year ago that the customer took to another shop and had a main seal put in. It leaked as bad as before, took it back and another seal. Still leaked. He called me and I asked him if they took a dial indicator and checked the side play in the crankshaft. He said: no. Brought it in. I went down to check the crank and didn't need a dial indicator, the crank would move up and down about 3/16 inch by grabbing the clutch and just pulling up and down by hand. We fixed it and it cost about 2500.00. Took a new crank PLUS. I think I posted pictures of it about a year ago, if anyone knows how to find them. One other issue. Not properly grounding an engine can result from the charging current in some applications to do the same thing to an engine. Sorry to run this so long. Al Eden
Posted
Thanks again Al. My Vanguard replaces the Onan in my 620, but the old clutch is still there. I guess the same problem could occur, but the old Onans appear to have run for a long time without any mention. Would the same monitoring work? Any advice on best practice for grounding?
Posted
Hi, I believe your clutch field coil bolts to the block and is grounded direct to the block with mounting bolts. This unit is quite safe. The problem is with the floating clutches that float on the crankshaft and the field coil frame is attached to the crankshaft. Al Eden
TomMaryland
Posted
Thanks for the info Al! Hey, was there ever a recall from Warner for turning tractors into EDM machines? With the right geometry, we could EDM the bearing seat in the crankcase, and drop roller bearings in, like it should have in the first place. :-) I'm going to tear this engine apart and really inspect it now. Also, do you know of the crankcase and roller bearing part # that I could swap out on this engine? Or is that too much trouble?
Posted
Hi, CAn anyone find the pics I posted of the Kubota engine in the grasshopper? I can't but don't know how to search very well. It shows clutch crank damage. Thanks Al Eden
Posted
I think this is the one you wanted [url]http://www.simpletractors.com/club2/topic.asp?ARCHIVE=true&TOPIC_ID=44265[/url]
Posted
Sorry that was part 2 here is part 1 [url]http://www.simpletractors.com/club2/topic.asp?ARCHIVE=true&TOPIC_ID=44263&SearchTerms=kubota,clutch[/url] B)
TomMaryland
Posted
Thanks Marty, The engine definitely comes apart tonight. I cranked it up last night for a few minutes and it ran fine. If I do find evidence of "EDMing" I'll take some pictures and post them. Also need to do a check on the clutch as well just to be sure.
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