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Old Briggs & Stratton leaking oil


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10-13-05, 03:10 PM   #1  
Old Briggs & Stratton leaking oil

I have an older mower, Sears Craftsman 19" with a Briggs&Stratton 4-cycle I picked up free from the local nursery as a way to teach my 8-year old son about engines. We gave it a good cleaning of the valve seats, new spark plug wire and spark plug gap adjustment got it to start like a race horse and run like a top. Here's my problem: there is a little rectangular can on the side of the engine block with a hole stuffed with some sort of fiber. The can is held into the engine with two screws. When removed, the valve stems and springs can be seen. I assume this can somehow lets excess pressure and gases escape while keeping oil in. But after running for 30 secs-1 min. oil starts spitting from the hole and becoming acrid blue-white smoke after hitting the exhaust. I stuffed it up a bit more with some steel wool, but oil still leaks out and due to thye amount of blue smoke coming from the exhaust still, I assume there is oil burning inside. Do I need an overhaul (new rings, seals, etc.) or is there something else that can be done? The little silver plate on the rear of the engine says Model 500.900.568 Serial 224377 and the plate on the mower itself says Model 131.81190. I can't match any of these numbers except the last 3 on the Model# kinda match up with the last 3 of the B&S ID guide (568 would mean vertical shaft, plain bearings, and side pull starter, respectively) Thanks for your help.

 
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10-13-05, 06:18 PM   #2  
wardog30
You are correct. That is the crankcase breather. First there is a diaphram type thing inside the cover. It should hve a little play to allow the gases to escape. If it doesnt move freely spray some carb cleaner in it. Shake it around abit. Second double check the oil level. It should be at the lower threads while on a level surface. Hope this helps.

 
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10-13-05, 06:47 PM   #3  
yes thats the breather....lets internal pressure out, without letting oil by.....so you've taken it apart? i wouldn't mess with it much more, just get a new one. small engine shop, online source......etc.

 
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10-14-05, 12:54 AM   #4  
Are you sure this is a Briggs engine? Sounds to me like a Tecumseh.

If it's a briggs, it shouldn't have the fiber in it. Anyway, ...That is the crancase vent. It allows pressures from inside the engine to vent. Excessive pressure in the engine will cause oil to blow out of it and smoke. This is normally caused by blowby (combustion pressure getting past the piston and into the engine crankcase). This is usually caused by bad rings, piston, and/or cylinder walls.


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10-14-05, 04:55 AM   #5  
I agree with Cheese. This is not a Briggs engine. It's most certainly a Tecumseh. Replace the breather. There is a one way fiber valve in one of the plates. It most likely is defective allowing air inside the crank case during push strokes. This can cause oil burning. Replacing the wool will do no good.

You can find the service manual at
http://www.cpdonline.com/692509.pdf

You should inspect the oil fill tube for breaches no matter how small. A small leak in the crank case will give the same result.

God Bless,
Dave237

 
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10-14-05, 09:24 AM   #6  
Hmm... I find it hard to argue with a big red sticker on the front of the engine that says "Briggs & Stratton" Besides, it looks NOTHING like what is described in the Tecumseh manual. I should add that my engine is a top pull start that pulls to the side not side pull as I said before (should I post a sketch?). Nevertheless, thanks for the advice. As I remember, the inside of the breather assembly had a little round area that resembles a diaphragm of some sort, there was no play in it at all, stuck open. I'll try cleaning that or replacing. There is no oil filler tube just a "winged" screw-in plug at the bottomright of the engine. Full of oil, still looks dark tan, not black. When we had the engine opened up, the cylinder and piston looked real nice, no pitting on the piston face, cylinder walls looked nice with just a trace of oil coating the wall. The valves were pretty sad, though. we scraped black gunk off the valve faces and did our best to clean up the crusty bits on the valve seats, maybe that needs more attention as well. I've seated valves on a '73 VW (I said seated, not ground) so it's probably not too much more difficult. Thanks for the help! I'll report back with the results.

 
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10-14-05, 02:44 PM   #7  
I'm with the concensus, I say you have a Tecumseh, despite what the sticker says. There is a right and wrong way to install the breather. Take it back out and look for a tiny oil drain hole (it will be on one of the corners), this needs to be down when installed properly. Otherwise it won't drain out and you will have a heavy smoking issue such as you have. If it is already installed properly then you likely have a crankcase leakage issue and could be one or more of the following: sump gasket, oil fill gasket, crank seal(s), improper weight oil, piston rings, valve guide(s) or governor shaft. For what little the breather assembly costs, I'd replace this first and then go from there. What are the engine ID numbers of the engine?

 
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10-14-05, 04:53 PM   #8  
For ID numbers, see my first post. I'll see what other numbers I can get off the ID Plate for next time. If I recall correctly (I'm at work right now) there was indead a pin hole at the bottom corner. The breather's mounting ears are offset just a tad, so the way it's in there now is the only way it can go. We'll certainly replace the breather first to see what that does and will check back in. My son and I are willing to tear the whole thing apart to get at the problem, if for no other reason than for the learning experience (we have another lawn mower, so we won't be missing anything), I'll check for all the things mentioned, thanks to all for the helpful suggestions. Remember, this is an old engine, no plastic whatsoever except for the fuel line (a long clear tube that passes behind the engine to the carb on the other side) which was another thing my son and I replaced. Oil-type air cleaner, bowl carb, air-flow governor (metal flap inside the engine cover that works the throttle rod as the air off the flywheel vanes go; yes the spring is still there to pull it back and still works) Metal dogs on the underside of the flywheel whiz by the magneto which throws fire to the plug. I can't locate anything that resembles a breaker point assembly although there is a setting for it on the ID Plate (.025 gap). I'll stay in touch. Thanks!

 
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10-14-05, 05:00 PM   #9  
BTW- It's so old, you kill it by pushing on a little metal ear mounted to the side of the spark plug to ground the coil. Does that help with the identification?

 
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10-17-05, 12:25 AM   #10  
Those are available as aftermarket kill tabs, but came on some equipment from the factory as well. It doesn't aid in ID unfortunately. I'd like to figure out exactly what we have here. Briggs did use a float type carb with an oil bath filter years ago...like the early '60s I guess. Could it be that old? The model and serial #s you gave aren't ordinary briggs numbers though.


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10-17-05, 02:18 PM   #11  
the shroud could be off of a briggs maybe?.... either that or someone stuck a briggs sticker on it...for some wierd reason.

 
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10-17-05, 03:56 PM   #12  
Yep, it looks pretty 60's now that you mention it, the handle is a y-type like an old push reel mower.Green painted aluminum (THICK aluminum) deck. Upon closer inspection, it's not a sticker, it's painted on in goldish yellow/green (age has changed the color a bit I imagine). On the ID plate, the info is paint stamped on, as in all the lettering is red and the number 500 is in red at the front of the box where the rest of the number (900568) is stamped into the plate. The kill tab indeed looks factory, as it has its own mounting spot in the metal plate that partially covers the cylinder head. Haven't done anything since Friday, I'll try to get to it tonight. If it's from the 60's, small wonder it's blowing oil. Bigger question is, can I get replacement parts anymore? or are rings & etc. pretty standard?

 
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11-16-05, 12:55 PM   #13  
OK, we got the thing all opened up and I got a craftsman wheel puller to yank the top off so we can get the crank and piston out. I can figure out how to do this, but I need two pieces of advice: How to make sure the timing is right when we put it all back together, and how to put the flywheel back on afterwards. Rubber mallet? Just now checking into old parts sources. Recommend any?
Thanks!

 
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11-16-05, 08:51 PM   #14  
there is a little dot and notch on the crankshaft and camshaft gears, when you put it back together you have to make sure they line up, that takes care of the timing.

yeah just slide the flywheel on, usually put the key on first though

 
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11-17-05, 12:29 AM   #15  
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This thing sounds like an old Briggs horizontal shaft, but where on the engine are you getting those numbers. Even back then, they used model, type and code.
On the horizontal, these numbers can be found either by the top starter housing mount, or to the side, on the starter housing, by the carb/manifold mount.
Those numbers hold the key.

 
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11-17-05, 10:26 AM   #16  
Nope. Vertical. Got the numbers off the front of the housing, there's a plate that is printed in red with the numbers stamped in. Maybe because it's a Sears (Craftsman) they put different numbers on there? I found the timing marks, but I was worried more about the flywheel (I think that's what it is) on top because that's part of what fires the plug. Guess we could make our own positioning marks before yanking it off.

 
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11-17-05, 10:53 AM   #17  
even though its a sears, numbers stamped on the housing should be the engines makers own numbers. you can get the owners manual and illustrated parts list from briggs's website, if it does use the usual model, type, and code that briggs uses. the flywheel should be a heavy metal one, no need for timing marks, it uses a flywheel key, little rectange of alluminum, put in a slot on the crank, slot in the flywheel fits right on, thats all the timing other then internal they have, which is simple, lining up the marks. make sure thats not sheared any, or worn on the sides, they are very cheap to buy a pack of em.

 
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11-17-05, 11:25 AM   #18  
I looked it up on B&S website, they don't have anything that matches my parts numbers. Maybe I'll email them. Thanks for the tip on the flywheel. Just found out the wheel puller I got is the wrong kind. I got the four-slot deluxe model that's made for pulling harmonic balancers and the like. I just need the kind with a screw pusher and two arms that grab the wheel from behind. Oh well 8 bucks or so at Sears (of course) or maybe I can adapt it...

 
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11-17-05, 09:41 PM   #19  
Stu
Are the muffler and carb on the same side or opposite sides?
Is the control mechanism mounted above the carb?
Looking at the front of the engine, is the muffler, carb and air filter on the right hand side, and the feul tank and dipstick on the left?
Are there numbers stamped in the housing above the spark plug or muffler?
How is the govenor linked to the throttle shaft?

 
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11-18-05, 09:48 AM   #20  
Are the muffler and carb on the same side or opposite sides?
Same.
Is the control mechanism mounted above the carb?
Yes. There is no manual mechanism. Just the airflow governor thingamabob I described earlier.
Looking at the front of the engine, is the muffler, carb and air filter on the right hand side, and the feul tank and dipstick on the left?
Well, from the viewpoint of the guy pushing the mower, (as in, if the "front" of the engine faces the "back" of the mower) yes. The spark plug and kill tab also face the operator so the kill tab can be engaged with the operator's foot (toe, actually). There is no dipstick, just a winged screw-off plug and a stamped instruction to make sure oil is full before operating.
Are there numbers stamped in the housing above the spark plug or muffler?
Nope. all numbers are stamped into a printed aluminum plate riveted to the "back" of the engine shroud ("front" of the mower, though.)
How is the govenor linked to the throttle shaft?
The governor, as described before, is a metal flap inside the shroud that has what amounts to a bent-wire rod that goes to the throttle shaft arm to which is also attached a spring about 4-5 inches long that is anchored on the engine so the throttle arm works against the spring.

 
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11-18-05, 11:31 AM   #21  
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This engine has me a bit stumped. Some old briggs engines had the muffler, carb and air filter on the right, and the feul tank and dipstick on the left, but only on about 8hp and 10hp vertical shaft engines, but these engines had a mechanical govenor. You say it has a red briggs sticker, well pre seventies (to my knowledge), did not have red stickers, they were like a brown decal, the old water applicated type. I don't know of a briggs or tecumseh, that has the 'check
oil before operation' stamped into anywhere, it's normally a sticker/decal. As for the metal govenor air vane, does anyone remember kirby-lausen (I'm not sure on
spelling), kirby-lausen has since merged with tecumseh, but they used to be stand alone engine manufacturer. Thats the only engine I can think of that may have a metal govenor air vane (in a vertical shaft). What do you think guys?

 
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11-18-05, 11:49 AM   #22  
Posted By: Stu This engine has me a bit stumped. Some old briggs engines had the muffler, carb and air filter on the right, and the feul tank and dipstick on the left, but only on about 8hp and 10hp vertical shaft engines, but these engines had a mechanical govenor. You say it has a red briggs sticker, well pre seventies (to my knowledge), did not have red stickers, they were like a brown decal, the old water applicated type. I don't know of a briggs or tecumseh, that has the 'check
oil before operation' stamped into anywhere, it's normally a sticker/decal. As for the metal govenor air vane, does anyone remember kirby-lausen (I'm not sure on
spelling), kirby-lausen has since merged with tecumseh, but they used to be stand alone engine manufacturer. Thats the only engine I can think of that may have a metal govenor air vane (in a vertical shaft). What do you think guys?
yeah, doesn't sound like a briggs, the shroud could have been changed. hate when that happens. or they just wanted a briggs really.....bad

 
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11-18-05, 12:04 PM   #23  
Stu
Just shot into work to check my old kirby manuals, and it's not a kirby, they've all got mechanical govenors!

 
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11-18-05, 02:47 PM   #24  
Yep, brown decal. Sorry, I was working from memory on my first post. The shroud was painted red. And if it was a Briggs shroud, you'd think I'd have extra mounting holes, eh? The only thing seems really out of place now is the wind-activated governor, hm? Don't bother me none what kind it is, I would just like to know what can be done to get it running without blowing oil. BTW- the diaphragm thingy inside the breather box slides back and forth a bit, but does not close and open as would be expected. And the box has 2 pin holes in the side; one toward the bottom corner, one towards the top.

 
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11-18-05, 06:31 PM   #25  
have you gotten a new breather for it? i would just try that first.

 
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11-23-05, 10:00 AM   #26  
I couldn't stand it any longer, I had to find out what this thing is so I can find parts. I stumbled on this list of 6-digit type numbers that corresponded my stamped number 900568 with model number 6B-H. A quick trip to the B&S site for the Owner's Manual... Jackpot . Now I can get a breather.

 
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11-23-05, 07:39 PM   #27  
man thats a old.......one....... they actually recommended "mobil 1"......"mobil gas" though don't follow that for oil weight, 10w-30 in the winter, or even 5w-30, 30 weight in the summer is fine

 
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01-09-06, 10:35 PM   #28  
OK, got the flywheel puller and a new breather. My son and I pulled off the flywheel, adjusted the points, pulled the piston off the crankshaft and hauled them out. The rings are still sharp but I notice there are shallow gouges running down the face of the piston and the cylinder walls. Is this ok? If they are, we are going to button it up and give it another go to see if our labor has produced any fruit.

P.S. Thanks for the oil tip, v8driver!

 
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01-09-06, 10:51 PM   #29  
Sounds like you found your source of the oil burning/blowby when you found the gouges. How do the ring gaps look? If you have too much clearance between the ends of the rings with the ring installed in the cylinder (somewhere around .030" or more), then you'll need new rings at the least. How deep are the gouges? Can you hang a fingernail on them while scraping across them? If so, you could try honing the cylinder a bit to help it out, but you may have to have the block bored and use an oversized piston and rings. If the ring gaps are too large, and the gouges aren't too deep, I'd try sticking a new set of rings in it and hone the cylinder and see how it does. It can't do anything but help. I assume this isn't something you plan to use for regular lawn maintainence anyway, right?

I have taken some engines with scored cylinder walls and honed them and used new rings and got them to quit or almost quit smoking. Usually it's on a piece of equipment that's not used often, or more for display (antique/oddity type stuff) where a patchup job is suitable and more feasable economically.


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01-10-06, 08:32 AM   #30  
It would be nice if it could be used, but it wouldn't break my heart. The other newer mower we got works, just needed a new spark plug, but it bogs when you tip it to one side (I forget which) and when going downhill. The older one (when it is running) goes like a racehorse no matter what direction it's going. I'm not relishing the idea of honing a cylinder but my son is having a ball tearing it apart anyways...
I'll have to check the gap on those rings, just kind of shove it halfway in and check it with the blade, right? In the manual, anything over .010 is "oversize"

 
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01-10-06, 11:19 AM   #31  
That .010" is in relation to the bore, not the ring end-gap. Use the piston and push each ring down the bore about one inch and then measure the end-gap. It should be no more that .030" +-. If really excessive, you may want to re-ring and you should also measure the bore for wear, especially if it has an aluminum bore.

 
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01-13-06, 05:17 PM   #32  
Hoo-boy, you could drive a lawn tractor through that gap... about 1/8" New rings coming in the mail. The piston and cylinder look ok despite the gouges, I can just barely slide a corner of notepaper between piston and bore. The gouges are actually not very deep at all, they look more like casting defects than something scraping the wall.

 
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01-13-06, 09:43 PM   #33  
If it has an aluminum bore, make sure you use chrome rings.


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01-16-06, 08:02 AM   #34  
Check. Also got a new points/condenser set and carb rebuild kit for good measure. Anybody know where to get a gasket set for 6B-H? Manual says it's part#293525. Google fails me on this one.

 
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