# 18.5 HP B&S... Blown up?



## kollinsb (Jul 25, 2005)

A few minutes ago I was mowing with my Murray M/N 46379X92A with a B&S M/N 43D707 engine and I heard a loud pop/grinding and it immediately stopped. It started smoking. I checked the oil in it and there was some in it but it wasn't full. I installed a gas shutoff because I was affraid of getting gas in the oil and it's my religion (joking) to turn it "off" and I've been mowing with it all summer so I highly doubt there was gas in the oil. Is it possible I'm over-reacting and it's not blown? If it's blown I'm ging to have to get serious about fixing the other engines I have to put on it. 1 14HP B&S and 1 12HP B&S because this yard is a bear to mow with a push mower.

I can post pics if necessary...

Any response is GREATLY appreciated!!!

Kollinsb, small engine n00b.


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## bbnissan (Nov 7, 2004)

FIrst question is...can you turn the engine over? It sounds like you ran it low on oil and broke the rod. More than likely you aren't going to be able to budge the engine, even with some extra leverage. If you do get it to break free, the engine probably won't have any compression.


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## kollinsb (Jul 25, 2005)

Thanks for the quick reply. 

I went out and turned the starter and it turns but has kind of a weird "pound" and of course won't start. (I didn't try too hard to start it, the pound kind of freaked me out) So, since it's not totally locked that's a good thing right?


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## bugman (Aug 12, 2004)

kinda, it sounds like it was run low on oil ( why i always emphasize on every time its started i check the oil ) fanatic on that part.... sounds like the rod is broken and slapping the side.... exactly how much oil was on the stick? its not like a car which some may think, they use more oil since they run alot hotter, and its gotta be in the operating range... i wouldn't even let em go half way the operating range... you could take the plug out and check to see if the piston goes in and out.


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## bbnissan (Nov 7, 2004)

The bad news is that it sounds like the rod is in fact broken. The good news is that if the piston isn't scored too bad and the crankshaft wasn't damaged, you can rebuild the engine.


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## kollinsb (Jul 25, 2005)

Well, I'll tear it apart this weekend and see what's going on with it...

Bugman, it was low on oil but it still touched the dipstick. I figure there's some spread throughout the engine. It was above the fill line but just barely. I'm sure it was too low.

Now, my question is. Do the sell rebuild kits for engines that will have the parts I need? I would hope I can find a rebuild kit but I'm not sure if that's all I will need. Wouldn't it be cheaper to by the individual parts and replace what needs replacing or is it smart, since I'm tearing it down, to do everything so it'll be good for me through next season too?


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## bbnissan (Nov 7, 2004)

They don't sell rebuild kits. You have to buy all the parts seperately. You are probably looking at a set of rings, a rod, possibly a piston and wrist pin, and a cam if the rod hit it. You will also need a head gasket, a set of oil seals, and a crankcase gasket.

Before you go out and buy anything, completely disassemble everything and inspect it carefully. Make sure that the crankshaft, camshaft, and valve tappets are perfectly straight. Also make sure that the journals in the block aren't damaged, check the counter weights for damage, and make sure that the cylinder is not scored.

If you got lucky, the rod broke right at the crankshaft and the whole piston assembly went up to the top of the cylinder without hitting anything. If you are unlucky, the rod broke off near the piston and beat the heck out of everything in the engine as it spun around.


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## kollinsb (Jul 25, 2005)

I had someone give me another motor. The one that's blown is a M/N 42d707 and this one is a M/N 422707. They look the same and are virtually the same engine. The one that was given to me was in a shelter without walls. When it was parked 2 years ago it simply needed new plugs and the carb cleaned. Should I do anything else to it since it's been sitting out so long?

Also, to take the old engine out of the frameI have to take the Stack Pulley Assembly off the engine because one of the pulleys is too big to go through the whole. I have no idea the best way to do this. 

Any help on one or both questions would be greatly appreciated.


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## bugman (Aug 12, 2004)

well, for that engine, new plugs and a good carb cleaning, airfilter, oil of course...... but for the stack pulley, have something to hold the flywheel, or a buddy with strong hands.... and take a ratchet to it to remove the bolt, the pulley should come off with little force. the old stack should fit on.


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## kollinsb (Jul 25, 2005)

Thanks Bugman... 

I can't find the bolt you're talking about. I can stick my finger all the way up through the stack pulley. Are you talking about the flywheel nut? It seems like it should just slide off but it won't. Is there a screw somewhere through the pulley and the camshaft?


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## kollinsb (Jul 25, 2005)

kollinsb said:


> Thanks Bugman...
> 
> I can't find the bolt you're talking about. I can stick my finger all the way up through the stack pulley. Are you talking about the flywheel nut? It seems like it should just slide off but it won't. Is there a screw somewhere through the pulley and the camshaft?


Nevermind... I found it way up in there... I got it off. Thanks Bugman!

It looks like the intake manifold is cracked in the center of the "new" engine. I will need to take the one off the old one and put it on the newer one. I'm debating on whether to go ahead and do the carb too since I can just do it all at once and I know the old one is good.

I've attached a picture of the "new" engine exaust manifold still on the mower it was given to me on.

Any ideas?


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## bugman (Aug 12, 2004)

wonder what couldv'e cracked that! as long as everything alse is fine, of course that right there should be replaced. well, for the carb. if the old one is fine, keep either one to sell or as a spare.


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## kollinsb (Jul 25, 2005)

Thanks everyone... Hopefully I won't have any more questions on it. This will be my first major repair. I will let you guys know how it goes.

I love this forum as much as a straight man can.

Thanks guys!!!


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## kollinsb (Jul 25, 2005)

O.K. I have the "new" motor on the mower now. I put the exhaust manifold and carb from the older engine on it. I go to start it after tripple checking everything is connected right and replacing the fuel line and it just clicks once. after messing around with it I realize the engine won't turn. I can rotate it backwards all day long but when I go the way it's supposed to turn it will stopp at a certain point and I can't turn it anymore. I thought I'd wait on doing anything drastic until I ran them by you guys. 

I thought that since the engine hasn't been started in a couple of years there is obviously no oil in the piston can I take the plugs out and shoot something down in there. I wouldn't think the internal parts would be messed up because it was a running engine when it was parked but has been outside in a shelter with no walls so it was weathered. Also, since it can turn backwards the pistons have to be going all the way up and down so I wouldn't thinks there was an obstruction. 

Anyway, any help would be appreciated.


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## bugman (Aug 12, 2004)

make sure the battery is charged up, may be hitting the compression stroke and hanging up due to a weak battery, or loose or corroded connections. that or the compression release does not work right.... try a recharged battery or even jumped from a car battery, that and turn it past the compression stroke.


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## kollinsb (Jul 25, 2005)

O.K. I changed the oil and filled it up (making sure not to overfill) and took the plugs out shooting WD40 in there. I still can't turn it past a certain point. It hisses right as it stops turning so I narrowed it down to where the hiss is coming from (like a burst of air or a burst of suction) the breather tube. 

I thought I could turn it backwards all day long (actually I'm pretty sure that was the case) but now I can't. It does exactly the same thing as when it goes forward. I do have an extra wire (a single wire) coming out behind the linkage bu t I figured that was the kill wire and it wouldn't effect it like this. It seems like it may be something very simple but I can't figure it out. 

It's getting a little annoying. 

Suggestions?


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## bugman (Aug 12, 2004)

maybe somethings hanging it up around the flywheel?


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## ranger_dood (Sep 4, 2005)

kollinsb- does it turn over freely without the plugs in?


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## bugman (Aug 12, 2004)

yeah forgot to ask that...try removing the plugs, if it turns freely, the compression release is messed up, or valve/s may be stuck


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## kollinsb (Jul 25, 2005)

It does the same thing with the plugs removed.

I seems like I'm being difficult but I'm not trying to be... It's the engine that's the difficult one. Sorry fellas. But thanks for the help so far.

I spin the flywheel as much as it will let me in both directions and I don't see an obstruction. Is it possible there's something internal? They said it was a running motor before it was parked but you never know...


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## bugman (Aug 12, 2004)

well if it was running, highly doubt internal.... pop the heads off to make sure of the valves, might as well clean it up while your there, the take the shroud off.....possiblility something you can't see readily


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## kollinsb (Jul 25, 2005)

Excellent... Thanks Bugman. I will try that tomorrow night. I may not be able to get back on till Friday but will definately let you know how it turns out.


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## kollinsb (Jul 25, 2005)

Well, the engine will need to be rebuilt. The camshaft is not straight and the connecting rod is broke. Any suggestions on where to buy a good engine at least 16HP? Needs to be a B&S though.


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## bugman (Aug 12, 2004)

feared that....sounds like maybe running on one cylinder? b&s for sure.....they are dependable little engines...... maybe a small engine shop? they may have a non payment sorta deal..... just sitting out there for sale. that or online....maybe e bay?


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## kollinsb (Jul 25, 2005)

Last night I thought I'd be a smarta$$ and take the 422707 apart to see about it. Well, the mower shop was smoking crack. I took the heads off and there was rust/standing water in one of the cylinders. I cleaned it up and now it turns very smooth. I'm getting a head gasket today to put it back together. **crosses fingers**


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## fords-n-mowers (May 6, 2005)

if possible put the head back on and fill the cyl with marvel mystery oil. if the cyl was that bad your sure to have stuck rings as well. i usually let it sit soaking in MMO for a few days then try to start it. this has never failed for me. :thumbsup:


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## bugman (Aug 12, 2004)

no, i don't think they were smoking crack, saw money to be more exact...... second that with the MMO, its also a good thing to add to the gas ( it'll say more on the bottle). you can pick up i believe a 32 ouncer of it at walmart for cheap.


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## kollinsb (Jul 25, 2005)

Is that the name of it? Will it hurt anything if I don't soak it and just mix it in the gas?


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## bugman (Aug 12, 2004)

yeah marvel mystery oil, its in a red container....you can get it at napa and other places. the gas use is if its running...pour it in there and let her soak a good bit with straight mmo. then when running well...read the bottle when you get it, its good stuff.


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## fords-n-mowers (May 6, 2005)

kollinsb said:


> Is that the name of it? Will it hurt anything if I don't soak it and just mix it in the gas?


with all the work youve all ready done take the extra time and let it soak.


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## kollinsb (Jul 25, 2005)

Just got through mowing the yard with the mower and it runs great!!! Thanks for all the input!!!


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## kollinsb (Jul 25, 2005)

would it be a bad thing to take the plugs out and let it soak after it cools?


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## bugman (Aug 12, 2004)

no, no need if it runs now....though follow the directions on the MMO for use in gas.... that and if you want that baby to run better, i even use mobil one in my main ones....great engine oil.


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## kollinsb (Jul 25, 2005)

Excellent... I'll use that when I change the oil next time and I'll be sure to use the MMO in the gas from now on... Thanks a million...


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## bugman (Aug 12, 2004)

though i do have to give a warning on using mobil 1....it is a true synthetic and may cause more leaks but thats if the seals were already bad, older seals and older syns didn't go along with each other...and caused problems today newer syns hardly have that problem, though i havn't had that happen when i switched......briggs engines just love the stuff..... but that MMO is truely great stuff.... if it does cause problems, just dump it back out mix with conventional


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