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B&S engine woes


kydar's Avatar
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04-17-10, 10:04 PM   #1  
B&S engine woes

I have a Murray tractor with a B&S 18HP single OHV engine. 31D777-0235-E1 is the model/type and 030221ZE is the code number, which tells me that it's 7 years old. When I put it in storage for the winter, it was running fine. I added fuel stabilizer and let it run for a few minutes to make sure it got into the carb.

When I tried to start it this month, it wouldn't turn over. Battery was charged and "trying" to turn the engine, but was jammed. I tried manually turning the fan/flywheel from the top and met a LOT of resistance. I think at that point I pulled the plug out and a lot of gas came spilling out, and then it would turn over. If I had to guess, I'd say the reason it wouldn't turn over was the cylinder was filled with gas and on the compression stroke the piston just couldn't rise.

After that, it turned over and started briefly but blew plumes of smoke (grey color). Died after about a minute. I pulled off the muffler and found broken metal shards in it!! I'm not sure where they came from. They're flat so they're definitely not remnants of piston rings. I think they may have broken off from the inside of the muffler itself. I do not believe (but cannot be sure) that any of these metal fragments fell back into the cylinder.

Subsequent attempts to start the engine were met with about 10 seconds of running okay, followed by the plumes of smoke, engine chugging and choking, and eventually dying out. Also, engine oil AND gasoline spitting out from somewhere near the muffler.

I did of course drain all the old gas out and put fresh gas in - no effect.

It seems to me there are a few issues with this engine:

1. Carb is most likely gummed up and needs a good cleaning.

2. Head needs to be pulled off to inspect for damage from these mysterious metal shards. Probably a good idea to replace piston rings since it is spitting oil out.

I used to rebuild automatic transmissions, and once I rebuilt a Kawasaki engine from the block up, BUT this was 25 years ago and I don't do much (ok, any) mechanical work anymore. Carbs in particular scare me. I don't understand very much about them but I know they're very finicky and a pissed off carburetor can ruin an otherwise fine engine. Also, there is a spring wire on the carb that is not attached to anything at one end and I can't figure out where it's supposed to go. I took a picture of it but unfortunately I can't see any way to attach a photo to this post.

I just bought the B&S repair book online, will probably take a week to get here.

Any suggestions? Anything I could try while I'm waiting for the book to arrive?

Thanks in advance.

 
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cheese's Avatar
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04-18-10, 01:07 AM   #2  
I'd just fix the carb and see what that nets you. If it is dumping fuel, you will get oil past the rings and gas in the oil.


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God bless!


Last edited by cheese; 04-18-10 at 10:52 AM.
 
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04-18-10, 05:55 AM   #3  
Pull off the carb and clean it and install a new kit. If you rebuilt automatic trannies, carb rebuilding is a piece of cake.
While you have the carb off, I would install a gas shut off in line between the gas tank & carb. As far as metal shards in the muffler, I wouldn't worry about it. Most likely from the baffles inside the muffler and there is no way they would get back into the engine as the muffler is 1 way-out only.
Change the oil as gas has most likely leaked into the oil.
I do not see any need to pull the heads off.
Look at your carb and get the name of the carb before going to get the carb kit. You could have either a Walbro or a Nikki carb. Kits are different.

 
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04-18-10, 06:53 AM   #4  
the carb

I agree with Indie. The single best thing you can do for your small engine,[and for yourself ] is to install a fuel line shutoff. and run the engine dry if it will be unused for any length of time. I do it with all my mowers and blowers, and my boat.
I have had the boat for 24 yrs, and just rebuilt the carb after 21 yrs, not because it was bad, but i thought it was probably time.
Sid

 
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04-18-10, 11:17 AM   #5  
I second Indy's motion, I install shutoff valves on all gravity fed riders I either own or work on.

 
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04-18-10, 01:52 PM   #6  
This is the easyest type to install. Just cut the gas hose and install.
Amazon.com: Briggs & Stratton 698183 Fuel Shut-Off Valve For Quantum and Selected Models, In-Line Valve: Patio, Lawn & Garden

 
kydar's Avatar
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04-18-10, 05:21 PM   #7  
Wow, you guys are great, thanks for all the help. I'm going to start by rebuilding the carb...but I'm going to wait for the book to arrive and pray that it's got a big chapter on carburetors with lots of pictures. Still can't figure out where that one spring wire is supposed to attach.

Is there any way to attach photos to these posts? The posting rules at the bottom say I'm not allowed to post attachments...is there a way to get that permission? Or is it turned off for everybody?

 
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04-19-10, 01:01 AM   #8  
I don't know if the photo codes are turned off again or not. I never use the option. You can post your photos to photobucket or similar site and link to them from here. The spring you mention if it is around the throttle linkage, it connects to the same holes the throttle linkage connects to.


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God bless!

 
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04-19-10, 07:46 AM   #9  
Pic of the carb with unattached spring wire

carb.jpg

 
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04-19-10, 08:58 AM   #10  
I believe that is the throttle tensioner spring, it goes in the same hole as the throttle control rod.

 
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05-05-10, 03:21 PM   #11  
update

While I'm waiting on the backordered carb rebuild kit ($32 for a new main jet, a couple of O-rings and gaskets, sheesh) I decided to drain the oil. When I took the drain plug out, the "oil" inside had the viscosity of water (i.e., gas) and smelled like gas. I'd guess that it's about 1/2 oil and 1/2 gas. I'm amazed the engine didn't blow up last time I tried to start it. Can all this be due to a faulty carburetor?? I'm really wondering if I should pull the head off and take a look inside. The problem with that is, I would then have to buy a $55 "engine gasket kit" to put it back together. Honestly, the prices they charge for a few pieces of asbestos are insane.

Off-topic...I just bought a nice Echo string trimmer from a girl I work with for 30 bucks. Problem is, she has no grasp of the concept of a 2-stroke engine, and she ran it for about 10 minutes on straight gas. It still cranks...I'm hoping that if I flood the cylinder with oil and lubricate the stink out of it, it won't seize.

 
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05-05-10, 03:31 PM   #12  
Gas getting into the oil is because the float and float needle valve is not shutting off the gas flow. may have been dirt around the needle or the float had holes in it.

Getting a new main jet may have not been necessary, thorough cleaning of the old one would probably have been sufficient. Even on the worst shape carbs, I've never had to replace the main jet.
Then, installing a new kit, with new float needle and seat(if it had one).

also, have to make sure the float has no pinholes in it, allowing fuel to enter, this weights down the float and it won't rise to engage the float needle in the seat to shut off the flow.

Thoroughly drain oil and gas, of course.

you shouldn't have to disassemble the engine in any way. just put in correct amount of oil before you start.

On the Echo, remove the muffler and see if the piston is scored, check compression as well. After running 10 minutes, did it quit on it's own or, did she shut it off?
hth

 
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05-05-10, 05:22 PM   #13  
make sure you change the oil twice or you will be putting a cam in the motor

 
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05-05-10, 06:02 PM   #14  
I was planning on putting a quart of oil into the engine, then hand-cranking it a few times to swoosh it around a bit, then draining and disposing of that oil, then refilling to whatever the correct level is (I believe it's about 1.5 quarts?) with "good" oil. Changing the oil filter too, of course.

I'm not sure what you meant by "putting a cam in the motor." ??

One additional question about the main jet...when I unscrewed the old one out, using a regular Craftsman steel screwdriver, it damaged the brass jet even though I was trying to be careful. Obviously, I don't want to damage the new jet when I put it in. Is there a special screwdriver or something that I should use? I was thinking some sort of "plastic screwdriver" if such a thing could be found (or made) would probably work better. I have no idea what the jet should be torqued to...I'm guessing just "snug"?

Re: the Echo...she shut it off. I even started it for about 20 seconds when I bought it....this was before she told me there was no oil in the gas. It seemed to run fine.

 
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05-05-10, 06:11 PM   #15  
Posted By: sidny I agree with Indie. The single best thing you can do for your small engine,[and for yourself ] is to install a fuel line shutoff. and run the engine dry if it will be unused for any length of time. I do it with all my mowers and blowers, and my boat.
I have had the boat for 24 yrs, and just rebuilt the carb after 21 yrs, not because it was bad, but i thought it was probably time.
Sid


I thought that running the engine until it quit didn't generally empty the carburetor bowl, and left the jets and things probably still sitting in fuel.


That's false? Or is running it dry a help, even if not a completely satisfactory method?

 
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05-05-10, 06:41 PM   #16  
Posted By: bob1908 make sure you change the oil twice or you will be putting a cam in the motor
That's not a bad idea, what I do is refill with oil, take sparkplug(s) out, then turn it over at least 6-8 times to make sure oil is in passages. Starter turns it over pretty good w/o plugs.
I put shutoff valves on all gravity fed riders.

 
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05-05-10, 06:44 PM   #17  
Posted By: kydar One additional question about the main jet...when I unscrewed the old one out, using a regular Craftsman steel screwdriver, it damaged the brass jet even though I was trying to be careful. Obviously, I don't want to damage the new jet when I put it in. Is there a special screwdriver or something that I should use? I was thinking some sort of "plastic screwdriver" if such a thing could be found (or made) would probably work better. I have no idea what the jet should be torqued to...I'm guessing just "snug"?

Re: the Echo...she shut it off. I even started it for about 20 seconds when I bought it....this was before she told me there was no oil in the gas. It seemed to run fine.
I would just use regular screwdriver putting in mainjet, no need to overtighten, just good and snug.

Echo - sounds like you'll be ok, if it ran 20 secs.....----maybe you got lucky.
hth

 
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05-13-10, 06:57 PM   #18  
Well the carb rebuild kit finally arrived after being on backorder for two weeks. I rebuilt the carb, spraying everything heavily with carb cleaner, and put it back together. I didn't pry off the welch plug, because oddly enough there wasn't a new one in the rebuild kit, and I didn't feel like waiting another two weeks for them to backorder one. I don't even know what's behind the welch plug anyway...presumably something that could have been sprayed and/or blown out, but I decided to just take my chances.

I put some a quart of cheap SAE30 in and cranked the engine a few times. Drained it...still had just a bit of gas in it. Put a second quart in, repeated, came out pretty clean. Then put the new oil filter on and used high quality SAE30 for the final fill.

Put the whole schmeil back together, and it runs like a champ!

Thanks again to everyone who contributed ideas and suggestions. I may be posting here again in the future since I got such good help here.

 
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05-13-10, 09:55 PM   #19  
Posted By: kydar
Put the whole schmeil back together, and it runs like a champ!

Sounds like symphonic music when it takes off, doesn't it?



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