Help with fouling spark plug on my 18hp B&S Intek

[pbm]

My 2007 Craftsman riding mower with an 18hp Briggs and Stratton Intek single cylinder started fouling the plug this year which I noticed due to hard starting. I ended up buying a new carb and replacing all the original fuel lines as recommended by SHOZ back in an August post (I never realized that it's recommended to replace the fuel lines every few years). It's still causing the plug to foul (black deposits as if running rich) and needs to be cleaned after each use.

A friend tells me to change the 17 year old coil because it could have a weak spark condition but I'm hesitating spending $40 if that's not the issue. I'm assuming that the spark must be OK if it starts easily with a clean plug. Any ideas as to why this might still be happening after changing the carb and fuel lines? Thanks

 

[Bud_One]

Sounds like your head gasket is blown.

 

[Fordiesel69]

Oil burning due to failed HG is common on these. Also valve adjustment goes out of whack all the time.

Also the camshaft fails and both the aftermarket and oem are equally as junk. Some make it 20 hrs, some make it 500 hrs. Usually not much more.

I rate these engines a slight bit better than the single cylinder kohler courage, but not but much more. At least the kohlers are easy to do camshafts on, but have other more serious issues.

 

[oldcodger]

Exactly what Fordiesel69 says, leaking head gasket. Just fixed mine this summer. I do not know if they are better, but you can get a solid copper head gasket for these engines. I plan to install one the next time mine fails.

 

[pbm]

I should have mentioned that it started using a little oil this year so I just ordered a new head gasket because it makes sense that that's my problem. Thanks guys. I won't get around to changing it for a few weeks but I'll update this thread with the results.

 

[Gyro Gearloose]

I had one that I had to do a camshaft replacement on last year. When I pulled the head I could tell the head gasket was leaking in the area by the pushrods. I can see that a big leak in that area could both suck oil into the cylinder and produce a lot of blowby which could carry oil droplets into the carb throat.

These engines seem to be ticking time bombs. Compression release breaking off the camshaft is a very common failure, head gaskets leak, valve guides back out and hit the rocker arms bending push rods, and they've been known to drop valve seats.

 

[tnt_motorsports]

I should have mentioned that it started using a little oil this year so I just ordered a new head gasket because it makes sense that that's my problem. Thanks guys. I won't get around to changing it for a few weeks but I'll update this thread with the results.

When you replace the gasket, check the head and block for flatness. If they aren't flat you are wasting your time. There are plenty of YouTube videos on how to "sand" the head and block smooth. I had to do this to my Kohler this spring and it's been good all summer. The real test is the load of the snow blower on it in the winter though...

Just my $0.02

 

[Fordiesel69]

I forgot to tell you, I did one of these and the head was warped 0.030 which is pronounced "thirty thousandths" and that was WAY out of spec. I sanded it down on a flat block and the headgasket worked for one mowing season before I sold it.

 

[Fordiesel69]

I had to mill so much off, I had to dremel the combustion chamber slightly.

What I was NOT able to find out, is there is another headgasket that is wider and often sold in kits on amazon, where they include both styles of gaskets but I never was able to find out if that would work as an upgrade. My engine was already re-assembled when it arrived so I passed the kit onto the next owner.

 

[pbm]

I had to mill so much off, I had to dremel the combustion chamber slightly.

What I was NOT able to find out, is there is another headgasket that is wider and often sold in kits on amazon, where they include both styles of gaskets but I never was able to find out if that would work as an upgrade. My engine was already re-assembled when it arrived so I passed the kit onto the next owner.

Thanks for this additional information. I ordered the gasket kit on Ebay and wondered how they could sell the whole gasket kit so cheap ($12).....I'm sure it's not the same quality as the OE which lasted 17 years. I'll try to determine if the head is warped but I'm wondering if it's a good idea to use some high temperature Permatex gasket maker in the failure prone area (as shown in numerous YT videos)?

PS: Earlier this past summer I was mowing and went into some weeds close to my shed when I caught a rope with a weight attached (that I had used to hold a tarp on the shed before replacing the leaky roof this summer). It immediately stalled the engine which started right up after I untangled the rope. I'm wondering if this had anything to do with the head gasket failing because the plug fouling seemingly started after that incident. Oh well, 17 years is a good run even though the mower probably only does 10 hours a year total...and no snow plowing.

 

[pbm]

I did the head gasket using a cheap EBay one and a few coats of Permatex copper spray gasket and so far so good. I’ve retorqued the bolts 3 times and will do it one more time as per Fordiesels recommendation. I also adjusted the valves. All seems good and thanks for the good info/ advice.