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Discussion Starter · #1 ·
Hey guys, sorry I dont have a picture, but the right plug (when your sitting on the tractor) was so carboned up you couldnt see the electrode or anything. Just one big piece of carbon.

Story goes, this thing has been starting to smoke and its just really annoying the guy.

Its a 23hp Briggs v-twin from 2008. With only 180 hours on it.

Other things Ive found are,
The air filter was literally plugged with dirt. I dont have a clue as to how it was running.
The intake valve is a tad loose. Definitely not the 5 thousandths spec.
And its smoking.

Intake wasnt dirty enough to make me suspect the rings are gone.
I think maybe the super carboned up plug was just causing it to smoke, but what would make that plug carbon up so bad?

Gonna clean the carb today, do a compression test, and put in new plugs then run her for a while and see what happens. Will also test for headgasket leak too. The motor is CLEAN on the outside minus the air filter.

Oh yeah, whats the correct plug for this motor? The guy has some kind of bosch in it. Any other plug recommendations?
 

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"Will also test for headgasket leak"

Good idea. I can send you a PDF copy of the Service Manual IF you like, address below, put in proper format and remind me, engine model number etc.

Walt Conner
wconner5 at frontier dot com
 

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Is it an OHV engine? A blown head gasket can cause a lot of smoking. I had a 14.5hp Briggs OHV, the gasket blew between the valve gallery and the combustion chamber, it smoked a lot until I replaced the gasket. I don't recall how the plug looked, but it's getting enough oil to smoke, then I'd expect it could also foul the plug.

Could a fouled plug cause smoking by itself? I could see the plug being so bad that it wouldn't fire at all, making you run on 1 cylinder. But I'm not sure how a bad plug could make the engine smoke, or encase the plug in carbon.
 

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I just had a 23 hp Briggs off a Deere with your same symptoms. Run the engine warm with the air filter cover off. If you see oil squirting out of the breather like mine was, it probably is serious. I noticed metal shavings in my oil after regular oil changes and about 250 hours on it. A local engine mechanic in my area says the last 5 years, he is seeing these engines left and right coming in with numerous problems.
I hope you fair better than I did. I found a comparable engine off of Craigslist and so far, so good but am strongly considering cutting my losses this year and moving up to a unit with a Kawasaki.
 

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Discussion Starter · #5 ·
alright so I pulled the heads and the headgaskets were fine. Found CHUNKS of carbon in the combustion chambers in the heads... literal chunks. HUGE chunks. I might have a picture tomorrow. Not sure. I cleaned all that out and its still blowing a little smoke.

Pulled the engine apart for the second time today. Pulled the pistons out and yup, rings are shot.

My theory is that the guy never changed the air filter. It seriously looked like he was trying to cut grass in the sahara desert. Thinking it got past the filters and into the conbustion chambers and wore the rings out some. Let oil pass by them and that fouled out the plugs and well....that caused all the carbon.

I have to have the engine back together tomorrow so Ill just be putting in new rings. I wont break it in yet till I get the rest of the tractor cleaned back up. Speaking of which,

If someone has the correct breakin technique for a 23hp briggs twin Id be overjoyed.

The guy really likes the mower, its a husquvarna yth123 or something like that. Its pretty slick, but he just wants a ring job done compared to buying something new. Darn thing looks brand new too.

Ill let him know about these engines not lasting very long. He wont be very happy to hear that, but with plastic ring gear on the flywheel and a plastic intake...its kinda obvious.

Thanks Walt, but I have one here already.

Red, yeah its ohv. Ive had a fouled/carboned up plug on my sears suburban before. Smoke like a train and had no power. New plug and shes golden.
 

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Carbon, is the result of combusting oil.

Id say, with new rings and a good honing...and proper care, should be fine. These were marginal engines at best.
 

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Just run it man..idle it to warm it up for a minute, then go out and cut some grass....

Change the oil after say, an hour of running, run SAE30...
 

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Yeah, these things needs to break in under a load, it helps push the rings out against the cylinders and beds in the rings more, before the microscopic coarse cylinder honed finish smooths over, at which point the rings are about 90% through break-in.

Ive seen engines that were rebuilt and idled on a bench for 20-30 minutes use oil pretty bad, as the cylinders dynamic compression was never increased from a load, and the engine never got up to full temp...the cylinder glazed over, rings never bedded in...used oil, had to re-hone the cylinder.

Im not saying to go out and flog it though, its always best to go gingerly at first, checking for leaks, smoke, odd noises....before putting it though its paces.
 

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The proper proceedure for breaking in the rings in a new aluminum bore motorcycle/bike/quad engine would likely work well for you too.
1) Warm engine fully
2) Run for about 1-2 minutes at 20-30% load, varying RPMs
3) Cool engine for 5 minutes
4) Run for about 1-2 minutes at 50-60% load, varying RPMs
5)Cool engine for 5 minutes
6)Run for about 1-2 minutes at 70-80% load, varying RPMs
7)Cool engine for 5 minutes
8)GIVE 'ER HECK!!! :thThumbsU

Got this from a racing bike mechanic and used it on my new Honda TRX250X last summer.

Like RED says, you have to have a load to seat the rings, and the hatch in the honed cylinder wears away pretty quickly in the aluminium.
 
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