craftsman/briggs&stratton going up in smoke

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chance

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I will try and shorten this headache best I can..I have a 4yr craftsman lawn tractor with a 21hp briggs&stratton intec model 331877 not many hrs at all..after winter storage .ran dry with sta-bil..time for spring maint. oil level was not low, it started right up for oil change warm up..have always used a 10w-30 synthetic with new filter every time ..this time used supertech synthetic and supertech 3614 filter..no problem till about 10-15 min. warm up then I
noticed an occasional miss with a puff of whitish smoke..warmer it gets the worse it gets after 30 or more of cutting grass and driving around the miss and smoke was real bad..turned off and checked oil level .. it was about a pint low and really black..the oil usually is still clear after a season of mowing..added a small amount of carb cleaner to gas and ran some more..no help? checked plug and it looked like a glob of tar.. new plug rc12yc no help..anyone know how I might solve this without tearing into engine .I don't have a wealth of experence..could a ring break or stick without some noise or warning ..maybe someone knows of something simple..an additive?? Lordy I hope so..only had a 2 yr warranty..anyone with a idea or knows what the problem is please let me know.. I greatly appreciate your help...
 
Glob of dark gunk on the spark plug along with the white smoke tells me it is burning oil. Head gasket failures are extremely common on those Briggs engines. When the gasket fails then the oil from the valve galley on the side gets pulled into the combustion chamber.

Donyboy73 on Youtube has a DIY video on replacing Briggs and Stratton head gaskets. The gasket is less than $20 and can be done with simple hand tools.
 
Not likely, but running the carburetor dry with Sta-Bil could have caused the rings to overheat and drawn the temper out of them.

A pint low is horrendously low for that small of an engine. Sometimes a pint low is low enough to cause lubrication starvation and is certainly low enough to raise the oil temperature.

Could be just typical Briggs & Stratton quality too
 
Thanks a million guys for your help...the breather,air filter is good..clean..I think there are clues but I don't know where to go..like why it doesn't miss/puff smoke until 5 to 10 min inital start up then the more you go the worse it gets..I have been very carefully not to go below the low mark on the stick..it doesn't seem to have lost any power maybe just a little..if it is a ring,valve,gasket would there besome kind of noise or something..and what would turn fresh oil black after only about 30 min of running..anything I might look at or look at short of surgery? if I did afresh oil,filter,plug change would that just be a waste..maybe with a additive if so what do you recommend...again thanks!
 
Last year my 4 year old Craftsman 21HP rider started smoking. Turned out it blew the head gasket which is quite common. You Tube has videos on this problem.
 
It does sound like a bad HG. Like said, very common, especially for the large single cyl OHV Briggs.
 
Is this a 1 or 2 cyl? Single are known for blown HG, double not nearly as much.

Repair is not too bad, but my friend with no mechanical knowledge took his to a JD dealer and paid $750 after waiting 3 weeks and paying the neighbor boy $150 to mow while waiting. I wish he would have asked me (and he will if there is a next time) and I would have done the job for less than half.
 
Originally Posted By: Cardenio327
I found the specs for the 331877 online and the total oil capacity is only 3 pints, so 1 pint low is probably enough to ruin the engine

link: click here


Not trying to be combative, but it's probably not low enough to damage the engine given the relatively short time the engine was ran.



I also agree that this is likely a head gasket issue. As to why it takes a few minutes to start smoking- I'm not sure but the last one I worked on did the same thing. Also agree- they're cheap and easy to do.
 
Originally Posted By: The_Eric
Originally Posted By: Cardenio327
I found the specs for the 331877 online and the total oil capacity is only 3 pints, so 1 pint low is probably enough to ruin the engine

link: click here


Not trying to be combative, but it's probably not low enough to damage the engine given the relatively short time the engine was ran.



I also agree that this is likely a head gasket issue. As to why it takes a few minutes to start smoking- I'm not sure but the last one I worked on did the same thing. Also agree- they're cheap and easy to do.


You're probably right about the head gasket, I don't know much about this type of B & S motor.

The OP did comment that he warmed the engine up 10-15 minutes, and afterwards mowed for 30 minutes before checking the oil though. Good thing it doesn't have splash system lubrication! I guess whoever pulls the head to change the gasket should be able to take a look and see if the liner is trashed easy enough
 
Hi guys, it's chance...thanks for all the info I really appreciate it...it's a single..and about the cost of repair I know exactly what you are talking about..
my money tree in the back yard is not growing too big..and yesterday I know it was a
long shot but I did a quick service on it ..oil change supertech 10w-30 ..filter supertech st3614 and champ rc12yc plug..and the results are the same..about 10 min.
after starting it starts puffing and the more you go the worse it gets..so I guess I'm going to get a lesson in head gaskets...thanks for your help!
 
They're easy on this thing. The trickiest part is getting the valves set correctly- and they're not that hard.
 
Originally Posted By: The_Eric
They're easy on this thing. The trickiest part is getting the valves set correctly- and they're not that hard.


+1 on the valve settings, as the compression release is keyed in on the exhaust valve clearance.
 
Originally Posted By: jeepman3071
Glob of dark gunk on the spark plug along with the white smoke tells me it is burning oil. Head gasket failures are extremely common on those Briggs engines. When the gasket fails then the oil from the valve galley on the side gets pulled into the combustion chamber.

Donyboy73 on Youtube has a DIY video on replacing Briggs and Stratton head gaskets. The gasket is less than $20 and can be done with simple hand tools.


In order to do the job right so that you do not tighten to much and strip the threads or under-tighten and have a leak, most engines will have a torque speck for the head bolts that you should tighten to with a torque wrench.
 
JUDGEMENT DAY GUYS !!! the votes are looking like I
I have a blown head gasket..I just ordered a repair set and have to run out to harbor freight and get a torque wrench and hope I get the right specs.I just want to say again how much I appreciate everyone's help..have learned /learning a lot..cost not too bad ..about 21 bucks for the gasket set..2.65 ea for a couple of plugs .can clean those up..2.84 ea for three filters ..17.47 jug of oil..19.99 torque wrench..tax and some shipping..I just hope I don't screw it up...everyone had good info and links and could someone tell me or link me to the torque specs I guess one of most important things ..I will start tearing it down..Thanks to all! ..chance
 
Hi guys..hang on for a minute..I think I counted my chickens before I caught them all!
I cannot budge any of the head bolts! Are they..the bolts torqued more from the factory?anyone know a "trick" I might try...it's possible I'm a little paranoid but I felt like I pulled hard enough to break them loose..lucky no rain in the forecast so ìt won't grow too fast...anyone have some info or tips I sure would appreciate it..
 
Hi guys,it's chance and I'm looking at the top of a black oil burnt piston..bolts were SUPER tight but I used a little cheater pipe and said win or lose the head is coming off..now the cleanup begins...a lot of work but I enjoy it..I'm sure I work cheaper than a pro.....I have one more question...I did not take the ohv cover off so the push rods are "loose"..will it go back together ok without adjustment to the valves?
Thanks,chance.1
 
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