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Hi all,


I acquired a used tractor from a friend (Briggs motor: 445677). It was running well for a few months and then started blowing black smoke. After reading various threads about Intek engines blowing head gaskets, I decided to replace the head gasket. When I took the heads off however, I did not notice signs of deterioration in the head gasket. Nevertheless, I replaced the head gasket as I had to scrape off bits anyway. I cleaned up a decent amount of carbon buildup from the top of the piston and I used fine drywall screen and seafoam to "sand" the bits of old gasket from all surfaces. Unfortunately, during the process of reinstallation, I over-torqued the head bolts (wrong setting on torque wrench). I, ultimately, torqued them to the correct torque (but I was sure I had at least compressed the gasket or worse, warped the heads). Anyway, I put everything back together and the engine still smoked. It also appear to have oil visibly leaking onto or from where the exhaust pipe connected to the head.


So, I suspected a warped head (either from my over-torquing or from previous overheating - the engine was quite dirty when I got it). I ordered two new head kits (came complete with head, intake and exhaust gaskets). This time when I replaced the heads, I filed down the exhaust pipe connection as it had quite a bit of old gasket material stuck to it. I also made sure all metal contact surfaces were cleaned again and I set the valve gap to .004. With new heads and new gaskets, I was SURE the smoking problem would be solved! Well...still smoking from, again, what appears to be around the exhaust port. This time, I don't see any visible moisture/oil from that area. I should add, that when I run the machine, I don't have the air filter hooked up (if that matters).

I should add, the engine now has an occasional stumble and it will backfire when moving from full throttle to idle. And, the engine smokes more at idle.


I've been reading threads about the issue, but thought I'd post to see if anyone has suggestions about any TESTS I can do to narrow down the problem. I've read the following:


1. take the exhaust pipe off and run the engine to see if oil drips out
2. take the valve cover off and shine a light into the chamber to see if oil is leaking into the chamber


Ideas of the possible problems:
1. is the engine block surface warped from over-torquing the head bolts? (except the same symptoms are occurring before and after the head replacement).
2. bad piston rings?
3. ?

Thanks in advance for any help.

Bad news ,
Sorry about this
Black smoke is either a rich mixture or retarded timing so everything you have done was not part of your problem.
OTOH you are now very competant in changing B & S head gaskets .
The carb probably have a float valve that is sticking or the main jet has fallen out .
Find your carb in this list from Outdoor Power information site .
You can buy a rebuild kit but most likely it will come good with a clean.
Check that all of the jets are there ,in good condition & correctly installed.

Oil burning causes white smoke.

Thanks for your quick reply and information. Does it matter that the smoke is not coming from the exhaust? It's coming from around the engine and specifically from what appears to be the union of the exhaust pipe to the head? Wouldn't what you are describing be black smoke coming out of the muffler? Thanks.

You can run the engine for a good 20 minutes or so without the blower housing on so your next step is to remove said housing and degrease th e engine thouroughly
Then fire it up and watch for oil rips .
The wind created form the blower is quite good at shifting oil all over the place but only the head & exhaust gets hot enough to make the oil smoke.
External smoking oil is blue-white in colour.
You can also remove the breather tube and if the smoking reduces then suspect rings paticularly if a lot of oil is being blown out the breather tube.

Update:

Thanks so much for the info!

So, I took a MUCH closer look when I ran the engine this time. The smoke was coming out of the exhaust and it was definitely blue (burning oil) not black. I didn’t notice any active leaks of oil on the outside of the engine. It was actually running pretty well, but at idle, it wasn’t maintaining a constant rpm, yet didn’t stall.

As mentioned, I did the following tests:

1. Compression test. Cylinder #1 = 120 psi, Cylinder #2 = 70psi. Added a bit of oil to cylinder #1, retested and it maintained the 120psi.
2. Took off the breather cover and ran the engine = didn’t notice oil coming out.

Question/Feedback:

With the 50psi difference in compression between cylinders, I’m assuming there is an issue with Cylinder #2. And, with a brand new head (including valves), I’m assuming it’s not the valves.

1. Am I correct, at this point to assume the piston rings are shot?
2. I haven’t done the oil compression test with Cylinder #2 yet, but do you think it’s even necessary?
3. Is there harm in running the engine with low compression in one cylinder (potential ring failure)? I just want to get through some of the spring cleanup tasks on my yard before I do further work to the motor!!
4. Are there other tests I should perform at this point?
5. Is it worth taking the block apart to fix the piston? (I’m already out the money for the new heads…lesson learned!).

Thanks so much for your help with this!

Check the oil .
As previously mentioned if the carb is leaking into the engine it will thin the oil and the thin oil will bypass the rings .
And running on thinned oil will drastically reduce the big end life .
Other than that just so long as you keep the oil level up, you will not do any further damage .
Because of the ACR fitted to most engines strait compression readings mean little and you really need to do a leak down test .
If you have some sort of compressor then a tester can be made quite cheaply.
Apparently HF have a low pressure one that works well .
You could probably run the engine as is all season and do the repairs in the off season .
You might need to keep on swapping the spark plugs if one continually fouls .
Mower engines are very low tech for now.
In the no too dstant future they will all be fuel injected and things will change big time.

Another Update:


So, it appears not all YouTube videos are created equal. I had watched a video showing how to set the valve lash by opening one valve all the way (one at a time) and setting the gap on the other valve when closed (.004 in).

In reading a few articles (one from Briggs) and watching a few other videos, I followed the procedure that calls for adjusting both valve gaps at the same time when the cylinder is ¼ past TDC.

In addition to adjusting the valves in what appears to be the correct way, I also drained the oil and refilled it with SAE 30 and added a Lucasoil additive (according to the directions).

When I rechecked the compression, both cylinders were around 170psi! When I started and ran the engine, there was no sputtering at full throttle or idle and now backfiring. There was still some blue smoke, but I saw visible oil on the outside dripping on the exhaust. I decided to be patient and keep it running while wiping some of the oil away. I suspected it was residual oil from after the oil change and from taking the valve covers off. After a while, I did not see any smoking and there was no blue smoke coming from the muffler.

So, I dethatched the entire backyard and rechecked the engine afterward. I’m happy to report, for now, there is no blue smoke and the engine seemed to be really running great. When I shut off the motor, there was no backfiring.
I think I will still check the carburetor, just to be sure it’s operating correctly. I just wanted to repost because it appears to be a simple valve adjustment when, before today, it appeared to be worn piston rings!

Thanks again and I’ll repost if there are any changes in the wrong direction. These forums have saved me so many times and have only added to my ability to learn as I go. I just really appreciate everyone taking some time to offer suggestions.

BTW, thanks so much for posting the link to the carburetor lookup and break down. It's great and I will surely consult it when checking out the carb.

Tomato Tomarto
Different ways of getting to the same place.

bertsmobile1 said:

Tomato Tomarto
Different ways of getting to the same place.

Click to expand...

Maybe but unless one figures they are more knowledgeable than the engineers who designed and built the engine, best stick with their recommended procedure.

Walt Conner

No arguement about that Walt.
I suppose some time I should go to the effort of clocking the cams but like you I have better things to do with my time.
Use both methods depending upon what is the recommendations .
However they are lawn mowers and if the passionate want to do it a different way then let them do it and be happy.
Like religious beliefs people seem to be way to passionate about the method of setting valve lash.
I look at it this way, at least they are setting the lash.

Question is are novices setting them to really proper clearance being advised to using alternate Methodists? We all know that B&S is tolerant and will "run" without necessarily being at the precise setting. Example many years ago when people started recommending to use a business card to set air gap. I mic'ed 50 - 60 business cards finding them running all the way from .008 to .018 with larger companies and more successful being thicker. The engines were running so was that advice OK? Now they are all pretty well uniform.

Walt Conner

PS: Another true story, about 65 years ago I was in the shop of the largest lawnmower dealer in Terre Haute, IN. I was looking over the Service Tecs. workbench and tools. I didn't see a torque wench. I asked him what he used for a torque wrench. He said. "My false teeth, when they grit, I quit tightening". Don't think he was pulling my leg as I couldn't find a torque wrench. His engines were running so that was OK. Actually, I was using about the same method myself at that time and my engines were running also. Did see a broken crankshaft hanging over his work bench to remind himself to use a puller rather than the pry and hit method.






his workbench and tools.

Funny you should mention the business card thing.
When we had the courier business and 2 customers did instant printing of photos for models & hand out photos for performers
We would regularly go to the paper suppliers & get sheets of board for him.
No 2 were ever printed on the same weight board.
I have always used stiff plastic wrapping , the stuff shirt boxes were made from back in the days when shirts were made properly & were an expensive & valued item of clothing.
Last one I checked was .006" so I am still checking wrappings to find some 0.010" to cut some more spacers from.
The old side valve long strokes do not care much about accurate timing but the square OHV's are lot more sensitive to timing than most would think .
Unfortunately we no longer teach kids physics or electricity any more so that can not appreciate that the gap width will vary the timing according to the inverse square law.