Head gasket, maybe???

[Arkie]

Briggs twin Intek OHV engine
Model 445577, Type 1187-B1, code 080721YG (445577-1187-B1)

I do not know any of the history of the engine other than it has NEW 30W engine oil.

Smokes very little if any when first started up cold.
engine smokes intermittently after get warmed up and sounds like it intermittently gets weak cylinder and when it does the smoke increases.
I checked the valve lash and all are at .006. Both plugs are sooty, not oily.

I have a leak down tester and compression testers.
I do not have any means of testing the oil sump pressure/vacuum but have vacuum and low pressure gauges?

Any idea how I might determine which of the cylinders is suspect of head gasket leaking into the oil galley so as to not have to pull both heads for inspection? (like maybe pull the valve covers and compare leak down air noise at each valve galley?

[bgsengine]

Leakdown test is what I always went by .. valve cover off so you can look/listen to the head gasket to valve area (which is almost always where they blow - between the cylinder and the pushrod galley.. if you can confirm it seems like air coming out in that area, you can be 100% sure by squirting some soap & water over the seam..)

[hanz63]

I seem to be getting more Intek twin coil issues over the last couple years. Verifying fire on both cylinders as it warms?

[KE4AVB]

Just thoughts....

Also depends on color of smoke. White smoke is oil smoke. Dark blackish smoke is usually over rich. With sooty plugs and having a Nikki I would be checking the main jets o-ring for loose fit. So far over the years I haven't this version of head gasket blown. With both sooty I suspect a carburetor issue myself.

Now as Hanz63 I have been more issues with the coils but usually it is the kill harness diodes becoming leaky.

As far a manometer they are easily to make a homemade. Just take a few feet of clear 1/2" or 1/4" tubing that you can make a loop in. Just about 12" of standing water in the loop. Mark where the water seeks level in the loop. Then connect to one of the vacuum, not the breather valve. With the engine running the engine of manometer should show a slight vacuum (water rise). If the water lowers then you have a positive crankcase indicting excessive blow-by.

Also when using a leak down test that operates with low input pressure such the HF one that I have. You can disable the valve train on these overhead valve engines so you can check for mid and lower cylinder problems. Briggs twin Inteks usually wear number two cylinder out before number one in my experience. Usually by ovaling and tapering the cylinder.

[Arkie]

The latest about the smoker Briggs Twin OHV Intek:

KE4AVB:
wrote this.
With sooty plugs and having a Nikki I would be checking the main jets o-ring for loose fit.

I did the leak down test using a OTC tester and air pressure at 80 and only about 5% leak at most at TDC.
So I went to the carb after your hint and the two little jets in the emulsion tube just fell out due to bad itty bitty bad o-rings when I removed the bowl. Found a emulsion tube from another old carb that same size jets were still a snug fit and installed and engine is now running really smooth.
My o-ring kits did not have any o-rings small enough for the two emulsion tube jets that fit into the bottom of the plastic tube.
Thought about just using a fast set epoxy around the jets and making them permanently secured. Carb IPL does not even show the jets as removable from the BOTTOM of the plastic emulsion tube.
Carb was causing a run rich condition but still have blue oil burning smoke.???



BUT lots of blue oil smoke when engines gets warmed up.
I noticed when I removed the carb that the breather tube was not plugged into the carb throat intake, therefore the engine has been sucking lots of dirt/dust into the carb throat where the breather tube should have been installed.

The check valve in the breather tests good and no oil mist coming out of the tube, just [b]Blue smoke I can see blue blowby smoke coming out of the breather tube after the engine gets warm and the longer it runs the worse the exhaust BLUE oil smoke gets and the oil level will drop after the engine is used mowing for about hour.
I checked the crankcase vacuum using a 0-10 inch vac gauge sealed plugged into the oil filler spout and it checks about 1 at idle and as engine is reved up it goes to zero but no pressure.
I compared this crankcase vacuum test to a good Briggs twin L-head and got same vacuum readings at idle and still a very slight reduced vac as the engine was reved up. Reading were very close to same on both engines.

The engine puffs most (more) Blue oil smoke right when throttle is set from high speed to low speed as the engine is losing rpms coming back to idle. (usually this is a sign of intake valve stems seals leaking or worn valve guides but both are ok???) The intake valves have no wiggle and the stem seals look really good.
The compression checks 130psi on both cylinders with engine hot.

I did not do the leak down test with the push rods off the valves so as to check leak down with piston at lower part of cylinders ??????????

Really suspect worn rings/cylinders due to engine sucking lots of dirt into the carb throat at the breather tube hole. Someone had taken off the carb/manifold and failed to re-install the breather tube when they re-installed the manifold. (but leak down does not confirm bad rings or bad cylinder???)
(lots of oily gritty dirt was built up on the back of the plastic manifold from the breather tube flopping around on the back of the manifold)
The oil does not seem to be getting gas contaminated from the vacuum pulse operated fuel pump. No gas smell in the oil and the engine loses (consumes) oil instead of making oil.

Any ideas other than checking for out of round cylinders and/or bad oil rings? (or lots of STP additive)
This is my own engine, not for a customer. It will kill mosquitos but Al Gore would be severely depressed at the Blue cloud it produces.

[KE4AVB]

I will pm you the PN for those tiny o-rings that Briggs don't list in the IPLs.

But at 80 PSI you are not going to be able to rotate the engine through by hand. MY HFT tester does this test at 12 psi.

[Arkie]

I will pm you the PN for those tiny o-rings that Briggs don't list in the IPLs.

But at 80 PSI you are not going to be able to rotate the engine through by hand. MY HFT tester does this test at 12 psi.

I'll try the leak down at low pressures. My OTC leak down tester has adjustable input pressure.
I did compare the leak down at low pressures at TDC and rotated the crank to make sure that the leak down reading came back to the same as the valves and piston came back to TDC. I was mainly looking and listening for a head gasket leak into the oil galley and checking the intake valve seals and guides, due to engine running rough and spitting erratic smoke.
I'm going to drop the muffler off and compare the smoke from each exhaust pipe to see if one cylinder is smoking lots more than the other when the throttle is reduced from high to low and the Blue smoke increases.
Strange to me that the engine does not smoke when cold, not even a hint but as it warms up it just keeps getting worse and worse. Even smokes lots at idle when it starts and intermittently increases and decreases as the mower is being used. The engine is clean on the outside, other than the heavy oily dirt build-up behind the carb air intake due to the breather hose not beings not being installed into the carb intake and engine not showing any signs of overheating due to clogged cooling fins etc.

The spitting and sputtering engine due the bad carb jets leaking causing the engine rpms to increase and decrease was mis-leading to me, causing the increase/decrease in smoke, Thinking the oil smoke increase/decrease was the cause of the sputter and maybe a head gasket leaking instead of the bad carb. (as engine rpms is reduced fast the Blue oil smoke increases)

I've never seen a engine smoke this much only when warmed up and the leak down NOT give a hint as to the cause??????????????

[bgsengine]

big quetion - how much oil does it use - as in how much does oil level drop, and how fast.. if oil level does not seem to be dropping or using oil , you might just be getting oil loaded up with gas/ unburned fuel? (check spark plugs for signs of misfiring?)

[Gerry]

Could be that the compression ring is still good and just the oil ring is whack.

[Arkie]

big quetion - how much oil does it use - as in how much does oil level drop, and how fast.. if oil level does not seem to be dropping or using oil , you might just be getting oil loaded up with gas/ unburned fuel? (check spark plugs for signs of misfiring?)

Thanks for the hint.
Other priority projects and weather been cold rainy.

The heavier oil smoke starts after about 15 minutes of running. No smoke when cold engine?????
Has symptoms of failed oil ring or rings maybe.
The engine now runs really smooth and starts good.
I do see the oil level drop and no gas smell in the oil. (but I have not operated it very long after doing the carb repair)
I'll drop the muffler and compare the smoke from each cylinder and also compare both spark plugs color after using the engine. (and try to vacuum test the pulse port (or use a clear looped hose on the pump to make sure no gas being sucked into the pulse port. I've seen engines smoke like this due to gas contamination in the oil but they would make oil and the oil would smell of gas.
I'll get back in few days with more test results and after putting the engine to use mowing, etc.