after getting my mower back from the B&S Technician for a carb rebuild, I was told that the engine is only working with one cylinder. They said that the cam shaft lobes for the 1st cylinder cycle where worn and not moving the rods enough to engage the intake and exhaust valves. I am trying to figure out if this is true or not, or does this guy just want me to spend move money? Could the lobes get worn down, how could they get worn down or is it something else? Engine sounds like it has from day one, guess I could have bought it broken, bought it used. It does bog down and stall if the grass is wet and to tall, which I try not to do but here in Florida lately it has rained almost everyday for a while now.
#2
EngineMan
Do a compression test on the cylinder that they say is not working, that way you will know.
Did he check the valve clearance and adjust? I would like to know how he came up with that diagnosis. Compression test will give us some idea of how to proceed.
Have seen one lobe get worn down to were it wouldn't open the valve far enough to be of any good. Both on single and twin cylinders, so it could be possible. I think the problem is sometimes one of the lobes isn't hardened properly leading to the abnormal wear. Will wear to almost a round shape.
Had one on a single cylinder that had no power and would run about half throttle, even with the throttle butterfly in the full open straight position.
I have seen that also, and in some cases Briggs has covered the cam even though it was out of warranty. Just wonder how the tech can call a bad cam without opening the engine.
They may have removed the valve cover, and the plugs, and turned over the engine by hand while watching the valves. If the cam lobe is worn down, the valve will not open to its full position. I have seen some that would only open about .030 when the lobe is about round.
Please read my lengthy thread in this forum about destruction twice of my 24 hp Intek. First time due to complete reduction of intake cam lobe to a "true circle" IMO your shop should not have allowed you to take back your mower in that condition as the cam and probably that head needs replacement. BS sent me a new head and cam after I penetrated their bunker. Why also the head? Because the Aluminum softens due to overheat and lets the valve guide gradually move upward, inhibiting and finally stopping intake charge. Ask if you want and I will respond.
Re: Briggs & Stratton 21 HP OHV Intek (single) engine with problem...
In the middle of mowing my large back yard my riding mower suddenly backfired and started running erradically. Engine popping and farting but still running. Neighbor and I determined that it seemed to be a valve problem because there was blow-by through the air intake. Decided to remove valve cover as suggested in thread above. Low and behold the set screw in the rocker arm adjusting nut had backed off along with the adjusting nut. What you might call the "rub pad" between the rocker arm end and the valve stem end had dropped off leaving the rocker arm flapping in the breeze and not bearing on the end of the valve stem. That quick separation apparently caused the rapid engine malfunction. Reassembly, adjusting proper clearance between rocker arm and valve stem and ensuring everything was tight, was all that was required. Engine was one month past 2 year warranty expiration. Thank goodness I decided to do a little investigation before assuming major breakdown (camshaft wear) and taking to repair shop.
tedbotts, I'm sure now that it is a plot to send the bad acting Inteks to WA....kidding. Anyway glad you were able to search out the thread. A couple items...Still check the protrusion of the valve guides (especially exhaust) above the head. Look thru the valve springs and do a rough measurement. If any is higher it may be on the move and signal more problems such as worn cam etc. Also the valve adjustment procedure on "stud" based rocker arms is trickier than most say , IMO. During tightening of the set nut the arm wants to wobble . That plus the low (?) specified torque of the set nut ( 60 in lbs) seems a bad combination for reliable clearance. I have not used an in-lb torque wrench , but I think I am snugging those 13 mm nuts beyond. The nuts are thin and soft also. Just be careful. And if your rider has morning sickness- burps, misses , backfires, especially when hot, go in and check clearances. Glad you caught it.
PS my dyt4000 Intek 24 was at about that age when it acted up
Now I have more problems...I am having a hard time starting the mower now. I even replaced the battery and it still won't start. All I get is a clicking sound, I hear the starter engage but it won't even turn it a complete turn.
neo, my dyt 4000 had same compression both cyls when exh guide killed cam lobe. If a valve is only lifting e.g., .030" instead of .300" not enough mixture is being admitted to fire. But my one cyl was ok and always started on one only.
Hello,
have a white zt50 with a B&S intek vtwin. went to start it in the cold and the starter was slow, then released key after it didn't start and the starter continued for about 10 sec. Now I just get a click of the relay/solenoid (I think) when I try to start it. Any suggestions???
