I apologize for the length of this post, but I feel I need to be as detailed as possible for any advise you may give. Let's start with the basics:
My riding mower is an Ariens Model A20H46 with a B&S 20 hp Intek 331777-2372-G5 motor. As Forrest Gump said, I AM NOT A SMART MAN". I am not a small engine repair guy so if describe something wrong or a part incorrect please forgive me.
My first sign of trouble was when I noticed how hard it was to start my mower. The flywheel would turn a few times very slowly before the motor started up. Eventually it got to the point where I thought I had a bad battery (even though it was new) and had to jump start it to get it running. Then one day I was mowing and climbing a hill and my RPMs dropped considerably to the point I thought it would shut off. I emailed B&S about the cause for the drop in RPMs and was advised to check throttle linkages and governor. I replaced all linkages and even a carb rebuild kit to no avail. It was still hard to crank and sputtered something awful. I had a friend of mine take a look at the carb and while adjusting the carb the engine banged loudly and suddenly the motor smoothed out and purred like a kitten. Ran fine until the next morning. When I tried to crank it cold there was still the hard start and would not fire.
Upon doing some research, I found out that my Intek engine has a spring loaded compression relief trigger on the cam shaft. This allows the valves to be bumped when starting to relieve the compression so the flywheel easily turns until it starts and then centrifugal force keeps the trigger out of way so the valves seat all the way properly. These springs or triggers sometimes break. So, I pulled the motor off and and looked at the cam and sure enough the trigger was missing off the cam shaft and about 5 pieces of the trigger fell out of the motor. I began to speculate that the reason for the hard start was that the trigger had broken off of the cam and it was not bumping the valves for easy rotation of the flywheel. I was mowing with this piece of metal banging around until, I believe, a piece of metal got hung up in a valve. The loud bang may have been from the valve clearing itself of the metal piece and that is why it ran fine afterwards. Again, this is just my speculation.
So, I replaced the cam shaft with the new trigger, set my timing marks and replaced gaskets and seals. I set and adjusted the valves to spec. I tried to start the motor and I was still getting the hard start and engine backfiring through the carb.
Frustrated, I asked my friend his advice and he said I may have had the cam not aligned properly and the timing was off. Once again I pulled the motor off and looked at the cam and saw that my timing marks were aligned. I did some more research and found a comment in a forum that when replacing the cam shaft, the tappets should be out of the way from the lobes and piston top dead center. So, I spun the flywheel one revolution and realized the tappets cleared the lobes but now my timing mark on the cam shaft was 180 degrees opposite of the other timing mark. It was then that I realized I had not replaced the new cam shaft at top dead center. So, I picked up the cam shaft and rotated it 180 degrees so the timing marks matched again and the tappets were not engaged with the lobes on the cam shaft.
I put everything back together again, set my valves to specs and now I have no hard start of the flywheel. It looks like the trigger is bumping the valves like it is supposed to do BUT...
...the motor still backfires through the carb. She will not start. The cadence is 1,2,3, bang. 1,2,3, bang. Ugh!! Checked the spark plug and getting good fire. Checked compression by putting thumb over spark plug hole and cannot keep it on there so the compression is good. No leaks. I am frustrated but I think I am very close. Has to be a timing issue I think. Any advice at this point would be great. Looking at new motor but really think there is a simple fix I am not thinking of. Even Forrest Gump got his mower running.
My riding mower is an Ariens Model A20H46 with a B&S 20 hp Intek 331777-2372-G5 motor. As Forrest Gump said, I AM NOT A SMART MAN". I am not a small engine repair guy so if describe something wrong or a part incorrect please forgive me.
My first sign of trouble was when I noticed how hard it was to start my mower. The flywheel would turn a few times very slowly before the motor started up. Eventually it got to the point where I thought I had a bad battery (even though it was new) and had to jump start it to get it running. Then one day I was mowing and climbing a hill and my RPMs dropped considerably to the point I thought it would shut off. I emailed B&S about the cause for the drop in RPMs and was advised to check throttle linkages and governor. I replaced all linkages and even a carb rebuild kit to no avail. It was still hard to crank and sputtered something awful. I had a friend of mine take a look at the carb and while adjusting the carb the engine banged loudly and suddenly the motor smoothed out and purred like a kitten. Ran fine until the next morning. When I tried to crank it cold there was still the hard start and would not fire.
Upon doing some research, I found out that my Intek engine has a spring loaded compression relief trigger on the cam shaft. This allows the valves to be bumped when starting to relieve the compression so the flywheel easily turns until it starts and then centrifugal force keeps the trigger out of way so the valves seat all the way properly. These springs or triggers sometimes break. So, I pulled the motor off and and looked at the cam and sure enough the trigger was missing off the cam shaft and about 5 pieces of the trigger fell out of the motor. I began to speculate that the reason for the hard start was that the trigger had broken off of the cam and it was not bumping the valves for easy rotation of the flywheel. I was mowing with this piece of metal banging around until, I believe, a piece of metal got hung up in a valve. The loud bang may have been from the valve clearing itself of the metal piece and that is why it ran fine afterwards. Again, this is just my speculation.
So, I replaced the cam shaft with the new trigger, set my timing marks and replaced gaskets and seals. I set and adjusted the valves to spec. I tried to start the motor and I was still getting the hard start and engine backfiring through the carb.
Frustrated, I asked my friend his advice and he said I may have had the cam not aligned properly and the timing was off. Once again I pulled the motor off and looked at the cam and saw that my timing marks were aligned. I did some more research and found a comment in a forum that when replacing the cam shaft, the tappets should be out of the way from the lobes and piston top dead center. So, I spun the flywheel one revolution and realized the tappets cleared the lobes but now my timing mark on the cam shaft was 180 degrees opposite of the other timing mark. It was then that I realized I had not replaced the new cam shaft at top dead center. So, I picked up the cam shaft and rotated it 180 degrees so the timing marks matched again and the tappets were not engaged with the lobes on the cam shaft.
I put everything back together again, set my valves to specs and now I have no hard start of the flywheel. It looks like the trigger is bumping the valves like it is supposed to do BUT...
...the motor still backfires through the carb. She will not start. The cadence is 1,2,3, bang. 1,2,3, bang. Ugh!! Checked the spark plug and getting good fire. Checked compression by putting thumb over spark plug hole and cannot keep it on there so the compression is good. No leaks. I am frustrated but I think I am very close. Has to be a timing issue I think. Any advice at this point would be great. Looking at new motor but really think there is a simple fix I am not thinking of. Even Forrest Gump got his mower running.