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Discussion Starter · #1 ·
Hello again. Some of you may have seen my last post about my Case 448 black frame Onan p218g. The Onan has a very slight ticking sound coming from the engine, it seem to be more audible from the left side of the engine. On my last post the Extremely helpful members guided me to check a few things. One of them being the correct amount of oil, I drained all the oil and put in a new short original size filter. Then I refiled it with 1.75q of oil. The dipstick reads perfect! I also adjusted the valves on the Onan, the right side was pretty well in adjustment. I stuck my feeler gauge in there and fine tuned it, .002 for exhaust, .001 for intake (according to the Onan manual.) The left side however the intake was pretty well in adjustment, but the exhaust was pretty far out of adjustment. Once the valves were finished I put everything back together and the ticking sound was still there. (I will be checking to make sure the vales keep adjustment later to make sure that the crank baring is still good.) I have also checked all of the parts to make sure the panels are not moving around. I did not find anything. Whats next on this poor onan? Will an intake manifold leak sound like a ticking noise? I had to unbolt the manifolds to get to the valves to find the gasket was in poor shape. I will be ordering a new pair soon, but left them on in the meantime. Is this a normal onan problem? The engine runs fine and has no loss of power. I put a rod to the valve cover and my ear and did not hear anything out of the ordinary. Thank you all for your help and for supporting this amazing forum. Have a great day! (I will try to get a video and pictures soon)
 

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My B43 ticks like that. Really annoying. The PO of the engine had mentioned possible cam bearing issue with it. When purchased I couldn't hear the ticking, but this was likely getting masked by the lack of muffler. I alos really didn't know any better. I decarboned it, adjusted valves and put it into service. While decarboning I could see that someone had already been into the engine because it had .10 over pistons. Like you, I removed tins and covers temporarily to see if it was something external making the noise. My next plan is to take the engine apart, not just based on the ticking, but due to some really bad smoking when running it hard. The crankcase is getting pressurized and blowing oil into the air cleaner. The #2 cylinder has low compression and a leakdown test showed that the leakage was not through valves, but past the rings. Due to other projects, this probably won't happen for another 6-12 months. Maybe run it a bit more and see if you get additional reasons to tear into it deeper.
 

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Discussion Starter · #8 ·
Hello everyone. I have a Onan P218g that had a horrible ticking noise. We discovered it was the valves and after adjusting them the left cylinder exhaust valve still ticks although not nearly as bad. The exhaust valve is much more carboned. Has this happened on your Onan engine and how were you able to fix it? All help would be greatly appreciated. Thank you very much!
 

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1973 Case 444, 1974 Case 644, 1976 Case 446, 1977 Case 646
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The only way I would know to stop the sticking valve would be to remove the valve and clean the carbon build up on the stem and valve guide.

Keep the Peace
Harry
 

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What you think is a valve tick could be the camshaft moving from side to side as it starts to open the valves when running.
On Onan P series engines along with the B series and others, the camshaft bearing on the flywheel end of the engine is pressure lubed, but the bearing on the other end is splash lubed along with the valve tappets. If a valve adjustment will not repeat after the crankshaft has been turned , then it is the rear camshaft bearing which has worn in an oval pattern allowing the camshaft to move side to side as valve spring tension increases during valve opening. Of all the small engines that I have dealt with over the years, Onans are the most sensitive to operating with low oil levels.
Low oil levels in Onan P series is partly due to incorrect procedure when checking the oil level. As the static oil level on these engines is above the bottom of the dip stick tube, as the engine cools after shutdown, oil is drawn up into the dipstick tube and on the dipstick. The correct procedure is to remove the dipstick, wipe it dry, allow the oil up in the tube to drain down and check the oil level by inserting the dipstick in the tube, turn it tight, remove and measure the oil level. Repeat if the tube hasn't fully drained into the oil base.
As these engines splash lube the tappets and rear camshaft bearing, operation with low oil levels reduces the splash of oil toward that area of the engine.
Years back, Onan upgraded the rear camshaft bearing to one with more surface area contact with the camshaft. However, replacing this bearing requires an almost total engine teardown unfortunately. :cool:
 

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Discussion Starter · #11 ·
What you think is a valve tick could be the camshaft moving from side to side as it starts to open the valves when running.
On Onan P series engines along with the B series and others, the camshaft bearing on the flywheel end of the engine is pressure lubed, but the bearing on the other end is splash lubed along with the valve tappets. If a valve adjustment will not repeat after the crankshaft has been turned , then it is the rear camshaft bearing which has worn in an oval pattern allowing the camshaft to move side to side as valve spring tension increases during valve opening. Of all the small engines that I have dealt with over the years, Onans are the most sensitive to operating with low oil levels.
Low oil levels in Onan P series is partly due to incorrect procedure when checking the oil level. As the static oil level on these engines is above the bottom of the dip stick tube, as the engine cools after shutdown, oil is drawn up into the dipstick tube and on the dipstick. The correct procedure is to remove the dipstick, wipe it dry, allow the oil up in the tube to drain down and check the oil level by inserting the dipstick in the tube, turn it tight, remove and measure the oil level. Repeat if the tube hasn't fully drained into the oil base.
As these engines splash lube the tappets and rear camshaft bearing, operation with low oil levels reduces the splash of oil toward that area of the engine.
Years back, Onan upgraded the rear camshaft bearing to one with more surface area contact with the camshaft. However, replacing this bearing requires an almost total engine teardown unfortunately. :cool:
My valves have maintained there adjustment when I ran it. Also It comes from the left side of the engine only at the head. Wouldn't the noise come from all around the engine or in the middle of the 2 valves? Also my cylinder bore was excellent when I took the head off. I figured that the bore would not be this good if it was ran low on oil.
 

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Did you remove the carbon from the cylinder heads and piston tops? This is what is called a decarb in Onan terms. The several P series engines that I have dealt with that had camshaft 'slap' had ticking a lot more often than a typical connecting rod knock. The ticking was more noticeable when I was a distance from from the running engine and standing behind the tractor away from the exhaust noise. I did have one P series engine that had so much carbon buildup on the piston top and combustion chamber of the head that it touched the head when at TDC and made a contact noise. I have a high time 6018L with a P 218 that makes odd noises periodically. I did do a decarb on it several years back but didn't do a valve adjustment. This engine runs smoothly so I haven't done a valve adjustment, I may in time. It did need a decarb as I could see where one piston was making contact with the carbon buildup in the combustion chamber. At TDC the pistons come right to the top of the cylinders. Piston slap is another condition that occurs on these engines. As the piston comes up to TDC on the compression stroke it tends to to be concentric in the cylinder bore. When there is spark, the air/fuel mixture burns and expands rapidly and this tends to force the piston to one side on the wrist pin as it travels downward on the power stroke. 87 octane fuel with ethanol burns much quicker than higher octane fuels and at a higher combustion chamber temperature. I recommend 89 or 91 octane fuels in Onan twins.:cool:
 

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Discussion Starter · #13 ·
I decarbonated the heads. Although I have not cleaned the ticking exhaust valve yet and it is heavily carbonated. At first I tried to adjust the valves and that made the ticking much louder. When we pulled the heads we found out that that it looked like the valve had been ever so slightly hitting the head. Apparently I adjusted the valves wrong and once they were adjusted properly the ticking became much quieter and less noticeable. Also the engine tick only comes on when it warmed up. If it is cold it is fine, but after about a minute of running the ticking comes back. Again it comes from only the left side of the engine. You can barely hear it from the right side. Thanks for your help!
 

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Discussion Starter · #14 ·
Hello everyone I have a ticking on my case 448 with a p218 onan in it. It seems to be coming from the exhaust valve on the oil filter side of the engine. I took the valve out an cleaned it and adjusted it. I put each piston to TDC and adjust the exuast to .20 and intake to .10. I ran it a while and checked the clearances and they still seem correct. Any things I'm missing? My plan is to completely overhaul the valves. Where can I get the springs/valves/keepers and anything else I need? All help is appreciated! Thanks!
 

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Those exhaust/intake clearances do not look right to me. A google search yields many conflicting answers.

You should make a call to Boomer. He will set you straight.

 

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Discussion Starter · #19 ·
Uh oh I started the Onan again today and at first no ticking then the ticking started to come back. After about 10 min of runtime the ticking was back again! Does this mean I have a bad camshaft?
 

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I tried to find an older post, and perhaps another member can help out?

The post I was looking for was about a ticking camshaft as well,, but in that motor, (Onan) it ended up being the rear bearing that was wore out. Anyone remember that post? How was it diagnosed?
 
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