OK Ill admit it I stuck some valves. I ran out of chipped fuel and ran a batch of pellets in one of our big machines. All was fine at first but when the machine transitioned over to the pellets things changed real quick. Ive ran pellets before without issue but I think the machine needed to fully adjust first to produce clean gas.
Well anyways it was a dusy, with bent push rods and the whole works. I dont know if any one else has posted a thread on what to do in this case, so I thought I would post what I did and how I did it.
First thing you want to do is pull all spark plugs and inspect them. This should tell what cylinders are affected.
If you have raw tared gas getting into your engine those spark plugs are probably fouled and need cleaning or replacement.
Next is remove the valve covers and check all rocker arms for looseness. If you find one is loose then a push rod is most likely bent or this valve is stuck and will not return to a seated position.
Next is to remove all intake rocker arms and remove any bent push rods.
Then with a brass punch and a hammer I gently tapped each of the intake valves to free them up. If they are stuck in the seated position I know of no other way unless you have a means of some sort press to push them or you have a guerilla. I have neither so a brass punch and hammer it is. By doing this you will know right away if the valve is tared up or not. If the valve is free of tar it will recoil right away and if it is tared it will stay in the position it has been moved too. Once freed from the seated position it may then be practical to push down on the valve or continue lightly tapping it down. On a larger engine and depending on the severity of the condition the valve spring should be able to push back to a seated position. However, it may move back up slowly, this was the case for me. So I continued to tap the valves affected and letting them return to the seated position. I also sprayed some penetrating oil at the valve stems; I don’t know if this helped or not but it was worth a try. I then continued this process until the valves moved as free as possible.
NOTE: If your engine is an interference engine be careful not to hit the valves into the top of a piston.
Next is it is a good idea to check the exhaust valves on the affected cylinders. Depending on circumstances if the engine was running and a cylinder was fouled, raw gases then could flow through the exhaust valve as well.
Now that all the valves have been freed I replaced the bent push rods and reinstalled the rocker arms.
Now for the fun part. Do not roll the engine over with the starter yet. I turned the engine over by hand feeling every movement to make sure I was not over forcing things. Once I had turned the engine over enough times and felt things were free enough I moved on to the next step.
Before reinstalling the spark plugs, I turned the engine over with the starter while dosing it with gasoline and a heavy fuel additive. This is to help break down the tar on the valves before engine starting.
For this step I media blasted and cleaned all the plugs and reinstalled them. These first machines are not dual fuel so in order to run them on petrol I have to use a spray bottle. What I did was use the same additive with petrol in a bottle. I started the engine and ran at idle, with slight tappet noise, I continued to run with the solution at this speed until the noise went away. I then gradually increased throttle listening for noise and ran at those speeds until the engine ran without any noise. After 15 min of running I let the engine completely cool down.
After the engine has completely cooled down I once again turned the engine over by hand. Residual tar can still heat up and continue its path to the valves and then cure there during cool down. So once I was sure the engine was free I repeated the engine run with the additive.
All is fine now and the engine runs great. I hope this helps anyone that may ever run into this.
The engine in this example was a zero tolerance engine, meaning that the rocker arms are non adjustable. So you may need to readjust the rocker arms if the noise does not go completely away on engines with adjustable valves.