smoke comeing from the valve cover

countryboy3010 · Post by **countryboy3010** » Sat Sep 15, 2007 3:36 pm

I went to start up my 420c this afternoon to put it to work and when i started it smoke was coming out of the oil fill neck. I know its not done that before, so i took off the valve cover and one of the tappets was pretty loose i dont know if that is what is causing it because i have never have seen the before with any of my other two cylinders. I looked in my book to adjust the tappets and it says to use a hand crank to turn over motor and i dont have a hand crank so how would you turn the motor over any help would be appreciated because this is something i have not run into before.

Pammark · Post by **Pammark** » Sat Sep 15, 2007 7:49 pm

I am not familiar with the exact engine, but in this case, all engines are similar. Smoke from the oil filler sounds more like blow-by to me. This is caused by worn piston rings and sleeves. The only way to fix that is to open the engine and do a ring job. Mic the cylinder walls to see if they are oval. If so, it is a boring job too. If the walls are good and round, you might get away with just a new set of oversize piston rings. Blow-by should have nothing to do with the valves since they are closed during the power stroke.

Now for the tappet adjustment. You have the valve cover off now. Rotate the engine over by hand anyway you can until you see the exhaust valve open. Keep rotating on to see the valve close and the intake open. There is a point when the exhaust valve is almost closed and the intake is starting to open. This is top-dead-center of the piston. Now rotate the engine crankshaft one full revolution to top-dead-center again. This is the power stroke and both valves will be closed. Adjust the tappet with the feeler gauge as per the manual. The exhaust valve will have more clearance than the intake because it runs hotter and has more stem extension. If you do not have a manual, use 0.008" for the intake and 0.011" for the exhaust.

Repeat for the second piston and you are done. Put the valve cover on and try it.

Mark

countryboy3010 · Post by **countryboy3010** » Sun Sep 16, 2007 8:09 am

thanks so if i have to replace the piston rings should i go ahead and rebuild the motor and what size should i use for bigger piston rings

Ray III · Post by **Ray III** » Sun Sep 16, 2007 6:03 pm

I adjusted the valve lash on my 420, here is what I did.

On the right side of the machine in the flywheel housing is a cover for a round hole held on by a screw. Open that and turn the engine using the fan, in the correct direction of rotation, until you see the letters "DC" in the hole. Set valve lash on #1 cylinder.

Replace the cover. Turn the engine, in the correct direction of rotation, one half turn until you see the exhaust valve on #1 JUST start to open, then set valve lash on #2 cylinder.

I wouldn't necessarily go rebuilding the motor as soon as you see smoke, if it still runs well and doesn't eat oil. It might even be just water evaporating out of the crankcase.

countryboy3010 · Post by **countryboy3010** » Mon Sep 17, 2007 3:01 pm

well its good to know i wont have to go and rebuild the motor just yet but if it still smokes after i adjust the valve lashes is it ok to use the crawler or will it cause damage to the motor

Post by **Lavoy** » Mon Sep 17, 2007 3:04 pm

If it is a broken ring, it is possible, if it is just wear, won't hurt anything.
Lavoy

countryboy3010 · Post by **countryboy3010** » Mon Sep 17, 2007 3:13 pm

is there any noises or anything i should pay attention to so i can decide what it is when i use the crawler because i am pretty much new to this type of problem and really dont know what to expect. thanks for the help

Ray III · Post by **Ray III** » Mon Sep 17, 2007 10:03 pm

Start the engine and run a few minutes, then pull out the dipstick. Is the oil a milkshake color? If it is it has water in it, change it, then see if it smokes less.

If the oil is clean and it smokes, pretty much all you can do is just use the machine and see if the smoke gets worse, unless you want to do a compression test or leakdown test to see if you can identify bad piston rings. Ask at Autozone if they rent a compression tester. A leakdown test would be better but you'd need a source of compressed air.

Post by **Lavoy** » Tue Sep 18, 2007 9:13 am

Also,
If the oil is milky, it can be one of two sources, condensation, or a leaking gasket or cracked head. One way to eliminate the condensation problem is to make sure that the engine has a good thermostat and warms up when being used. Up here condensation in the Winter is always a problem in engines that don't run long enough to warm up and "burn" the moisture out. I have heard the figure of 140 degree oil temp for 30 minutes to get rid of moisture.
Lavoy

Tigerhaze · Post by **Tigerhaze** » Tue Sep 18, 2007 9:16 am

If you have water in your oil I would recommend draining it as soon as possible. I ruined connecting rod bearings in my gas truck in the past because I didn't get to it quick enough and the bearings sat in the milky mixture and subsequently caused knocking.

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