Valve problem

[Larry in Maine]

At the very end of this season, my Atomic 4 starting producing white smoke out of the exhaust. The spark plugs were very sooty so I replaced them. Smoke continued even after a long warm up. The local marina came out and said that "they suspect that there is a valve that is sticking or not closing all the way. There is a definite miss when idling and there is a bit of a pop sound. Also smelled unburned fuel in the smoke. Head will need to be taken off and work done on the valves."
Does this make sense? What is the next step in diagnosing/fixing the problem?

[Dave Neptune]

Perhaps some sense. Was a compression check done? Sooty plugs indicate a rich mixture, oily plugs indicate poor rings. The missing could be a carb adjustment or even a weak spark. How long since a tune up? Do you have points or an EI type ignition?

I would do a dry then a wet compression test. If you do not know how to do the test just advise and I will post instructions.

The white "smoke" is probably steam condensing in the exhaust. Is there any blue or black smoke?

You could have a blown head gasket however I would to the compression test before removing it. And sticky valves can often be delt with without removing the head.

Dave Neptune

[Larry in Maine]

Valve problem

Thanks Dave. Posting instructions for doing a compression test would be very helfpul.

LS

[Dave Neptune]

First you will need a compression gage, a cheap one will do as the accuracy is not as important as how the finding relate to each other as the gage will be consistent with itself.
First close the water intake through hull we don't want to fill the exhaust with water if you are raw water cooled. Be sure the batteries are fully charged too. Then disconnect the positive side of the coil as having it powered up while throwing no spark can overheat and destroy it. That's why you should never leave the "key on"
Remove all of the spark plugs. If any are wet remember which cylinder they were in or line them up in order and post a pic of them for evaluation.
Now be sure the choke is off (fully open) and the throttle is fully open at wide open throttle. If the plugs or a plug is wet with water especially ones next to each other may indicate a breach in the head gasket
Now test each cylinder and record the findings for each cylinder at least twice or even 3 times. This is called the "dry" test which is done first.
Now spray some oil or add a small amount (thimble full) into the cylinder to be tested. Again record and test at least a couple of times. Then repeat the oiling for the testing cylinder until all four are done.
Once the testing is done compare the values. If they are close to the same on each cylinder the rings are good. If one or more of the cylinders is really low in both tests you either have a stuck valve or a breach in the head gasket.

Dave Neptune

[Larry in Maine]

Valve problem - compression test

Oil or Marvel mystery oil?

[joe_db]

At the very end of this season, my Atomic 4 starting producing white smoke out of the exhaust. The spark plugs were very sooty so I replaced them. Smoke continued even after a long warm up. The local marina came out and said that "they suspect that there is a valve that is sticking or not closing all the way. There is a definite miss when idling and there is a bit of a pop sound. Also smelled unburned fuel in the smoke. Head will need to be taken off and work done on the valves."
Does this make sense? What is the next step in diagnosing/fixing the problem?

IMHO that sounds a lot more like a head gasket leak than a stuck valve. My previous engine had a sticky valve and you knew it was stuck when the engine lost some power and ran rougher. No smoke was involved. White smoke sounds like water is getting in.

[Dave Neptune]

Larry, any oil even spray oil works as it can be sprayed in easily. WD-40 will work however a lubricating type works better.

Get us a pic of the plugs in order it may give good info and save some work for you.

Dave Neptune

[Larry in Maine]

Valve problem

Dave,

Here are the compression results:

Dry: 90/80/90/90
Wet: 92/95/95/95

Larry

[Dave Neptune]

Larry, number 2 is a bit low dry and excellent wet so the rings are leaking a bit. I have seen many engines run very well with far worse numbers. Nothing to worry about there. The numbers also indicate the valves are OK.

How long since a good tune up? Including cap and rotor. Are the plug wires in good shape? And have you tried to adjust the carb at all?

What kind of ignition do you have points or electronic? What plugs are you using and are they gapped properly for the type of ign?

I think you may be missing because the ign is getting weak so #2 is not firing properly at idle speeds. Does it run smoother as the throttle and RPM's increase?

A pic of the plugs would be really helpful now.

Dave Neptune

[Larry in Maine]

valve problem

Dave,

That sounds like relatively good news. I replaced the spark plug wires this spring. Plugs are the correct ones and the gap is .035". Electronic ignition installed about four years ago. I have not done anything with the carb.
Don Moyer also said the compression readings were OK and suggested I check out the flame arrestor to see if it was clogged.
Thanks for all of your help. I'll send you what I find.

Larry

[Dave Neptune]

The flame arrestor if clogged will affect bigger loads on the engine however not so much the idle. Do check it though.

Try leaning the idle screw on the carb. To lean is to turn out or counterclockwise and turn it out about a 1/4~1/2 turn. This may cause it to take a few more cranks to start which is normal with an updraft style carb.

Also try opening the gap on the #2 plug to .040 It should help the idle by creating a bit more heat around the plugs electrode at idle. The EI will handle the extra gap just fine.

Dave Neptune

[capnward]

I have read somewhere on this forum that when you have EI it is best to gap the plugs at .040 instead of .035. That seems to work well for me.

[edwardc]

As a long term measure, try including between 4 to 8 ounces of Marvel Mystery Oil (MMO) in with the crankcase oil at every oil change. This "bottom oil" will, over time, help de-gunk any stuck oil rings. Also helps stave off sticking valves. I've been doing this for years.

[capnward]

MMO is for real.

That's what I have been doing for 23 years, usually 8 oz. per oil change. In 5,000 hours, maybe more like 10,000, since the rebuild in 1999, I have never even had to look at the valves. Compression is still near 100 on all cylinders. Somewhere on this forum I have read the story of when, back in the 1950's, Universal had a team of engineers testing the engine. They swore by MMO, both for the crankcase and in the fuel. For the fuel I mix 2 oz. per 5 gallons. It really works, as far as I can tell. Don't let the wintergreen smell fool you.