Zero Compression cylinders 3+4

[T27_478]

Hello All,

I've been slowly but surely correcting a bunch of problems with my "new to me" A4. It has always ran but very poorly. To date I have done the following to help weed out some potential problems. 1) Electronic Ignition and spark plugs 2) New water pump and thermostat, 3) verified no exhaust blockages and rebuilt the hot-side of the exhaust.

I have always had trouble getting the engine to rev up under load {thus the exhaust work and water side work}

I finally got around to checking compression today after I got the engine warmed up a bit and have the following: #1{nearest flywheel} 100psi, #2 100psi, #3 0psi, #4 -0psi. My guess stuck valves on 3 and 4 so I poured in some MMO and will let it sit overnight. I'm not too thrilled about removing the head and subsequently valves etc if I don't need to. Are there any tests to verify stuck valves are the culprit here and not a gasket? I also have a feeling that running on 2 cylinders for this long has only added to the crud on the valves that are stuck if the spark plugs are any indication as they foul up almost instantly.

Hopefully solving this will get everything running right, it's only been 3 months...

[romantic comedy]

There is a test called a leak down test. It blow air in the cylinder, and you can see or hear where it leaks out.

You can just shoot compressed air in also.

The easiest? way is to remove the valve cover, and see if the valves are working as you turn the engine over.

[Sony2000]

Removing the valve cover and you will see and touch the stuck valves. Here and thru the spark plug holes, you will lower them. Don't force them too much.

[Skywalker]

I had the same problem earlier this season. Pull off the side plate and have a look. I had to give one a couple of taps and it snapped free. Been fine ever since.

Chris

[T27_478]

Side Plate

Can I get at the side plate without removing the manifold? Carb? I have good access to the engine as tartan 27's have the engine under the removable companionway steps. Will I need a new gasket for the valve cover? I don't want to cause more trouble. New gaskets are on the way but if I can do this today all the better.

[Skywalker]

Yes, easy access without removing manifold. Pull the carb off. I'd use a new gasket.

Chris

[sastanley]

T27, it is late now, but the data you got from Chris is good. The valve cover gasket is cork if I remember. It is hit or miss if they come off in one piece. The carb gasket is paper, and as Chris said, I'd use a new one if I had it.

There is not a lot of activity on the valve cover side, so you might be OK with some permatex to re-seal the cork.

My personal plan of attack since I've owned my boat is to have one of EVERY gasket the engine needs on board the boat as a spare. The ones you would expect to use up frequently (carb, t-stat, maybe water pump) I'd have 3 or 4 on hand, but at least one of everything, including head gasket, valve cover, water jacket side plate, etc....oil pan gaskets are show stoppers since you would need to pull the engine on most boats, but I do have a coupling gasket & manifold gasket aboard. The gaskets are cheap, so you might as well bulk ship them in one order...some you may never use, but you have the ones you may use frequently. I have a shoe box size plastic container with a snap lid with all my engine spare parts in it...works great.

[edwardc]

You can fit all your spares in a shoebox???

[sastanley]

ed, almost.

That does not include spare coil, fuel pump, carb, etc. They are in a separate box.

All of my gaskets, o-rings, fuel filters, and Permatex fit in there though.

[T27_478]

So there's yer problem...

Finally got back out to the boat after a week away visiting family. I removed the head in 30 minutes flat; no stuck nuts, it was almost too easy. Gasket was fine, no leaks between cylinders. Once open I found the exhaust valves on 3 and 4 stuck open. I rotated the engine so both of these should be closed and progressively tapped the stuck valves harder and harder until then begrudgingly {much harder than I expected, thanks to a light hammer and dowel} went back down to their seats. Rotated the engine a bit more and they opened back up and stayed there, more tapping {still hard, but a bit less} and they scooted down. I tried rotating them while up next and it took quite a bit of trying to twist at all.

How do I get them completely free? I would like to avoid removing the springs if at all possible so I left some MMO along the valves to hopefully work some magic overnight. What else can be done, I want everything moving smoothly before I put the head back on.

[sastanley]

progress is good!

T27.. I had a sticky #4 exhaust valve. Not 100% stuck, but #4 was much weaker than the others and had 25PSI or so less of pressure, so, I squirted MMO in the cylinders after every use for almost a whole season..it got progressively better.

I am not sure exactly what the real solution is, but continued massaging may help...but I think running it is likely best now that you've got them 'un-stuck'. Dave Neptune likes to run some good 2-stroke oil in his gas to help lube the valve guides....the real issue here is these are exhaust so the oil won't help too much since we expect it got burned on the compression stroke..however, it can't hurt. I'd also be liberal with the MMO (I did 4 or 5 squirts with an oil can) after every run for a while and see if it helps.

[T27_478]

removing the valves

From reading others' posts it appears that the "keepers" are keeping the valves down in the guides, this is the friction I'm feeling when trying to twist no doubt. Can I remove these without releasing the spring? i REALLY do not want to have to by new tools to re-install a spring. How are the keepers removed so I can pull the valve, sand off any rust and reinstall?

[sastanley]

T27...I think the answer to your question is no...

Even though I have not had to use it (yet), the PO left a valve spring tool on the boat. I am pretty sure he got it from Moyer, but he beefed it up just a little bit with a cross brace. It compresses the spring, so you can pull the keepers and get the valve out. He reported frozen valves in the past from water intrusion (overcranking) events, and he had to clean the rust off the valve stems and ream the guides out using a reaming tool (also on the boat), which I assume came from Moyer too..I think they've bumped the original diameter from .314" to .316", perhaps to help with this exact problem, but those numbers are from memory, and need to be verified with an authoritative source like Ken in the Moyer parts dept.

Be careful not to drop the keepers into the oil drain holes in the bottom of the valve chamber...lots of people lay a rag into the bottom to keep stuff from falling into the oil pan. There are some other notes related to the keepers here on the forum that are likely helpful..I guess sometimes they are hard to re-install since they are small and us humans have big fingers...a search would probably help you out there.

[romantic comedy]

Keepers are the little pieces that stop the spring from going off the end of the valve. The valve has grooves in the end of the shaft. The spring goes on the valve, then the retainer, then the keepers. The retainer is like a washer that covers the spring. The keepers go around the stem, to hole the retainer on the stem.

The valve slide in the guide, that is pressed into the engine. Build up of material causes friction between the valve stem and the guide. This is what holds the valve open.

Guys use different solvents to dissolve the buildup. If the valve was bent, it would stick also. Since you have the head off, removing the valve is not that hard. This would be the best way to clean the guide, and assure that the valve worked.

[Carl-T705]

Don't think that if the valves been stuck that they will just pop free and go to working that quick. you'll have to fool with them for quite a while if you want them to free up without removing them . It can be done , I've done it , it just takes time and continued working of them up and down with liberal doses of oil, you may want try using gun cleaning oil. They will free up, unless in your forcing to free them up you bent the valve stem.I'm glad to hear you removed the head to see what your working with. It's best to see what you're actually forcing to move It's a pretty easy task that will get you more comfortable with working around this great little engine. Some think it's mandatory to remove the head studs, but if they are not loose or damaged I leave them intact, don't create more problems that are more difficult to repair. Valve stem clearances are measured in the thousandths, keep that in mind if you have to remove and sand down for clearance,