If sparkplugs could talk

[tenders]

There are two scenarios that bear mention for sticking valves.

The first is a stuck valve that will not move and that shows diminished or zero compression during a test - your reading shows your engine doesn't have this.

The second might be better termed a "sluggish' valve in that SOME of the time in operation it doesn't move to the fully closed position for each cycle, making the engine run rough. My engine has no thermostat and a completely closed bypass, so it runs relatively cold, and exhibits this symptom very slightly sometimes. I run the bottle-recommended dose of Marvel Mystery Oil in the fuel 100% of the time and it solves the sluggish valve situation 100% of the time. Don Moyer has suggested you can run double the recommended dose without concern. (I think two-stroke outboard oil accomplishes the same thing, with perhaps a little more smoke.)

Maybe this will clear up your situation, and once the valve cycles a few hundred thousand times you won't need the additive any more.

[tmcdonagh]

Progress?

There are two scenarios that bear mention for sticking valves.

The first is a stuck valve that will not move and that shows diminished or zero compression during a test - your reading shows your engine doesn't have this.

The second might be better termed a "sluggish' valve in that SOME of the time in operation it doesn't move to the fully closed position for each cycle, making the engine run rough. My engine has no thermostat and a completely closed bypass, so it runs relatively cold, and exhibits this symptom very slightly sometimes. I run the bottle-recommended dose of Marvel Mystery Oil in the fuel 100% of the time and it solves the sluggish valve situation 100% of the time. Don Moyer has suggested you can run double the recommended dose without concern. (I think two-stroke outboard oil accomplishes the same thing, with perhaps a little more smoke.)

Maybe this will clear up your situation, and once the valve cycles a few hundred thousand times you won't need the additive any more.

Thanks Tenders for comments and ideas. Here is a summary of what I have done.

1. Checked compression and all cylinders are at about 90 psi cold.
2. Changed oil and found it to be dirty but not water contaminated.
3. Changed out spark plugs gapped @ 0.03.
4. Replaced spark plug wires, distributer cap and rotor. I have electronic ignition.
5. Treated cylinders with MMO for 30 minutes.
6. Checked spark and found to be good on all cylinders.
7. Checked gas for particulates and water from hose going to electric fuel pump. I have no filter/water separator before the pump. I am working on installing a Racor unit. Fuel seemed clean and waterfree

After all this, the motor starts right up without any complaints. I can run the throttle up to max rpm with no load. When loaded she can handle up to 1/4 throttle or so but maxes out at the midrange rpm. If I push the throttle higher I see no increase in rpm and if I push to 3/4 and beyond, the motor sputters, backfires and quits.
I am now investigating fuel quality, blocked fuel tank vent pipe, weak fuel pump and carburetor issues.

Thoughts?

Thanks,

Tom

[JOHN COOKSON]

Thanks Tenders for comments and ideas. Here is a summary of what I have done.

1. Checked compression and all cylinders are at about 90 psi cold.
2. Changed oil and found it to be dirty but not water contaminated.
3. Changed out spark plugs gapped @ 0.03.
4. Replaced spark plug wires, distributer cap and rotor. I have electronic ignition.
5. Treated cylinders with MMO for 30 minutes.
6. Checked spark and found to be good on all cylinders.
7. Checked gas for particulates and water from hose going to electric fuel pump. I have no filter/water separator before the pump. I am working on installing a Racor unit. Fuel seemed clean and waterfree

After all this, the motor starts right up without any complaints. I can run the throttle up to max rpm with no load. When loaded she can handle up to 1/4 throttle or so but maxes out at the midrange rpm. If I push the throttle higher I see no increase in rpm and if I push to 3/4 and beyond, the motor sputters, backfires and quits.
I am now investigating fuel quality, blocked fuel tank vent pipe, weak fuel pump and carburetor issues.

Thoughts?

Thanks,

Tom

Have you checked the advance yet?
Why are you posting the same information in two different threads?

TRUE GRIT

[tmcdonagh]

Advance issues?

Have you checked the advance yet?
Why are you posting the same information in two different threads?

TRUE GRIT

Hi John,

I will have to research the advance. I posted to the other thread as I think this thread moved away from electrical and was more fuel oriented.

Sorry for the cross post.

Tom

[JOHN COOKSON]

The forum would be able to help you better and more efficiently if you started a new thread detailing the current problem(s).

TRUE GRIT

[tmcdonagh]

An update

With suggestions from the forum members and Don, I disassembled the distributor, exercised the advance weights and springs and treated with light machine oil. Before this, I could not hand turn the rotor shaft. The motor runs well not with no issues. Thanks to all that have made suggestions and have encouraged me to keep moving forward on this project.

Tom

[Boat]

have you timed the motor? i havent seen in here where you have. the tan color on the plug should be at the bend in the tip.

[tmcdonagh]

Have I timed the engine?

Hi Boat,

Thanks for the suggestion. I have not done this as of yet. I am reading up on the topic and trying to find any marks on the engine to facilitate the process. If I can’t find marks, I am guessing I need to determine TDC for cylinder 1 then go from there. I am new to all this mechanical stuff and the learning is like drinking from a fire hose. I’ll keep you updated! Thanks.

[roadnsky]

...I am reading up on the topic and trying to find any marks on the engine to facilitate the process. If I can’t find marks, I am guessing I need to determine TDC for cylinder 1 then go from there.

Here are a couple of instructions for finding TDC and Timing
(The 2nd page of the Troubleshooting doc has a simple timing procedure)

Also a couple of good threads here and here for you.