1972 Lark Carb Problem?? (update)

[jayhawkokie]

I have a 1972 Evinrude Lark engine on my 16' Kingfisher bass boat. It has been running fine except it seems to "load up" after shutting down the engine after running it at top speed.

This morning I dropped my buddy off at the ramp and backed out so he could back the trailer into the water, the engine died on me, but started up after 3 tries. I advanced it to full throttle to clear the engine like I always have and at full throttle it only ran above idle, and it was smoking, I could never get it to clear out.

I checked the gas tank vent, it was open, the bulb and hose are new. I even pumped the bulb a couple times to make sure it was still primed. It acts like the engine is running rich. There is a knob on the front of the engine for lean-rich adjustment, but it has been disconnected. I don't have a manual, so I'm afraid to try any adjusrments to the carb and the guy I bought the boat from passed away 5 weeks ago.

Do I need to get the carbs rebuilt? Has the ethanol blend gas possibly messed up the carbs? I'm going to pull the plugs to see what they look like, they were replaced before putting the boat on the lake this spring.

Thanks for your input

Jayhawkokie
Grand Lake O' the Cherokees
Oklahoma

 

[Vic.S]

Re: 1972 Lark Carb Problem??

Re: 1972 Lark Carb Problem??

I guess thats the idle mixture adjustment you are referring to.

You might find it worth while looking at Joe Reeves Thread on carb adjustments in the Engine FAQs HERE

 

[F_R]

Re: 1972 Lark Carb Problem??

Re: 1972 Lark Carb Problem??

I would say that it more than likely is an ignition problem. It requires more energy to fire a hot spark plug. In addition, the coils don't put out as much energy when they are hot.

 

[jayhawkokie]

Re: 1972 Lark Carb Problem??

Re: 1972 Lark Carb Problem??

About an hour after backing it into the driveway I pulled the plugs, they were wet. I hooked the garden hose attachment on the lower unit and hit the switch, it fired up immediately and I was able to accelerate right up to full throttle without any hesitation.

It may be possible that is is the coils, the engine runs fine cold, it's only after it warms up good that I have a problem.

Where is the best source for coil for this engine.

Thanks for the help.

 

[DJ]

Re: 1972 Lark Carb Problem??

Re: 1972 Lark Carb Problem??

About an hour after backing it into the driveway I pulled the plugs, they were wet. I hooked the garden hose attachment on the lower unit and hit the switch, it fired up immediately and I was able to accelerate right up to full throttle without any hesitation.

It may be possible that is is the coils, the engine runs fine cold, it's only after it warms up good that I have a problem.

Where is the best source for coil for this engine.

Thanks for the help.

Running on the hose/muffs is NO indication of engine health. A 2-stroke will run pretty well on one of two cylinders.

By the way, running it to full throttle-NO LOAD-is a real quick and easy way to scatter internal engine parts all over the yard.

Before you throw parts at it. You need to find out what is happening. You are losing one cylinder, for one reason or another.

You can get parts, right here on iboats.

 

[jayhawkokie]

Re: 1972 Lark Carb Problem??

Re: 1972 Lark Carb Problem??

I just pulled the cover off the engine and did a visual inspection of the coils. You can tell they are old and one of them has cracks in the plastic insulation. I believe it's time for new coils.

The old engine seems to run pretty strong, and I've had no issues with the electric shift. I keep my fingers crossed every time I go out that it will keep working. I'm keeping my eyes out for a good deal on a used engine to replace it.

Jayhawkokie

 

[DJ]

Re: 1972 Lark Carb Problem??

Re: 1972 Lark Carb Problem??

I just pulled the cover off the engine and did a visual inspection of the coils. You can tell they are old and one of them has cracks in the plastic insulation. I believe it's time for new coils.

The old engine seems to run pretty strong, and I've had no issues with the electric shift. I keep my fingers crossed every time I go out that it will keep working. I'm keeping my eyes out for a good deal on a used engine to replace it.

Jayhawkokie

I don't diasagree with your visual inspection. That/those very well may be the culprit.

 

[tx1961whaler]

Re: 1972 Lark Carb Problem??

Re: 1972 Lark Carb Problem??

GO ahead and replace the coils, plug wires, condensors and points while you're under the flywheel, if you haven't done it for awhile. That way you start with everything fresh, and the coils are the expensive part anyway. Then you won't have to worry about that part anyway. The electric shift is fine, until it gets water in it or the wrong oil, or the control switches wear out.

 

[jayhawkokie]

Re: 1972 Lark Carb Problem??

Re: 1972 Lark Carb Problem??

As suggested I replaced one of the coils, I could only get one coil until next week. I plan to replace the other one as soon as one is in stock at the local dealer.

I've comfirmed that I have good hot spark to both plugs and the plugs are firing good when I ground it out and have the missus hit the starter while I hold the plug and watch.

The engine starts and idles fine. When I put it in the water and put it in gear and advance the throttle all I can get is just above idle speed, even with full throttle. I checked the fuel filter screen and it is clean. It just seems like it's not getting enough gas. Is it possible that the fuel pump needs to be rebuilt? I was going to pull the carbs for cleaning and rebuild this winter.

Until recently I was having to run gas with 10% ethanol, a local station just started carrying 100% gasoline again so that's what I'm using now. I've heard that ethanol can harm older fuel components.

Where do i check next?

 

[Vic.S]

Re: 1972 Lark Carb Problem?? (update)

If you have a good hot spark at both plugs and it starts easily and idles well there's not much wrong with the ignition, although its good plan to replace the coils if you can see they are cracked.


You can check for a dodgy fuel pump by pumping the priming bulb. If the pump is not pumping properly you'll keep things going OK by doing that.

It sounds to me like the high speed jets in the carbs are blocked so If it were mine I would do a thorough carb clean, paying particular attention to the main jets and associated passages.

 

[DJ]

Re: 1972 Lark Carb Problem?? (update)

If you have a good hot spark at both plugs and it starts easily and idles well there's not much wrong with the ignition, although its good plan to replace the coils if you can see they are cracked.


You can check for a dodgy fuel pump by pumping the priming bulb. If the pump is not pumping properly you'll keep things going OK by doing that.

It sounds to me like the high speed jets in the carbs are blocked so If it were mine I would do a thorough carb clean, paying particular attention to the main jets and associated passages.

Agree.

 

[jayhawkokie]

Re: 1972 Lark Carb Problem?? (update)

I agree with yor regarding the carb rrebuild. I stopped by the Evinrude dealer in Joplin, Mo yesterday and told their Mech my symptoms and the diagnostics I had performed, he recommended rebuilding the carbs, so i'm soaking them right now.

I'll report back later if this step is successful.

 

[Vic.S]

Re: 1972 Lark Carb Problem?? (update)

Soak them by all means but sometimes the only really sure way of cleaning the jets is to poke a wire through them. A soft copper wire though not a steel one!
I have seen nylon brush bristles suggested. Some nylon monofilament fishing line might do the trick.

 

[jayhawkokie]

Re: 1972 Lark Carb Problem?? (update)

I got the carbs cleaned and put back together. I made sure the main jets were clean. I put it in a barrel of water and it started right up. I'm having trouble getting the idle adjustment right and after it ran for several minutes it was hard to start when I would kill the engine trying to adjust the idle needles. I am now able to get it to run at wot, I just ran it up and right back down.

I'm concerned that i may have low compression on the #1, so I'm going to O'Reillys tomorrow and rent their compression tester. I can pull the plug wire off #1 and it still runs on #2, but when I pull the wiire on #2 and leave the wire on #1 it dies. I've comfirmed that i have good fire to both plugs. When I screwed in the idle needles I was getting a change in rpms on both carbs.

My next alternative is to call my cousin's friend who is a boat mech and pay him to fix it.

If I have low compression is a toip end overhaul pretty expensive? I don't want to spend a lot of money on this motor, I'd rather spend the money toward a newer motor..

Jayhwkokie

 

[tx1961whaler]

Re: 1972 Lark Carb Problem?? (update)

Get a spark tester while at O'Reilly's. It's 6.99.