1962 18 hp johnson missing/backfiring

[Brianjason6]

This motor has had the following work. New coils, condensors, points, plugs, wires, boots, soaked a rebuilt carb, head gasket, fuel pump, fuel lines, new mix fuel 24:1. Rechecked the following. fire from coils to boots, point gabs, plug gaps, fuel mixture, carb settings.

The to cylinder is builing up carbon. Heavy and thick. The compression is 95 and 95. My only thought is to recheck the carb but...I CLEANED IT AND PUT A KIT IN IT. I'm hoping someone has a better idea or at least will back this one. Here is a video of the motor starting, running high idle...let the idle down slightly and it dies violently. Only after backfiring or missing several times. I assume it would be a miss because it doesn't seem to make the big splash in water that a backfire would.

http://www.youtube.com/watch?v=WQYwIXTgCEk

 

[rjezuit]

Re: 1962 18 hp johnson missing/backfiring

Blow a fan on it. You might be sucking in too much smoke from the exhaust. Blow the smoke away from the carb intake and see how it runs. Rick

 

[steelespike]

Re: 1962 18 hp johnson missing/backfiring

Hard to tell with the way the exhaust sounds but I think you may be on one cylinder.
I think I here the other cutting in and out at high idle.
I'm guessing the top cylinder is building carbon because it is firing.
Didn't seem that smokey.Did you torque the flywheel nut?
Bore and shaft dry?

 

[Brokeback Johnson]

Re: 1962 18 hp johnson missing/backfiring

If the carburetor does not respond to the low speed jet there is likely an obstruction in one of the passages and will need to be cleaned.

 

[samo_ott]

Re: 1962 18 hp johnson missing/backfiring

Hmmm... I'm running my '62 Evinrude 18 right now, so the same engine.

Some random thoughts:

Possible intake manifold gasket leak? Loose carb shafts that air's getting in? Sure seems to be carb. Did you pop off the welch plugs on top of the carb when you soaked it and cleaned out the little idle holes in there? Is there some packing nut jammed in the low speed needle hole... link and sync? are they lined up?

I don't know much about reed problems as I've never had em So don't know if this is one, maybe someone else will throw there 2c in if they think it might be..

Another thought, try spraying some 24:1 premix in the carb throat as it's dying. see if that helps it smooth out... that will show a carb issue for sure if so...

 

[F_R]

Re: 1962 18 hp johnson missing/backfiring

brianjason, keep one thing in mind as you troubleshoot your motor. It only has one carburetor. That one carburetor feeds both cylinders. So it is impossible for the carburetor to cause just one cylinder to mess up.

 

[Brianjason6]

Re: 1962 18 hp johnson missing/backfiring

The reason I mentioned the carbon is because it's soot like. Thick like you've a fireplace would get after burning pine. However, I have resoaked the carb for a couple of hours and reblown any possible junk out. I'm leaning toward one of the low speed passages beging obstructed but won't know untill I try it out again tomorrow. Thanks for the help.

 

[Brianjason6]

Re: 1962 18 hp johnson missing/backfiring

Blow a fan on it. You might be sucking in too much smoke from the exhaust. Blow the smoke away from the carb intake and see how it runs. Rick

I'll try that tomorrow. Makes sense. Motor needs oxygen not smoke right?

 

[Brianjason6]

Re: 1962 18 hp johnson missing/backfiring

Hmmm... I'm running my '62 Evinrude 18 right now, so the same engine.

Some random thoughts:

Possible intake manifold gasket leak? Loose carb shafts that air's getting in? Sure seems to be carb. Did you pop off the welch plugs on top of the carb when you soaked it and cleaned out the little idle holes in there? Is there some packing nut jammed in the low speed needle hole... link and sync? are they lined up?

I don't know much about reed problems as I've never had em So don't know if this is one, maybe someone else will throw there 2c in if they think it might be..

Another thought, try spraying some 24:1 premix in the carb throat as it's dying. see if that helps it smooth out... that will show a carb issue for sure if so...

Yes. I changed the plug when I soaked it. However not today's second soak. Kit only included one that fits. I'm not gonna bust it.

 

[Brianjason6]

Re: 1962 18 hp johnson missing/backfiring

If the carburetor does not respond to the low speed jet there is likely an obstruction in one of the passages and will need to be cleaned.

I do have this symptom and just didn't think much about it. It does react but it's not at all touchy. Hopefully todays reclean took care of it.

 

[Brianjason6]

Re: 1962 18 hp johnson missing/backfiring

Hard to tell with the way the exhaust sounds but I think you may be on one cylinder.
I think I here the other cutting in and out at high idle.
I'm guessing the top cylinder is building carbon because it is firing.
Didn't seem that smokey.Did you torque the flywheel nut?
Bore and shaft dry?

I think what you hear there is my camera phone trying to control the noise..

 

[Brianjason6]

Re: 1962 18 hp johnson missing/backfiring

Nothing worked. The motor is still acting the same. However I found if I pump the bulb it straightens right up. The fuel pump and carb kit is new. Along with all of the other goodies so I'm still stumped.

 

[bktheking]

Re: 1962 18 hp johnson missing/backfiring

The carb has junk in it, when you pump the bulb you are forcing more fuel at it, bet you if you partially close the choke when it's starting the backfire problem it will straighten itself out as well. Closing the choke will cause it to draw more fuel which is what it needs when it's backfiring, it's running lean. It doesn't take much to mess up air/fuel mix, the tinyest amount of dirt can do it. I've had to clean carbs 3 or more times to get them right. Did you seal the welch plug with clear nailpolish, is the idle needle nice and straight. Once you find out the carb problem it should run right provided everything else is in order.

Or try a different tank and fuel line, I still think it's a carb issue.

 

[bktheking]

Re: 1962 18 hp johnson missing/backfiring

At the same time as the backfire I saw no attempt in the video to richen the mixture to counter the lean running, was it attempted today?

 

[Brianjason6]

Re: 1962 18 hp johnson missing/backfiring

At the same time as the backfire I saw no attempt in the video to richen the mixture to counter the lean running, was it attempted today?

It dies too quickly. I've attempted several times to adjust but just a small turn of the throttle and it starts backfiring. I'm going to get another kit and soak the carb in actual carb soak this time. Letting it set for a couple of days. Then blow it out. Then add the new kit. Hopefully that will do it.

 

[Brianjason6]

Re: 1962 18 hp johnson missing/backfiring

Alright..The carb is extremely clean. Used another carb kit and soaked the carb. Blew out all ports and anything that could have possibly been a port. Now the motor is running much better. It still won't idle down very far and doesn't seem to react much to the slow speed needle going in. Actually seem to run smoother at about 2.25 turns out instead of 1.5 and working it. The motor doesn't idle up like normal when its turn in. It's a very smooth sharp needle so I'm unsure why. However this carb is spotless.

I'm gonna leave it be and run it at a slightly higher idle. It's not too high to shift the motor so I think it will be good for a while.

 

[6hpboat]

Re: 1962 18 hp johnson missing/backfiring

I vote burnt points.

 

[6hpboat]

Re: 1962 18 hp johnson missing/backfiring

Or fuel pump not setup right.

 

[bktheking]

Re: 1962 18 hp johnson missing/backfiring

I vote burnt points.

If the points were fried no spark, he replaced them and the fuel pump.

 

[bktheking]

Re: 1962 18 hp johnson missing/backfiring

When you did the kit, did you replace the packing washers? If the washers are bad on the idle side it could be creating an air leak. If it's idling high it's not idling. You should be able to get that motor right down to idle just like any other 2 stroke. Just do a test for me- as the motor is about to die half close the choke and see what it does. If it runs @ idle it still points back to air/fuel issue. Maybe as Samo_ott said, intake leak.

Back to points- could also be a timing issue, did you set them to exactly .020 on both sets?

Pull the plugs and inspect the condition, are they both identical, one worse than the other?