1958 Lark 35 hp loud bang

[ceelonium]

Had my 1958 Evinrude Lark 35hp Electric start out on the lake. Had been running just fine days prior. But on this day, she started up ran for a few minutes but idling rough. She died, I started her back up, then a rather loud bang and fire coming out of front of Carb. It was louder than your usual backfire and really scared the heck out of me. I took the fire extinguisher to her and that's that.

I haven't tried to turn her over since that incident.

Anyone have a idea what this could be? I have read similar posts where people say the gas fumes build up under the cowl and then some ignition source ignites the fumes.

I notice that when I run her in the test tank or out on the lake, there is usually some fuel driping out of the front of the carb (air intake?) when I am cranking her and pushing the choke. Is this normal?

Any insight is greatly appreciated.

 

[Chinewalker]

Re: 1958 Lark 35 hp loud bang

A loud bang of that sort usually means the timing is way off - indicative of a sheared flywheel key.

Fuel dripping out of the carb when choking is fairly normal. A motor in proper tune should start easily enough that it is minimal - the longer you have to choke it, the more fuel is going to dribble out...

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

Thank you for the quick reply. Do you think that the timing became erratic at some point, hence, the loud bang. I am not sure, but the loud bang to me was more of an "explosive" nature - and not necessarily a mechanical one. What exactly happened if it turns out that timing was off? What would cause that loud bang if timing is off? misfiring of Cylinder?
Thanks again for the quick reply.

 

[HighTrim]

Re: 1958 Lark 35 hp loud bang

As Scott stated, sounds like a sheared flywheel key, usually due to improper torque. Pull the flywheel and have a looksee.

 

[1946Zephyr]

Re: 1958 Lark 35 hp loud bang

You might also want to check your flywheel inspection cover, to make sure it's present. A missing flywheel inspection cover, can also create a fire hazzard too. Simply because you have points in there sparking a lot and gas fumes can help it go "BANG"
And yes, choking a motor will help gas drip out the front of the carb.

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

Thanks for the insight. I will have a closer look at the flywheel and all and report back. Here are some detailed pics. Can you tell by these if the flywheel inspection cover is missing? Thanks again for the help!

I

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

One last thing I forgot to mention. The explosion was enough to break the bracket which holds the throttle in place toward the upper part of the motor (held in place w/2 bolts)

 

[lindy46]

Re: 1958 Lark 35 hp loud bang

You have to remove the recoil starter to see the top of the flywheel where the inspection cover is.

 

[Chinewalker]

Re: 1958 Lark 35 hp loud bang

I can't imagine an explosion of any sort busting out the screws that hold the vertical throttle arm. I'm guessing they were loose to begin with and perhaps the flywheel hit the mag plate when it spun out, causing it to pull on the throttle arm.... I would pull the flywheel and inspect the keyway and coils - if the flywheel was loose enough to hit them, it may have damaged them...

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

I pulled the pull start housing and can see that there is indeed a cover on the flywheel. There is also a oval-like access that uses two flathead screws. I took those screws out and had a look inside. As I manually turned the flywheel I looked through the oval-like access I could see all the way around and determine that most of those components in there look brand new, as if they were installed yesterday. The previous owner did say that it had quite alot of things done tune-up wise.
I have a feeling if I clean out the carb and crank her up, that she' start up fine.
Is it possible to clean a carb out without taking it completely apart? More or less I want to get the fire retardant out of the intake on the carb enough to where I can start the motor.

 

[1946Zephyr]

Re: 1958 Lark 35 hp loud bang

I would check the flywheel key first.

 

[dodgeboy1979]

Re: 1958 Lark 35 hp loud bang

no to get all the dust from the extinguisher off you have to pull the carb and clean it thourough. It has a type of ammonia in it so any wiring it came in contact with clean really well as it will deteriorate the rubber coating

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

I will never ever ever use a fire extinguisher again, unless someone's life is in utter danger. This engine is covered from head to toe by this white retardant coating. No crevice is untouched by this stuff. I created more problems for myself by using an extinguisher.
Next step; get a pulley tool to get the flywheel off. I trust that the "flywheel key" is the small metal splint that locks the flywheel to the camshaft?

 

[nwcove]

Re: 1958 Lark 35 hp loud bang

you should look at this link, the exploded views should help you along somewhat.

http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1958&hp=35

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

Ok so I finally got the flywheel off, after some days of PB blaster plus several trips to the autoparts store.

The flywheel key seems to be intact. I have not actually tried to remove it from the shaft, but I have included pics below. Also, the slot on the flywheel housing itself, which the flywheel key slides into, is also fine.

Two things that did stand out for me:
1. One of the point sets (breaker points) is literally touching. There is no gap whatsoever. The other point set looks fine, but I don't have the tool to check that the gap is .020", which is next on my shopping list.
2. The metal plates that wrap around the coils. One of the outer edges is black and has slight damage, where you can tell it has been rubbing against the inside of the flywheel where the magnets pass by.

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

and some more pics with flywheel removed. Your input is always greatly appreciated:

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

 

[Chinewalker]

Re: 1958 Lark 35 hp loud bang

Flywheel was definitely rubbing against the one coil lam. Also looks like the screw(s) that hold the plate down may be loose (centermost screw head in first photo is not seated). That would allow the mag plate to float around a bit and could be part of the problem.

 

[ceelonium]

Re: 1958 Lark 35 hp loud bang

indeed, the screw was loose. When I took the pic I didn't notice it until after I had a look at the pics on my computer.

I will read up on how to adjust the breaker point gaps, but if anyone has tips, don't hesitate to pass them long. Thanks

 

[Chinewalker]

Re: 1958 Lark 35 hp loud bang

Easiest way to set the points is to align the crankshaft keyway with the rider on the point rocker, then gap the points to .020.

Double check all the other screws...