1967 Johnson 100HP - carb leaking gas

[jon705]

Rebuilt the carbs late last year and am starting her up for the first time this year. Primer bulb gets firm after a few pumps. A couple days ago while testing, she was idling and a steady stream of gas was flowing out of the float bowl cover (out the hose that exist through the cowl). I took off the float bowl and adjusted all four floats to be parallel with the gasket when turned upside down. Started her up this afternoon after putting it all back together and she idled a bit - no leak.

However, she was stalling consistently after running for 10 seconds. After doing this start, idle 10 seconds, stall process for about a 5 minute period she started streaming gas at the float cover again. Any ideas what else may be causing the bowls to take in too much fuel?

Thanks in advance!

 

[jtexas]

Re: 1967 Johnson 100HP - carb leaking gas

Couple things come to mind: failed bowl gasket, float valve sticking open, failed float valve o-ring, or valve needle and/or seat worn out needs replacing.

 

[F_R]

Re: 1967 Johnson 100HP - carb leaking gas

"Parallel with the gasket" doesn't get it. There is a special gauge for setting the floats. Or, lacking the gauge, I have the dimensions. PM me your e-mail address if you want the specs. Remind me in the PM what you need so I don't have to search for what we talked about..

 

[glassmaster68]

Re: 1967 Johnson 100HP - carb leaking gas

yeah ,stuck float maybe,,,maybe broken needle valve tip,,,,but also check the packing around the needle valve/s and make sure it is tight there,having to apply a lil pressure to turn it,esp since you rebuilt carbs last year,they can get warm and expand like an exhaust manifold and need retightening after a couple of warm ups ,,,,,, they will vibrate loose start sucking air around the needle valve and send too much fuel ,,,cant burn it all ,,spits it out,,,and /or floods it out and /or fouls plugs,,,,the only other thing i could think of is reeds,,,,if theyre not seating due to wear or carbon buildup,,that will also cause a spit back of fuel.

 

[R.Johnson]

Re: 1967 Johnson 100HP - carb leaking gas

I have'nt rebuilt one of those carbs in years. Seem's the last one I did, the needle , and seat's were about $30 apiece. I don't know where you would find them now.

 

[F_R]

Re: 1967 Johnson 100HP - carb leaking gas

381709 needle & seat is listed as No Longer Available. But they come with a carburetor repair kit, 382059. $300.60.

 

[R.Johnson]

Re: 1967 Johnson 100HP - carb leaking gas

F-R: The rest of that kit is all gaskets'. Make's you wonder what those needle & seats' would cost if you could buy them alone I had one of those engine's, you could'nt haul gas to it fast enough.

 

[jon705]

Re: 1967 Johnson 100HP - carb leaking gas

yeah ,stuck float maybe,,,maybe broken needle valve tip,,,,but also check the packing around the needle valve/s and make sure it is tight there,having to apply a lil pressure to turn it,esp since you rebuilt carbs last year,they can get warm and expand like an exhaust manifold and need retightening after a couple of warm ups ,,,,,, they will vibrate loose start sucking air around the needle valve and send too much fuel ,,,cant burn it all ,,spits it out,,,and /or floods it out and /or fouls plugs,,,,the only other thing i could think of is reeds,,,,if theyre not seating due to wear or carbon buildup,,that will also cause a spit back of fuel.

I'll need to check those needle valves. Since it was leaking from the float bowls I've only focused my attention there.

When I took it apart a couple days ago I found that the bottom float valve o-ring had ripped apart. I assumed that was the cause of the leak so replaced it (have a donor engine in the garage) but the leak continued. That's when I took apart again to adjust float level only to have the same leaking issue.

 

[R.Johnson]

Re: 1967 Johnson 100HP - carb leaking gas

I would have to check, but I believe I have a full set of those needle and seats' that I saved. They would be a used set, but ok when removed. I also have that float guage. Send me a PM if you wish.

 

[jon705]

Re: 1967 Johnson 100HP - carb leaking gas

yeah ,stuck float maybe,,,maybe broken needle valve tip,,,,but also check the packing around the needle valve/s and make sure it is tight there,having to apply a lil pressure to turn it,esp since you rebuilt carbs last year,they can get warm and expand like an exhaust manifold and need retightening after a couple of warm ups ,,,,,, they will vibrate loose start sucking air around the needle valve and send too much fuel ,,,cant burn it all ,,spits it out,,,and /or floods it out and /or fouls plugs,,,,the only other thing i could think of is reeds,,,,if theyre not seating due to wear or carbon buildup,,that will also cause a spit back of fuel.

This motor has adjustable needle valves - not sure how common this is - to richen or lean out the mixture. There's a plastic bar connecting four plastic adjusting arms, each attached to one of four needle valves. I pulled the plastic adjusting arms off of each the needle valves, removed the valves, and inspected. Nothing looks out of the ordinary. Screwed all four valves back in hand tight then reattached the adjusting arms and connecting bar at the leanest setting.

It was too early this morning to fire it up - neighbors probably wouldn't appreciate me! I'll give it a go a little later today and hopefully report back with success.

 

[jon705]

Re: 1967 Johnson 100HP - carb leaking gas

This motor has adjustable needle valves - not sure how common this is - to richen or lean out the mixture. There's a plastic bar connecting four plastic adjusting arms, each attached to one of four needle valves. I pulled the plastic adjusting arms off of each the needle valves, removed the valves, and inspected. Nothing looks out of the ordinary. Screwed all four valves back in hand tight then reattached the adjusting arms and connecting bar at the leanest setting.

It was too early this morning to fire it up - neighbors probably wouldn't appreciate me! I'll give it a go a little later today and hopefully report back with success.

Started 'er up at lunch and she still leaks gas. Screwed needle valves all the way in and she still leaked from the float bowls. If I squeeze the primer bulb it will keep the stream of gas flowing from the float bowl. Not normal, right? With that symptom I say floats are not doing their job of shutting off fuel when full. Do I need new needles? Lower floats more?

 

[jtexas]

Re: 1967 Johnson 100HP - carb leaking gas

yeah, if you can push fuel out the carb with the primer bulb, it's the valves all right.

You can test those off the motor by blowing into the fuel inlet. Held upside down, no air should pass. I recommend draining the carb bowl first.

 

[jon705]

Re: 1967 Johnson 100HP - carb leaking gas

yeah, if you can push fuel out the carb with the primer bulb, it's the valves all right.

You can test those off the motor by blowing into the fuel inlet. Held upside down, no air should pass. I recommend draining the carb bowl first.

Man, wish I woulda done that air test the first time! There's certainly a leak and I'm stumped why. (Luckily I hung on to my donor motor - almost sold it a couple weeks ago.) Pulled the float bowl assembly off the donor and did the air test and that one works fine - no leaks. However, the float bowl assembly on the donor motor does not have a vent tube.

Didn't have enough time this morning but am planning on swapping the screw plugs and inlet needles from the donor to my current motor. Too bad the donor motor float bowl assembly doesn't have a vent tube, or I'd swap the whole assembly.

Thanks for the advice!

 

[R.Johnson]

Re: 1967 Johnson 100HP - carb leaking gas

Those valves you screwed in, and closed are the low speed needle valves.They will have to be put back in proper adjustment for the engine to start, and run properly. Are you trying to work on this carb without a manual? If your having a problem with knowing the low speed needle valves', from the inlet needles,your in for a problem. When you get to those floats'with the spring loaded inlet needles, they have to be in proper adjustment also.Like most OMC carb's, it is not all that difficult, but thing's have to be in proper order.

 

[jon705]

Re: 1967 Johnson 100HP - carb leaking gas

Those valves you screwed in, and closed are the low speed needle valves.They will have to be put back in proper adjustment for the engine to start, and run properly. Are you trying to work on this carb without a manual? If your having a problem with knowing the low speed needle valves', from the inlet needles,your in for a problem. When you get to those floats'with the spring loaded inlet needles, they have to be in proper adjustment also.Like most OMC carb's, it is not all that difficult, but thing's have to be in proper order.

Glassmaster's description seemed to be referring to the low speed needle valves which is why I adjusted those. Now that I know where the problem really lies I can put those back within spec. Thanks for calling that out.

 

[jon705]

Re: 1967 Johnson 100HP - carb leaking gas

I removed the float bowl assembly again, cleaned, inspected and adjusted the floats. With the assembly turned upside down I could not blow air through. Reinstalled and attempted to fire 'er up only to find gas leaking overflowing again. Guess I need to find another good donor motor.

 

[jon705]

Re: 1967 Johnson 100HP - carb leaking gas

Finally solved the problem. It was a bad set of needle and seats. Even though the air test (upside down, blow through, no air should pass) checked out ok on the old set they weren't doing their job correctly. Thanks to R.Johnson for sending me a good used set of needles and seats. Installed them this afternoon and she's running great again. No leaks through the carb, idles great, and I am able to throttle up without 'er choking out.

 

[glassmaster68]

Re: 1967 Johnson 100HP - carb leaking gas

float valves werent seating?glad you got it,,,happy motoring

 

[jon705]

Re: 1967 Johnson 100HP - carb leaking gas

float valves werent seating?glad you got it,,,happy motoring

That's correct the float valves were not seating. The replacement set worked for a short test run, now the same issue has popped up again. One of the float valves is not fully seating and a stream of gas is leaking out the float assembly vent while the engine runs. What would cause the float valves to seat properly some times, then gum up? I've cleaned them really well with carb cleaner and compressed air - as well as the rest of the fuel system.

Any other suggestions? This motor has been setting for a while. Does anyone think old gas/varnish is making its way back through the lines and gumming up even after thorough cleanings?

 

[glassmaster68]

Re: 1967 Johnson 100HP - carb leaking gas

just a week ago,my float started sticking,its just 2months old.after checking and cleaning and checking again,i found two problems.the pivot pin for the float was plastic in the new carb kit,i used it.after a bunch of trips of the float up and down,the curled hinges of the new cork float wore a stop in the plastic pin that hold the float.the remedy for that was to put the orig metal pin back in.for some reason my float was also barely hitting the inside of the bowl,therefore catching it and holding it open.i took needle nose pliers and gently rolled the hinges of the float slightly in,bringin the float a little closer to the pivot point.also made sure the small spring that holds the needle to the float was tight against the bottom of the float,slack in that spring was not good for me.the needle valve has to move with the float now,anyways everything working again good now.so maybe make sure float is free,blow through the carb right side up and upside down and see what you get ,,,rs up open,,upd closed.if you havent replaced the needle and seats together,could be a prob.if you have clean fuel lines and good fuel,using the right mixture,there shouldnt really be any gumming up.check that float and needle valve/seats.dont give up youre almost there.working on these old motors are just part of their constant joy they give us,even though the premix,motor,barrel, sometimes look like the only thing missing there is a match.