Unequal Fuel Distribution - 1969 25hp Johnson

[Brucer]

Hi guys,
I am struggling to have my 25 hp Johnson idle properly after a full ignition replacement and a carb re-build. I am now suspecting that I may have a different kind of fuel problem. If I take out the plugs and put a piece of cardboard against the head, turn over the engine a few times, it is evident on the cardboard that the bottom cylinder is getting substantially more fuel than the top cylinder. Can any of you tell me if this is normal, or do I have an air leakage problem in the crankcase somewhere? I am at my wits end at this point. I have tried just about everything else I have read on this forum that relates to poor idling on these types of motors. It runs well at higher RPM's, just not at idle so I'm not sure if I'm on to something or not.
Your expertise would really be appreciated.
Thanks,
Bruce

 

[tashasdaddy]

Re: Unequal Fuel Distribution - 1969 25hp Johnson

well with the plugs out the reed valves are not going to work properly. have you checked your compression, it would effect idle much more than at high speeds.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[Brucer]

Re: Unequal Fuel Distribution - 1969 25hp Johnson

It has 125lbs/side. I will follow your instructions on the low speed idle and see what happens, but something tells me there is something else going on.
Thanks for the tip.

 

[F_R]

Re: Unequal Fuel Distribution - 1969 25hp Johnson

Well, the cardboard test probably isn't in the book, so who knows?

How about the puddle drain valves? Or the drain hose clogged?

You are sure it is gas and not water, right?

 

[JB]

Re: Unequal Fuel Distribution - 1969 25hp Johnson

Whether the plugs are in or out will have no effect on reed operation. Compression will have little effect on scavenging.

Look for leakage into the top cylinder crankcase; reed plate gasket, crank seals, bypass cover gasket, fuel pump gasket and diaphram.

 

[Brucer]

Re: Unequal Fuel Distribution - 1969 25hp Johnson

It is definitely not water as I was doing the cardboard test out of water. I am not familiar with puddle drain valves. Where would I locate those?

I have found oil/gas mix below the brass plate that holds the armature in place (top crankshaft seal). Is this easy to replace?

As far as looking for other leaks, should I spray all the surfaces with dishsoap/water mix and look for bubbles?

Thanks again for the help guys. I would really like to get this old girl running like new.

Bruce