How Do I Inspect Reed Valves [15hp]?

[bobgritz]

Engine immediately floods out. This engine has been a workhorse for me for over 2 years always starting on first or second pull and idling like a top. Compression is 110 in both cylinders.

The first thing I did was to rebuild the carb (removed all caps, soaked it and blew it out) with no change. I next swapped it with a different carb but had the same problem.

I rebuilt and swapped the fuel pump. Next, I tried bypassing fuel pump with gravity feed ... same flooding.

I've never dealt with reed valves but cannot figure out another option. I've read where some folks say that they can be inspected after removing carb but I don't think so. I believe that they are nesting behind the intake manifold.

1) Does anyone know if reed valves can actually cause flooding?

2) Can they be accessed WITHOUT pulling the powerhead?

 

[robert graham]

Re: How Do I Inspect Reed Valves [15hp]?

Maybe carb float needle valve seat is bad not stopping fuel flow when float rises?...

 

[bobgritz]

Re: How Do I Inspect Reed Valves [15hp]?

I swapped it with a different carburetor from a backup parts-motor. Had the exact same problem and although possible, it is doubtful that the second carb has same problem (rebuilt and cleaned that one too!). Thank you for advice and I'll pull the valve seat and check it with a magnifying glass.

 

[Joe Reeves]

Re: How Do I Inspect Reed Valves [15hp]?

You keep using the word "Flooding". Is the engine actually loading up with fuel? Reed valves will not cause flooding.... if broken or stuck open, the downward thrust of the related piston will result in fuel being blown out the carburetor throat.

A engine flooding would have fuel pouring out the front of the carburetor or passing thru the fuel pump diaphragm into the crankcase.

What exactly is that engine doing or not doing... and what year is it?

 

[metriccrescentwrench]

Re: How Do I Inspect Reed Valves [15hp]?

1) Does anyone know if reed valves can actually cause flooding?

What I've read (and it does make sense) is that bad reeds will cause the engine to run rich, especially at idle, because fuel/air mixture will get spit out through the carb and then sucked back in, resulting in extra fuel being added to the mixture.

On the engines I've worked on you can kinda' sorta' inspect the reeds with the carbs off, but to really see them you need to remove the intake and reed block.

Yes, as Joe says, describe the symptoms - maybe it's a different problem altogether.

 

[bobgritz]

Re: How Do I Inspect Reed Valves [15hp]?

Update:

After reading above comments, I decided to go back to the beginning and start all over. The first comment (by RG) questioned the 'float needle valve seat' so I inspected it with magnifying glass and it looked perfect. HOWEVER, I noticed that the replacement needle was slightly different than the one removed. The new one had a metal point (presumably ss), then the rubber seal, then more metal. My original needle had a rubber tip followed with all stainless. I reinserted my old 'rubber tipped' needle then checked the float setting(s) and re-assembled it. I just tested it out and the motor is running again. Although, it has a slightly new wrinkle which may not actually be a direct flooding problem although it gives one the misinterpretation of too much gas.

In neutral, the throttle handle must be held wide open or it stalls. When I checked the plugs, the top spark plug is wet whereas the bottom is normal. I restarted the motor and pulled each plug wire separately. There was little to no change to the running engine when I pulled the top 'wet' wire but it would stall immediately when the bottom wire was pulled.

The coils are hard-wired to the circuitry so I cut and swapped the 'yellow' wires basically changing top to bottom. Similarly, I switched the plug cables (from the coils to the plugs) then restarted the motor. Once again the top cylinder is not firing while the bottom is doing all the work. This basically rules out a bad coil (please note that I also switched plugs and plug cables). I pulled the plugs and am getting a nice blue spark from both. I realize that although the spark appears strong, this doesn't mean that it's firing at the proper time.

Before ruling out the reed valves (even though it's looking like an electrical problem):

Do both cylinders share the atomized gases within the crankcase ... or, does each cylinder operate independently of one another, in other words, is each reed dedicated to a single cylinder? It would seem that they each need to operate separately since each cylinder has different strokes at different moments? If this is the case, couldn't one reed be dumping too much gas into the top cylinder's cavity causing it to overload? When I put the transmission in gear and open the throttle to high speed, the motor runs strong which makes me question the electrical concerns and brings me back to a fuel overload question.

 

[metriccrescentwrench]

Re: How Do I Inspect Reed Valves [15hp]?

Do both cylinders share the atomized gases within the crankcase ... or, does each cylinder operate independently of one another, in other words, is each reed dedicated to a single cylinder? It would seem that they each need to operate separately since each cylinder has different strokes at different moments?

You're correct, each cylinder is independent of the others. It needs to be that way because as a piston is coming 'down' it's compressing the fuel/air mixture ahead of the inlet port opening. If all cylinders drew in fuel/air mixture from a common space the mixture wouldn't be able to be compressed since one piston is up while the other is down and the total volume would always equal out.

You'll want to get a variable gap spark tester, most auto parts stores sell them for around $10 to 15. The spark should be able to jump a 7/16" gap. If it passes that test it's probably time to start looking at fuel issues.