Johnson JW & Evindrude Lightwin carb issues

[LeeRoy Wisner]

I have been pulling my hair out on this one.  Currently working on a Evinrude 1966 3632E folding motor. This carb has the fixed mainjet. Compression is (#1)  100#, (#2)  95#.

My issue is I have rebuilt the carb using a Sierra #18-7043 kit.  Pulled the top welch plug, the idle & mid speed holes are clean.  The issue is as soon as I turn on the fuel valve, gas comes out of the carb throat.   I have torn it apart about a dozen times, even went back to the original cork float & needle, SAMO,  SAMO.   The float works open/closes when tipped with blowing on the carb inlet fitting.  All seals are in place.

Am I wrong in thinking that the float needle should stop the flow once the fuel bowel is full enough to activate the float needle valve?  But with the fixed mainjet, could gas bypass an go up the high speed tube & lowering the fuel level???  The guy I bought it from said he ran it, YAH I KNOW.!!!!   Everything looks like it should be fine, BUT what am I missing here?  Is there something internal that I am overlooking?  I am getting cross eyed & need someone else’s ideas.

This is not my first of these motors as I own/worked on at least 5 others so not a virgin here.

[crosbyman]

if  fuel comes out then the inlet needle is not being pushed up on the seat  or not seating   when fuel lifts the float… same for  a toilet bowls at home. !

You do have the fat donut  in place on the high speed tube ?

any chance the  gasket  is snagging the float stopping it from closing the inlet ?

if you flip the carb upside down can you blow air insidethe carb via the inlet nipple ?  you souldn’t !!!

is the carb  float level  with the carb body when held upside down ?

is the float upside down ??

if you replaced the needle and seat…. did you try  the old needle and seat…

 

 

Joining AOMCI has priviledges 🙂

• This reply was modified 2 years, 5 months ago by crosbyman.
• This reply was modified 2 years, 5 months ago by crosbyman.
• This reply was modified 2 years, 5 months ago by crosbyman.
• This reply was modified 2 years, 5 months ago by crosbyman.

[frankr]

IF, if, if, my guess/assumption is correct, you have a blocked bowl vent.  As fuel enters the bowl, the level rises and shuts the needle valve.  But it can’t rise because of the air bubble above it.  Therefor since it can’t rise, it doesn’t close the inlet needle and just continues to flow in and up and out the high speed nozzle.  BTW, congratulations on your thinking.  You almost got it right.

If my assumption of a blocked vent is wrong, then I dunno.

[LeeRoy Wisner]

Thank You frankr,  Yes everything looks fine,    I did look for a external vent but was unable to locate one.    The only thing I have not done yet is pull the lead shot passage plugs.  So pull it apart the unmteenth time.   And when I find it, you can be sure there will be a BIG mark on the wall to remember next time.

[seakaye12]

I witnessed a similar situation at one of our meets.  A member who knew his stuff was also pulling his hair out for the exact same reason.  Then it dawned on him….do not assume that all the lead shots or similar “plugs” should be there.  Maybe a previous owner;  out of frustration related to stopping a leak caused by a bad needle valve……decide to plug one of the holes that gas was coming out of.  So….the vent hole was plugged…..but of course it should not have been.  We removed that plug and…..with the vent restored….everything was good.

Maybe compare with another JW carb…..and see what lead shots should be there…..and which ones might have been “added”…..

[frankr]

The vent on OMC carbs are the big holes above the air inlet (choke end of the carb).  Mud daubers love to pack them full.

[LeeRoy Wisner]

OK guys, good news.   I tore it completely apart trying to decipher just how this carb works.   I spent NUMEROUS hours of poking & measuring depth of drill bits into all the holes under the lead plugs.   Rather confusing.

Apparently this carb is vented out holes on the front (thru slots) under the breather.   However there were no holes out the upper part into the float chamber.  One hole went straight down to withing 1/8″ of going into a flat boss in the chamber.   I just drilled it deeper & into the chamber.   Then replaced all the plugs, and reassembled.   It did not flood and started on second pull.

I am still unclear as just how that was supposed to be vented, but IT RUNS.

On all the other OMC carbs that I have worked on there was a vent hole somewhere on the upper outer part of the main body.   Like I said, there will be a big mark on my shop wall for this one.

Than you frankr, maybe someday we can get together for a beer.

• This reply was modified 2 years, 5 months ago by LeeRoy Wisner.

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