Johnson 6hp hard start

Rpiazza6857

Cadet
Joined
Oct 30, 2020
Messages
26
Hi I have a new to me Johnson 6hp serial number J6RE1A that has trouble starting cold, so far I have rebuilt the carb with an OEM kit, done the link and sync procedure, changed the water pump and compression checked it with 110 on both cylinders. It runs well once running. To start it however I have to either spray a squirt of gas mixed with two stroke oil in the throat of the carb or an easier method is to put my hand over the throat. Choke is working correctly but doesn't seem to be enough, when I cover the throat completely with my hand it will fire on one or two pulls. The airbox is off for me to do this but I think it should start regardless. Wondering if the fuel pump could be the issue? Or is there something else to look at.
 

Rpiazza6857

Cadet
Joined
Oct 30, 2020
Messages
26
One other thing how the heck does the airbox come apart I would like clean it but it seems to be glued together I have not tried any force because I do not want to break anything
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,032
I do not believe there is anything inside that box that needs cleaning.
 

Vic.S

Rear Admiral
Joined
May 4, 2004
Messages
4,690
Hi I have a new to me Johnson 6hp serial number J6RE1A that has trouble starting cold, so far I have rebuilt the carb with an OEM kit, done the link and sync procedure, changed the water pump and compression checked it with 110 on both cylinders. It runs well once running. To start it however I have to either spray a squirt of gas mixed with two stroke oil in the throat of the carb or an easier method is to put my hand over the throat. Choke is working correctly but doesn't seem to be enough, when I cover the throat completely with my hand it will fire on one or two pulls. The airbox is off for me to do this but I think it should start regardless. Wondering if the fuel pump could be the issue? Or is there something else to look at.
Are you sure the choke is closing fully..
Are you filling the carb bowl fully with the primer bulb. If that is done then the fuel pump is not a consideration.
Have you tried opening the throttle further . ( Mine is an earlier model which has an interlock between the throttle and the starter. I open the throttle as far as that interlock will allow)
 

Rpiazza6857

Cadet
Joined
Oct 30, 2020
Messages
26
I have triple checked the choke, I even went as far as flipping the bellcrank over to make sure it was on correctly, it is defiantly closing all the way. I am priming it with the bulb and it is staying hard, I also pulled the drain out of the bottom of the bowl to make sure there was fuel in there. I also put the airbox back on just to see if it would make a difference and it does not. As an experiment I put masking tape over the holes in the airbox and it fired right up, same idea as putting my hand over the throat. It would not fire until I put the tape on. When it is running I can pull the choke and it almost instally dies as well, so it would seem it is working. I figured since it runs well once running I could rule out the fuel pump.
 

Rpiazza6857

Cadet
Joined
Oct 30, 2020
Messages
26
Sorry forgot to answer about the throttle positioning, there is no interlock on this engine and I have tried multiple throttle settings from wide open to closed, makes no difference, I would have thought at full throttle even if I didn't get everything out of the carb it would pull off the main jet that way, btw the carb was pretty darn clean before I rebuilt it.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,032
On this 1991 motor does spark jump a gap of 3/8" ( 1 cm ) or more ?----Checked reed valves ?
 

Rpiazza6857

Cadet
Joined
Oct 30, 2020
Messages
26
I checked spark with a tester and have strong blue spark however I did not measure the gap, I can set the gauge there and check it. I did not check the reeds are they visible with the carb off?
 
Top