98 johnson 50hp wont idle

[Jathan1234]

Hey guys I'm working on a 98 johnson 50hp for my cousin. I Rebuilt the carbs and put a water pump in. Last summer he said it didn't want to idle at low rpm so that's why I rebuilt them. I didn't notice any dirt or gunk in the carbs.Now it will start and idle for maybe 10 secs then die. Pulled carbs back off and double checked the floats they are in spec. Checked compression its 150 psi and spark jumped 7/16 across open gap. Any ideas on what might be causing the issue. Thanks

 

[rowerowe101]

Hey guys I'm working on a 98 johnson 50hp for my cousin. I Rebuilt the carbs and put a water pump in. Last summer he said it didn't want to idle at low rpm so that's why I rebuilt them. I didn't notice any dirt or gunk in the carbs.Now it will start and idle for maybe 10 secs then die. Pulled carbs back off and double checked the floats they are in spec. Checked compression its 150 psi and spark jumped 7/16 across open gap. Any ideas on what might be causing the issue. Thanks

Have you adjust idle speed jet on carb?

 

[Jathan1234]

Have you adjust idle speed jet on carb?

I put them at 3 1/2 turns out as the manual says and have turned them in 1/4 turn at a time to 1 1/2 out and turned them out 1/4 turn at a time to 5 turns out don't seem to make a difference

 

[rowerowe101]

Have you adjusted idle speed valve on carb?

I put them at 3 1/2 turns out as the manual says and have turned them in 1/4 turn at a time to 1 1/2 out and turned them out 1/4 turn at a time to 5 turns out don't seem to make a difference

Did you do that while it was running or engine off?
If there is a high speed jet on this model I would adjust that as well, it can effect idle speed too.
How did you clean the carbs?
Carbuerator's can be tricky and need to be thoroughly gone over.. Ultrasonic cleaning and blowing out with an air compressors is the best way in my opinion.
If the motor has a primer bulb I would pump that when it starts to die to rule out the pump.
Also verify everything from tank to carbuerator is operating properly... (if tank has vent and if its open or not, fuel line not sucking air or leaking,filter not clogged, etc)

 

[oldboat1]

You didn't post a model number, but will guess it's a plastic topped carb. The idle passages are up there at the top of the carb (hence the needle for the air mix) -- need to remove the plastic cover and thoroughly clean every passage and opening you can find. I carefully use soft wire or monofilament, and follow by carb spray using the plastic nozzle directly in the openings. Make sure you use the correct gasket for the model.

 

[Jathan1234]

Have you adjusted idle speed valve on carb?

Did you do that while it was running or engine off?
If there is a high speed jet on this model I would adjust that as well, it can effect idle speed too.
How did you clean the carbs?
Carbuerator's can be tricky and need to be thoroughly gone over.. Ultrasonic cleaning and blowing out with an air compressors is the best way in my opinion.
If the motor has a primer bulb I would pump that when it starts to die to rule out the pump.
Also verify everything from tank to carbuerator is operating properly... (if tank has vent and if its open or not, fuel line not sucking air or leaking,filter not clogged, etc)

I adjusted them while the engine was off. It won't idle long enough for me to adjust them. I thought the high speed jet was in the bowl behind the bowl drain bolt and thought it was non adjustable. I disassembled it all sprayed with carb cleaner and blew out all the holes with air compressor. It has new float, needle and seat, and low speed jet. I didn't notice any debris or gunk when I took them apart. I tried to keep pumping the bulb before it would die with no results. It has a fixed tank, I don't think there is a vent. I'm thinking maybe pull the vro pump and seeing if the diaphragm is dry rotted? I noticed today that the idle speed set screw thats attached to the timer base doesn't even touch the stop like something may be wore out there? I attached a pic and circled it. The manual says 1/2" from the end of the bolt to the end of the lock nut which is what it's at in the pic

 

[Jathan1234]

You didn't post a model number, but will guess it's a plastic topped carb. The idle passages are up there at the top of the carb (hence the needle for the air mix) -- need to remove the plastic cover and thoroughly clean every passage and opening you can find. I carefully use soft wire or monofilament, and follow by carb spray using the plastic nozzle directly in the openings. Make sure you use the correct gasket for the model.

Sorry the model is J50TSLECC and you are correct plastic top SV style. I didn't run anything through the holes just sprayed carb cleaner like you said and followed up blowing air behind that. Gaskets looked the same.

 

[jakedaawg]

The timing cam roller has lost the outer layer. You will not get it to idle well without that. Replace roller. Might check the throttle cam follower roller as well.

 

[Jathan1234]

The timing cam roller has lost the outer layer. You will not get it to idle well without that. Replace roller. Might check the throttle cam follower roller as

Thanks man I'll get parts ordered and post an update

 

[Jathan1234]

Thanks man I'll get parts ordered and post an update

Ok put new rollers on it and got everything adjusted. It idles longer but same thing just acts like you turn it off and dies. Driving me crazy lol

 

[racerone]

No high speed mixture adjustment.----Are both carburetors closed at idle, yes or no ?-----possibly bump up idle speed.-------Checked flywheel key?---Possible issue with lower crankshaft seal ?

 

[Jathan1234]

No high speed mixture adjustment.----Are both carburetors closed at idle, yes or no ?-----possibly bump up idle speed.-------Checked flywheel key?---Possible issue with lower crankshaft seal ?

I dont think there is a high speed mixture screw. Yes both carbs are closed at idle and I've tried bumping up the idle speed set screw and idle mixture screws. How would you test lower crankshaft seal or what are the symptoms?

 

[racerone]

That is what i said ---no high speed mixture adjustment----Perhaps pull the simple VRO apart for inspection.----Likely the fuel pump donut seal needs replacement.----Air motor is likely OK.

 

[oldboat1]

built in tanks -- might want to check for water. Pump some in a glass and let it settle out -- water would appear on the bottom.