Johnson TN-26 Fuel Mixture

[Woodruff]

I am ready to start the 5hp TN-26 today and could use some help with proper fuel mixture. Could someone provide the correct ratio? I'm using 24:1 in the 1959 3hp Evinrude. Will that work?

 

[racerone]

The 24 : 1 will work fine.-----You are aware of that L-shaped mixture needle for the idle intake port / rotary valve ?

 

[Woodruff]

Yes.. I have removed and inspected/cleaned that needle. All looks great.
Today is the big test... will it run?? I'll post an update. Thank you!

 

[Woodruff]

Started the engine and it runs for 30sec or so then backfires out of the air intake/silencer and rotary valve intake and dies.

-Adjusted high and low speed jets with no change

-Checked fuel flow from tank (previously cleaned tank filter). Flow is fine.

-Attached an inline spark tester and no evidence of loss of spark on either cylinder.

I’m thinking perhaps a sticking float and when the bowl runs dry the engine backfires?

Any ideas?

 

[Crosbyman]

I never started mine up but I think they are a bit finicky to adjust have you openned up the LS needle or anything else to get the fuel to flow in the carb. recheck the float but I suspect it is OK being an upside down inlet needle ..check side clearances in case it does snag in the full UP position stoping the inflow of fresh fuel . it must drop down to allow more fuel in the carb.

all filters cleaned ?? does the TN 26 have one at the carb bottom ?? all I have is a TN 27 list of parts

tank vent open and any or all vent holes decrudded with a paper clip.

fuel flow may look ok but stops after a while (try to run with the tank cover open just in case) .

ex: the 2 small vents on the JW ..under the screw must pass light maybe your TN has the same kind or set up. look for two minuscule holes .

TN experts will chime in.

 

[Woodruff]

Tank vents are clean. LS needle has been adjusted from 1/2 to 1 1/2-2 full turns out with no change. High speed needle has been adjusted in many positions. Once it stalls I do have to hit the primer a few times so I think this is fuel related. Now I'm suspect of the small screen that surrounds the check valve. Could be residual dirt has clogged that screen.

 

[Crosbyman]

easy to clean ...

 

[Woodruff]

I think that pdf is an earlier model than the TN but it is similar so it is helpful. The TN I have doesn't have a barrel valve for air intake.

 

[F_R]

I suggest you re-visit that in-tank filter. Does it have the original sintered balls filter? Those things are famous for getting plugged up and restricting flow to the carb, so the carb doesn't get enough fuel to replace what was burned--then it runs out of gas and dies.

You say it has good fuel flow, but does it? Another famous problem is the filter gets plugged mostly in the bottom half. So, you get plenty of flow when the tank is full, but not enough when half full. ALSO, consider the fact that the motor as it sits on the transom it possibly is off-level as compared to how it was sitting when you checked the flow. In other words, the fuel level might be lower AT THE FILTER.

These are common problems. Check it out, don't assume.

 

[Crosbyman]

I think that pdf is an earlier model than the TN but it is similar so it is helpful. The TN I have doesn't have a barrel valve for air intake.

it is a general T model document from the johnson service manual

 

[Woodruff]

I suggest you re-visit that in-tank filter. Does it have the original sintered balls filter? Those things are famous for getting plugged up and restricting flow to the carb, so the carb doesn't get enough fuel to replace what was burned--then it runs out of gas and dies.

You say it has good fuel flow, but does it? Another famous problem is the filter gets plugged mostly in the bottom half. So, you get plenty of flow when the tank is full, but not enough when half full. ALSO, consider the fact that the motor as it sits on the transom it possibly is off-level as compared to how it was sitting when you checked the flow. In other words, the fuel level might be lower AT THE FILTER.

These are common problems. Check it out, don't assume.

I have a new sintered ball filter due in on Saturday but thought I'd start the engine after cleaning the the old one. Perhaps fuel flow isn't as good as it should be and the NOS filter will correct the problem. In the meantime I will inspect the filter screen around the check valve just to be sure any remaining dirt hasn't clogged that screen. The engine ran remarkably well when it was running and I'm quite impressed considering its age.

 

[Crosbyman]

try removing the sintered filter for a test ... or you can install a small round filter for lawn tractors or similar on a temporary fuel line.

 

[Woodruff]

I replaced the sintered filter, cleaned out all the ports and screen on the check valve and the motor runs well now. I do need to replace the leather washers in the primer pump because it leaks while priming. Does Lloyd Lautner still offer these replacement leather washers?

 

[Crosbyman]

yes pretty certain... drop him a PM here and on the AOMCI site

not certain but I think some folks have used o-rings ( find and fit them to size you may be ok )