Johnson TN28 no low-speed fuel

[memays]

Been trying to resurrect my dad's old TN28. I have good spark and compression, I can't seem to get the low speed system to siphon for it to run. I cleaned the carb and all looks good. I believe the float is working, but if I hold it down via the hole in the top, the fuel never overflows out the top. The primer is a little flakey, and when it primes, it starts right up for about 1/2 second then stalls. If I pop it with starting fluid in the hole, I get the same result.
Does the primer have to have a good seal in order for the low-speed to siphon properly, or is it just to get a fuel shot shot to start it?

If so, I saw a post from someone who has replacement leather primer seals and I can try to order them. If not, then perhaps I'm back into the carb again.?

 

[racerone]

Have you adjusted the low speed mixture screw that feeds the rotary valve ?

 

[Crosbyman]

Did you look up the Poche family TN service for the carb. ??

Basic Carburetor Servicing Johnson H and T Series

Johnson Outboard Carburetor Servicing H and T series

pochefamily.org

special leather seals are needed for the primer pump.. visit aomci site and Loyd will provide info seals are about 15$ by snail mail

Antique Outboard Motor Club,Inc

www.aomci.org

 

[memays]

Have you adjusted the low speed mixture screw that feeds the rotary valve ?

Yes, 3/4 Turn, 1 1/2 Turns, 2 1/2 turns - same result. Also peeked in the hole and the rotary valve seems to be turning normally.

 

[racerone]

Rotary valve is just holes drilled in the crankshaft.

 

[memays]

Did you look up the Poche family TN service for the carb. ??

Basic Carburetor Servicing Johnson H and T Series

Johnson Outboard Carburetor Servicing H and T series

pochefamily.org

special leather seals are needed for the primer pump.. visit aomci site and Loyd will provide info seals are about 15$ by snail mail

Antique Outboard Motor Club,Inc

www.aomci.org

Yes, I have the Poche document - Thanks!

 

[flyingscott]

i just put orings in instead of the leather seals

 

[memays]

i just put orings in instead of the leather seals

how did that work for you? thought about it, but other reports said it didn't work. I think I will give it a try...

 

[TN-25]

At low speed, in theory the carburetor doesn't even come into play, it is just the low speed mixture valve. Rotary valve 2-strokes are different.

Your motor is a bronze bushed motor. That means it had very tight, hand-reamed tolerances when built. It also means the bearing can't be replaced, so when the motor gets excessive clearance in the bearings it is time to replace the motor.

With too much clearance between crank and bearing, it can mess up the running. As one side gets pressurized in the crankcase to get pushed through the port into the cylinder, leakage between cylinders via excess crank clearance will reduce the pressure charge, and also mess up the neighbouring cylinder's cycle. I didn't believe it at first, but it is true. One sign of this is the motor won't consistently idle down to a smooth troll. The TNs are wonderful trollers when not worn out.

I have a TN-26 that dad claimed ran funny because of worn out bearings. I thought that sounded non-sequitur, but as it turned out is was true. I found another block & crank within wear limits (a TN-28) and re-ringed it. All is good (once the leather plunger seal was sourced). Until I replaced the plunger seal it didn't prime well, and it leaked fuel.

 

[flyingscott]

Use the 2 metal washers and you have to have fuel resistant orings. people who had them fail used plumbing orings