Johnson TN26 5HP 1950/51

[Bobby Day]

I just found this antique engine and am not surprised to confirm that it doesn't run. Feels like it has good compression and turns over easily but lots of fuel leaks and haven't yet comfirmed spark. There is an existing excellent thread on rebuilding this engine with info on obtaining rare parts such as primer leathers, etc,but it is from 2012 or 7 years old. Wondered if anyone knows if the source for primer leathers still exists. Additionally, this engine requires something like a 16 to 1 fuel ration which can use regular motor oil. Can a higher ratio be used with modern 2 cycle oils?

 

[F_R]

A guy named Lloyd makes those primer seals. he hangs out at the Antique Outboard Club's website www.aomci.org

First thing you need to do is check the ignition coils. You are wasting your time until you do.

Discussing oil is akin to starting a war. So I'll start it. You can use 24:1 if you insist. But that 3rd port engine needs oil for sealing. 16:1 is what it was designed for.

 

[kbait]

Use two stroke outboard oil tcw3 rated. Mix 16:1. Lots of folks run 24:1.. you will get many opinions!
Not sure on carb part sources, but ignition should be standard universal magneto used on 3-40 hp twin cylinders from early 50’s - early 70’s, so parts are easy to find..

 

[Crosbyman]

delete

 

[flyingscott]

I just use o-rings instead of the leather washers. Find 2 the right size and sandwich them between the 2 steel washers in there

 

[Bobby Day]

Thnks for the input. I was wondering about using O-rings.

 

[TN-25]

Those old TNs used the guillotine-style points. It wasn't until the TN-28 of 1952/53 that they converted those T-series motors to the universal automotive-type breaker points.

I started out with a 1950 TN-26 but during the restoration I ended up with a TN-28 block with the newer points. Be aware that the TN-28 used a different flywheel & even the pull starter (because of the flywheel). Ask me how I know...

Those old bronze-bushed motors need the oil film thickness to maintain running clearance. Even if the cylinders have decent compression, being a rotary valve 2-stroke it also needs to have tight clearances in the big-end because if not, compression can leak to the adjoining cylinder that is 180 degrees out of phase and all sorts of weird running problems can occur.

They are 70 year old motors but when everything is right they run very smoothly & quietly. Give it adequate quantities of oil.

 

[Crosbyman]

my tn27 uses regular OMC ignition.. see that picture above with the deleted text and attached picture