TN-28 won?t run w/o priming.

[burnt clutch]

I am stumped on this thing. I worked on it last year cleaning the carb and replacing the coils and I actually had it running for 10 minutes about a year ago. Shortly after it ran it wouldn?t run for more than a second or 2 at a time. I shelved it since it was September and I haven?t looked at it again until this month. Since my initial compression numbers were low I sprayed some WD-40 and into the Cylinders and later I poured a mix ATF of Sea foam into the cylinders hoping to loosen up the piston rings and break up any carbon that might be in the engine. Before I ran it I pulled the spark plugs and flipped the engine over to drain out any excess fluids. I tried to start it yesterday and it still won?t run for more than a couple of seconds. I got curious and removed the exhaust/Intake cover looking for reed valves but I couldn?t find anything that I think would interfere with it getting gas. I also took the carb apart and ran pipe cleaners through all of the orifices but couldn?t find anything clogged or that looked out of place. Is there anything else I should check before giving up on it? The carb has a new plastic float and new primer washers from Mr. Lautner. I guess getting a book on this thing should also be on my list ? would the Johnson Outboard Owner's Manual 302768 be a good choice as a service manual or should I get a different book? Sorry for the long winded intro and thanks in advance for your help!

-Karl

 

[burnt clutch]

Re: TN-28 won?t run w/o priming.

I took some pics of the intake cover and cylinder for posterity..

-Karl

 

[TN-25]

Re: TN-28 won?t run w/o priming.

You won’t find any reed valves on that motor, as it literally was the last of Johnson’s rotary valve motors.

You do realize there is a little L-shaped rod that hangs down at the front of the motor, barely protruding below the shroud. That little rod is the slow-speed needle and it controls the flow of fuel. It is possible that the rod is turned and seated so that the flow of fuel is completely stopped. Remember that on the TS/ TD / TN and other T-series motors the low speed needle controls the fuel flow. At low speed the fuel bypasses the carb altogether and simply flows via the little Y-block in the fuel line into the crankcase, where it sprays into the compressed air charge in the crankcase and then travels into the combustion chamber later in the stroke via the 3rd port.


I have taken the liberty of including the 2 relevant pages out of the owner’s manual. It should help you understand what is going on.

 

[HighTrim]

Re: TN-28 won?t run w/o priming.

I have found 5/8 turn out from seated on that low speed needle about perfect on almost all of the TNs Ive tuned.

This may help as well

New Page 1

 

[burnt clutch]

Re: TN-28 won?t run w/o priming.

TN-25, thanks for the scans of the manual - I'll try it out after I put it all back together. The only info I have on these engines are what I've gotten off of the Poche family's webpages and the occasional threads over here, so any tidbits of info are a big help. I'm still worried about bad compression with the engine. Is there a way to identify a bad head gasket just from looking at it? I see some deposits on the top of the cylinder head that are tan/white colored and am wondering if that is a bad sign. Also, can I re-use the intake plate gasket if I clean the parts up? If not, where is a good source for the gasket?

-Karl

 

[burnt clutch]

Re: TN-28 won?t run w/o priming.

I went ahead and cleaned up the plate w/ 220 grit sandpaper. Should I try to clean up and re-use the gaskets for this assembly or should I make my own? I'm assuming they're probably no longer available due to their age. Thanks again,
-Karl