Johnson TD Project

[adam1961]

I have decided to pick at a TD that was given to me. I have never looked at a TD or TN series motor in much detail, so though that it would be a good motor to learn on.
I have read the service manual and understand the carbureation setup. That seems to be the most unique feature. I have noticed that the engine pulls over with more resistance that a CD 5HP or other similar sized engines. Compression was 60psi on both cylinders before disassembly. The crank does turn freely when one piston is near TDC and the other BDC. I have removed the powerhead to confirm that the lower unit was not causing the resistance. I pulled the head to look at the cylinders and they look OK. The resistance seems to be caused by crankcase compression when both pistons are covering the ports. There is a noticable release of air when the first set of ports are exposed. I have never worked on an alternate firing engine that uses the 3rd port design. Is this normal?

[aquasonic]

There is a different feel to a TD than the later CD or Fisherman Models. The TD has a little more of a “thump” feel to it when the compression is released. If the motor has one of the factory wire core pull cords, as opposed to a nylon replacement, then the effect is even more pronounced. Hopefully there is no issue with your motor.

• This reply was modified 5 years, 1 month ago by aquasonic.

[frankr]

TD has the old style starter with smaller pulley than the CD ’56-up that has the large elliptical-shaped pulley. Short story, TD pulls harder.

60psi compression is low.

A puff of air is normal when the ports open. In fact, it is necessary.

[PAUL PENDERY]

I have a Johnson TD20 and spent a good deal of time on it this last year. Solved spark and carburetor issues (I think) but still can’t run it at low speed. Found compression is only at a little over 60 PSI in both cylinders. Is the most likely answer for inability to run at idle speed then the low PSI, and thus at least a ring job? Is there any chance it could be the low speed jet is clogged and low PSI is ok? One more bit of info, The motor seems to react accordingly to adjustments in the setting on the low and high speed valves.

Thanks!

[Buccaneer]

PAUL PENDERY wrote:

I have a Johnson TD20 and spent a good deal of time on it this last year. Solved spark and carburetor issues (I think) but still can’t run it at low speed. Found compression is only at a little over 60 PSI in both cylinders. Is the most likely answer for inability to run at idle speed then the low PSI, and thus at least a ring job? Is there any chance it could be the low speed jet is clogged and low PSI is ok? One more bit of info, The motor seems to react accordingly to adjustments in the setting on the low and high speed valves.

Thanks!

My best idlers in the TD and HD series Johnson are the ones with the compression
close to, or above 70 psi compression. Doesn’t sound like your low speed circuit
is plugged. A ring job may help, depending on the overall condition of the cylinders,
pistons, etc. Make sure your current rings aren’t froze in their grooves first.

Prepare to be boarded!

[lloyd]

Buccaneer has covered it. They need 70-75 psi to idle nice. Highest I have ever measured on those models is about 77 psi. And as he stated, make sure the rings are not stuck from sitting a long time. Use a lot of penetrating oil and warm up the block while rotating the crank forward and backwards. This may free the rings without disassembly.

[adam1961]

Hi Everyone,
Thank you for the input. I am going to disassemble the motor to hone and install new rings. I will get to that as soon as I get the carb rebuilt. I have spark, but will replace what look to be the orignal condensors.

Lloyd,
Do you have the primer seals available for these? I pulled the primer out and it looks like part of it is still stuck in the sleeve. I need to look at the manual again and see exactly what came out and what is still in there.

Adam

[lloyd]

Yes Adam. I still have a limited number of Primer Seals that come with complete instructions and diagrams to replace them. Getting very hard to find the proper oil tanned leather to make more. You will surely need them for your motor. Send $10.00 (cash only, no checks) and a SASE (self addressed stamped envelope) to Lloyd Lautner, 9289 North Long Lake Road, Traverse City, Michigan, 49685. Sorry if this sounds like an advertisement, but you asked, and I tried multiple times to post a classified ad on this new website without success. Good luck and have fun!!

[crosbyman]

ADAM… DO YOU HAVE U.S. STAMPS FOR RETURN SASE…. 🙂

Joining AOMCI has priviledges 🙂

[Eric McNett]

Some of the best motors built, had a 48 TD20 idled down real nice with out anywork. Do miss that motor, have a 49 td20 under resto and a mint 52 TN27 ready for new ignition and water pump.

Eric McNett
Seattle AOMCI Member

• This reply was modified 5 years, 1 month ago by Mumbles.

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