Re: Johnson 5hp TD20 ignition timing facts & figures?

[legendre]

Hey Frank & All,

Correct me if I’m wrong, but this model lacks any type of conventional crank seals – yes? It must accomplish sealing by virtue of the plain-bearing bottom end & crank – only 0.0005"-0.001" clearance in the journals – which, in theory, is fairly well-stopped by oil in those tight spaces.

So unless the main bearings are loose (they are not) we need not worry about leaks between the two crankcases, or between the outer mains and atmosphere. So that leaves us with leaks to atmosphere between the joined case halves.. which I suppose might be a possibility. The POs did do some damage near the case parting lines (chisel / screwdriver) but I couldn’t detect any warping. For the record, I sealed the cases together with the Permatex "Ultra Gray" product, which is automotive OEM approved for gasket-less joints (Nissan / Honda / Subaru / Chrysler) and seems to be well up to the job – but I’ll take advice on that.

I did find a promising lead two days ago, but chased it down and got nothing. However, I’m using a new diagnostic tool for the ignition, and it seems that I just might have some spark issues with the lower cylinder. Changed the wire & condenser for that one, to no effect. Next I’ll change the coil and take a very good second look at the points.

And having spent time carefully listening to it run, I +swear+ this motor is dropping a cylinder when I try to take it below 1/2 throttle.. and that’s what’s killing the low-idle range. It starts to shake, sound and feel very rough, the exhaust note sounds off too..