1959 35 hp johnson Model #RDSL-21

[shipwreck]

1959 35 hp johnson Model #RDSL-21

Just pick this motor up, has compression release valves on the head.
What should the compression be if has release valves? The standard 120 psi -down.

I am get 60 psi one number one and 30 psi on number two.
I poured a little oil into the cylinders and pulled thru 10 times
then retested still same.

I pulled the engine apart to check ring end gap #2 .029 and 1# was .020
Manual says .017" max. End gap

Then i measured the bore each bore in 5 different spots #1 3.0614 #2 3.0625
manual says 3.06

I bought this motor for 15.00 bucks with the thought that would not be rebuildable but with rings seem to be the problem and have the tools i need to rebuild , i may give a try. just a few question

Questions: What should the compression be if has release valves when trying to pull a compression test?

What are the valves near the spark plug with the spring on them i can't find anything about them in 3 manuals i have?

Does any one have a parts manual for 1959 35 hp johnson Model #RDSL-21 in (pdf) the want to trade , i several parts manuals to trade.

 

[tmcalavy]

Re: 1959 35 hp johnson Model #RDSL-21

The spring valves near the plugs are the compression release mechanism, should be connected to a flat bar that goes up/over/onto the top of the recoil mechanism. Good compression is 100+ per cylinder, with no more than 10% difference between them. Stout old motors, the Johnson RD's, easily rebuildable if not too corroded.

 

[shipwreck]

Re: 1959 35 hp johnson Model #RDSL-21

Block and heads are in good shape.
Piston look good too.
Compression seems real low for just bad rings.

Is there anything special thanks need to be looked at on valve compression release as far as adjustments ?

 

[tmcalavy]

Re: 1959 35 hp johnson Model #RDSL-21

You set the compression valve clearance with a feeler gauge, but I forget the number. The guys on the Ask A Member board at www.aomci.org will know for sure. That's all the adjustment possible, except to make sure the grooves in the top of the recoil are clean where the compression release bar rides/sits.

 

[F_R]

Re: 1959 35 hp johnson Model #RDSL-21

Those compression numbers are way too low for the ring and bore measurements you quoted. Something else is wrong here.

You have to disable the compression relief to do a manual compression check. Just remove the two screws from the flat bar and remove it. The clearance is .018-.025". Anyway, it is not critical at all. Just so there is some clearance to ensure the valve reliably closes completely.

 

[shipwreck]

Re: 1959 35 hp johnson Model #RDSL-21

no i did not check that way FR
compression seem pretty low for just rings
The seals at top and bottom of crank shaft plus o-rings are in bad shape .
The rings end gaps on #2 are way out .029 should be .017 max
both bores where excellent shape where not out round and again where book spec for model and year.

FR is the compression 100 psi with valve release in place right?
also if manual check in done would would normal compression be?

 

[F_R]

Re: 1959 35 hp johnson Model #RDSL-21

OMC never did publish compression numbers. But I'd say if you are getting 100+ and equal, it is fine. However you originally reported 60 and 30. Way, way off, even with worn out rings.

Are those compression relief chambers burnt (paint)? That is a sign of the valves not closing. And if the heat destroys the gaskets, there goes your compression.

BTW, your accurate measurements of the bore sizes tells me that you know what the heck you are doing. Or at least have great tools.

 

[BoatBuoy]

Re: 1959 35 hp johnson Model #RDSL-21

shipwreck, when you pull on the rope starter, the arm actuates the comp. relief valves and opens them. If you use the electric starter, the valves are not opened. So, when doing the compression check, use the electric starter or, disconnect the compression relief arm as FR said and use the pull starter.

 

[shipwreck]

Re: 1959 35 hp johnson Model #RDSL-21

Roger that , i will check with the bracket for the valve compression release disabled and pull rope ( start missing- was stolen) with five pulls

thanks all
ps FR__ I will check the for burnt paint.