Need help with 1968 1.5 HP Johnson model SC-10S

[andreipou]

Hi, I got this motor (model SC-10S) after it was sitting 5-7 years in the basement.
It had good compression, so decided to fix it.
It did not have spark.
So, new coil, condenser, point, spark plug wire and plug..
Soaked and rebuilt carb with carb new kit, new fuel line.
New impeller.
That is like 3/4 of the motor is new now.
It starts with first pull and idles at 550-560 rpms as per manual.
Now the problem: when I start to move armature plate to fast it speeds up to about 900-1000 rpms and stalls.
Can not make it to run fast.
Any advice/idea why?

thanks.

 

[Vic.S]

Check cam and cam follower are opening the throttle valve correctly. I assume the cam will be marked where the throttle valve should just start to open. Should be fully open when control is moved to max position.

Is the high speed needle valve adjusted to the recommended initial setting? ( 1 turn out)

 

[Crosbyman]

old style carb going back to the 60's


idling sucks gas from the top of the carb so that works

higher speeds suck gas from the HS nozzle feed by the bottom HS needle.
Have you tried openning up the HS needle a bit left (counter clock wise) ?

Or... try closing the needle a bit in case it is open to much and floods the engine

 

[F_R]

Many of those old 1.5hps have rust and crud in the fuel tank. Does yours?

 

[Crosbyman]

anything simpler would be called oars...

check tank filter . float is not upside down is it ?

 

[andreipou]

Luckily , I have original service manual for this little guy.

1. Throttle follower was adjusted as shown on the pic1. I had to fill small dent on follower from cam with JB Weld to make it smooth and flat.
2. Carb was disassembled (including aluminum plugs) and soaked in PineSol for 3 days and blown with carb cleaner.
New gaskets, packing washers, needle valve, float, plugs.
Needle tips look good on LS and HS.
No visible crud was in the carb.
3. I took fuel tank off to blow fuel shut-off valve, net filter and tank. No visible crud was there.

Manual says to open LS 1&1/4 turn and HS 1/2 turn. I tied to increase/decrease those values, but the best idle was with recommended values. 560 rpms as per book.

I did not replace flywheel key , but it did not look worn or loose.

Not much left in this motor to play with....

 

[Crosbyman]

how is compression ? maybe crankcase vacum leak reeds ?

you can always sell it and get a nice 2 cyl JW

 

[andreipou]

Compression is 110 on cold engine.
Motor came with canoe I bought locally.
Considering its good condition, extreme simplicity and parts availability I expected it to be as easy as a "sneeze" to fix it.
I do have experience with OMC motors from 6 to 85 HP.
I had similar issue this summer fixing 1968 (cursed year?) 6 HP Evinrude. Turned out that carb was not original for that model despite it looked the same as in manual.
I checked this motor and it looks like everything is original. This motor contains like handful of parts total...

I will try to start over and do all steps again to see if I missed something...

 

[racerone]

Critters need homes.-----Did they build a nest somewhere ?

 

[andreipou]

in my basement

 

[andreipou]

Little guy is very stubborn.
Reset points to .02 instead of .022.
Spark jumps 1/4' gap on the tester.
Disassembled carb and blew with cleaner and compressed air.
Checked the float.
Set the follower as on the pic above.
Took the tank off and cleaned it , took the valve out , blew filter , put new 1/4'' gas line.
Checked compression again -115.
Starts and runs forever in START position.
Increases rpms if I turn lever until about 1/4 of distance between START and FAST position and stalls after that.
Pic shows position when it starts to die.

Can not figure what is wrong...
Any feedback will be appreciated.

 

[racerone]

Those run very well if everything is in order.----Mixture needles mixed up by any chance ?----Low speed needle tip twisted off by any chance ?----Gasket in place on the nozzle ?-----These motors need 4 things to run.------Correct amount of fuel.-----Crankcase compression.----Spark at the right time.------Cylinder compression.-----Should be an easy fix I say.

 

[F_R]

Check the magneto ground wire. It may be broken inside, making it lose electrical continuity when flexed. The mag needs to be grounded by wire because it is mounted on a non-conductive plastic bushing. Yes. I have seen it before on those particular motors.

 

[Crosbyman]

check for sparks (plug out and grounded ) across the whole range of the cam. spin it with a drill

....does it spark at all magneto cam positions ??? if OK the suspect a fuel issue then.

it is drowning or starving did you try to adjust the HS needle since LS does not seem to be an issue here. ?

did you remove the HS center pipe and clean out the small side holes that allow fuel to properly emulsify ?

fat donut installed ??

 

[Crosbyman]

see pics

 

[andreipou]

Check the magneto ground wire. It may be broken inside, making it lose electrical continuity when flexed. The mag needs to be grounded by wire because it is mounted on a non-conductive plastic bushing. Yes. I have seen it before on those particular motors.

I put jump wire in parallel and it did not help.

 

[andreipou]

Those run very well if everything is in order.----Mixture needles mixed up by any chance ?----Low speed needle tip twisted off by any chance ?----Gasket in place on the nozzle ?-----These motors need 4 things to run.------Correct amount of fuel.-----Crankcase compression.----Spark at the right time.------Cylinder compression.-----Should be an easy fix I say.

HS (right)
LS (left)

 

[andreipou]

check for sparks (plug out and grounded ) across the whole range of the cam. spin it with a drill

....does it spark at all magneto cam positions ??? if OK the suspect a fuel issue then.

it is drowning or starving did you try to adjust the HS needle since LS does not seem to be an issue here. ?

did you remove the HS center pipe and clean out the small side holes that allow fuel to properly emulsify ?

fat donut installed ??

will play with spark plug.

HS and LS needles turning did not do much.
HS pole was removed and cleaned with wire and air.
Donat installed as part of rebuilt kit.

 

[andreipou]

Plug sparks from max left to max right positions.

 

[Crosbyman]

your HS needle is very pointy... seems they are usually more blunt than that
certain it is the correct needle ? wild guess maybe

fat donut in place ?