TOPIC: '68 Johnny 20hp Questions

I'll start by apologizing for the length of this story but felt I need to throw it all out there to eliminate any questions that I have already covered.

I picked up a 1968 Johnson FD-20M recently for a good price. Previous owner said it was his grandpa's and sat for many years. He replaced a bunch of stuff..... points, condensors, coils, fuel pump, carb kit etc. but said he could not get it to start. For the price I took the chance.

As soon as I got it home the first thing I noticed was the female fuel line connector was missing and the spring holding the shift lever was gone. Next I noticed that someone had reefed the throttle handle too far and it had jumped a tooth into/past WOT position and now into the flat spot on the gear with no teeth. Next pulled the cowl and see that the metal cover over the carb throat(with silencer or whatever in it) is missing.

Checked compression first and it was good----110-115 on both cyls.
Checked spark....good on both plug wires.
Hooked up fuel line directly to fuel pump and when I squeezed the ball it was leaking at the pump(more on that in a minute)
Placed it in a barrel and began the process of probably tearing my rotator cuff pulling on it. No start.
Checked the idle needle and it was about 2-3 turns out. Reset to a little over 1.
Squirted some premix in plug holes and she fired right up.

It ran decent at a high idle but was bucking and coughing like heck when I started to throttle down and would soon die a violent death.

Played with the idle setting and it would seem to get where I wanted it....ie RPM's would increase and level out so I slowed throttle but it again started bucking like it was too rich. Just could not get it correct. Suspect timing/synch out on cam follower setting. Manual says cam roller should be in between two marks before any advance begins on throttle. It starts to advance well before it gets to the two marks. There are adjustment screws under armature plate but I have set as far in as I can. Maybe it is not the issue. Other thoughts...I have also noticed that there are supposed to be two packing washers or whatever on the idle needle but I only found one on mine. I cleaned carb and checked adjusted float level and drop etc. Float is newer black composite and bowl gasket is brand new I see. One thing I don't see that I expected was a small clip holding the needle to the float arm....is there supposed to be one? Guess I will order a new carb kit. I am also wondering if the missing plate/silencer/cover on the carb would affect idle?

Now back to the fuel pump. I know that it is brand new as the guy gave me the oem box with the old parts pieces in it but I cannot stop the leak. I have disassembled and reassembled a few times and am wondering if I have all the pieces together properly. I fear that these fuel pump assembly's are not serviceable because I cannot find any detailed diagram of the pump internals and only find the following which is no help:


***UPDATE*** I did just find a great explanation on rebuilding these fuel pumps:
www.leeroysramblings.com/Rebuilding_fuelpump.htm

Thoughts and ideas are greatly appreciated. One last lingering question...how does the spring actually attach to the shifter arm?

Thanks,
Tim

The "gear jump" on the throttle handle may explain the mag cam/ throttle sync issue. If you can remove the tiller, move the mag cam to the roller marks, twist the tiller to the "start" position, and reinstall the tiller. If things are off a pinch, readjust the cam afterwards. This will get the link and sync issue done. Where is the fuel pump leaking from? If the diaphragm has a pinhole in it, it may allow fuel to enter the crankcase and upset the fuel mixture, and give little to no fuel flow at low speeds. The carb is also suspect. The missing silencer should not be critical, but may affect fine tuning once the other issues are found and fixed. Not sure about the shifter, but hope this helps a bit. Good luck.

Thanks for the ideas Kerry.

I have the fuel pump issue fixed thanks to LeeRoy's ramblings....a great site full of info...especially this fuel pump rebuild.

As for the wrong positioned throttle handle... I don't think that it is the cause of the mag not being positioned correctly. I can advance the throttle(and hence the throttle plate across the cam follower wheel fine all the way thru the slow to fast range. It starts pretty easy even cold and runs well on fast idle....at this point the cam roller is in between the two marks on the plate. When I reduce throttle it immediately starts to buck and cough no matter what I do with the idle screw.

Am I correct in reading that the cam roller should be between the two marks before it starts to open the throttle on the carb? If so it is opening it way before that and hence the fast idle when in between. I'd like to sort this out first and then get onto looking into it being a carb issue.

Thanks
Tim

From STOP on the grip, slowly advance the throttle until the cam FIRST TOUCHES the roller. The two marks on the cam should line up with the roller. If not, adjust the cam. This is the point that opening the throttle any more will also open the carb butterfly.

Should have read your response better. The roller should NOT open the throttle before the marks. The tiller gears only move the mag plate, the cam moves the throttle. The tiller gears are off. Sync the cam and carb roller like I posted, remove the tiller, set the grip to "start", and reattatch the tiller. The mag plate is your timing, so ignition timing is WAY off the throttle setting. Realigning those gears on the tiller should solve the running issues.

Thanks Kerry....yesterday I found out how the only way to get the synch adjusted properly as there was no more room using the screw on the cam under the plate. I loosed the nut on the throttle arm which allowed the throttle butterfly to close completely...I then adjusted the cam to have the roller lined up between the two marks on the cam and them lifted the throttle arm moving the roller to touch the the cam and tightened the screw while holding it. Now the cam will travel to the marks before engaging the throttle...as it should.
As for the throttle handle....I always know where I am by watching the cam on the roller but would like to get it fixed properly. The problem is in the gears between the pilot shaft on side of motor moving the cam and the rod/gear being driven by the throttle handle.(the one after the elbow). I need to figure out how to remove that rod to reposition the gear mesh correctly. I will figure this out in time.

BUT...this right now has nothing to do with my idle issue. Even though I have the cam advance corrected...it will still not idle. It has to be in fuel delivery and I think it is possibly needing the proper packing on the idle needle. I am going to get a rebuild kit soon and am tearing the carb off again in prep for a complete R&R.

Anybody have a picture of a late 60's tiller OMC showing how the shifter arm is held by the spring(which I am missing)?

This may help a bit. web.ebscohost.com/serrc/pdf?sid=736f789d-8371-46ff-a73e-d4d378420151%40sessionmgr15&vid=5&hid=17

Thanks again Kerry... that is a different version that I have already but the diagram is the same and I see the spring for the shift rod but can't really tell where exactly it connects?

I will pour thru the rest of it to maybe figure out my idle issue.

Tim

I am now officially out of ideas. I removed the carb again and purchased a rebuild kit. Cleaned everything really well(again) and replaced the needle/seat/spring/float and pin/welch plug,all packing/washers in high speed nozzle and low speed needle. Verified float level and drop etc.

It will still not idle below say 2-3k rpm. It has to be the timing/synch. All of the manuals I have say that it should be adjusted so that the cam roller just engages the throttle when it is between the two marks on the throttle cam. Well...it is engaging the throttle already as I have to move it to lower the armature plate back onto the flywheel. By the time it gets to the marks the throttle is 1/2-3/4 open. I can only see one place to adjust. There is no way to adjust the throttle arm or Cam Roller arm. Only place is a screw on the cam where it connects it to the armature plate and I have it set in as far as it will go as you can see here in this blurry picture:


Also notice in this picture that the cam roller has a line lower on it that indicates that it at one time was riding much higher on the cam.

Scott are you out there? I bet you may have an idea here. I am really stuck.

Im thinking 2 things, reed valves, and crank seals. upper and or lower.
if the reed valves are rusty-bent-somthing stuck in them , that would cause this idle issue. crank seals would let intake air in leaning out the mixture. fire it up put your hand carefuly in front of the carb. if it spits or you feel air or fuel mix comming out ck the reeds.

Im thinking 2 things, reed valves, and crank seals. upper and or lower.
if the reed valves are rusty-bent-somthing stuck in them , that would cause this idle issue. crank seals would let intake air in leaning out the mixture. fire it up put your hand carefuly in front of the carb. if it spits or you feel air or fuel mix comming out ck the reeds.