Timing issue?

[Stickler]

Hi everyone, iv recently had some free time and have been working on my 1971 4hp johnson(4W71D),what i have done so far is
-complete carb rebuild
-new head gasket
-new coils,points, and condensors
-new spark plug wires and boots as well as spark plugs(champion J8C)
-new fuel lines
When i did the initial timing i followed my manual procedure , checked for spark , alll checked out well so i re installed the fly wheel and set up the motor in my test tank.The reason i think it may be a timing issue is due to the fact that it takes up to 5 pulls usually to start it, idles nice,when i accelerate, the rpms dont increase like i believe they should be,(not a big difference)so i figured i needed to fine tune fuel delivery ,as it was not adjusted yet. I braught the motor to 3/4 throttle and turned the high speed needle in 1/8 of a turn and waited for engine to respond (RPMs should increase)but the motor doesnt react, so i kept turning the needle in and waiting ,no change, eventually it started to bogg out and i couldnt richen it quick enough to prevent it from stalling,when i tried to restart the motor it wouldnt go, i ran out of tinker time and had to leave at this point for the time being.
The throttle response , the hard starts,and lack of reaction to fuel adjustment is what leads me to believe it may be a timing issue,im not 100%, but it is somewhere to start, let me know if you think im on the right track or if there is something im overlooking , any suggestions are appreciated as always, Thanks again.
-Stickler

 

[F_R]

Re: Timing issue?

Timing is fixed within the range allowed by the throttle movement, and no adjustments are possible. What is adjustable though is the synchronizaton (link & sync) between the magneto and carburetor. It is somewhat complex, and must be done in the correct sequence.

What kind of test tank do you have that you are able to run it at 3/4 throttle? One would need a commercial tank and a test prop to do that. Is that what you have? If you are that sophisticated, you must know about the synchronization.

 

[boobie]

Re: Timing issue?

Will the spark jump a 1/4 " open air gap on a spark tester or did you just check it with the spark plugs ??

 

[Stickler]

Re: Timing issue?

What i run my motor in is a tire dunk tank that is 4ft long x 2ft wide x 2ft deep, the water level is just below the exhaust /water spit holes, i wasnt aware that you couldnt run it at that speed, seen people run them in garbage cans on the net at those speeds,but like i said the rpms are low so 3/4 throttle seems more like 1/2 throttle.Half the fun of this small motor for me is trouble shooting such things, and talking to people with a common hobby,im definetly no hot shot out board guy, and make no claim to such things , just learning as i go.when you say link n synk ,do you mean lining up the the cam on the stator with the cam on the carb, because what i did was line up the edge of the cam follower on the carb with the mark on the the throttle cam on the stator,( with the throttle in the stop position , then moving the throttle lever just until the cam contacts the carb cam ,causing the throttle plate to just open slightly, and aligned with the mark on the throttle cam). If this isnt the way to do it, i would like to know the procedure that you use,i could have done something wrong, like i said, learning as i go,thanks.
-Stickler

 

[Stickler]

Re: Timing issue?

Hi boobie,I did just check it with sparkplugs grounded out,had a good blue spark,and nice little snap, ill double check it with a spark tester( it is a more telling test) and post my findings when i do,thanks .
-Stickler

 

[F_R]

Re: Timing issue?

Sorry, I mis-read your question. I thought you said 40hp, not 4hp. A 40 would instantly empty a garbage can.

Moving on, it sounds like your motor is running on one cylinder. Try it with one spark plug lead disconnected and grounded, then the other one. Chances are it will make no difference with one grounded and won't run at all with the other one grounded---that is the good one.

Then troubleshoot the one that is not firing. Poor spark?? No compression??

 

[Stickler]

Re: Timing issue?

After i replaced the head gasket, i performed a compresseion test and had (95psi)in both cylinders so im confident with those numbers, as for spark, that is something i will check, i replaced the entire ignition system,including wires and plugs, i only checked the spark by grounding out the plugs and it had a good looking spark on both, but u never know right,something could be acting up.The reason i was suspecting ignition timing was because when i set the points i hooked them to a multi meter rotated the crank just until the meter read open circuit, indicating the moment they opend,then placed th fly wheel on the crank to check the aligning marks were close to centre, then repeated on the next cylinder. This was the first time i had done this on an outboard, and thaught maybe if for some reason they were out slightly(opening to soon or to late) it may cause this condition, but im unsure of the tolerances.Again thanks for the feedback,ill double check my spark,let me know if im thinking this through correctly or missing any details,Thanks again.
-Stickler

 

[F_R]

Re: Timing issue?

That is a valid way of setting the points.

You still need to do what I said and see if it is, or is not, running on one cylinder. Then you know where to focus your attention. Otherwise, you are guessing.

 

[Stickler]

Re: Timing issue?

You're correct , i will check to make sure both cylinders are firing and post my findings ASAP.Just a thaught , wouldnt u notice rough operation if one cyl was dead,especially considering there are only 2 cyl,just wondering because it seems to run pretty smooth,but on the other hand when the top cyl spark plug is removed it is clean, but the lower cyl plug was fuel fouled which adds up with your theory.Thanks.
-Stickler

 

[F_R]

Re: Timing issue?

You wouldn't be the first one to be fooled by that and you won't be the last. They will run surprisingly well on one.

Aha!!! Fuel fouled lower plug??? Isn't the fuel pump located on the lower cylinder? Prime suspect is the fuel pump diaphragm. Remove the pump, hoses attached, and give the squeezer bulb a pinch. If fuel comes out the back side of the pump, I have guessed correctly.

 

[Stickler]

Re: Timing issue?

So when the pump is removed the diaphram is visible from the back?,i will check this as well,i did remove the line from the carb and gave it a pull to ensure pump operation,and fuel came flying out with a good pulse,so with a small hole in the diaphram the test i did could still give me false indications. On the down stroke,the low pressure created causes the diaphram to flex inward , drawing in fuel through the diaphram, and fouling the lower plug,this is the theory ,correct? Ijust want to make sure im getting this correct,thanks for your replys (F_R ),appreciate you sharing your knowledge with me,most helpful.
-Stickler

 

[F_R]

Re: Timing issue?

As the piston moves up and down, it creates alternating pressure and vacuum in the crankcase. That pressure/vacuum moves the diaphragm back and forth, which alternately pulls fuel from the tank and pushes it on to the carburetor.

You can't actually see the diaphragm without taking the pump apart, but you can see the hole through which the pressure/vacuum pulses travel. The pulses are on the "dry" side of the diaphragm, the fuel on the other side. A hole in the diaphragm allows the fuel to get from the "wet" side to the "dry" side, and on into the crankcase.

Beware: Don't take the pump apart without the instructions to put it back together. It is possible to assemble it a dozen ways or more, but only one right way. Even with the instructions, it ain't easy.

BTW, I assume you aren't old enough to remember when fuel pump diaphragm leaks would fill the crankcase with gasoline on older cars, huh? Bet you don't remember when the fuel pump ran the windshield wipers either? Now you know how old I am.

 

[AlTn]

Re: Timing issue?

I recall well when the wipers ran off intake manifold vacuum, but never saw any that ran off the fuel pump, or if I did, I didn't know what I was looking at

 

[Stickler]

Re: Timing issue?

Hi everyone, so today i decided to re-check my spark, set air gap to 1/4 inch and pulled the rope,top cylinder nice blue spark and snap, bottom cylinder , absolutely nothing:facepalm:. I was a surprised only because after i installed the ignition system(all new parts) i had spark on boyh plugs,So off came the fly wheel ,about ten seconds in, it was pretty obviouse, the #2 cyl capacitor wire had been rubbed through,so when i first ran it, after replaceing the parts, it probably only took a minute or two to rub the wire through causing the capacitor to discharge at its nearest convenience. It didnt seem to damage any wire so i put shrink tube over the area and sealed it up,when i put the flywheel back on,turned it over and wouldnt you know it, nice blue spark jumping the gap. I didnt have the time to hook it up and try running it, but im expecting hopefully an easier start up, and better rpm range, as usual i over thaught the problem, and it turned out to be quite an easy fix. Tomorrow ill run the motor and adjust the fuel, hopefully with better results, ill keep u all posted on how things turned out, Thanks again.(Oh yeah,i did relocate the wire to prevent any more rubbing)

-Stickler

 

[boobie]

Re: Timing issue?

Re-read post # 3. LOL.

 

[boobie]

Re: Timing issue?

F_R, I remember the fuel pumps and the intake manifolds that ran the windshield wipers and neither was worth a s##t. I liked the hand operated ones they had on the Model A Ford better. Not much difference today where they now have a cell phone in one hand.

 

[Stickler]

Re: Timing issue?

Ha Ha ,i know, when i did check the spark it was after i replaced all the ignition components, checked by grounding the plugs and they both worked fine, everything looked clear of the flywheel but i guess not. i only ran the motor once after the ignition rebuild, and thats why it didnt cross my mind when i started playing with it again,and yeah, i feel like a dope:facepalm:

 

[boobie]

Re: Timing issue?

Don't feel like a dope. As Grandpa said " a man who doesn't make a mistake in a day isn't doing anything". Glad you found it. Bet you learned something tho'. Right??

 

[Stickler]

Re: Timing issue?

You bet, thanks for all the help everyone, i was just wondering, i have some carb questions ,but i dont know if i should start a new thread,or continue this one as it pertains to the same motor. Thanks

-Stickler