JW Running on one cylinder only

[billy-t]

Hi folks

Well here is my issue, rebuilding yet another JW 1964 version I believe. Compression is 72 top and bottom. I replaced the coils checked the condensers and tested good and cleaned and regapped the points.

Used new ignition wire and new spark plugs. In line testers show spark on both but when I fire it up in the tank running on bottom only. So pulled it apart again replaced the coil with another new coil checked the points, checked for any potential shorts and couldn’t find anything. Buttoned it up again and still only running on the bottom cylinder.

I guess my next move would be to replace the points on that one cylinder only thing that hasn’t been ruled out completely.

Anything else that i might be overlooking on this one?

Thanks for your time

Bill

[frankr]

So, does it have spark on the top cylinder while it is running? If so, you might consider a broken reed (rare).

[aquasonic]

Try swapping the condensers, or better yet, replace the top condenser. Condensers can have the correct capacitance reading, on a meter test, but still fail under load. They can also work intermittently.

[billy-t]

Thanks for the responses.

I did swap out the condenser when I changed out the coil.

At first for spark, I was using the neon in line testers and would get indication of spark on both cylinders, but when I used the spark gap tool I was getting no spark on top and healthy big spark on the bottom.

I will swap out the points and see if I have any luck. Hope it is not what Frank suggested… Though it doesn’t seem to have any spark on the top when running. When running and I ground out the top it keeps running but when I ground out the bottom it dies instantly.

Likely still an ignition issue.

Thanks for your time

Bill

[billy-t]

I just checked the coil I changed out with a multi meter and got the following

0 ohms across the primary

and 4.55 ohms across the secondary

Which should be okay I think?

Bill

[frankr]

billy-t wrote:

I just checked the coil I changed out with a multi meter and got the following

0 ohms across the primary

and 4.55 ohms across the secondary

Which should be okay I think?

Bill

With this new info, forget what I suggested about the reed.

Around an Ohm would be normal on the primary, however many multimeters cannot detect such a low reading. I say you probably are ok.

[billy-t]

Thanks again

[crosbyman]

secondary is 4.55 Kohms (4 thousand + 555 ohms) if you are reading 4.55 ohms coil is bad

Had identical issue on a non shifting 5hp… drove me nuts….. to this day I am not certain what it was…..

you have only one option…

take all known good cyl gear ( points, wire, condenser,plug ) put it in the bad cyl circuit and it should fire

if ok you have a bad or two bad or three bad components begin swapping

Joining AOMCI has priviledges 🙂

[billw]

With the wires disconnected at the points, test the points for continuity. If you have an analog (old fashioned, sweep-hand) meter, make sure you zero it out, first. When the points close, there should be ZERO ohms resistance across them. Even ONE ohm or higher, is a problem. With the points open, there should be infinite resistance on the high ohms scale. Any meter fluctuation is a problem.

Like Aquasonic said, unless you have a honest-to-goodness magneto analyzer, Like a Stevens or Mercotronic, you can’t really test condensers fully. They are cheap money and a good investment. It is really best to replace them, or you may end up flogging this problem for hours and hours.

Long live American manufacturing!

[billy-t]

Thanks again for the suggestions.

I am fortunate enough that I have been gifted a merc-tronic model 79 ignition tester from a small engine mechanic buddy who doesn’t work on “any thing that #@$% old”. LOL

I have four new OMC coils and they all show the similar readings off my multi meter which is not a real expensive one, but I am assuming that they cant all be bad and if the are all reading 4.75 across the secondary that that should be okay.

I will remove everything from the top cylinder and replace the coil condenser points and wire and see if I remedy the issue.

As the old saying goes, “there is no job that is so simple it cant be done twice”

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