JLO/CUYUNA Spark Problems - Snowmobile Forum: Your #1 Snowmobile Forum

cmorlock · 01-15-2013, 11:33 AM

I am working on a '76 JLO/CUYUNA 440 engine with spark on #1 PTO cylinder only. I have changed points & condensors, then disconnected external coils. Then I hooked up a continuity light hooked from the blue wire leading from #1 points to the corresponding external coil & ground. As the #1 points start to open the light dims just as it should. When I try the same with #2 points blue wire and ground, there is no change at all. I have checked continuity on the 2black wires coming off of internal ignition coil to both points, no apparent break in circuit.

This is the typical BOSCH stator used on points type ignition of the '70's, with a heavy wire internal lighting coil on left and then 2 coils stacked on the right with ignition being the bottom coil and then a small lighting coil on top.

Can anyone let me know what could possibly be causing me so much grief in diagnosing why the #2 points/condensor won't generate a spark?

**RJ Gleason** · 01-15-2013, 03:02 PM

If you isolate the components, does it show proper function?
The other option is that the charge coil is shorted out.

The single large coil is the lights and the paired is the left and right cylinder charge coil.
Test each for continuity and resistance.

cmorlock · 01-15-2013, 05:19 PM

From my manual the single coil on left is lighting 120 W, the top to the two paired on right is also a small lighting 30 W and then the lower coil on right is supposed to be ignition which makes sense as this is the only coil which has wires going to condensors and points. The others have yellow and green wires which are supposed to be for lights.

If what you are saying about the 2 coils on right being 1 for each cylinder then I have been tackling this all wrong.

If I have been correct in what I think each coil does:

Tell me this, if I unsolder both black wires coming off of the bottom internal ignition coil from the condensors and test for continuity and or resistance any idea what kind of values I should expect?

Also is it possible the lead coming off top end of this coil which goes to #1 could be good and the lead coming off bottom which goes to #2 could be bad? I guess what I am thinking is the actually 2 separate windings in the internal ignition coil 1 to service each coil and points? Or am I way out to lunch?

I have to go out tonight but I look forward to your thoughts on this set of questions.

Craig

**RJ Gleason** · 01-16-2013, 07:11 AM

I might be incorrect as to your particular system, but most are as I described.
I have seen a dual output coil be good on one end and bad on the other. A continuity check would show this as it would be open. I do not have any Ohms values for those.

Old Man · 01-16-2013, 08:59 AM

I think RJ is right. This attached link to a JLO Service manual shows the magneto as he describes it.

http://www.vintagesnow.com/Engine_ma...F-440-3_SM.pdf

cmorlock · 01-16-2013, 05:02 PM

Could you fellows check out this manual:

http://www.vintagesnow.com/Engine_ma...F-400-6_PM.pdf in the CUYUNA/JLO/ROCKWELL list on Vintage Snow.

If you look at page 4 and the parts break down, you will see why I am confused. Item 6 is shown as 100 watt & 7 as 20 watt lighting coil. Item 8 is shown as ignition coil.

My engine is actually a 2F-440-7,8 or 9, but I am not at home right now to check for sure. I know from the manual I have (for '76 Massey Whirlwind made by Scorpion which this engine is from) the watt values of 6 & 7 are highter .

This leads to my current confusion about what items 6 & 7 actually do on my engine.

All thoughts and suggestions appreciated.

Craig