Coil test

[petrolhead]

Er, I guess this is the right forum to ask this question. I recently acquired an old J.A.P. 34cc single cylinder 2 stroke engine, they were used on all manner of things especially lawnmowers, but also on a very unusual outboard called a Buckfast.<br />Anyway, I'd like to use this engine as it's in very good condition, the problem is it has no spark. I managed to find a new condensor that fits just to eliminate that possibility, and have also fitted a new HT lead. The points are good and have been cleaned and gapped, and the magnet in the flywheel appears to be OK, it's still magnetic anyway.<br />So what I want to know is how do I check the coil without using any fancy equipment? I have a very good multimeter.

 

[rickdb1boat]

Re: Coil test

This may work, using an Ohmmeter touching each side terminals looking for 0.75 to 0.81 ohm of resistance. Then go from the primary (Spark Terminal) to each small terminal, should read 10,000-11,000 ohms. If not within readings, replace.

 

[petrolhead]

Re: Coil test

I already tried that, the readings I got were 5.55 ohms and 5,240 ohms respectively which I thought seemed reasonable? But I know that getting good readings with a meter doesn't neccessarily mean it's OK as it can still be breaking down internally.<br />I know there's a way to test it by applying a voltage across the coil to create a spark, but I can't remember how to do it!<br />Replacement is almost certainly not an option, it's a very old engine and the coil is very specific, the chances of finding a new one are about zero, and a good used one not much better!<br />My only options would be to either have the coil rewound, or bypass the magneto and use an external coil and battery, retaining the existing points and condensor of course.

 

[force01]

Re: Coil test

petrol<br /><br />the only way to test it is on a coiltester the one we use is a ghram electronics but merc o tronic also makes one there are so many styles of coils available i think you will be able to match one up if yours is bad good luck bret<br /><br />If you need further assistance please email me @forcepower01@yahoo.com thanks,Bret

 

[BillP]

Re: Coil test

I took two old outboard coils to my local lawnmower shop and they checked them for free. The coils were 20+ yrs old. The motor wasn't getting spark so I automatically suspected them. I ended up tracing the spark issue to incorrect connections by the previous owner when he was diddling with it. The funny part is the owner sold it to me cheap because it had no spark.

 

[rickdb1boat]

Re: Coil test

Great idea, Bill! Lawnmower shop!!

 

[petrolhead]

Re: Coil test

That's a good idea, I have a lawnmower shop nearby who often has some very old machines, now why didn't think of that?<br />BTW, I found out how to test the coil at <br /><http://www.steamengine.com.au/ic/faq/testingmagnetocoil.html>, haven't done it yet though, I may let the shop try it first and see what they say.