Bosch coil check

[JamesHorwatt]

Good evening all, I'm starting to think I have a weak on my 72 Berkshire 100 barnfind rebuild. set and checked timing 3-4 times, set points to .015 and and compression is 145psi. I place spark plug on head and kick it and it has little spark but looks weak to my eyes. install plug and nothing....no burp,fart,cough nothing!!!!!. would anyone have the values or resistance specs for the coil and its a Bosch ignition.

Thanks Jim

1975 175 Cross County
1972 Six-day
1971 Berkshire 100
Secretary Penton Owners Group.

[LeeBuff]

Do you have a good ground on your coil to the frame?  If its not grounded properly the spark will be weak.

Hope this helps, Lee

[Daniel P. McEntee]

Never underestimate the possibility that the condenser is bad. If it's old, they can go bad and I was told when I had to deal with this a long time ago on my 250 Husky that when they go bad they suck up all the voltage and send it to ground. Try replacing the condenser. I had a har4d time finding on at the time I was dealing with it but it did solve my problem, and is cheap. My thoughts at the time was that "these things never go bad!" but that isn't true and that's why they sell new ones!!
  Type at you later,
   Dan McEntee

[slvrbrdfxr]

James,
As Lee mentioned, check to be sure the coil has a good clean ground path coil to frame,  also where the engine cases meet the frame and between the point plate to the engine cases. I usually clean all these areas with a bonding brush and then use dielectric grease between the points of contact when installing the points plate, coil and engine. The dielectric grease not only provides a good solid ground path to the freshly cleaned metal parts but also helps these areas resist corrosion. As far as checking the Bosch coil, the primary winding usually checks at about 3 ohms and the secondary winding at about 7500 ohms. Another thing to try is to remove the spark plug cap from the plug wire and check for spark directly from the wire without the spark plug cap installed. If the spark gets better then I'd suspect a bad spark plug cap or it's possible that someone could have installed a resistor cap which isn't correct. If you do end up replacing the spark plug cap then be sure it's a non resistor type and I'd suggest trimming back the end of the spark plug wire by an 1/8" or so to expose some fresh conductors for the new spark plug cap to touch. Hope this helps. Good luck and keep us posted on your progress.
Dave McCullough

[JamesHorwatt]

Hello everyone, Well I checked my in question coil out today and as per Dave McCullough values mine was bad I had 2.5 ohms on the primary side (Good) and " get ready for this " 1.3 Milliohm's the secondary side (Bad)should be 7500 ohms. Luckily a friend ( not a Penton guy) had one laying around his shop...Cleaned off all the old dirt and have great grounds all the way around and best of all a very big spark. running out of time tonight to recheck timing, maybe tomorrow. Also whats with moving the points opening mark on the flywheel a 1/4 to the right of the former mark?

Thanks Jim

1975 175 Cross County
1972 Six-day
1971 Berkshire 100
Secretary Penton Owners Group.