Purpose of condenser?

eyhonda · Post by **eyhonda** » Thu Jul 22, 2010 6:23 am

What is the function of the condenser? My missing problem came back and I traced it back to the condenser. When I put 12v on it momentarily and meter the condenser, it doesn't hold a charge. Also, I noticed a lot of spark happening at the points. That explains the weak spark. I know the condenser is fully discharged when the points are closed. When the points open and the plugs fire, there is an inductive voltage spike from the primary coil and the condenser (aka capacitor) charges slowly (relatively). The only thing i see it doing is suppress a really large voltage spike. But I'm not really sure what it really does from a birds eye level.

48lesco · Post by **48lesco** » Thu Jul 22, 2010 7:58 am

You got it right - the condenser absorbs the self-induced current in the primary coil as the field collapses. This reduces arcing across the points, and when the points close again, it adds back to the primary current for the next cycle. The secondary voltage at the spark plug depends on how fast the field collapses (how sharply the primary current is cut by the points opening). Without the condenser, the primary current would just kind of ramp down due to arcing (current flow) across the points. Also, the ability of the condenser to accept a charge depends on the case being solidly grounded.

eyhonda · Post by **eyhonda** » Thu Jul 22, 2010 8:36 am

Thanks for the explanation. I made the mistake of not using the ground strap. As you mentioned, it needs a good solid ground. I filed the mounting hole in the frame for the coil brackets. Maybe this is not good enough?? I think my motor is not grounded good. The ground strap is used to ground the motor to the condenser? At the battery, I connected the negative to the frame. I also rechecked the condenser at work with better equipment and the condenser is good.

48lesco · Post by **48lesco** » Thu Jul 22, 2010 12:22 pm

The ground strap grounds the condenser to the engine. The engine also needs to be grounded to the frame - I think the best is to strip the paint off of the inside surfaces of the upper mounts. The coils and brackets do not need to be grounded - just the condenser. The negative batt cable also has to go to a good ground (usually the inside of the left lower engine mount).

Just checked out your website - Cool!

Chuck

eyhonda · Post by **eyhonda** » Thu Jul 22, 2010 1:18 pm

Thanks, though I wish I had more time to update it. The build is more updated here under the restoration section.

I'm waiting on a set of Dyna coils before I put it back together. I'll make sure to make a solid ground to the frame and motor (via ground strap).

So my missing issue is more likely the ground strap but partially. It was only missing on the left cylinder. When I checked the spark out of the engine, both plugs had a small yellow spark. I'm thinking the coils are borderline weak (the left being worse). When I swapped the coils the missing followed the coil. That's one reason I ordered the Dyna coils. The other is I want a strong spark so as to eliminate one less weak point.

Hopefully my next report is a good one. Thanks for the help.