Faulty points??

[timtune]

I was using a battery powered light and alligator clips to do a static timing check. The light was dim until the points closed and then it got bright. WTF??
When I checked with my multi meter from the point lead to the base plate I was getting about 6 ohms (meter set to 200) with the points propped open. Both sides (1976 CB750F). I expected zero continuity.
Pulled them apart and they look good although the small insulator that keeps the bolt from contacting the metal is rather chessy.
Bike runs ok but top end seems just a bit lethargic.
These were brand new points - aftermarket not OEM.
Not fully understanding the voodoo that is the condenser I unhooked that but still had voltage leaking through the open points.
Thoughts???

 

[GreyGhost]

Condenser should show as open circuit. Leaky condenser is no good. That is obviously not your problem. Open points leaking have to be through the backplate or wires. I am sure others with more experience will chime in.

Check your multimeter by putting leads together to make sure that it shows roughly zero (probably 1-2 unless you zero it out). Still not your problem but quick and easy check to help insure valid data.

 

[bitzz]

Connectivity from the points to ground is no beuno.
When the points open the ONLY path to ground has to be the plug, or you'll get weak spark.
The condenser is there to give the electrons somewhere to go the nano second the points open, as the condensor has less resistance than arcing the points, the condenser stores those electrons till they get dumped into the coil. The motor will run without one, it'll just burn the points.

 

[timtune]

So I must have a weak spark, yet the bike runs pretty good.
The only path to ground has to be through the points - brand new points. Arrrrrgh.

 

[GreyGhost]

So I must have a weak spark, yet the bike runs pretty good.
The only path to ground has to be through the points - brand new points. Arrrrrgh.

It shouldn't be the points. Find the electrical path. Maybe down through a screw? Maybe a pinched wire? Take out parts to find what breaks the circuit.

 

[Merkid]

Grey Ghost nailed it.

If bad points or weak condensor, your bike would feel like it is shutting down in a jerking fashion under various throttle positions due to intermittent spark.

If things get worse as the bikes warms up suggest you have a coil load tester handy as it would be worth seeing if the original coils are good.

As a side note, I picked up a '79 CB750 barn bike and I was losing top end performance and was convinced the coils were shot but it turned out to be dirty carbs.

 

[timtune]

The multimeter check shows continuity from the incoming lead to the base plate when the points are opened. I think the little plastic insulator caps at both ends of the bolt holding the lead are insufficient. Had em apart and everything looks fine but still they leak juice. I'm wondering if OEM points would be better insulated.

 

[timtune]

Ok so I dug farther and found out it's not the points - I had a "hot" line in my harness that was grounded somewhere. The points just happened to be where I stumbled upon this excess juice.
After unhooking just about everything I found out I have an issue with my regulator. Per the manual it's serviceable. I'll set the gap and adjust it, then see if I need to steal one from the "stash".

 

[timtune]

Ok so all three of the regulators I had lying about (TL1Z-38 is printed on the cover) show continuity between the green and black leads. So I assume that's how they are. As soon as I install them I will have power at the points again (with the key off).

Am I missing something? None of this testing has been done with the ignition on. Does turning on the key power this up and open it's internal points? Calling @bitzz
Regulator shown below.

Honda CB550K CB750K CB550 CB750 Voltage Regulator TL1Z-38 12V 1969 - 1978 | eBay

Find many great new & used options and get the best deals for Honda CB550K CB750K CB550 CB750 Voltage Regulator TL1Z-38 12V 1969 - 1978 at the best online prices at eBay! Free shipping for many products!

www.ebay.ca

 

[timtune]

Yup!! Add 12v to those two leads and the circuit opens.
Been chasing my tail for two days. Arrrgggghhh!