90 Wiring/Spark

[subrew]

I'm putting a 90 back together, and have what are no doubt some basic questions about wiring it up.  This is going to be a little cafe racer build, so for now I have no intention to have functioning lights.  I just want basic ignition.  I have the wiring diagram from the service manual, and the harness from the stator is intact.  I also have the coil.  I understand with a magneto system I don't need the battery for the ignition side to function, which is how I have several old pushrod Honda 50s wired up and functioning.

Looking at the diagram, it appears straight forward.  Black wire from stator to a switch, through the switch to the black wire off the coil.  Then the green/white wire from stator to the green/white wire off coil.  It also appears as if the switch needs to be grounded.

I get zero spark.  Whether I ground the switch or not, or have the switch "on" or "off".

I have cleaned and set the points, which actually look fairly fresh.  It also has a good plug. 

As luck would have it, I've never had to deal with a bad condensor, or bad coil on any of my other project bikes.  So I lack troubleshooting knowledge in testing those components.  I have various multi-meters, but frankly am having a difficult time understanding exactly how to check the operation of these components.

 
Any hints on troubleshooting this rather basic circuit/components?

I'm also curious if just switching to a 12v battery ignition as outlined in the 100 hop-up manual is a good solution.  I have plenty of 12v coils.

Thanks,

Chris H.

[reed]

Subrew
I would start by replacing the condenser and points first,they don't cost that much!
Then you can test primary continuity 2.5 3.00 ohms and the secondary continuity
15.000 on the coil etc. In the workshop i have a condenser tester but it would be
easier to buy new as i said they don't cost that much.
Try Richard for your points and condenser first.
Many Thanks.
Steve.

[subrew]

Just thought I would post a quick follow-up.

Always go back to the basics!  While I was cleaning and servicing the existing stator assembly, I of course was lubricating a few things.  While I swiped a bit of emery cloth through the points, I didn't realize I was using a piece of emery that was dirty/wet with penetrating oil. 

Tonight, I cleaned everything with contact cleaner, and made a final swipe through the points with clean strip of paper soaked in acetone. 

I instantly got a big fat spark at the plug. 

Since I also had fabbed up some quick jumpers at lunch, I decided to make sure I knew how to convert the bike over to a 12v battery ignition.  I wired it up per the hot rod manual, using a small 12v battery and 12v Bosch coil from my Formula Vee race car, and again got a nice big fat spark.

As a trick, to make sure I wasn't imagining anything, I swiped the old dirty emery cloth back through the points one time.  No spark at all.  I then cleaned the points with contact cleaner and the acetone soaked paper, got spark back.

Absolutely amazing how a bit of oil/dirtyness can affect points.

I am still going to get a new set of points ordered and assemble the spare stator I have.

Chris H.

[reed]

Subrew
Glad you have worked out your spark problem!
Nice job on the Bridgestone.
Thanks
Steve.

[subrew]

It runs!  A bit too smokey, as I had the tank coated with a thin spray of oil to keep off demon rust, but it runs.

YouTube        - running 001.avi

Still need to get a throttle assembly, fab up a rear brake lever, and a host of other small items.  But it is close to rolling down the road for the first time in a long time.


Chris H.

[mcseitz]

That Sir, is one good looking bike! I assume you are gearing the 90cc so it will break 100mph to comply with the spirit of cafe racing?

[OldSwartout]

That Sir, is one good looking bike! I assume you are gearing the 90cc so it will break 100mph to comply with the spirit of cafe racing?

It looks like there must be some really nice long steep hills around Chico.