Lack of (no) spark 78GS1000

[petersenj20]

I spent all day Saturday trying to diagnose a no spark and gave up for beer. Not worth recapping.

Back at it today and find 1 and 4 (same coil) both have spark-White wire to the points.
2 and 3 plugs (same coil) do not fire-Black/Y wire to the points.
12 volts from Black/Y and White wire as they enter both points sets.

I swapped the White and Black/Y coil primary wires and swapped the problem so both coils work.

The points the white wire enter, spark as they open and close. The other points do not spark even though they have voltage. Supposed to be a new set of points when I bought it (owner gave up trying).

I swapped the condenser from the white side to the other and still no spark. I swapped the condenser from the black side to the white side and no longer sparks.

Seems to me both the points and condenser on the black side are dead even though they are supposed to be new.

 

[rustybronco]

The points the white wire enter, spark as they open and close. The other points do not spark even though they have voltage. Supposed to be a new set of points when I bought it (owner gave up trying).

I swapped the condenser from the white side to the other and still no spark. I swapped the condenser from the black side to the white side and no longer sparks.

what no longer sparks?


hook up a voltmeter, one lead to the wire junction on a set of points, the other lead to ground. turn the key on and check the voltage while turning the crankshaft over by hand. the voltmeter should read near battery voltage when the points are open and near 0 volts when closed.

if the voltage never gets near zero, then you have either a maladjusted set of points, an improper point ground, contaminated points, or excessive pitting.

if the voltage stays near zero then you have either points that are not opening, are shorted to ground, or you have a condenser that is shorted. disconnect the condenser and re-check again.

if you have a bright white spark on a set of points, either it has a grossly pitted set of points, or a bad condenser.

 

[petersenj20]

I seem to have pinpointed the spark problem. I opened up the points gap to .023" instead of the manual recommended .013"-.016. Once I did that I started getting fire. I managed to get it to crank on SF. I was reading about the coil mod, but I am getting 12v already. Points are new to me. Any idea why they have to be that much of a gap to work for me?

Now no fuel. Today I finished rebuilding the carbs. The float bowls and jets were plugged shut and had gas that looked more like oil. Is there some trick to getting the airbox back in place. It has the right mounts but seems like the wrong box. I put pods on it for the time being.

It is very hard to start. I ran out of SF before I could really get it going. I checked the compression and got 1-110, 2-80, 3-80, 4-100. I forgot to test at wide open throttle though. Adding a bit of oil to each did not improve the numbers.

I am sure it has set for a while and hope once it is running and warmed up it will bring those to more respectable numbers. I can't seem to find actual numbers anywhere although 150 seems like what I am looking for. That and all within 10% of each other.

The real problem I foresee at this point is how loud it is. It has a 4 into 1 pipe with a big megaphone outlet and zero baffle. Sounds cool, but will have the law here at some point I am sure.

I have included a picture at this point how I got it. The seat is clearly the wrong one for the bike. I saw a cool one I am gonna try to make down the road. There are no turn signals on it and no front fender. The frame and suspension and everything else was blacked out. Maybe someone was trying to play.

I like the way it looks and sits. I think I will be pleased with this one.

 

[mike_of_bbg]

If you're planning to keep the bike for a while, I'd highly recommend ditching the points and going with a Dyna S ignition (~$130, never buy points again). Should work OK with stock coils so long as they're OK.

Those compression numbers aren't anything which would stop it from starting. And since you weren't holding WOT and the engine was cold there's not much to really glean from them. The rings will seat better after you get it running and ride it hard for a while. That variation and hard starting says to me...

Check the valve clearances. Check the valve clearances. Did I mention you should check the valve clearances?

 

[Big T]

Looks like you need to stop wrenching for a bit and read thru the BassCliff website. Use the list of common problems as your guide to gettiing your bike running

As for the airbox, post up a picture. Otherwise, how are we to know?

 

[rustybronco]

Is there some trick to getting the airbox back in place. It has the right mounts but seems like the wrong box. I put pods on it for the time being.

Having just had removed the carbs on my '78, I can tell you it will be a "pain" to re-install the carbs if your boots are old and hard. it's that tight!

 

[petersenj20]

I wish I could afford an electronic ignition. Not at the moment though.

Looks like you need to stop wrenching for a bit and read thru the BassCliff website. Use the list of common problems as your guide to gettiing your bike running

How do you think I learned how to rebuild the carb I have read and read and was time to start some work. I enjoy wrenching more than reading.

As for the airbox, post up a picture. Otherwise, how are we to know?

I'm workin on it. Don't bust my chops.

 

[Big T]

Well, I've got 2 78 airboxes, so I can tell you in a sec.(If I could see a picture)

You have to have the airbox in first and fit the carbs between the airbox and intakes. Hard boots on either side make this just about impossible.

And, I agree, ditch the points. My Dyna S has been going strong since the mid 80s

 

[rustybronco]

You have to have the airbox in first and fit the carbs between the airbox and intakes. Hard boots on either side make this just about impossible.

as an aside... any spare filter housings?