'80='81 Ignition Unit

[Dennyz]

I am working on a SG that does not run right. Upon further inspection I discovered it has a 2H7-10 ignition unit. I am sure this is the problem as it does not have adjustable timing on the pickup plate.

Does anybody have the correct ignition unit for this bike? I have a good '78-'79 ignition unit to trade.

[TopCatGr58]

Hey Denny,

IF your 80SG has cent. adv. weights, then the 2H7 IS the correct unit. You might not remember that the FACTORY put those fancy break off bolts on the timing plate so they could NOT be adjusted by the OWNER....EPA stuff , but it should still have the cent. adv. weights and vacuum adv. pot, so the 2H7 should work, but IT could be damaged?? Did you do any electrical diagnostics on the TCI or PU coils?? Only the 81 uses that 4RO TCI, but there are no cent. adv. weights/parts under the timing plate!

It might be cheaper to get the Cent. Adv. parts IF a PO swapped them for some reason, but I'm suspecting that you're seeing the locked/break off bolts of the 80!
T.C.

[Dennyz]

Thanks, TC. I think you are correct. I have spent most of XS time looking at '78/'79s. This '80 seems to have a little from all years on it.

[Dennyz]

OK, need some collective experience. What have I forgotten. This SG will start and run fine when cold. As it warms up it gets worse until it dies and then won't start. It runs on all cylinders (no cold pipes) until it dies. The bike acts like it is running out of gas, but it is not.

Fortunately I have an excellent running SF to swap parts with.

We have swapped:

TCI
Carbs (with Octopus and lines)
Tank & Petcocks
coils
ballast resistor
New Battery

We have measured and tugged on the pickup coil wire with no effect. We are getting ready to swap out the pickup coils (arg!).

This bike has the original fuse box, but can't find any bad connection.

[boyat68]

[Dennyz]

Hey boyat68, did you have a thought?

[Dennyz]

OK, changed out the ignition plate with pickup coils. No change.

[boyat68]

Dennyz:

Ii had said to swap tanks, but after re reading your post I found out you had already done this, so I erased, but it would not let me delete.

[TopCatGr58]

Originally posted by Dennyz
OK, need some collective experience. What have I forgotten. This SG will start and run fine when cold. As it warms up it gets worse until it dies and then won't start. It runs on all cylinders (no cold pipes) until it dies. The bike acts like it is running out of gas, but it is not.

We have swapped:

TCI
Carbs (with Octopus and lines)
Tank & Petcocks
coils
ballast resistor
New Battery
PU Coils

This bike has the original fuse box, but can't find any bad connection.

Have you tried running it on PRIME?
Are you using the Enrichener/choke to start and warm it up?
While warming, can you run it and rev it to a decent rpm?

Have you checked for spark at the plug wires once it dies?

Did you check the valve clearances? Long shot but if too close, might be expanding and then not allowing valves to close completely, loss of compression when warm/Hot?
T.C.

[Dennyz]

-Have you tried running it on PRIME?

Yep, on both tanks

- Are you using the Enrichener/choke to start and warm it up?

Tried it both way, no change

-While warming, can you run it and rev it to a decent rpm?

When it is cold I can run it up and down the drive way in all RPM ranges, but the longer I ride the worse it gets

Have you checked for spark at the plug wires once it dies?

Spark good, even when it dies.

Did you check the valve clearances? Long shot but if too close, might be expanding and then not allowing valves to close completely, loss of compression when warm/Hot?
T.C.

I adjusted the timing chain, re-torqued the head, checked compression. I am leaning towards the valves. The bike only has 19K on it (cherry SG). I have noticed that running a bit, the left side starts to pop out the exhaust, then the right side joins in and the motor stumbles to a halt. Could have some tight exhaust valves.

Valve check coming up.

Stay tunned...........................

[Ken Talbot]

Originally posted by Dennyz
What have I forgotten.

You probably haven't forgotten it, but you also haven't mentioned it specifically - tank vent?

Any chance it has E or F carbs with the upper vent hoses connected to the non-drilled nipples of a G or H airbox?

Rodent nest or plugged filter element inside the airbox chokinf off air supply - see also squashed snorkel?

[Dennyz]

You probably haven't forgotten it, but you also haven't mentioned it specifically - tank vent?
Any chance it has E or F carbs with the upper vent hoses connected to the non-drilled nipples of a G or H airbox?

Rodent nest or plugged filter element inside the airbox chokinf off air supply - see also squashed snorkel?

Good suggestions,

The air box is drilled out. It does have e/F carbs and matching air box. All vents check clear.

Valve check revealed 2 intake valve where pretty tight (around .125mm). Seems to run better now. Won't know until we get all the original stuff back on. We are replace one thing at a time and test running. The last things I want is to put everything back and it run like sh%$^.

[Dennyz]

Well, I am stumped. Time to step back, have a drink(s) and think about this.

I can hold the throttle (throttle lock) at 3k rpm and the motor will slowly die. Once it dies it will not start until it cools off.

maybe after some mind altering contemplation, the truth will be revealed.

[skids]

Check the plugs. As an engine heats up, it tends to run "richer."
It is either that, or as has been suggested, fuel delivery problem. Clogged fuel filter, clogged screens in the needle valve (I hate those) or a bad vacuum hose to the petcock or octopus.

Originally posted by Dennyz
Well, I am stumped. Time to step back, have a drink(s) and think about this.

I can hold the throttle (throttle lock) at 3k rpm and the motor will slowly die. Once it dies it will not start until it cools off.

maybe after some mind altering contemplation, the truth will be revealed.

[Geezer]

have you removed a drain plugs from the carbs when it dies to see if the carbs are dry?

The only other thing I can think of is theres some corroded connection somewhere that gets hot and fails. You wouldn't have to completely loose spark for it not to run. Check the resistance on the kill switch and the ignition switch.

These are only guesses but I didn't see them covered in the other troubleshooting steps.

Geezer