Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

The first condenser was the one that was in there when I got the bike about a year and a half ago. I was having a different problem and someone suggested changing the condenser so I bought the one that Treatland recommended for this engine type and put it in there. When this new problem arose and someone suggested it might be the condenser I put the old condenser back in and it performs exactly the same as with the newer Treatland condenser.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

Here’s a pic of the spark when the engine is cold. It flutters from whit to blue/purple, but is mostly white.

1CB67055-D31A-462C-8829-0F6D1898A35E.jpeg

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

Here’s a picture of what the spark looks like when the engine is hot and will not start. It is mostly always blue/purple. When the engine is cold the spark flickers between white and blue/purple. When it’s hot it’s almost always purple/blue and not quite as bright as when it is cold.

592C802F-6302-44F1-8929-6F796D459ADC.jpeg

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

Could be your first coil or the ht coil.

I had something like this happen last week but the coil finally shit the bed will on the work bench & I couldn’t even start the bike.

You should try just spinning the magneto over a few times without the bike running and see if the spark plug starts to act up. You could ride the bike around lightly not letting the temps run high then rapidly cool the bike with fans and see if the spark is acting the same.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

Dan (high idle) Conway /

I'm gonna say it sounds like an ignition coil issue too. Had a very similar problem on a hobbit recently, drove me nuts lol.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

How old is that plug?

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

♣Slew Foot♣ /

Bypass the high-tension coils safety feature by grounding the tail light to the frame and running the blue return wire write the frame as well from the Magneto also have a ground strap because the sax has rubber bushings

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

could it be as simple as the breather in the gas cap is clogged? try cleaning the breather out on the cap or try running with the cap loose for a bit to see if that helps.

I had that issue and there was negative pressure created - not allowing enough fuel into the carb.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

is it hard to take a picture of spark?

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

Seems most folks think it's the ignition coil. Is there a way to test the one that's in there before replacing? Thanks!

To answer some of the questions posed/suggestions of things to try:

@themotorhead

The plug is a little less than a year old.

@ggspeed

I took a video of the spark and then grabbed a screenshot of the frame with a spark.

@curlyt

I blew through the hose and it wasn't clogged. Also, when it's hot, I can flood the carb using the fuel tickler and it still won't start.

@thewhitedog

I'm down to try what you suggest, but I'm not sure I clearly understand your directions.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

If I test the ignition coil and it's kaput, maybe I should throw this in there?

https://www.treatland.tv/puch-bosch-style-MEGA-UPGRADE-COIL-PACK-p/puch-bosch-coil-mega-pack.htm

"this is a superior 6v high tension coil party for that spark in your life you've always been waiting for! comes with 2ft of the best 7mm plug wire, bosch style HT coil and genuine ngk boot hundreds of times better than your shoddy old plug boot.

its such a basic important part of your ignition system why not go with a nice little upgrade!!!

this can be used on pretty much any 6 volt points ignition as well. this is identical to the ones found on all stock puch bikes! except better with updated / modern / higher quality parts."

puch-bosch-coil-MEGA-PACK-2T.jpg

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

First pic of spark looks good.

Second is questionable.

On my phone in "comfort view" it filters out the most all the blue so that the second pic looks mostly orange with a hint of blue while first pic still looks strong and white.

Change the plug first. Its like $3

Then look at the High tension coil.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

♣Slew Foot♣ /

Did you ever buy pass the safety on the HT coil bye we running your tail light return ground to the frame and giving it a ground strap if it will start right up with the front brake lever held in it might be the safety on the high tension coil the ceramic resistor hidden inside the tail assembly could be heating up and then it would separate and break contact and then give it the appearance of a bad condenser but really it's the tail light being wonky

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

I was having electrical problems last year, it turned out to be an aftermarket tail light (Sachs w/ burnt out tail lights kills the ignition). I replaced the taillight and made sure all the wiring was up to snuff last year. I don’t suspect it’s the tail light again as this is a good taillight. And I don’t know how that would only be a problem when the bike was hot. But maybe I’m not understanding it?

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

♣Slew Foot♣ /

Well just to eliminate that as being a problem just rewire it so you buy a pass the break return ground going to the Magneto from the tail light and run a ground strap from the engine to the frame. It could be a wiring problem anywhere in the circuit so it could be a bare wire inside of the frame where it runs from the wheel

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off.

Losing spark when hot...

Spark plug resistor not good (should not have a R plug if you have a antiparasite cap)

Antiparasite plug cap resistor kaput (run without one or get the NGK 5Ω replacement)

Condenser no good (replace with external one not the soldered one, remove it)

External coil (either 1 & 15 wires switched or internal wire damage)

Exciter coil (tired from overheating - time to replace)

AND

" Not condenser " I suppose means you replaced the condenser, which could be factory defect OR already heat fatigued from soldering... try a external condenser perhaps...(edited)

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off.

Yep something electrical as mentioned by RB.

More obvious with blue filter on.

Screenshot_2019-07-13-22-00-28.png
Screenshot_2019-07-13-22-02-31.png
Screenshot_2019-07-13-22-15-35.png

(edited)

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

no guarantee that you are getting spark under compression, or strong enough - not only looks weak when hot, but DIFFERENT = good variable to chase.

try an inline spark tester.

+1 for primary ignition coil or HT coil

swap known good components until problem goes away.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off.

♣Slew Foot♣ /

Like I said bypass the safety just to rule it out and you know what it could be just that your cylinders oval and when it heats up you lose compression I would take the Piston out and look for Blow by

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

Blaine- The artist formerly known as Plumber Crack "(OFMC)" /

Replace the spark plug.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

Not sure if this has been said, but my Garelli did the same thing and the culprit was the clutch rubber. Replaced it and now it runs for hours.

Re: 1979 Sachs Prima G3 dies when hot, won’t restart until cooled off. Not condenser

It was the HT coil! Swapped it out and it’s been running great ever since.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account