FZRSupport: the FZROnline Archive

I got a 1973 Kawasaki G3SSD 90cc 2 stroke that runs great for about 4 miles, and then it starts loosing power sharply until it won't idle anymore. After waiting 15 minutes, back to life she roars for another 2 miles, at which point it's second verse same as the first.

The best I can tell, the condenser behind the flywheel is getting too hot and shorting out. Sounds easy enough, except I can't pull the flywheel off. The two shops I've sent the bike to can't pull the flywheel off. The flywheel shaft is starting to mushroom, and I'm running out of ideas. I'm thinking about venting the flywheel cover, but that is less than ideal.

Someone either tell me I'm barking up the wrong tree, or give me a ladder . . .

The other option is your tank vent is plugged; as you pour fuel into the engine and empty the tank, air has to replace the fuel. If it doesn't, a vacuum forms which eventually prevents fuel flow to the carb. In the 15min or so of waiting, air slowly seeps into the tank, and the carb refills.

basically , you GOTTA get that flywheel off. Venting the cover wil just get you road grit in there tearing sh*t up.

At some point (probably last year) it is going to need points (and condenser).

It isn't going to get easier to get off as time goes by.

Penetrating oil, and heat, a QUALITY flywheel puller (think: OEM piece), and an impact wrench

I thought about it being the tank vent, but it's done this with the fuel cap off, so it's not a vaccuum issue. I was hoping for that. My puller is an OEM piece, but heat is an excellent suggestion. I'll probably work on this bike this weekend, I'll keep ya'll updated. Thanks for the guidance.

mk2davis wrote:I thought about it being the tank vent, but it's done this with the fuel cap off, so it's not a vaccuum issue. I was hoping for that. My puller is an OEM piece, but heat is an excellent suggestion. I'll probably work on this bike this weekend, I'll keep ya'll updated. Thanks for the guidance.

Yeah, get some penetrating oil in there-maybe let it sit overnight and then use a pretty pinpoint torch and heat the flywheel right around the crankshaft. You can do this with your puller installed and a bit of load applied on it. You will likely hear a "tink" noise when the bond is broken between the crank and the flywheel

The shops you dealt with probably didn't want to risk cooking your crank seal...and you MAY cook it yourself. It will be pretty cheap, and fairly easy to replace from the outside and will be a small price to pay for being able to service the points/condenser.

If you DO replace the crank seal, good idea to squirt some of your favorite two stroke oil into the bearing when the seal is out. If the heat gets the seal, it will also have dried the bearing out.

Well there are a couple of things you could try.

The condenser is basically a capacitor and is used in most 'points' systems to soak up extra charge and stop arcing across the points, burning them out faster. When they fail they can overheat and then short the points to earth, basically disabling the ignition. If it were my bike, and seeing as it only runs for 4 or 5 miles any how, I would be tempted to reach through if possible and snip the wire to the condenser. The bike should still run, but the points will spark more. Either way the flywheel will have to come off, to replace the condenser and the points (might aswell - how many times you wanna pull it ).

Didn't they used to do transistorised ignition systems for these?? You keep the points but thats it? Boyer Brandsen springs to mind, sold loads of kits for the coffin tank RD's.

Either way good luck! I love the small geared two stroke bikes

Chris