Now that my riding season is over, I have a bit of time to write. A problem that I had this summer involved the carburetors on my 1972 Suzuki GT750J.
About two months into the riding season the engine started to idle erratically. Then one day after returning from a tuesday night ride, it wouldn?t idle at all. The engine would just quit unless I kept blipping the throttle. Time to change spark plugs I thought?initially. It's a 2-stroke after all. But the idling problem went right on just the same. Poking around with my flashlight, I saw that fuel was dripping from the middle carburetor. OK?the float needle wasn?t sealing. I had seen this before and was caused by a worn float needle or some dirt on the float needle seat.
On the ?J?, each carb is removed individually starting with the left or the right carb. I prefer to start on the left side as that is where the fuel hoses are disconnected from the petcock. The middle carb out, on the bench and stripped showed a float needle & seat that looked brand new (I had replaced the float needle when I rebuilt the bike a few years ago). So, I concluded, it must have been some dirt that was evicted when I stripped the carb. Everything re-assembled and fuel on?and fuel was still leaking from the middle carb.
Carb removed and stripped again to check for dirt. Cleaned in my ultrasonic cleaner, and all orifices and holes blown out. Re-assembled, fuel on and?still leaking.
At this point I should have taken a step back and done a bit of analytic troubleshooting, starting with ?what else could cause this symptom?? Instead, I did the removal and carb strip thing again. By now I was good at it. Mounted the carb in a little bench stand with a little auxiliary fuel tank to see if I could duplicate the problem and well, did. Stripped the carb again (4th time now) and for some reason rattled the float and bingo! Fuel was sloshing around inside one of the little float chambers. When I squeezed the float chamber, fuel came squirting out in tiny streams. In other words, the float was not floating properly. Rather it was sinking. The leak was at a rough area of the float that appeared to be copper corroded; possibly because of the acid soldering flux used when the float was manufactured.
The solution: I replaced the float, adjusted the float level using my bench stand and re-installed the carb in my bike. Idle was now perfect and no fuel leaks. I re-installed the old spark plugs and the idle was still perfect. I?ll carry the new plugs on the bike and change them when needed. (An Allen Millyard trick: you can rejuvenate 2-stroke plugs by burning the ash off with a propane torch. Get the ground electrode red hot and when cooled off, clean with a brush). I ran the old plugs for the rest of the season and will run them next year as long as they continue to work.
Olaf
