Note: The following tip was in answer to a question posed to HONDAMOTOTECH, as follows:
"I'm getting ready to buy a 1981 Honda CB750. It was improperly stored for a year. Basically, it was parked and left as is. The gas was not stabilized and went bad long ago. The battery is probably gone. And I know there are other issues common to all improperly stored bikes, I just don't know what to expect (or what to look for, for that matter)."
The biggest problem by far with improperly stored bikes is the fuel turning into a varnish inside the carburetor float bowls. Also if the fuel tank was not completely filled it may have rust in the tank.
The next thing is the battery. If the battery wasn't on a battery tender type charger or some other type of trickle charger then they go south pretty quickly. But this may be a good thing in the scheme of things and let me tell you why.
If the fuel in the float bowls has turned to varnish, the last thing you want to do is try and start the motorcycle. What happens is the engine tries to suck all that solid varnish material into the idle and main jets and clogs the heck out of them.
The first thing you want to do is drain the tank and make sure there is no rust and trash in there. Check the condition of the fuel in the tank and see if it, in fact, has turned to turpentine or has any solid varnish particles floating in the fuel. If it doesn't have that or rust in the tank then flush it out with fresh fuel and put some fresh fuel in it.
Pull the hose off the petcock (fuel valve) and make sure fuel comes out (CB750s have a filter in the petcock) and the filter's not clogged. While you have the hose off, drain each float bowl on each carburetor by opening the drain valve screw on the lower outer side of each carb's float bowl. If the original drain hoses are still attached, you will have fuel coming out of these four small hoses at the bottom of the bike. If the hoses are gone, then it will drain right on top of the lower end of the motor. Main thing here is you want to inspect this fuel very carefully. If it just smells like bad fuel but doesn't have a bunch of trash in it is a good sign. If a lot of brown crud comes out with it, then you will have to pull the carbs and have them cleaned and synchronized by someone that knows how. If the fuel looks OK then put the fuel hose back on, turn the fuel valve on and let some fuel run through the carbs and flush out the float bowls, turn the fuel valve off, close all the drain valve screws on the floats and turn the fuel back on. Hopefully, no fuel will run out any of the hoses anymore. If it does, then you have trash in the needle and seat portion of the float and you will have to pull the carbs and clean them.
If all is good so far, then make sure you clean up any fuel that came out from the bike and the floor (you don't want to burn up your new investment).
Install a new battery, change the oil, pull out the choke and start that bad boy up!
Let it warm up for several minutes and see how it idles. If it idles like total crap and won't "clean out" until you twist the throttle a little, then you have clogged small (idle) jets and you need to pull the carbs and clean them. In some severe instances the mains can be clogged and it won't run at all but if you found no trash when you drained the floats, then you shouldn't have that problem. The main thing here is if you find trash in the fuel coming out of the floats don't mess around. Just pull the carbs and clean them. DON'T try to start it as you may be sorry later when you try to clear the idle circuit.
If by some chance you luck out, (A year isn't really that long on fuel. I've seen worse.) then make sure the tires are good -- no dry rot cracks and have proper air pressure. Make sure the chain and sprockets are in good shape and lubricated, no rust or kinks, and no worn teeth on the sprockets. Then go ride!
|
