1983 Yamaha virago. If i remove the YICS box the bike will start fine, but revs to really high rpms. If i put the box on the bike the bike would not start and smells as if carberators are flooding but acts as if the bike is not getting any fuel at all. Also with the bike off it back fires and i have to keep a hand on the throttle to keep it from dieing when it cuts out.
Check your YICS box for leaks. 1. There is a seperation in the middle of the box, check for visible possible leaks. If you seem to have nothing visible, put a plastice tube in one side and the other. Block one end of a tube and blow into the other. You should get resistance as if no air is able to escape. Youcan also take one tube and place it in a continer of water. When you blow into the other end you should get NO BUBBLES; if you do there is a leak. You can use a high temp gasket maker to re-seal the box, make sure of course that you keep the gasket aterial ONLY where it is needed to keep the compartments seperated as they are. After these tests there is a way to re-seal the center seperation but it requires a band saw and a perfect cut down the center of that seperation. Please! do not attempt this without more information as a mistake will most likely ruin the box.
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2 things need to be done first start your bike get a can of wd40 after your bike is warm and running spray around the carb jointsall 4 of them if your engine changes rpms up or down you have a intake leak ether your carb joint gaskets or o-rings need replacing or your carb joints are old and need replacing. at this point wont hurt to have you carbs cleaned also
Ok on a dry day take a spray bottle with water in it and spray different areas on the bike like the plug ends - coils- fuse box- handel bar switches- Any where there is a connection. Even dehind the head light where the wires go in. You are haveing a moisture problem getting in and shorting the egishion system.
The rubber seals and fittings between the carbs and cylinder head get hard and brittle. They can develop small cracks and also loose the seal they had when new and pliable. This means that extra air gets into the air/fuel mix as it heads for the intake valves. The air that has not gone through the carbs leans the fuel mix and causes the high revs. The seals and fittings will need to be replaced. Dealers have parts in stock for 10 years. Your bike is 22 years old. Google yamaha virago 750 parts also Google vintage motorcycle parts. Babbitt's would be a good source if the '87 and '88 parts match up. They list an '88 and have all the parts in stock except one hose line. Go to the site below where you can see a parts diagram for your specific bike. You will select the actual brand, year, model, etc., once you go to the site. Part numbers and prices are also shown. You can order parts from this site. In the event no price is shown on a particular part and/or the notation "Not Available" is in the description, the part is not in stock. www.babbittsonline.com/pages/parts/viewbybrandand/parts.aspx
Offhand, even if the the stator / charging coil is defective or for that matter even the regulator, the bike should start and run on a fully charged battery. The only problem would be that the bike would die eventually. If haven't been tried, have the battery load tested not just voltmeter test.
Please postback after the load test. Hopefully by then, I would have the wiring diagram.