Motorcycle Repair/1988 Honda Shadow VT600c - cold start issues
I have a 1988 Honda Shadow VLX600 that I bought from a local Honda dealer back in September of 2012. When I bought the bike, it had roughly 12k miles on it. It now has 13.5k. The bike ran great after removing the aftermarket LED's that were draining the battery. However, with the arrival of cold weather came problems. I park the bike behind my house on our concrete patio. When I get up to go to work in the morning (about 5am, it's about 30 degrees outside) I attempt to start the bike as follows. Full choke, put key in the ignition and turn to acc setting, crank throttle a few times, start button. The bike fires right up almost every time, no matter how cold it is out. However, it will run for a few minutes, then sputter out and die, after which I cannot get it restarted. (once it dies I can crank and crank all I want and it won't start). Prior to the cold weather i ran an entire bottle of Seafoam and Berry's B12 chemtool through the bike (had to fill tank like 10 times) in anticipation of letting it sit over the winter. (i know this isn't the same as stabil) Any ideas would be greatly appreciated. I don't want to take it to the dealer for a wild goose hunt.
Vincent, well freezing temperatures are hard on a motorcycle, especially when you are getting them fired up in the morning.
Once you get the bike fired up, you should be gradually reducing the choke as it warms up. Do not leave full choke on it while warming. If you are leaving full choke on the bike, after a minute or so the spark plugs will fuel foul and the sparks get shorted down the side of the plugs instead of jumping the gaps like they are supposed to.
Another phenomena might be what is called carb icing, where the incoming air is so dense and cold that it creates ice in the carb throat inlet, blocking air passages which creates an over-rich condition.
I would certainly keep some thick blankets over the bike at night to help reduce the cold effects on the fuel system. Even a small electric blanket or heating pad set at low settings, near the carbs, might help.
I would also try draining the fuel bowls at the drain screws, to release any trapped moisture that might be in the system. Alcohol fuels often separate and layer in the fuel tank and float bowls, causing the engine to try to run on alcohol only which they are not calibrated to do. Even though you ran chemicals through the carbs, there may still be some water present from condensation. Always keep the fuel tank full to prevent the air space from condensing water into the tank. You may want to check the fuel filter for signs of clogging, as well. Berryman's B-12 is very aggressive stuff and can cause o-rings inside the carburetor to swell up or soften or dissolve. Stabil would be a better choice, although Sea-Foam is supposed to be a similar product.