How much SeaFoam should I put in the gas tank? I bought a can, but don't know how much to use.
Also, on a car, you're supposed to let the engine suck it in through a vacuum line to clear carbon deposits, can this be done through each vacuum port on the carbs? How much should I let it suck, if it should be done?
You have gotten good advice from all previous posters I think.
Seafoam can be used in several ways, and I think most of them have been covered in this thread.
1. You can suck it in straight through the vacuum hose to clean carbon from combustion chamber as you have done.
2. Pour in a stiff dose of a 1/2 can (8oz) or more, then start the engine and let it run for 5 or 10 minutes to get it into the carb bowls to soak and dissolve any gum or varnish in the entire fuel system. I use a similar dose for winter storage of 5 to 6 months up here north of the 49th.
3. Seafoam recommends a maintenance dose of 1 oz. per gallon used regularly. If that helps your bike run better, and you are happy with it, go with it. If you don`t notice any difference in the way the engine runs when you don`t put any Seafoam in a tank full, maybe you don`t need that much, and only want to put 3-4 oz in every few fills of the tank, as baldy suggests.
After saying all this, Seafoam is really a fuel stabilizer and preservative more than a system cleaner. A local rider and independant mechanic told me that if you really have a gummed up tank, carb or whole system, pour in some carb cleaner or fuel injector cleaner to try to dissolve the varnish.
IMHO, as you get out and ride more, how much to use all comes down to your own judgement, depending if you can tell any difference in starting, idling smoothness or power when you roll on the throttle.