re starting trouble cbr f in article z sf rpi edu chungy aix rpi edu yau felix chung writes i am having trouble starting keeping running my cbr f i have had problems with it since last year but it seemed to have subsided now it s back again problem persists regardless of choke usage pattern gasoline type brand octane and pretty much anything else i can imagine to change the dealer is stumped it s still under warranty i start the bike it runs great for a while seconds then the engine starts to slow down decreasing the idle setting will increase the engine speed increasing the choke increases the engine speed regardless the engine will eventually slow down and stop once stopped it will not restart even after flooded engine drill if i let it sit minutes it starts beautifully and runs great for ever so i go out ride it hard for miles and bring it back ride it easy for a few miles to let it cool down and put it away next day i go thru the same drill to get it going any ideas has anyone seen this before another f rider had similiar problems and this is the mail i sent him hope this helps resolve you problem at allen tobias writes check the vent tube to the tank sometimes the tube is clogged or constricted this prevents gas from flowing into the carbs because of the vacuum created by the displacement of the gasoline this is the small tube on the bottom of the tank the large tube is the overflow you will have to remove the left side tail section to get access to this area good luck but if it was clogged wouldn t this interfere with engine operation all the time when it runs it runs well good point did not catch this in the original post the only other things which come to mind since this is a gravity feed fuel system is this the fuel petcock valve is vacuum controlled from the carburator let suppose there is a small hole or bad seal either in the hose itself or the vacuum valve in the fuel petcock when it is cold the hole is open enough to open the valve just enough to allow gas to the carbs with the choke on since the choke creates more low pressure in the carbs when on to draw gas and as the engine and surrounding area warm up the hole seals up one way to check fuel flow through the valve would be to pull the side panels off and remove the fuel hose to the carbs connect a tube of the correct size preferably clear tubing to observe fuel flow on the output side of the fuel petcock remove the control hose from carburator make sure the tank is full place the valve in the on position and apply vacuum to the control hose preferably with a vacuum device with a gauge to check for air leaks with vacuum applied fuel should flow freely to see if there is a vent problem do this with the fuel filler cap open and closed if it flows a lot faster with the filler cap open then there may be something in the vent airway which changes position and depending on the position may clog or partially clog the vent i have heard of some f fuel tanks being replaced to fix this problem so the things which might be defective are the control hose from carb the petcock valve and possibly the fuel tank vent now if all of the above shows no problem of fuel flow when cold then there is something in the carbs screwed up but there are so many things to check i would be typing all day to list them all here are a few with everything back together apply vacuum to the petcock valve and open the drain holes on the carbs one by one to check fuel flow open up the airbox and check for foreign debris or clogged airways on the carbs there are quite a few on each carb i hope something is flushed out with all this trouble shooting if american honda does not resolve this get mad as hell and report them to the bbb and call the honda customer service hotline it is a number but i don t recall it off the top of my head i called just about tires for my f and a few days later a customer satisfaction inquiry card arrived at home asking how i liked the support i received here would be your chance to tell them what you think buy the service manual on the f it is an invaluable source of information for working on your bike and i might add trouble shooting
