Hi, I have been an owner of a 2000 F4 for 10 years now (since new) and have been fortuneate to have a great running bike and items besides normal maintenance was a few pump. However now I am faced with a problem I can't solve and was hoping some of the forum experts could lend a hand.

Anyway I am thinking I am having carburator problems. My bike refuses to start. It backfires thru the carb and exhaust and have had a few moments when I thought it wanted to start but nothing. I have tried draining the gas, carb cleaner, pulling the plugs etc I even pulled the carbs cleaned the bowls/main and slow jets/floats and also removed and cleaned the vacuum chambers...still the same problem. Pulled the plugs a dozen times, cleaned and re-gapped (plugs only have 1000 miles or less on them), checked for spark. When I pull the plugs they are wet with gas so I believe I have compression, fuel and spark but the bike refuses to start !!

Do I need a carb rebuild or to get them professionally cleaned ? What in the carb would cause fuel to get in the cylinders but not to start at all ? Any info or suggestions would greatly be appreaciated. Thanks.

 

Too much fuel might do it. Try taking the air filter out and starting it

 

Thanks for the tip. Been trying to start it w/o the airbox/filter. Just recently gave it a try with the airbox/filter and it actually "tried" to start very briefly. Don't know if it was coincidense or not, figured the cylinders were flooded by now after continually trying to start so I pulled the plugs and let sit overnight. Going to give it a try later today.

When I cleaned the carbs I did not remove the pilot screw (did not have tool). What in the carb would basically not allow correct fuel/air mixture that would not allow the bike to not start at all ?

I have not problem taking the carbs in to the local shop, but my fear is after spending $$ the problem will still be there.

 

Looks like this is going to cost me big time. Called a few shops and most want me to bring in the bike, can't say if it is the carb or not. Carb "cleaning" runs $100 or so and sounds like all they do is clean the jets mostly (??); complete dissassembly (which will cause the carbs to out of synch) run over $400 in labor; I can't be throwing that kind of coin on a guess that it is the carbs. Any suggestions ? Thanks.

 

This is what my carbs look like right now


Didn't necessarily have to clean them, though I did find a clogged jet. In the middle of several other projects that needed the carbs out.

This is the 'tool' you're talking about


It's not truly a tool. Just a metal tube with a bend in it. You can make one yourself. A pair of needle nose might also do the trick for getting them out.



Tho I'd recommend taking something like play-doh, making a cast and going to home depot to get a tube of the right diameter. The needle is very fragile and you don't want to bend / break it.

You said it sounds like it tried to start when you put the air filter back on? Might be an air issue. Check your hose routing first, making sure all hoses are connected where they're supposed to be. Then after verifying the hoses, you can try restricting the air flow more.

Take some duct tape and cover the air filter with strips of it. If you can get her to start with the air filter blocked, you could have either a hose routing issue or the carbs aren't tightly sealed to the engine. Check that the carbs are fully seated and sealed at the boots.

 

Thanks for the tips/info Kuroshio !

Maybe it has been my fault...all along I have been trying to start it w/o the air filter/box and all of the hoses disconnected ! I was under the assumption it should at least start ?? But I will assemble everything correctly and give it a try.

About 2 years ago I had a similiar problem (starting), ended up cleaning the carbs on bike w/ carb cleaner but that fouled up the plugs, bought a new set and it fired up no problems. Just talked to a mechanic and he suggested I get a new set a plugs that for some reason once they get fouled and if cleaned and gapped (what I did) that they have problems igniting the fuel...kind of sounds strange since they are standard plugs (NGK CR9EH-9) and not the iridium tipped ones...I guess it's worth a try but the cheaper plugs are like $10 ea ! Maybe its a combo of week spark and vacuum leak form hoses not hooked up ???

 

Well you said earlier
You forgot the 4th element: Air

Need to have air in there too. Too much or too little and you won't start either. Try the plugs but before you do, verify the hoses and the carb seating. From your previous post, you've been in and out of your carbs several times. You could easily have a leak somewhere letting too much air in.