Go everyone, I'm in need of help here and getting frustrated! My 2001 f4i has been getting horrible gas milage. I'd say I calculated 22 miles a gallon. It's killing me. The bike has 45,000 on it, and I havent done a complete tune up due to money. The previous owner didn't take care of it. It has an aftermarket knn air filter and a yoshi exhaust. A few weeks ago t was acting up on me and bogging I was told it could be the fuel pressure regulator so I bought one and changed it and I thought the new one they gave me was a bad one but I checked it and it wasn't leaking. I'm thinking the bike is running rich as well. Don't know the last time the plugs were changed but a buddy of mine is going to going to check/ adjust my valves and while the bike is apart change the plugs and oil and possibly the cct, cause the engine is making some noise. Also sorta smells like some gas is in my oil as well. Anyways I wanna fix this problem so if anyone has some advice or can help me out anything will be helpful. Thanks

 

Looks like you're on the right track, start with the basics, air/fuel filter, sparkplug, oil/filter change.. when was the last valve clearance check? 45k on bike seems like a good time to check the valves.

 

what was the average mileage you were getting before you noticed the drop off? could you tell if the mileage seemed to drop off almost suddenly or did it gradually get worse? Im with "A" on starting with the usual problem areas. checking the cct and all your valves may give up the situation. I only ask those questions because my friend has the same 2001 f4i but his bike only had 7000 miles and had the same sounding issue. hard to say exactly what the problem was but we ended up changing the cct to a manual and replacing two of the valves that were warped slightly and not only did the bike run night a day better but the economy went back up too. hopefully you find some answers. keep us filled in and good luck

 

I have no clue when the last time the valve clearance was check. But my buddy is hopefully going to check them this weekend, I'm
Not sure and before I was getting about 35 -40 mpg and I wanna say it just dropped in mpg instead of slowly getting worse.

 

Too rich either means a sensor went bad, an injector, or the FPR which you already replaced. OR, the engine is miss firing so badly that the normal amount of fuel isen't getting burned and dumping into the oil.

 

Boredandstroked... What do you think it could most likely be. My sensors seem to be fine cause I checked them and working properly, ex specially the MAP sensor. What are the actuall symptoms of miss firing, cause I'm
Not to familiar with bikes that much, I'm still learning the matinece on the bike.

 

Are you absolute sute your running on all four cylinders? you could of had a plug go bad. i know its alot of work, with a bike that wasnt taken care of, i would start with a spark plug change. As i was getting my bike running last summer/fall i did a plug change myself and it made a night and day difference.

 

Since checking the sensors would mean looking up electrical values and using a multi-meter on each one, I'm a little lost on how you know how to do that but can't figure out how to diagnose a poor running engine? Motorcycle, car, boat, doesn't matter they are all internal combustion. Use a temp gun to check each exhaust header. Then check to make sure your getting full spark. Pull the plugs and check their condition. If all that checks out, then move on to compression test, fuel pressure test, injector tests. You move down the line until you find the problem.

 

Ceebear: I'm not sure actually, but I will start with a spark plug change and see if that will help and hopefully solve my problem, my buddy is going to do a valve adjustment on it sometime so would probably change while the bike is apart, but might have to wait cause I don't know what size shims for this bike, but I will try the spark plug change, cause it does seem like it's doesn't have the power it should have.


Boredand stroked; I will check the headers with a temp gun and sparkplugs, I'm sure that they are probably fouled.

 

yeah F4i's are touchy to plugs, at least mine is. book calls for 14 or 16k changes [cant remember right now] and I can easily feel when its getting close to that mark.