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'01 F4i bogging down - TFI installed

Old 08-03-2010, 02:49 PM
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Join Date: Jun 2008
Location: Idaho
Posts: 10
Default '01 F4i bogging down - TFI installed

Hey all,

I have a 2001 CBR F4i with a TFI module installed. I purchased the bike used and have owned it for almost 3 years (TFI was installed by previous owner). I have not had any problems with the bike until about 2-3 weeks ago. The bike bogs down / hesitates a lot when starting out from 0mph and continues through about the 4-7k rpm range. Is the bogging down a sign of too much fuel into the cylinders? I noticed that with the TFI module, if I adjust it to add more fuel the symptoms seem to get worse and when I scale it back the symptoms aren't as bad. It seems worse after the bike is fully warmed up past 200F. Also, the FI light will randomly come on when it's bogging really bad and occasionally the bike will stall out. Am I looking at a problem more extensive than a TFI box or should I just scale it down until I am happy with performance? It has a few other mods to the bike (straight piped, bigger rear sprocket). I checked the fuel tank for rust (none), replaced spark plugs, and cleaned k&n air filter. Any other thoughts on what the problem could be?

I never had a problem with the TFI before and now it started acting up.

I'm lost as where to go from here. I attached a pic of a spark plug I R&R
Attached Thumbnails '01 F4i bogging down - TFI installed-img_0450.jpg  

Last edited by mjobie12; 08-03-2010 at 03:05 PM.
Old 08-03-2010, 06:50 PM
tanrush's Avatar
Join Date: Jan 2010
Location: Parts Unknown, TN
Posts: 85

Three words, Fuel Pressure Regulator. A bad one made my life hell. After a couple of months of doing everything else a new one fixed my problem. Now it runs like a bat out of hell. It is cheap 65.00 from Honda and easy to install. Search other FPR posts, their is a good tutorial on how to change it out.

Poor gas mileage 25 mpg.
Strong gas odor parked and running.
Black/rich carbon on tail pipe.
Bike ran like crap. Had a terrible time getting it to move in first gear. Not as bad of a problem in 3rd + gears.
Good luck
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