Hello, I'm new here nice to find a place with people that have the same bike.
My F4i 2002(F Sport) always had some electrical problems from the previous owner. At one point I changed the Regulator/Rectifier (with a cheap version though) and everything seemed to start working fine.

Now after 3 months, I've noticed that sometimes the lights are dimmed and it starts with difficulty so I bought and installed a display unit for checking the voltage on the battery. Based on observing the voltage during riding:

I start the bike, it starts charging until 13.5-13.8 even more if I rev it . I start riding and everything still works fine, every time I rev it I can see a hike in voltage comparing to idle. Fan goes in or I switch the high beam, the voltage takes a dip, but after switching them off it returns to 13.8-14 V.

Now totally randomly (from a lot of observations) the voltage suddenly starts dropping and it levels at (what I think) is the battery's independent voltage (12.3-12.8) and there's absolutely no increase in voltage if I rev it. Now the strange thing is if at any time during this issue when it's not charging anymore I restart the engine, the bike will start charging again to 13.5-14 V. I've tested with low rpm riding, high rpm riding, there isn't any difference. Sometimes it happens after 30 seconds after I start the bike, sometimes after 20-30 minutes.

Anyone has any ideas ? I have already followed the Electrosport troubleshooting guide, but it s almost impossible to diagnose it because when it's idle in the parking it ALWAYS charges correctly.

Any ideas ? Thanks a lot !

 

Have you physically looked at the r/r and the connections yet?

 

I've looked again right now, all connections and wires look good. The Reg/rectifier is on the aluminium plate and on the frame so it should dissipate heat well enough. But as I said in my first post, sometimes it charges well at any RPM even after 20 mins of riding, so it shouldn't be a problem of heat for the R/R i think. I have yet to look into the Stator though, that is my next stop.

 

If you have a multimeter, check the resistance between the 3 yellow wires on the stator (check it evry which way) you should show between 0.1 - 1.0 ohms every which way, if so, ur stator is good.

Your positive the connection is good? The main one that goes bad is the yellow plug from the stator to the rectifier. Make sure your battery terminals are tight, and the main ground wire that connects directly from the battery to the mounting bolt for the starter is tight.

The bike wont really charge at idle, it doesn't really start to charge until you are up in the rpm, especially if the fan and/or highbeam are on. It will most likely lose power slowly with the highbeam and/or fan on at idle. Does it drop below say 13.5v if yourrpms are over 2500-3k?
They rate the stator to output full power at 5,000rpm! But it still charges fairly well at 2500+.