Hi guys I got a 98 f3 that im having a problem with and im about at my wits end. so I bought this bike a few years ago as a rolling chassis parts bike and decided to piece it back together one winter. put on a set of delkevic headers and a shorty gp pipe. rebuilt the carbs and upped the jets a couple of sizes cant remember exact numbers at the moment. im also running a uni air filter. now the bike has ran perfect the last few years with this setup has had plenty of power for a 600 and ive been happy with it but this year its giving me fits. it started with a batch of watered down gas I got that gunked up the carbs and rusted the inside of the tank. I cleaned the carbs out and got it running but it was still running really lean. would only have power at cruise if I covered half the ram air and turned on the enrichment circuit. so I pulled the carbs again and there was a little junk in them so I went through them again and replaced the fuel filter as well. this time the bike is running much better rode it home from work 75 miles and notice the longer I ride the less responsive and doggy it is and coming through town its got a nasty low speed pop that wasn't there before and im smelling gas. I get it home and it sets for a few days and I can smell gas all around it so I check the tank sure enough its empty. made the mistake of trying to crank it it turns once then stops lights dim. figure its got a cyl full of fuel. sure enough number 3 plug is soaked. so I pull the carbs again find rust in the bowls. I cleaned the tank and petcock filter thoroughly and replaced the float needles and spark plugs and change the oil. start the bike it runs perfect then it starts missing and black smoke comes out when I hit the throttle and miss goes away. did the temp test by hand on the pipes cyl 3 is significantly cooler than the rest. take it down the road and anything under 5000-6000 its loading up and non responsive. im at a loss figure im gonna be pulling carbs again. not sure what else would cause this if the floats are good I leaked checked # 3 float while I was doing the needles and it didn't have any leaks. sorry to be so long winded just figure more info is better than less.

 

It sounds as if you didn't get all the crud out of your tank and it's making its way into the rest of the system. What does the screen on your petcock look like? Also take a look at your fuel filter. If there's anything in them, that is a telltale sign.

 

The screen doesn't look bad now since I cleaned it and the tank at the same time. I done the fuel filter then too. Im wondering if one of my slide diaphragms is messed up. Ive never had one fail so im not sure the symptoms

 

It might be but I'm not sure. Have you tried hooking up an aux tank and testing it that way? I would after you clean the carbs again.

 

I haven't yet but I will when I pull the carbs.

 

I just finished messing with Matt's F3 and a cool cylinder 3.
it was running terrible, sounded like it was running on 2 cylinders. I pulled the plug. Looked way better than I thought it would. After hours of messing, turned out the vacuum plug on 3 was cracked and half gone! We're fixed! Cylinder 3 temp is now matching the rest and the bike is running great again 👍

Im going to replace all 3 (#1 is fine of course)

hope it helps