Hi I'm new here, I hope someone can help.
I've just bought a lovely yellow, blue n black 1999 fx; one owner and just 7k miles. I bought it private and for the first 50 miles she ran very well, with just a rough idle to worry me. Then when out the other day I noticed it seem very flat when accelerating from around 4 to 5k. Upon further testing I found it just would not rev past 4.5k without changing down, even with throttle wide open .it would easily up the red line from 6k.
So I took it home, wiped off the tank and checked the fuel tap, fuel filter and pump; all seemed ok. I then took out the plugs; they looked new but even though 1 n 3!looked fine, 2 and 4 were very black.
Suspecting the coil packs on 2 n 4!, I swapped em for those at 1 and 3, n put it all back together.
Another test ride.later, I took the plugs about again to find the plugs (previously cleaned) on cylinders 2 and 4 were yet again fouled, so not the coil packs ( individual on the Fx n Y) then. That's as far as I've got; the previous owner said his garage cleaned out the carbs just before he sold it.
So I have no clue as to what is going on here, she really is a lovely bike, that I now can't ride. Please, if there is someone who has come across this issue, let me know, many thanks, jon

 

Welcome to the forum Jon.
Lets see some picture as we all like pics.
I hesitate in saying, but it sounds like it like the carbs have not been cleaned properly, having swapped the coils over and eliminating that as a cause it could be plugs, but two out of four being bad is very unlikely.
When you checked the fuel filter, how clean was it?

 

 

Very nice, pride of place in the kitchen.... like it!

 

Hi, thanks for your reply, the fuel filter looks like it had been on the bike since forever, so I've ordered a new one. It seems very odd that only two of the cylinders are running rich, but I agree that I am gonna have to take carbs off, n clean em. I have an ultrasonic, so will have to do em one at a time.

 

At lease you will then know that they are properly clean. There are a number of posts on here which identify the areas to concentrate on when cleaning, lots and lots of photos will help with the rebuild and of course a gentle touch and patience!

 

Ok, many thanks, I've done many slide carbs (two strokes) in the past, but never a bank of four Cvs. I will look up some hints, maybe before they just cleaned what they could see, rather than where they couldn't, cheers, j

 

Try this one for example
https://cbrforum.com/forum/stickies-...cation-124026/
An IDoDirt special.