I have a 2000 f4 that backfires while idling at 1500rpm, and revs up hesitantly and very slowly up to 2000 rpm and smoothly but slower than it should from there. If I put the choke on to make it idle at 2000rpm, it doesn't backfire and will rev up smoothly, but not as quickly as it should. I just put in new plugs gapped to 35.

 

Did it do it before you changed the plugs? What kind of plug did you use? Checking the gap on platinum or iridium plugs will ruin them.

Could be a carb issue. When was the last time they were cleaned and synchronized? Did the bike sir for a long period of time?

 

Before I changed the plugs it would barely start, only with very careful modulation of the throttle, a little starter fluid and full choke. It has been sitting for about a year, Prior to that it ran fine. When I changed the plugs I noticed the coil on #2 wasn't a snug fit, I couldn't feel it click into place like the others. So I had to pry out the little tab inside the coil to get a solid fit. Could it be that? 50k miles on bike, as far as I know carbs have never been cleaned or Sync'd.

 

Sitting a year and have 50k on them? I would say they are due for some attention.

What did the old plugs look like?

 

They looked fine, and I was gonna put them back in, BUT after going through the PITA process of taking them out, I replaced them with new CR9EH-9. So I should pull the carbs and clean them? Or rebuild them?