Hello. I just picked up a F4i. 26k miles, dynojet and Danmoto exhaust. A couple of issues that I noticed...

- chain slack is pretty loose
- I was trying to be proactive and put some seafoam into the gas tank and crank case.

I noticed that the throttle is kinda rough, or seems to hiccup around low range and around 5-6k.

I was coming down a hill and pulled into a parking lot. A guy came out and said he had the same issues with his GSXR and he replaced the spark plugs.

Question: Could it be the spark plugs? If so, should I change after the tank of gas? I heard seafoam can foul spark plugs?

 

Only if you dumped a whole bottle in with around 1 gallon of gas... I think you're fine. Fresh plugs will make a difference if your old ones are very old. The stutter around 5k could be your map on the power commander. What map are you running? A generic one from their website? Or a custom tune from a dyno run?

 

Im not sure about the map since I only bought the bike a couple of days ago. I checked the power commander website and didnt see one for Danmoto? Im not sure if it matters though.

I wouldve thought a loose chain wouldve accounted for the lag in low rpms (up hills, turns).

I ordered new plugs and a K&N online.

 

Just a thought - but this might be relevant - Is your F4i equipped with the standard header pipes? Take a look at the headers - are the 1+2 and 3+4 header pipes linked near the top with small horizontal pipes (otherwise known as crossflow/balance pipes).

Some people replace their old rotted headers with cheaper after-market headers which come minus the crossflow pipes - this causes the kind of stuttering/bogging you describe at around the 6k mark (the crossflow pipes are there to improve torque in the mid-range - fitting after-market headers minus crossflow pipes results in a hole in the mid-range).

 

Just replaced new spark plugs and engine kill switch, that didnt resolve the problem.

Its like, it would hiccup around 2-5k rpms.

I did a forum search and it could be anything, either fuel injectors or fuel pressure regulator?