I have been riding my CBR all winter. But in the past 5 weeks or so my 2002 F4i has been acting up. When it starts up and for the first minute of riding or about 3 minutes of idling it sounds like a 2 stroke dirt bike. If I ride during that period it has about half the power. And after it starts to warm up a bit, the sound becomes smoother, and the power literally kicks in. During that change as well, it backfires like crazy if im above 5k as it transitions from the half power to full power situation.

I wanted to take a video, but I don't have a go-pro or anything. But its very odd, and almost seems like it is running on 2 cylinders during the cold period. But the problem isn't 100% all the time. 1 out of every 6 rides or so it doesn't do that and acts normal from the get go.

My F4i has about 8k miles on it, has a Two Brothers Exhaust, stock Air Filter, I do my own oil change of Castrol Full Synthetic, and has new Denso Spark Plugs with about 600 miles on them.

 

Is it only running on 2 cylinders during warm up?
Find out which cylindrs are running or not, just touch the header pipe to check.

 

Well thats what it feels like. I feel literally a surge of power around 105-115 when it starts to ride

 

105-115? rpm? mph? degree F?

 

My same question too. 105-115 what? Because i am trying to figure out why my bike is no longer going past 136 mph and i believe your thread can help me figure this out.

 

Degree f. After it warms up a bit...sorry for lack of info.

 

Have you tried to determine if you engine is only firing on 2 cylinders before it warms up?

 

No, so how to check?

 

Fire up the engine and:

Header pipe get hot= cyclinder firing

Herder pipe does not get hot=cylinder not firing.

Best put some nytrile gloves on than bare finger tips.

 

Well, i had a similar problem and as everyone has told you, you are probably running on 2 cylinder (well, your bike), when was the las time you checked your valves??

Is it hard to start?? I guess so, check your valves, I bet they're tight, and only when you rev your engine will it get hot, thus it starts running fine.