I just recently replaced the motor in my 02 f4i. Once I started it it began popping out the exhaust not rapidly but every so often. I changed the plugs and I changed the coils. But when it idles it still pops and sounds like its on three cylinders. When I ride it it has a distinct misfire from take off til I hit about 7000 then it takes off like a rocket ship. Anyone know what would cause the misfire I am getting on the bottom.

 

timing?

 

I was thinking the timiing myself but it seems as though it would be way out and there is not ping or detonation when I ride. I am going to attempt to check it anyway but thats all comp controlled. So from there I guess I need to start changing stuff if thats the problem.

 

A common cause of misfires are loose battery terminals or connections. Its the easiestthing to eliminate before you start any expensive trouble shooting. Do a search on the forum.

 

My terminals are clean and tight. Checked the main motor connections they are all plugged in properly and clean. Tried to sync the throttle bodies with a vacuum gauge but that just doesn't work they vary so much with the idles speeds that you could never get them right. Gonna get the proper gauges tomorrow. Changed the plugs again numbers one and two cylinders were golden color. number 3 was slightly wet and black and number 4 was completely black. Very confused right now.

 

Ok so I changed my plugs again. This time cylinders 1-3 where white and 4 was completely black again. Number four cylinders is cutting out on idle. I checked the Valves one of the valves on number four was at .021 and the other was at .011. Anyone know if this might be part of the problem.

 

valve clearance can definitely cause misfire. If you have that much clearance between the cam and valve bucket you should have a good seal. Valve misfire normally happens when the valve isn't closing due to improper clearance or a leak which kills your compression. You may have a burnt valve, or cracked valve seat. The reason the bike takes off at 7000 is it "picks up the cylinder" due to the valve overlap (the valves are not fully closing before the plug detonates the mixture at that RPM). I'm not sure what the valve lash is suppossed to be for the F4i (call your local honda dealer they can tell you). Set it to it's proper tolerance, you will hopefully find you problem goes away. If not you may have a more serious problem.

 

.007-.009" intake, .010-.012" exhaust.

If the #4 plug is a sooty, dry black and not wet, then it's running too fat on that cylinder. You said you replaced the engine, but is that all? Did you get one with all the injection stuff still on it, or are you using all your old hardware(throttle bodies, injectors, etc.)?