To port or not to port that is the question. I am currently rebuilding the engine in my 02 F4I . I'm going from 67 to 69mm pistons and from 12:1 comp. to 13:1 New stock valve's and of course a valve job. Cams are yet to be determined probably factory hard welded cams from Web Racing Cams "no regrinds". I have been told by more than one person that the intake ports on the head are to big from the factory and that There is power to be had by by decreasing the port volume to increase air velocity "to an extent" thus increasing volumetric effic. They are talking about a total of 15 to 20% reduction will yield a gain of 5 to 7 HP. Felpro makes an epoxy made just for this purpose. I am just collecting opinions at this point. Let's here yours.

 

when i had my new cams put in i had the head ported and polished.

 

If you want the best you can have done, simply box up the bare head, and send it to Vance & Hines. There is a reason they do all the heads for all 4 factories...

Not to mention, they will get you a lot closer to the factory supersport hed than you will be able to get, ever. They have just done them a hundred times, and have a full on CNC program that does it over and over again....

Best bet really.

 

With the amount of miles I put on this bike 48,000 so far, reliability is a "MUST". So far the only thing i've bought that worries me at all are the pistons and that is only because of the comp. rating. What I want to due is maximize my low end and midrange hp. without having a negative affect on high rpm perf. Every one of the shops I have found that offer porting for bikes say that if I port the head the areas of performance i am trying to increase will decrease. Also I forgot to say IGN. timing has already been addressed.

I took the head to a friend with a flow bench and tried valves that were stock in diameter, but had different sized tulips "some more and some less than the factory valves" on the valves. We found that a slightly larger tulip on the intake valves increased velocity at all simulated valve lift increments without raising air pressures inside the ports. I could use these valves but they way a fair bit more than stock and would require new springs. I also realy like the factory valves and would rather keep them and work around them.
This reaffirms my thoughts that the ports are to big from the factory.

 

Another way to increase velocity and gain some low/mid end torque, would be to put stacks on the throttle bodies...I'm actually looking for a set myself. Anyone know where to get them for the f4i?

 

Erion used to do work on the F4i. Do they still provide that service? Their work is as good or better than the factory jobbies. I'm thinking about porting and adding highlift cams, but my work would be for increased mid and top end for trackdays. I just bought a full Leo Vince system for it, so I'll run with the stock valves and heads for a while to see what kind of effects porting and new cams has.

 

I'm getting no where fast. I don't know what to do. I guess in the larger scheme of things, this is really no big deal. The bike hauled *** stock and the mod's I already have planned should make an already fantastic bike even better. I think I'll wait to hear from WEB Cams. Once they recieve my cams and inspect them, they will let me know they recommend based on what I told them I wanted to do with the bike. Such is life.