HI,
Last June I bought a one previous owner 2004 CBR600f4i with a low 5000 miles. (PIcture Above)
In that year i've tinkered and covered 8000 miles, 2 track days and the California superbike school. This is my opinion.
Oil.
I've Changed the oil every 2000 miles.
Silkolene 10/40, Motul 5100, Motul 7100 and Motul 300v. Of these the 300v is in a different league. I was amazed how smooth the engine and gearbox became with this oil. For me the search is over. Any oil that can make a Honda gearbox from the early 2000's smooth is a winner with me.
Tires.
The bike came with practically new Michelin power pilot 2ct front and rear. These performed faultlessly on the road for 2000 miles and were destroyed in quick order on track. But excellent road tire. I then stuck Bridgestone S22's on and got 4000 miles out of them. Again faultless on the road. Excellent on track. Now she is shod in metzeler m7rr which due to Covid have only seen the road. I don't ride in the wet if I can help it and feel pretty much any tire will be fine on a dry road. Pretty much stuck with 36/42 in the summer and dropped a couple of psi when it got colder. Just me tinkering.

The SP engineering exhaust is ok and fitted just to keep the original pristine in my shed.
I've replaced the springs with K-Tech 0.9 n/m linear springs, i weigh 75kg ( 170lb ish ).Also used Castrol 10w synthetic fork oil. Slightly heavier than standard.
The originals were OK on road except for the fork dive on hard braking which unsettles the bike. The rear has been fine and I find the Adjustments available really effective and noticeable.
The brakes are frankly shocking compared to modern sportsbikes . I've changed pads, HH sintered, installed Braided lines, Racing brake fluid, still poor. A work in progress. I've recently rebuilt some calipers and am considering installing a 18mm Brembo master cylinder.

Short levers are purely cosmetic and I prefer longer lever so won't be around long .
Eazi-grip tank pads are excellent and highly recommended. Although they do ruin you leathers.
I have raised the rearsets ( see photo). This was fine but recently I raised the ride height by 10mm by placing a 3.4 mm washer (3:1 ratio) under the rear shock top bracket. Was 74 cm now 75cm. I also fitted a lowered seat (not in photo) and now my knees are low on the tank so I will make another bracket and raise them a bit more.
I have also lowered the front 8mm. The accumulative effect of this tinkering is that the bike tips in much better and changes direction a lot faster than before. You can definitely feel the extra weight on your wrists and hence over the front end. I have an Ohlins steering damper but you don't need it on the road.

The gearing has been altered to 15 tooth (-1) on front , 47 tooth (+2) on rear. I believe the bike should have had a 46 on the rear but it was a 45. This has transformed the bike.
Gone is the annoying flat spot at 3000 rpm making pulling away much smoother. The bike feels more responsive down low and the 8000 rpm surge is more pronounced. Only downside if you can call it that, is you can't just pin the throttle wide open from take off. It is also noisier than the rubber cushioned oem front sprocket.

Carried out the clean air mod mainly due to planning on a power commander. Not sure if it's worth the £300 quid since changing gearing. Can't find a well recommended exhaust system other than the micron so if one turns up, Maybe.

The Cam chain tensioner started making a nasty noise at 5500 rpm after 8000 miles so I changed it. Fiddly but no sweat. Went with another automatic as adjusting a manual is awkward.
The double bubble screen is not good in a tuck but good ear plugs make it ignorable.

That's about it. Basically I have taken a brilliant bike I purchased for commuting and made it less comfortable. It now turns more to my liking but not as well as a similar year R6 or 600RR but i've had fun playing.

I wrote the above as over the year I have gleaned loads of advice lurking on this excellent forum and felt I owed you all.

 

Hey that is a great write up. It's always nice to hear some insight based from honest experience.

 

good write up nice looking bike

 

Great pics and write-up, man!

I've added my thoughts below if you're interested...

I've been running 2CT's and like 'em as well. They were very torn after my most recent track day but I'm pretty sure I was running them way too low on psi. That, coupled with the fact that I didn't really take time to warm them up and that the track was sizzling (95 air temp), has me thinking of running them much higher and remembering to take a warm up lap.

Do you recall what psi you were running on the road and/or track? I've found they feel much better on the road at 42 both front and rear...

Upgraded springs make such a nice difference! I also changed the front pads to HH sintered. A little difference from stock pads, but not much, and a little too grabby on initial pull for my liking. Not quite ready to get into all that other stuff yet!

I tried tank pads on my previous bike and, yeah, they worked great but I was wearing holes through multiple pairs of armored pants. I did a lot of looking when I got my F4i and found that foam deck padding for boats works great (admittedly not as good as the pads but good enough for me) and didn't obscure the graphics as I could cut to form.

Ah! Totally forgot the front sprocket had that cushion! I've been having screws and bolts fall off all the time since changing my chain/sprockets if I don't really cinch them down and the foot pegs are definitely "buzzier" since then... Anyway, I dropped a tooth in front, kept the rear the same, but went to a 520 chain. I like the difference in acceleration but for any distance riding, the higher revs and vibration can be tiresome...

Always nice to "make it your own"... even if it's not always for the better! lol