Close Guilfordin, I'm running a Honda 250/4, and have sorted out all my fuel issues now.
These Hondas are happy until an indicated 18,000 rpm (it's actually 17,200), then the valves tend to bounce (surprise !
)although power peaks @ 15,200 (actual) , anything more is just for young bloke bragging rights,,,,,I have a spare engine (parts only) that had dropped a valve, all pistons had polished valve pockets from valves bouncing off 'em, Honda got the cutouts right, the valves hit square onto the piston cutouts.
http://youtu.be/oNbWwK05phQThe exh valves are Titanium standard, or more correctly, the tulips are, the stems aren't and they also contain a fair bit of unobtanium ( a set on evil bay UK at the moment for 50 quid each !)
Engine consumables are also rare, Honda NEVER made 0/S pistons, big end shells are impossible to buy (so far), as are mains.
When I rebuilt my engine, I used CB250F cams (zero overlap, .5 mm less lift), which upped the pre-determined boost from 9 psi, to 15, with no blower drive changes, the bike has done very little testing @ 15 psi, I re-geared the blower to drop back down to 10 lb, once I actually get a slip,,I might go for broke with 15 ?
Red cup racing from Canada have a turbo'd 250/4 they are sorting out now, plus a de-sleeved 250/4, which is now a 175/4
I with them well with their racing year.
Hopefully, I'll get some salt in my veins soon