Does anyone know of any resources with details on modding a B25 for racing? I am in the hunt for a race bike and would like to see what I would be up against if I got into a 250. I have heard bad things, but seen a lot of them on the track.
I spoke to Ed V and he essentially but unintentionally warned me off the B25 project. The amount of work required to make the bike trackworthy is not terribly excessive, but probably required right up front, as opposed to a CB350 which you can build up as you get faster and it won't blow on you.
He detailed a crank pin mod, lightened flywheels, carrillo rod, slight head work and intense lightening of valve train components and a new cam. Special clutch required. Transmission sucks but nothing to do about it.
That is a project for another day, once all of the other bikes actually run!
John -- I'm sure it sounded better coming from Ed than me!! Done a lot with him on the B50's (my racers) and know he doesn't mince his words. The B50's cost a lot to get major HP, but --- they are very competitive. The B25 is really just the slug it was when the factory built them, and a hopelessly outclassed 250. Says something, that back in the day, if you bought a 650, they gave you a B25 FREE!! Cubic dollars will see it make a lot more HP than stock --- but, not competitive against the Japs.
i have to agree i wouldnt chose one to race competitivly but lets not be too harse a starfire was the fastest stock british 250 @ 89mph,and well up there with other 250s of the time,it came second in the european 250 mx titles 4 times up to 1970 up against the mighty 2 strokes,as for giving them away with 650s well to be polite thats just american talk.
If you are doing something in a 250 class then I guess its got to be a Starfire. I've owned all three (B25, B44 and B50). I have a cousin that has two B25's and a B50. He said he would give me both B25's if I fixed up his B50. He still owns all three bikes. The B44 will do everything a B25 will do with considerably less effort and the roller big end is a big plus over the oil starved plain bearing of the B25.