Steve,
No doubt S'Hunky would be going on his experience of the very first model Astro 250 (M90 from memory) that DirtBike tested in Feb73 issue. It kept seizing on them & spitting the riders off. So he's thrown the baby out w the bathwater by the sound, & (w all due respect to him) revealed how much he doesn't know about Astros. As the saying goes, "You can prove anything where 'n' = 1 !"
I read many years later somewhere (or maybe Don Newell told me) that their only problem was that the big-end side clearance was set too tight on the first batch. Free that up & they ran fine.
I never owned Astros myself (& only raced Pursangs & Shepa Ss), but all the Buls I've owned were stone reliable w a little regular maintenance. I only ever rode a friends Astros (both 250's) & felt the powerbands were broad enough to ride in MX also. Gearbox ratios are closer than pursang. Diff pipes too. The early ones used a pursang like frame; later ones used diff frame from pursangs.
They were very very competitive (both 250 & 360) in flattrack, as any US mag of the day will show in the results of AMA professional events.
326 Buls ran 83.2mm bore & 60mm stroke.
Serco sell many diff size little end brgs & often have some Bul pistons. Otherwise, Don Newell & Peter Schoene in Oz. Both have lots of parts.
