Anecdotally, I’ve heard a lot of Beta 2-t owners have left their top ends for up to 120 hours between changes. I read yesterday of a bloke in Europe with 300 hours on a top end and 600 hours on the motor, a ‘13 RR300.
After checking with a very well-regarded motorcycle mechanic mate I ride with (P.C. Gas Gas) & having never left a top end for more than 55 hours, I thought I’d open the bike up and have a look. It was recommended I check the piston spec & ring gap. It was said fresh rings at least would enhance the service life of the bore and maintain performance.
As some Beta 2-t owners have had oi malfunctions & some just don’t trust the system, I was most curious to see how the oil injection had left my piston, rings, barrel & crank after 60 hours.
After removing the head* & barrel, I was pleasantly surprised. The barrel is in top shape, clean as a whistle. The power valve had minor carbon build up that came away easily. The head had a tiny amount of soft carbon on it, too - it wiped off with a rag.
I then measured the piston (‘B’ size) on the mike & using the manual’s instructions; 71.95mm - in the middle of the manual service measurements. Then the ring gap - 0.4mm; at the end of the recommended service life. The rod has zero up & down play and the crank is lubed nicely. I use Motul 710, 98RON fuel.
Other stats - squish; was 2.04mm, base gasket was a 0.6mm.
The new base gasket is a 0.3mm, giving me a squish of 1.74mm. I should get a smidge more bottom end (all I use, really).
Outcome - I just replaced the rings this time. They are $75AUD per pair & a Beta top end kit is $294AUD. I will do a piston & rings at 120 hours. Torqued it all up, coolant in, head stay on, seat & tank on, fired up first stab. Love that feeling
I’ve had 2 xRR300’s now & I find the Beta’s easy to work on, really well put together & reliable. Just what a 2-t is supposed to be! I am also REALLY happy to report my oi appears to be functioning as per design so far.
* Due to Euro 4 restrictions, the head has 1 x 6mm security hex bolt. As the frame clearance wasn’t enough to get my impact driver onto the bit, I got creative by inserting the 6.3mm drive end of the security hex bit into a 1/4 inch socket ($5), and then onto the torque wrench.