Yamaha RX125 gearbox alternatives?

[mcetp001]

Hi - I have been lurking here reading the Team ESE and other related 2-stroke threads for a while - great stuff. It has certainly inspired me to have a go at tuning my GP125 (commuter) and Yammy RX125 (racer).

I just started racing on the 1977 Yamaha RX125 in historics over in South Australia. Started with it completely stock, bar an expansion chamber, just to get into it and quickly realised that I need to do some porting etc to get it competitive. But I was also thinking about the gear box and was wondering if anyone with experience with these engines knew if a suitable 6-speed gearbox is compatable with th RX?

Thanks.

Tim.

[F5 Dave]

probably not. 3rd, 4th & 5th are virtually the same gear as you will have found.

At some point you have to decide when to pull the plug on a particular engine or bike. Sooner is better than later.

[mcetp001]

Thanks for the reply dave...not to worry, it is just a bit of fun and I am racing against H100s and CB125s so the RX holds its own. Just need to give the cylinder a tickle...

[F5 Dave]

H100 should slaughter it with some development & you can fit the excellent 6 speed from the MB50 or aircooled CR80 if your rules allow it.

That said RXs go okish with a light tickle.

[mcetp001]

Yep - the H100 has the 6-speed gear box and some other CR goodies...goes alright!