Aprilia piston problems

[swanne]

Hi all..
Newbie here. Just bought a 2000 plate Aprilia RS125 with Rotax 122 engine... The RAVE valve/function has been removed and bodged with a screw holding the valve half open.. On my way back home this screw fell out, allowing the valve to interupt the piston and damaging the crown.
I would be very grateful if anyone could advise me on;

1, the most suited make of piston for the 122 engine?

2, what position i should fix the valve to? (after taking the burr off it)

Thank you in advance,

Carl

[Kickstart]

Hi

Loads of makes of piston and to an extent you get what you pay for. However PJME sell the Mitaka pistons but with different rings and people seem fine with these.

As to the valve, fully open will give you the top end power but stuff all at low revs (can be fun, but moving off with a pillion will be difficult and it will be a pain to ride round town. With the valve fully closed it will be restricted and have about 14~15hp but a reasonable amount at low revs. I presume what you have in a blanking plate that has been shortened to try and give full top end power.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[swanne]

Thank you for getting back to me and helping me. There is a blanking plate and screw that controls the length of the valve. The screw wasnt locked off. I am thinking about positioning the valve about half way and locking it off. Does that sound like a good idea?
Mitaka pistons are available on ebay for 20-25 quid and a top end gasket kit about the same. Will that all be ok?
Thank you again

Carl

[Kickstart]

Hi

Not sure how you can lock it in the half way position without a spacer. Not really enough space for a lock nut.

Personally I think I would just lock it in the fully open position.

The Mitaka rings are not meant to be that good. PJME want £40.84 for a Mitaka piston with Riken rings (Vertex piston is ~£70, Wiseco ~£125). You only need a few gaskets for the top end. The head gasket O rings can be reused a few times while the base gasket is available from Rotax on its own for a couple of quid. However it is probably best to buy the kit so at least you have some spare O rings (sods law, if you don't have spares you will need them).

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[dangerousdave]

Just had a look the the original equiptment Aprilia piston 170 quid ! Ouch !

Can you get hold of a replacement powervalve actuator - that way you'll get the smoothest power ?

https://cgi.ebay.co.uk/Aprilia-RS-125-RAVE-POWERVALVE-AND-CASE-CABLE-NEW-RX-/170503678358?pt=UK_Motorcycle_Parts&hash=item27b2cfa996#ht_2291wt_1152


Otherwise bolt it wide open - power will come on hard but its good fun !
____________________
1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50