No powervalve

TheHunter · Derestricted Danger Joined: 02 Jul 2009 Karma :

I have a question.

With moto-x bikes it was possible to remove the powervalve for hillclimbs (as low/midrange isn't used), well would it be possible to do the same for a road bike, namely a prilia mx125?

Theoretically it should be possible, and wont cause any damage so im just wanting to know the best way to go about doing it.

binge · Emo Kiddy Joined: 03 Jul 2004 Karma :

I know with the Yamaha engines they have a rotary style Powervalve. But the Aprilia 125s have a blade style powervalve I am sure.

You could take it out I suppose, but low end power will be non existent.

I am sure I heard somewhere that the racers just take all the springs out of the blade style powervalves, Polish them right up, And just let them move naturally with the air pressure.

Ben

TheHunter · Derestricted Danger Joined: 02 Jul 2009 Karma :

You can do that with the diaphragm based PV systems but the aprilia uses a solenoid so that cant be done. I was just going to remove it but them im left with a hole in the cylinder, which could be problematic lol!!

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

The early Aprilias did use a pneumatic power valve operating on exhaust gas pressure. The switched to the electronically operated ones on the road in about 1989 (few years later on the race track).

No reason you couldn't modify the blade top be in the open position all the time, but not really any reason to. You would save a tiny bit of weight (just eat one less pie for the same effect) but would lose low down power.

Just removing the blade would probably lose you both bottom end / mid range and also top end power.

All the best

Keith
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mad4it028 · World Chat Champion Joined: 04 Jul 2006 Karma :

broke the powervalve on a kmx so made it permenently open but intop gears it was guttless so i replaced it n was alot faster
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Vincent · Banned Joined: 16 Oct 2006 Karma :

I've seen a few racing Yamaha RDs with the valves stuck open but they're usualy tuned to run at top revs all the time anyway, Moto-X bikes might be a bit different as you need a bit more low down power sometimes. I wouldn't really connsider leaving the powervalves open on a road bike.
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TheHunter · Derestricted Danger Joined: 02 Jul 2009 Karma :

Tried it without the PV.....its different! Nothing..nothing..nothing.....BAM! 30bhp right in the face! Shocked

Epic fun through the twisties, utterly useless in traffic!

So i decided to put it back in and made a startling discovery - the PV was in upside when i got it. Put it back in the right way up its transformed the bike. Pulls flawlessly through the entire rev range.

Just like being on a MotoX bike again (albeit a bit less go), so it was a worthwhile experiment, even if the original plan went the hell hehe