The 50

**husaberg** · 28th November 2013, 17:44

this was posted a while back
http://www.underdogsracing.com/fospipe/
frits has also posted a pic of his 50pipe that has won the last 5 euro championships or something i have it somewhere.

Originally Posted by Frits Overmars

Tim, right now you may be more interested in ' All that you wanted to know about the Aprilia RS50'. Here are some numbers to play around with. Exhaust pipes don't come any simpler than this, but don't let that fool you; this pipe was good for eight championships. Just don't show it to the Poms; year after year they keep trying to beat those Dutch 50 cc bikes

.
About the step in the exhaust duct: if there is a step and you remove it, you lose power. I think the main reason is that in removing the step you increase the duct volume. The Malossi cylinder I experimented with has no step at all, but as you can see in the pipe drawing, the exhaust duct is quite narrow. That works.

**F5 Dave** · 29th November 2013, 10:18

Ahh, you mean 83 ATDC not 183 as that would give you -6* of exhaust duration. Frits's example above has a scant 31deg of blowdown which must mean they are doing some pretty extreme aux port sizes. On conventional single ex you would be crazy to talk those numbers. Unless perhaps these guys know something I don't. . .what's the chance of that though

**cotswold** · 29th November 2013, 16:59

Originally Posted by F5 Dave

Ahh, you mean 83 ATDC not 183 as that would give you -6* of exhaust duration. Frits's example above has a scant 31deg of blowdown which must mean they are doing some pretty extreme aux port sizes. On conventional single ex you would be crazy to talk those numbers. Unless perhaps these guys know something I don't. . .what's the chance of that though

are you moolses daddy

**cotswold** · 29th November 2013, 19:32

Originally Posted by cotswold

are you moolses daddy

86atdc so 188 duration? sounds about right, but I've been wrong all week and I think blowdown is 30 at the moment

**F5 Dave** · 30th November 2013, 08:44

No if Max was my kid Cyps would have been involved as he's a cheeky little git when he was down here. Nah I like im but Hope my kids don't sass me like that.

**husaberg** · 30th November 2013, 08:49

I see kids as a mirror to our own personality Dave, we can see the worst in the as wells as the best. did you sas your parents Dave?
did your parents ever say wait to you have kids............

**F5 Dave** · 30th November 2013, 08:56

Certainly not. But there's two parents for every child. . . My 3yr old is running around like a lunatic with some ear defenders. That'll be her mothers side I bet

**husaberg** · 30th November 2013, 09:23

**Henk** · 30th November 2013, 12:26

Originally Posted by F5 Dave

No if Max was my kid Cyps would have been involved as he's a cheeky little git when he was down here. Nah I like im but Hope my kids don't sass me like that.

Still a cheeky little git.

**cotswold** · 10th December 2013, 12:31

Well my ignition has turned up at last and I ripped open the packing with no small amount of excitement, then I saw the rotor and that feeling of happiness dislolved like a fiat in an English winter. To make things worse the backing plate is also incorrect.
A question to the wise and clever ones out there, is it possible to taper bore the 8mm hole out to fit the MTX crank and make a backing plate addaptor or do I have to send what I have back and wait for the correct bits.

**190mech** · 10th December 2013, 13:20

Yes it is possible with careful machine work on both accounts!

**F5 Dave** · 10th December 2013, 14:43

Dear oh dear that is a cock up. Yes it is possible with caveats. I've done RM80 to fit Honda (or rather entrusted it to someone better than me on a lathe) as you can make the hole too big/deep real quick.

But (and its a big butt . . .see what I did there?) there should be a steel insert & that has to be big enough to take the new taper.

Backing plate should be simple enough but you will need a locating outside or inside step on the plate so you can locate the stator (a dodge is wrap a thin bit of card around the flywheel to get clearance every time you move the timing.

**mr bucketracer** · 10th December 2013, 17:20

easy done but get the taper right but machineing a dummy bit of material . you can also put the keyway in useing the lath

**cotswold** · 11th December 2013, 10:37

I sent the supplier an Email but just silence from their end. If this is what I have to work with, anyone want to make some xmas dollars by fixing this for me as I know my limitations on a lathe and this is way beyond them. I can send out my spare bottom end anywhere across the NI.