Aprilia RS50 9 Pipe Test, the results page!

[RpR]

First: Dell Orto makes some of the best carbs out there. About 90% of the tuners i know use DO's. They're cheap, reliable and very easy to tune.

Your stock crank will not survive the TP Due Plus kit forever.
I'd say 2000 - 3000km at most, if you drive the bike hard that is.

And what that about 18000rpm? You'll never get a ~39mm stroke engine to rev that fast anyway. Piston speed would be way too fast and the piston would seize.
The TP kit is build for around 10 - 13k rpm max, depending on the exhaust.
If the Rieyus left you behind very badly, it's probably because of the setup or them not running stock TP 75's.

Oh, and more power without increasing the size of the engine always comes at the expense of more RPM and a more pipey engine.

[Limey]

Okay so the Del should not be an issue. What kind of difference does ignitions and porting make?

I don't have a problem with a top end oriented motor - I just anitipatied some comments about a race set up RS 50 not being a bike to teach a new rider on (past experience on another site).

[suzuki1]

The Rieju (sp?) uses the same AM6 motor as the RS's, so if both bikes had the TP75's then it's all about tuning and attention to details.

As far as the carbs goes, it seems like there are a lot of guys using the Dell Orto carbs with lots of success, but we had better luck with the Mikuni. With the Dell Orto on the bike, first we had problems getting the air/fuel mixture dialed in, then for the 1st race of the season the bike ran good in the morning but as the temp increased it was dog slow. When we bolted up the Mikuni for the next race and it was easier to dial in, and once the jetting was set it ran great on cold and extremely hot days. The carbs are made differently, and based on what I read from the D.O. info on the techtips page it sounds like you adjust it different than you would with a Keihn or a Mikuni too... The D.O. carb is obviously a good carb because it's the carb of choice overseas, but we've had better results with the Mikuni mainly because our time was limited so we just stuck with what we knew.

And the 18k rpm crank that you're probably referring to is hype. As Rpr mentioned you'll never get the motor to spin that high. With mild porting, raised compression, and jetting you can pick up and extra 2-3hp, but just stick with the stock ignition. Shedding weight from the bike may help too if you haven't already.

[Limey]

Now I feel like I'm starting to get a picture. I looked at the whole thread and noticed a few guys running 28mm carbs. If I'm going to send out my cylinder and head for porting and milling, wouldn't it have to be matched for either a 23mm or 28mm carb and matching manifold. I imagine that the 28mm carbs are for more velocity at high rpm, ie more top end hp. I'm a decent rider, so keeping the thing pegged on the track isn't too hard. Giving up 2-4 bhp when you're only making around 14bhp is hard to overcome with just late braking.

I'd be very happy gaining another 2-3bhp! Lets go ahead and say I am definately going to send my cylinder and head out for grinding. How much more of a difference would a different carb from my 23mm Del and a new manifold/reed set make?

FYI- I will be racing the bike on plenty of "big bike" tracks with Team Promotion track days against their Riejus, so there will be plenty of long straights to tap the bike out on. I don't have to have a $10,000 sleeper minibike, but I don't want to be getting left for dead on the straights either. So I'm trying to get an idea of the $/bhp ratio and an idea of which way to go.

Thanks!

[Micah / AF1 Racing]

A 28mm carb is good for another .7-1 bhp. A higher rpm pipe would make your little RS sing, consider Jolly Moto, or Malossi Wild Lion or Gianelli even. Using a proper race fuel like Ultimate 4 and premix at 24-28:1 will be another 6-7% gain in bhp. Finding some dyno time will let you get it all dialed in to work flawlessly.

Your stock ignition can be adjusted to suit your needs too.

[RpR]

Originally posted by rawkus
One thing I think of, maybe it doesn't matter much, but does weight savings from switching from a stock pipe to aftermarket make up some of the power that's lost at lowend?
Dan

It sure does in my oppinion. Loosing weight matters a lot when speaking of accelleration and handling.
Some smart guy once said that 3kg of weight lost equals 1hp when we talk accelleration. That's a thing worth remembering.
Did i just spoil your appetite for all those fatty and weighty x-mas goodies?

[cornellracing]

just a quick question, are these rearwheel or crank figures?

I'm just trying to enlighten some young kids who talking about 20 - 25 HP in their rs 50's!

[Micah / AF1 Racing]

These are all rear wheel numbers....crank numbers are probably 20% higher.

[LorryDrvier71]

Just a thought, but when you put the slip on can on the stock pipe, the stock can gave a smoother curve. So what about puttin the stock can on a different pipe?

[cornellracing]

Thanks, so some kid throwing on a 75 cc kit, arrows etc, slightly bigger carb, no dyno tweeking, carbon reed, we are looking at aprox 10hp rear wheel, 12 hp crank?

[RpR]

More like 12hp rear.
Already fitting, let say the Polini 68cc kit, gives around 10hp on the rearwheel with everything else stock.

[ip2]

15000 rpm is not high for 39 stroke crank , its actually low considering 100cc Kart engines rev +20000 rpm with 50mm stroke , full circle crank required to reach higher revs so i think thats what he meant by high rpm crank ..

also your link to dyno graffs dont work ..

[RpR]

Originally posted by ip2
15000 rpm is not high for 39 stroke crank , its actually low considering 100cc Kart engines rev +20000 rpm with 50mm stroke , full circle crank required to reach higher revs so i think thats what he meant by high rpm crank ..

also your link to dyno graffs dont work ..

I'd very much like to see that cart, any links? I'll believe a 20000rpm stroker with a 50mm stroke when i see one...
And my links work perfectly, it's the forum that messes them up. Copy the link into your address bar.

[Micah / AF1 Racing]

I actually have one of those KT100 karts...and yes some folks are revving to 20,000 and making over 30bhp.

Mine needs new crank bearings and clutch plates before running it again.

[ip2]

Any 100cc european kart engine (w/reed)out of box rev to 20000 rpm , thats normal RPM and how they come from factory without needing any tunning or modification except jetting

Rotax ,parilla , ital systems , Vortex ,IAME , DAP just to name a few .. just check out your local kart track , they really scream ..

new ones dynoed 28 hp stock with pump gas , i have a dyno sheet making around 27 and it was an old aircooled engine runing on pump gas ! email me if interested , they pull very strong from 8000 to 19500 rpm , the rotary valve version claim 29hp stock , modified with race gas can make well over 30

KT dont have reed valve and only revs to 15500