The Helios Project (Aprilia RS 125 Rotax 122 Biaggi Race Replica)

[Calum]

@declan Should have some updates later in the week.

[finnerz89]

@calum I've had 2 bikes with hydraulic clutches, recognised the cylinder lol

[NINJA]

@calum I'm just curious, are the Magura Hydro clutches not compatible???

[Calum]

@ninja They're mega bucks though ain't they.

And probably not.

This is the clutch actuation on these engines

[Minia]

This is really looking sweet

[NINJA]

@calum The Magura clutches are expensive, but apart from the cheap Chinese ones on ebay, there's not a lot else too choose from. I want one on my MX for-sure, can you post a link to the thread you found detailing the hydro conversion please???

[Calum]

@ninja You won't like it, lol. It was using PhotoFuckit and all the photos are messed up.

I'll have this one done by the end of the week.

Here is how Honda did it

They've used the original clutch actuation for it.

Here is the thread.

http://www.125ccsportsbikes.com/forums/index.php?showtopic=100907

[NINJA]

@calum OK Thanks, perhaps if you have the time you could post a tutorial on how to do it and the parts needed etc. please.

[Calum]

@ninja I plan to

[NINJA]

@calum COOL Thanks, does either bike have the choke/hot start lever incorporated in the overall clutch lever/mount???

[Calum]

@ninja Built into the left hand controls.

[NINJA]

I want a SuMo one;

https://www.youtube.com/watch?v=Nxxasvsbe_Y

[Calum]

@ninja I know mate, but you got to import them and by which time they are really expensive.

[NINJA]

@calum True but isn't owning rare gems every enthusiast's dreams???

[Calum]

@ninja I think, for the money, you could have a supermoto Honda CR500.

So it's kinda like, well they're rarer and better.

[Calum]

So this arrived this morning.

It's the Italkit Gilardoni 140cc cylinder kit for the Rotax 122 engine.

I feel like a bit of history is needed to really appreciate this cylinder.

Gilardoni is the original designer of the Rotax 122 cylinder way back when.

Original Barrel for reference

A few years ago he revises the cylinder in the form of this cylinder. This cylinder reflects lessons learnt over all of the years people have been racing these engines. All of this is reflected in the barrels design.

Now I was tossing and turning trying to decide what route to take with this engine. Initially, sticking with the Gilardoni Rotax 122 original cylinder, opting to have it ported to reflect my systems designed.

But no matter what engine I bought, the cylinders were all scrap,and it was going to cost £300 to remanufacture the cylinder to usable condition.

I have ridden Aprilia RS 125's since I was 16, that's a little under a decade of riding experience on these engines alone. I have ridden bad ones and I've ridden good ones. I've ridden bog standard ones, and highly tuned ones.

The thing that stuck in my mind the most is how the original engine revs to 14K, and I always appreciated that out of the original cylinder.

When riding Polini's 160cc kit, you lose around 2K over rev. This isn't the case with this barrel. It'll continue to pull hard to 14k, granted it's not the extra CC's that give you the bang.

The porting work on this engine is superfluous, it's extremely well done for a casted material.

Sure there are further refinements that could be done here, a few edges taken off and some minor flaws altered, but on the whole, it's a very well designed cylinder.

Combine this with PJME's Reworked VHM billet head, and you have yourself a very capable top end.

The cylinder is running a relatively high 12.1:1 compression ratio, less than ideal for reliable road use. The fueling on this cylinder needs to be finely tuned to avoid running the risk of detonation. This engine must be run on Shell Super Unleaded, else it's just going to detonate.

All this power is no good if you can't stop for the corners.

I've ran these on my DT, with the older style Aprilia braking system. So running this on the radials will surely surprise me.

These Brembo Sintered brakes are £40 a pop, if you can find a set. Were sold out everyone I looked.

I refurbished the brakes themselves back in Christmas time, and I've just ordered titanium retainer pins and titanium bolts to fix it to the forks.

So far so good.

I need to calculate the squish on the engine I'm building to ensure I get the right compression ratio, then drop the engine into the frame.

I need to order some titanium head bolts, V-Force3 Reed cage and 34mm inlet. The dellorto racing carburettor has been ordered. Some £1000 spent this month already, with more to follow...

[declan]

@calum im expecting the very first attempt to start the bike on here

[Calum]

@declan Yeah I'll get a video up when that happens don't you worry

I'm still probably another payday off yet.

Needs CDI (Zeeltronic), indicators, wing mirrors and a good number of other electronics.

I've got the radiator now and hoses.

I expect there is going to be the odd bit here and there left to do.

Fairings have been ordered. They are made to order so they take ten days plus shipping.

And then there are the custom fabriacted bits, plus a little more painting that needs doing.

Should have it dyno'd towards the later end of the summer, see what she's making.

[Irongamer727]

The compassion ratio on my Athena is supposedly 13:1. And yours 12:1:1? What's the difference? Cool stuff you got there!

[Calum]

@irongamer727 That's savagely highly.

The stock DT is 8:1 lol.

The higher the CR, in general, the more extremely the powerband and the less torque.

I'd be very surprised if the somewhat powerless Athena kit is 13:1. You can have too much which has adverse affects.

I'd be more inclined to say the Athena is a lot lower, as it's generally a more torquey setup.

The higher the CR the more...unreliable an engine becomes. A lot of stresses on the bottom end and components you see.