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

Calum

LOL at this engine. It was sold to me as :

Came from a Sx in good condition just had new piston con rod main bearings been running for about 5 mind what you see is what you get

It was also listed as a Rotex engine, not what it should be as Rotax.

So I can't say I am really surprised. Item was well wrapped and delivered within 48 hours and I got what I actually wanted. But check out the rebuild on this engine.

Firstly the head is absolutely ruined, straight in the bin this went.

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Secondly the bore is totalled, but it's an aftermarket Mitaka one so runs a steel liner, meaning it can be rebored so isn't totally scrap. But definitely affects my resale value Was hoping to claw back a few sheets on this engine to pay for the conversion.

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I didn't get a photo, but the crank journals have a nasty score in them which I would want to fix. Shame. The crank looks okay, although given the damage done to the rest of the engine, I would have it rebuilt.

And the little end, which was probably what caused the fault in the first place.

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Prepped the cases to shot blast next weekend.

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I'm going to use this engine as a base to fabricate up the part I want. It's gutted other than the bearings, purely has a means to protect the journals. But in time I will rebuild this engine and leave it as a spare.

Now back to my engine

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As you can see, it's now dual wielding both the Starter motor and the kick start mechanism, which is nice.

Just missing a titanium bolt that secures the kicker in place, I shall get that ordered.

Engine has been timed up and all new gears installed.

Just waiting on PJME to get new clutches in and then hopefully sort the top end out next month. Got some tasty ideas for the top end.

declan

@calum don’t know what your on about mate looks ready to race to me what did the piston look like

Calum

@declan Piston wasn't too bad. Could have used that. But I threw it in the bin. Wasn't even forged.

declan

@calum so maybe a stupid question but was it rebuilt badly or not rebuilt at all

Calum

@declan Nah man I don't think it's a stupid question.

So it's been stripped before.

There was a rusty bolt on the inside of the engine. That suggests that they just used a bolt that would normally be outside the engine on the inside. Since it was an OEM bolt.

Also, the crank is really solid.

I reckon, someone who didn't know what they were doing, rebuilt it poorly. Started it up. heard a horrendous noise, and then gave up on the idea after sinking too much money on it.

The barrel doesn't look to have been rebored. So it was likely a new barrel at the time. The piston wasn't the highest quality, but it was a decent piston.

I doubt the mains were changed, and they clearly didn't bother with the gearbox bearings. I reckon the minimal amount was done. But once it still didn't run right, they gave up on the idea.

It's funny though.

As I say, the cases are handy for my next project I'll be doing on this bike.

And all I really wanted was the kickstart. I've managed to sell some of the bits I've stripped from it on eBay. So that's some way of clawing the money back out of it.

declan

@calum sold bits already? Well it’s a good thing You didn’t want the engine as a whole isn’t it

Calum

@declan Literally just wanted the idle gear and the kickstart mate. The rest I already have.

But for this tasty little conversion I am going to do, it would be nice to have a pair of crankcases to hand

I ain't saying no more than that, you will see the results when I finish.

Calum

Updates are coming...

But who can guess what custom modifications I will be doing on my RS?

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I won't take credit for the idea. I always wanted to do it on my DT, but just couldn't justify the price.

I then found a thread detailing a certain other bike made by Honda, whom did the exact conversion on these engines.

HM CRE 125 if you're wondering. Looks awesomse, same engine as these RS's, except they ran electronic oil inject for 50% less oil consumption. Amongst other mods.

But after not being able to find the parts I wanted, I gave up.

Then I found this build thread on a certain other website, and mans was like...yes I'm doing that.

finnerz89

@calum hydraulic clutch?

Calum

@finnerz89 Spot on mate. How did you know?

declan

@calum damn give me a chance lol

Calum

Front Mud Guards Arrived

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I look forward to fitting that this weekend

declan

@calum that looks slick how’s the engine coming along?

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

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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???