What gear to buy? Yamaha Aerox (minarelli lc)

B

Ben Dover Swe

Well-Known Member
Hey!

I have a stock Aerox with a Gianelli Go exhaist, and without variator restriction, and 17.5mm carb, stock air filter, stock reed, stock intake manifold (is it restricted?).

I am looking for a reliable setup without too much noise (low rpm power?). I want a city toy, pulling like crazy at the red lights, dropping jaws, power-wheelie power if possible, top speed not need more than 80kph (50mph). I don't mind changing piston rings once a season (~2000-3000km per season / 1200-2000 miles per season)

Budget would be about $300-450 if possible. If the perfect package cost more, it's ok - bang for buck is everything =)

My thought 1) Stage6 street race, but not sure it is powerful enough. Sport exhaust.
My thought 2) Sport pro mk2 or even racing mk2 (more reliable for street because of lower rpm than sport pro, according to daniel in a thread?) with a more silent exhaust (basically a more silent/less powerful exhaust and a more powerful cylinder to compensate).

If top speed gets too high, then gear down to use excess power to accelerate instead of top speed - bad idea?

What do you suggest for package?
 
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Hey Ben,
Thanks for posting this here! The thing is, that the higher the output power of an engine is, the more narrow the power band is and usually also, the higher the power, the higher it is ranged in the RPM. For example a stock scooter engine has about 5hp. It peaks at about 7500 rpm but it has a very wide band. You probably have 4hp at 5500 rpm already. This makes it very easy to adjust and find a matching exhaust. Basically you can't do much wrong unless you go to the extremes.

Then there are racing cylinder. Some of its power is produced due to the increase in bore (70cc), but most of it is due to port layouts. A good sport cylinder kit can produce 12hp, however the power band is much more narrow. it will produce 12 at 10500rpm and but at 9000 rpm it might only produce 6hp.
The amount of rpm is highly dependent on the exhaust design. The exhaust allows the engine to rev higher (it also can move the powerband around a bit, but that's not so important right now) and reach the ideal rpm for the cylinder kit.
The genius of the CVT engine is that (like the name implies) it is a variable transmission. Unlike traditional shifters, it changes gears (or ratio) automatically. This is why you're scooter goes faster when accelerating but sounds like it is staying at the same rpm (it actually does stay at the same rpm).
To your problem: If you say you want to pull wheelies and stuff, this usually means you need quite a bit of power. The Aerox has a Minarelli engine, which is great for tuning and performs very well out of the box already. Like you said already I'd say the Stage6 Cylinder Kits are a very good choice because of their price, quality and performance.
The Sport Pro MK2 produces good power and has quite a lot of torque and a reasonable power band. It is also a good match for the 17.5mm carb and works with a good range of exhausts.
The Stage6 Racing MK2 on the other hand produces quite a lot more power and it also feels stronger because it is more peaky. Tho, it is harder to setup as you need to hit the power band exactly and it also requires a higher revving exhaust (Stage6 R1200 or Yasuni C20). It will also consume a good bit more of petrol and requires more maintenance (high rpm is really not so good for an engine).
If you are not so experienced with carb jetting, CVT transmission setup etc. I would suggest to go with the Sport Pro MK2. You have a good choice of exhausts here. The Sport Replica works well and is not too loud, the Sport PRO (non replica) is hard to find but performs even better and the Yasuni C16 or even C20 would also work if you upgrade in the future to the Racing MK2 cylinder kit.
One thing with the minarelli engines is the crankshaft. By default it uses a 10mm gudgeon pin, which is ok for some tuning, but can break when running under a lot of pressure (Racing MK2 with a good exhaust). Thus I would recommend to replace the crankshaft to a 12mm one as one of the first steps. A full circle crank also reduces engine vibration at high rpms.

To sum things up and recommend a setup:
  • Cylinder Kit: Stage6 Sport Pro Mk2 (Racing if you dare ;)
  • Exhaust: Stage6 Replica or PRO (non replica), Yasuni C16 or C20, or R1200 if you want higher performance but they are quite loud
  • Crankshaft: Anything with 12mm full circle, tho the Stage6 HPCs are good
  • Bearings: Get a set of new bearings (NTN or SKF) when replacing the crank. Ideally some high performance ones like the Stage6 and such
  • Intake manifold: Get a tuning one. I believe the stock intake mainfold is restricted to 12mm.
  • Airbox: Read about tuning your airbox and make sure to clean it regularly
  • Reed Valve: Replace the stock metal valves with kevlar/carbon ones, or get a sport reed valve block. No need for the expensive ones.
  • Variator: You need to adjust the rollers to match the rpm of the cylinder kit. You can get a roller kit, or directly get a sport variator (Stage6, or Malossi. Malossi is better I think but also pricey)
  • Clutch: Harder clutch springs bring the sensation factor as the engine clutches in at much higher rpm. If the stock clutch is worn, you can switch to a sport clutch. Stage6 is good and les sof a pain to handle than the Malossi one.
  • Clutch Bell: The clutch gets crazy hot in the summer, especially when riding in the city. Get one of these CNC clutch bells by Stage6, Polini or Naraku.
It's quite a list but the small parts like springs, rollers and such are really cheap. Each of the items listed I would consider a must-have. Regarding your Gianelli exhaust: You could give it a try with the Sport Pro MK2. Giannellis are usually very compatible. Performance would be comparable to the Stage6 Replica exhaust.

Hope this helps for now. Let me know if you have further questions!
 
Sweet list, nice! :)

Regarding crank, Im not that handy and might need to get it swapped professionally - what time consumption would be normal? To budget calculate.. (engine mounted on scooter vs turning in engine on the counter)

If it ends up beyond budget, would sport pro mk2 in lower band (i noticed it has wide peak) be ok with stock crank? What exhaust to match?

As last resort - what alternative cylinder kit/exhaust to avoid opening engine?
 
mhm a shop should be able to do it in less than two hours for engine only and less than three for the whole scooter. In general it i not so hard to do, but you'd need to buy some special tools to remove some parts and install the bearings, etc. The tools can be bought on ebay for a total of less than $50. No pro stuff, but good enough to do the job at least once or twice :)

The problem is mostly that you are running the scooter in the city, which is the most common but also the most stressful environment for an engine. Sure you could go with heavy rollers in the vario and a low power exhaust, but then you would just end up with a slightly better performance than the stock engine and certainly no wheelies... This basically goes for all cylinder kits...
However, there are a lot of people who ride the stock crank, but it depends a bit on how many km's you are planning to go with the engine. You might be safe for 10.000kms but after that parts failure becomes quite likely, be it the bearings or the conrod...
 
Ok mate, almost shopping time! =D

Second-last question:
What kilometer/hour/whatever recommendation would be a good exchange for piston ring (normal-agressive street/urban use) for A) streetrace B) sport pro mk2 and C) race mk2? Trying to get a feeling about the level of maintenence =) I know there is no way to be sure, but if you manufactured a users manual, what number would you put in it for maintenence?
 
Hey man,
This is indeed really difficult. I believe malossi and Polini state every 1000km, but I don't know where these numbers come from. If you're on the track you only go about 50km per run, and you would usually replace them after every weekend. And on the street I believe you are usually save for at least 2000km. The thing is, the rings don't break, when setup correctly. They just loose some compression and you loose some power. It is nothing dramatic. Maybe 10% if at all. Since it is happening gradually, you probably won't even notice...
 
TuningMatters said:
Hey man,
This is indeed really difficult. I believe malossi and Polini state every 1000km, but I don't know where these numbers come from. If you're on the track you only go about 50km per run, and you would usually replace them after every weekend. And on the street I believe you are usually save for at least 2000km. The thing is, the rings don't break, when setup correctly. They just loose some compression and you loose some power. It is nothing dramatic. Maybe 10% if at all. Since it is happening gradually, you probably won't even notice...
Click to expand...

Sweet, good info! I was warned that the racing mk2 and c16 was loud if you are "loud sensitive" as i am, is there any more silent exhausts for this one, even if losing power, that is worthwile to change to? I prefer low end/acceleration?

(I have found a deal on a used bike with racing mk2 and c16 and the seller himself is recommending me to not buy his bike for daily/street use :P Its a good price so I might go for it anyway, and replace exhaust or muffler or whatever.)
 
Hey Ben,
The problem really is the small displacement you get with 50cc scooters. Torque is usually generated by increasing displacement and power relates more to the RPM. With 70cc you will always have to choose between low power at low RPM or high power at high RPM. The Racing and C16 are definitely loud and very high revving. You can take it to more extremes with a C21 or R1400 exhaust, but still we are talking 10-11.000 RPM here even with the C16. Some people manage to reduce the noise by installing 125cc silencers. Back in the days the 125cc Giannelli silencer for Aprilias RS125 was very popular (http://www.giannelli.com/eng/prodotti/linea.asp?ID=43).
Does this help?
 
The thing with the streetrace is that it's based on the old Sport Pro, not the MK2. The MK2 performs a lot better than the MK1 (approx 2hp more possible if fully tuned). Have a look here: http://www.tuningmatters.com/news/news-stage6-sport-pro-mkii-and-stage6-racing-mkii/

The reason why PedParts state the Streetrace would perform better is because it is easier to setup due to the wider powerband. If setup correctly a Sport Pro outperforms the StreetRace in acceleration and top speed. Also you would always prefer an Alu Cylinder versus a cast iron.
Acceleration always goes hand in hand with high top speeds. There is nothing you can do about it. If you want to keep the top speed low, you just stick with the original gearing but it comes at a cost as the constant high RPMs will harm your engine quite a lot. Also from about 15hp the scooter becomes quite uncontrollable as it pulls a lot of wheelies, which can get very annoying in stop and go traffic.
I believe the Sport Pro would be the right choice for you as it is a good compromise between power and durability!

Peace,
D
 
Hello, hope all is great! =)

Well basically, we ended up getting the stuff you recommended (list below) on another used Aerox.

Since this thread apparently ended up very high on search rankings, I guess a lot of people will come here for help, so lets help! Perhaps we can finish it as a go-to guide for all minarelli ac's who want a complete tuning-package! =)

I fill in what I think, with source. Please correct/comment what ever you notice!

CARB
Main jet: 85 (note: Brand new not braken-in cylinder, perhaps 90? 95 even? Using 3% oil pump)
-Source: (http://www.tuningmatters.com/how-tos/how-to-quickly-determine-the-carburetor-main-jet-size/)
Pilot jet: Stock
-Clueless what other to use or whether it is worthwile or not.
Needle: Stock
-Clueless what other to use or whether it is worthwile or not.
Airbox: Stock
-Clueless what other to use or whether it is worthwile or not.


DRIVETRAIN
Target rpm: 8600 or 9000 or 10500 (?)
-Source for 8600: Stage6 Streetrace + Stage6 Replica (Wrong cylinder! But has similar peak rpm if I recall correct): http://www.tuningmatters.com/reviews/exhausts/scooter-tuning-exhaust-test/ )
-Source for 9000:
http://www.pedparts.co.uk/blog/stage6-sport-pro-mkii-cylinder-kits-a-closer-look (1st chart)
-Source for 10500:
http://www.pedparts.co.uk/blog/stage6-sport-pro-mkii-cylinder-kits-a-closer-look (3rd chart)
(note: I value low noise levels highly)

Variator:
Stock. Have no idea if changing it is better or even worthwile.

Roller weights for target rpm:
8600 rpm: ~4.5g
-Source: Estimated from chart at http://www.pedparts.co.uk/blog/moped-tuning--rollers
9000 rpm: ~4g
-Source: Estimated from chart at http://www.pedparts.co.uk/blog/moped-tuning--rollers
10500 rpm: ~3g (?)
-Source: Estimated from chart at http://www.pedparts.co.uk/blog/moped-tuning--rollers

Clutch springs for target rpm:
Max power at 8600 rpm, engage at rpm: No clue
Max power at 9000 rpm, engage at rpm:: No clue
Max power at 10500 rpm, engage at rpm:: No clue
-Source: http://www.upload.ee/image/1275406/malossi_clutch_spring_chart.jpg (image-googled for "clutch springs malossi fly clutch")

Contra spring:
No clue, currently stock. I have understood that I should start light and look for signs of needing harder contra spring (slow up hill/does not maintain rpm when coming to up hill but instead rpm go down, OR when braking/losing speed and then accelerating again, accelerates slowly. Source: http://www.apriliaforum.com/forums/...ights-and-contra-spring-mechanics-for-dummies)

Parts list:
  • Cylinder Kit: Stage6 Sport Pro Mk2
  • Exhaust: Stage6 Replica
  • Carb: Geniunie dellorto 17.5mm with 75 main jet (apparently too lean - will upjet asap!)
  • Crankshaft: Stage6 HPCs (came with the engine, its 10mm pin AND according to its S6-part number its apparently for minarelli vertical ac, while I have horizontal lc - hope this will not mean trouble! Please either alert me or calm me.)
  • Bearings: NTN or SKF or similar (was installed already)
  • Intake manifold: Stage6 intake and reed package. (glass fiber petals i think)
  • Airbox: Stock airbox, not modified
  • Reed Valve: package with intake
  • Variator: Stock with 4,6g weights (3x 4.7 and 3x 4.5)
  • Clutch: Stock with stock springs. Got a good price ($8) for a malossi flyclutch with white springs. Not installed yet. Hope it does not suck.
  • Clutch Bell: Stock, hope it will not melt. Might upgrade belt to be sure it's high quality and can take the heat.

Regards,
Patric, spent almost 2 hours creating this guide, got a headache too =P
 
Reporting back for those of you coming here for tips/info:
As I mentioned above, I got the gear specified, and now assembled and tested some. Wow it REALLY kicks ass, I was actually happy the first time I tried it without adjusting weights etc. It accelerated very well and smooth, and then when the variator ran out of space and the RPM started increase (30-50kph?), BAM it took off like a rocket - I was so chocked I had to pull over and chill down, was not expecting that from a scooter =P

I guess my weights (4g, stock variator) is riiight below the optimal powerband, so lowering weights just a tad will do it! A neighbour who is used to drive ktm's came out wondering who drove the speedy sport bike he just heard swooshing by his window, "what!? was it the scooter??" =P

Question:
Will a performance variator improve acceleration from standstill?
 

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