Brand new build - too loud/too high RPM, unusable bike :(

[Ben Dover Swe]

Hey!

I posted my project here:
http://www.scooterforum.net/threads/what-gear-to-buy-yamaha-aerox-minarelli-lc.204381/

The bike runs super - but sounds like a motocross. The noise volume is prohibitive while running around in a city, its a police magnet - police would stop me the instant they heard me several blocks away. Also, neighbours would kill me. It is ok to crawl with (<20kph) and idle noise level is OK.

What can I do, do I have to sell the scooter? I am really only interested in good acceleration and top speed of ~70kph/~45mph. Stock derestricted exhaust with heavy rollers?

Yamaha Aerox, minarelli horizontal lc

• 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
• Variator Weights: 3.5g

 

[TuningMatters]

Hi Ben,
Sorry to hear that. Whilst a 70cc cylinder and exhaust make your scooter louder, it should not exceed about 95dbu with your setup. Di you have a chance to do some measurements? Smartphone have some apps to do dbu evaluations.
Some things to check: Try heavier rollers. Maybe your engine is overrevving.
Is the exhaust new, or used? Maybe someone removed the wool from the silencer.
Try hooking up the stock exhaust. Should still be louder than stock (since 70cc and higher revs) but less than with the stage6.
Higher end exhaust have better noise levels but are much more expensive. Yasuni C21 carbon and kevlar for example.
If you install harder clutch springs, the initial revving wil be much higher to get you started. if you want to keep the noise down, i'd stick with the stock springs.
Make sure the exhaust is mounted properly and not leaking...

Hope that helps!

Best,
D

 

[Ben Dover Swe]

Hello D, thanks!

• "Try heavier rollers. Maybe your engine is overrevving."
  Powerband felt way too late with 5g (kicked in at ~40kph/30mph). When reaching this speed, it really accelerated great after this point, but it was very lackluster up till that point. Also, it sounded like a motocross bike when revving above this speed. I presume the variator ran out of gears and started over-revving into its optimal powerband, leaving its weak low powerband. I tried lowering variator weights from 5g, to 4g, to 3.5g - then I overcame the sloppy acceleration curve and got very nice acceleration only 1 second after takeoff - better but not good (want acceleration at takeoff, not after). This could probably be remedied with stiffer clutch springs. HOWEVER this low roller weight maybe meant that the engine was over-revving as you suggested. The loudness make the bike impossible to ride in the city. Also not only loudness, but high revving as well. The noise level was making people turn around and be angry as I passed. BUT, without this rpm, the acceleration from stand still (which is what I want) is better even using the stock exhaust.
  
  
• "Is the exhaust new, or used?"
  Brand new from Pedparts. De-restricted though, so there have been some handling of it. Can you somehow improve the silencer? Change fluff inside of it? Dyi-silencer? Paint it with thick exhaust paint to reduce vibrations? Other stuff?
  
  
• "Try hooking up the stock exhaust. Should still be louder than stock (since 70cc and higher revs) but less than with the stage6"
  I tried this (de-restricted). Indeed more quiet, and with 5g weights it accelerates from stand still better than the Stage6 Pro Replica. But the takeoff-G-force is the same as the Pro Replica gets then it kicks in (already travelling at 30kph), indicating that this exhaust really unleash the power of the cylinder - making me wish that this cylinder kit has a LOT more to give from stand still than stock exhaust. Or is the stock de-restricted aerox exhaust really the best exhaust for take-off (while somewhat quiet and low rpm)?
  
  
• "Make sure the exhaust is mounted properly and not leaking"
  I kind of remember when assembling the scooter in the "garage" and first start - it felt very quiet. Although only idling. The only thing I can imagine we changed since then, was changing exhaust bolts to exhaust studs+nuts - is it even possible that it somehow got louder with studs+nuts instead of bolts? Used 7Nm torque wrenched. When removing it to install stock de-restricted pipe, the gasket looked perfect brand new, not melted/hard as they use to look. I will try bolts again, and see if there is any change.

I have no clue to get out of this dilemma. I am very sad, from being very eager. I feel I spent all my money and now I am stuck here with items I cant use. To quote myself "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).". But I see now that power wheelies will probably not be possible while somewhat stealth. I feel I might have the wrong 70cc-kit, the Polini and Malossi kits seem more powerful at stealth/low rpm. Maybe just sell the 70cc+exhaust and get a malossi/polini 70cc+some other exhaust, but the risk is I end up with the same problems/loud exhaust since I am clueless, and can't afford to buy several exhausts and try them out Any help - what would be the best course of action - would be appreciated.

Regards,
Patric

 

[TuningMatters]

• "Try heavier rollers. Maybe your engine is overrevving."
  HOWEVER this low roller weight maybe meant that the engine was over-revving as you suggested. The loudness make the bike impossible to ride in the city. Also not only loudness, but high revving as well. The noise level was making people turn around and be angry as I passed. BUT, without this rpm, the acceleration from stand still (which is what I want) is better even using the stock exhaust.

Ok, I don't think the engine is overrevving. If at 5g, when acceleration kicked in the engine was still too loud, then it's not excessive noise due to overrevving!

• "Is the exhaust new, or used?"
  Brand new from Pedparts. De-restricted though, so there have been some handling of it. Can you somehow improve the silencer? Change fluff inside of it? Dyi-silencer? Paint it with thick exhaust paint to reduce vibrations? Other stuff?

You can replace the silencer wool, tho it won't be too much of a difference. Back in the days, people used the Giannelli silencer for the Aprilia RS125 (Link). It fitted the Polini Evolution exhausts. not sure if you can mount it onto the Stage6.

• "Try hooking up the stock exhaust. Should still be louder than stock (since 70cc and higher revs) but less than with the stage6"
  I tried this (de-restricted). Indeed more quiet, and with 5g weights it accelerates from stand still better than the Stage6 Pro Replica. But the takeoff-G-force is the same as the Pro Replica gets then it kicks in (already travelling at 30kph), indicating that this exhaust really unleash the power of the cylinder - making me wish that this cylinder kit has a LOT more to give from stand still than stock exhaust. Or is the stock de-restricted aerox exhaust really the best exhaust for take-off (while somewhat quiet and low rpm)?

You need to lower the weights, if acceleration only kicks in at 30kph. Try maybe 3.5g with stock exhausts.

• "Make sure the exhaust is mounted properly and not leaking"
  I kind of remember when assembling the scooter in the "garage" and first start - it felt very quiet. Although only idling. The only thing I can imagine we changed since then, was changing exhaust bolts to exhaust studs+nuts - is it even possible that it somehow got louder with studs+nuts instead of bolts? Used 7Nm torque wrenched. When removing it to install stock de-restricted pipe, the gasket looked perfect brand new, not melted/hard as they use to look. I will try bolts again, and see if there is any change.

I assume it is correctly mounted

I have no clue to get out of this dilemma. I am very sad, from being very eager. I feel I spent all my money and now I am stuck here with items I cant use. To quote myself "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).". But I see now that power wheelies will probably not be possible while somewhat stealth. I feel I might have the wrong 70cc-kit, the Polini and Malossi kits seem more powerful at stealth/low rpm. Maybe just sell the 70cc+exhaust and get a malossi/polini 70cc+some other exhaust, but the risk is I end up with the same problems/loud exhaust since I am clueless, and can't afford to buy several exhausts and try them out Any help - what would be the best course of action - would be appreciated.

It is a bit difficult to help you here First I think you need to understand how loud a tuned scooter is. Are there any other guys around with racing exhausts and cylinder kits? A tuned scooter will always be about 20dbu louder than stock, when the cylinder and exhaust is being replaced.
Also, power comes with rpm, or bore. Your scooter is 50cc and more bore than 70cc isn't an option (unless you are a crazy engineer). That means the only way to generate power is via rpm. Pulling wheelies and dropping jaws won't happen, even with the Stage6 Sport Pro MK2. Sorry for that :-/
Here is a comparison of the Sport Cylinder Kits and the Sport Pro Mk1 (Link). As you can see, they have a only slightly higher power output than the stock cylinder kit. Thus, my recommendation would be to sell the Sport Pro Exhaust and fit the stock exhaust. Then take the money from the exhaust and fit a sport variator (Malossi is great) and a racing clutch (Stage6 Sport Clutch). Also, a stiffer pulley spring would be in order. This will give you a much better acceleration from stand at a much lower noise level!

Hope it helps,
D