The Yamaha Aerox Blog

July 2009 - Posts

  • Reed pettles, Valves and gearing issues..

     Well with Cylinder done, run-in and running oh so sweetYes, it was time to play with the reed valve.

    I fist remove the standard reed block, removed the metal standard reeds because I am revving the motor to 9500rpm now (1000rpm over standard redline), so I was conserned about the metal reed pettles snapping off and potentially destroying my engine. I next installed some Malossi 0.3mm Carbon reed pettles into it..

    I didn't notice any speed increase with this modification but it gave me some peace of mind because if carbon reeds break off at high RPM, there little chance they will do any damage to the engine. Strangely enough though, the engine did begin to start up much easier in the mornings from being dead-cold. Starting on very first turn of the key, with a little choke on. Hmm Cool

    I got a call 2 weeks later from GPS Imports (my usual dealer for parts here in Melbourne), telling me the Malossi Reed blocks for Aerox 100cc had just arrived.. yes I couldn't resist to get one and find out if they were different to the original, and if so, how.

    About $100bux later and here it was. Big Smile

    The first thing I had noticed was that the whole body was coated in rubber, as opposed to the original which is bare metal and lightly rubber coated on the surface the pettles flapped on. Also on the new Malossi unit the pettles were slightly larger in length and width. I thought there was not a great deal of difference to the original.. until I turned it upside-down.

    From this view I could see that the total valve area was much much larger than the original. Longer opening and wider opening. If I was to guess, I'de say the Malossi value could pass/flow about 30% more volume of Air-fuel mix through it.

    The full thick rubber coating on the Malossi value body also allowed me to not have to use a paper gasket on the mounting surfaces as the rubber coatings provide a good seal to engine and intake manifold.

    With the new valve installed, the easy cold starting was still there and I've noticed more top speed of about 5kph although its getting hard to measure top speed now because the numbers on speedo end at 120kph. The needle looks like its pointing at  about 130-135kph so the Aerox winds off the speedo heaps.

    Gearing issue's..

    For a long while now, the Aerox has had 20-60kph problems not excelerating hard like it does after 60kph. This is because the gearing is shifting up taller too early and not letting the engine use its most powerful RPM's of 8000rpm+. At 20kph-60kph it revving from 6000rpm-7500rpm, which its still putting out decent power but no where as much as it does after 8000rpm.

    I've been stratching my head for ages trying to figure out what could be causing the gearing to up change too early. I've tried changing Contrast springs from standard to yellow (which I use now) and even tried a red spring with no difference at all. I've tried different belts and even adding a spacer washer in-between the variator, thinking maybe the gearing issue was to do with the wider malossi Kevlar belt being wider than standard and sitting too high in the variator. This wasn't the case because the spacer made no noticable different at all, only lower my top speed slightly. So I'v been running no spacer in variator and using Yellow Malossi read contrast spring now for a long time.

    Today I had an idea to dis-assemble the read torque pulley completely and check for anything unusual. This was a great idea lol, because it turned out that the problem is coming from badly worn out guide chanels in the rear pulley.

    As you can see the chanel where the pin run allong to control opening and closing of the pulley is very worn out and causing the pulley to open up (raise gearing) too early and too easily.

    So next mod is definately a new real torque pulley from either Malossi or an eBay shop from Taiwan item made by Prodigy, a standard Yamaha Item could also be used. Over the next week or two I will be working on fixing this problem up and post results and pic here in my blog. Yes