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Thread: The Guernsey PHVA Tuning Challenge

  1. #1
    apriliaforum expert ToraTora's Avatar
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    Cool The Guernsey PHVA Tuning Challenge

    It is often said by us tuners that because of conditions we can't really tell you what to put into your bike to set it up. I posted something that prompted Mark to do the below. He didn't offer this as a challenge, but since I currently have the opportunity to accept it I figured hey lets do it. I just got the Silver bike running. It's got a stock carb, pipe, and kit. Now this is the North American build, but it's the same carb, and probably mostly the same other things. Today I went to treats to get the same carb parts. I was able to get most of them. The one difference is the main jet is a 104 vs Mark's 105. That was the closest that Treats had.

    Now I've got a couple of these PHVA 17.5 carbs laying about from machines that have had BBK systems installed. I plan to keep the stock carb the way it is, and set up a second carb as per Mark's machine. We'll see how close the bike is to one on the other side of the planet.

    Quote Originally Posted by mdomaille View Post
    This is an interesting point I decided to put to the test this morning. My lad's got an Aprilia SX 50 (Derbi D50B0 motor) and I've got the Aprilia RS4 50 (Derbi D50B1 motor). We both have the Dellorto PHVA 17.5 and both the bikes are running 13/53 final drive ratios with the stock de-restriction (Exhaust washer and carb baffle removed).

    I thought it would be an interesting exercise to swap carbs (and needles) just to see what the other went like. (Albeit the atmospheric conditions are consistent)

    The SX had 90MJ, 32 IJ, 208HA Atomiser and A25 needle on N4

    The RS4 had 105MJ, 34 IJ, 210GA Atomiser and A12 needle on N4

    The results were that the RS4 ran worse than it did and performance was closer to the original feeling that it was being ridden with a brake on. On the SX this setup wasn't as noticeably bad.

    The SX ran really well using the RS4 carb - really smooth, progressive take off clean revving, right up the rev range and felt 'free'. (So much so I have ordered the same components to fit into his carb)

    Whilst I'd agree that every bike is unique and needs an individual setup, I also think there is mileage in trying 'known good' combinations of components where engines and states of de-restriction are identical - even if it is only in pursuit of starting on the road to perfect tuning and trying a relatively in-expensive way of a 'possible quick fix'.
    This bike was produced in 2003. It's basically completely stock. It sat rotting for about 11 years, and I've been going through it cleaning it so that it will be viable again. Plus replacing/fixing things that were messed up during its time where it was neglected. It came with a 17.5 PHVA carb so that makes this a pretty easy test. Now Mark's bike has the DB engine, and the Silver Bike has an EB engine. But I can't believe that the cylinders are all that different. One of you guys could always do a port map of the DB. I can upload one of the EB. And the air box is completely different too. Even still it should be a good bit of fun doing this test.


    Guernsey 49.4500 N, 2.5500 W, 30.1 sq mi
    San Francisco 37.7833 N, 122.4167 W, 46.87 sq mi

  2. #2
    apriliaforum prov-nov
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    How exciting! It will be very interesting to read how the bike goes with this combination.

    My 'final' setup was slightly improved on the above by changing the IJ to 36 and I went back to the A13 needle on N1, but other than that everything else was as you posted.

  3. #3
    apriliaforum expert ToraTora's Avatar
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    Wink Collecting the proper materials

    I went back to Treats yesterday, and totally forgot to swap out the parts to the current stats. I'll do so next week.

    I'm really impressed with the stock set up though. The bike is running great. The other needle you had looks more like a cylinder than a needle. Is there any taper on it at all?

    But yeah for sure this sounds like fun.


  4. #4
    apriliaforum expert emX50's Avatar
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    Quote Originally Posted by ToraTora View Post
    I went back to Treats yesterday, and totally forgot to swap out the parts to the current stats. I'll do so next week.

    I'm really impressed with the stock set up though. The bike is running great. The other needle you had looks more like a cylinder than a needle. Is there any taper on it at all?

    But yeah for sure this sounds like fun.

    It's definitely a worthwhile test for fun
    It never ceases to amaze me, the spread of different configs that are being used to good effect.

    Your post, highlights the range of carb settings that have been used:

    http://www.apriliaforum.com/forums/s...=1#post3938280

  5. #5
    apriliaforum expert ToraTora's Avatar
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    Wink Charting an adventure

    The interesting thing about that chart is it doesn't list many options of the GPR with the PVHA 17.5. I'm going to have to see which PVHA is in the bike, and its stock settings. The chart lists the 17.5 on a GPR with a 98 MJ, A15/4th Needle, 34 IJ, 212 FA Atomiser,

    Stock Derbi Carb Settings


  6. #6
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    Hey Rob,Did you ever get any further in your quest to duplicate my carb settings and see how your beast ran with it setup the same?

  7. #7
    apriliaforum expert ToraTora's Avatar
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    Unhappy さむいです


    Hey Mark, it's so cold here now that it wouldn't be a proper test. I'm hoping to get to it once it warms up a bit, but...I may just cave in, and install the hop up parts. These bikes are a joy to ride with just a little bit more power, and this weekend when I went riding in the Marin hills I found it a bit disappointing at times. For instance being stuck behind an illiterate Prius driver that ignored the use the turnouts signs, or the Lexus SUV driver that couldn't be bothered to read the signs, or the I'm oh so entitled Audi SUV driver who felt he was to good to use the turnouts. With a kit I would have just passed their slow ass cages, but with a stocker I only had enough pull up the hills to pass the Prius. \_(ツ)_/


  8. #8
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    Quote Originally Posted by ToraTora View Post
    The interesting thing about that chart is it doesn't list many options of the GPR with the PVHA 17.5. I'm going to have to see which PVHA is in the bike, and its stock settings. The chart lists the 17.5 on a GPR with a 98 MJ, A15/4th Needle, 34 IJ, 212 FA Atomiser,

    Stock Derbi Carb Settings
    Very useful chart!
    Are there more like this available?
    Sorry for replying to an old post, but it's new to me.

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