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Thread: Aprilia RS4 50 tuning problem

  1. #16
    apriliaforum prov-nov Doser's Avatar
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    Thank you all for you spending time. I understand now situation better and better.
    I think too, at first will do better carburator adjusting. My thinkig was not change needle position, but change Main jet on thinner. Looking so, what mix rich now.
    Additional: before 4k rpm bike well too. from idle till 4k all good with power. after 4k power lossing = more acceleration with grip > nothing, and after 6k new power borning.

    Here sound of exhaust then bike become stupid from 4k - 5k rpm:

    Last edited by Doser; 02-17-2019 at 03:53 AM.

  2. #17
    apriliaforum prov-nov Doser's Avatar
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    One question. Mix regulation with Needle or with Main Jet different diameter it is same result?

  3. #18
    apriliaforum Member HeM's Avatar
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    Approximately this means ... Main jet size -throttle position from 3/4 to full throttle. Needle position - throttle position from 1/4 to 3/4. Throttle position from close up to 1/4- pilot jet size and air screw position. This is only approximately.
    Last edited by HeM; 02-14-2019 at 10:07 AM.
    Aprilia RS50 1999. Bidalot RR 70 , Top Racing (Jasil) crankshaft, Motoforce PWK 24 carburetor , V-Force 3 reed valve , Polini Big Evoliution air filter , Top Performances intake manifold, Stage6 R/T digital internal rotor ignition PVL, Top Performances kevlar clutch, Metrakit Pro Race 3 exhaust , 13/47 gearing

  4. #19
    apriliaforum prov-nov Doser's Avatar
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    In some words, but all clear. Great, thanks.

  5. #20
    apriliaforum prov-nov Doser's Avatar
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    Hello, all. Today we put needle one step lower (needle clip one position higher) for leaner mix. Bike drive much better. Now bogging not so strong and moves to 5-6k rpm (before 4-5k rpm). We do short test on speed and have easy 100km/h on 11000rpm.
    I still think about next carburator regulation. Spark plug looks clear if compare with previous (befor needle adjusting). But plug not brown, looking still black. Clear and black. Please look my photo.
    I think, should change needle position again for leaner or not?

    Click image for larger version. 

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    Last edited by Doser; 02-15-2019 at 10:48 AM.

  6. #21
    apriliaforum Member HeM's Avatar
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    Hard to say. You can try to move the needle through one groove. If it works well, check the plug again. It is important to do the tests with a well warmed engine. In fact, the color of the plug should be checked after a full load, running a few kilometers on a 6 gear full throttle. But in this way you will check the size of the main jet. Difficult to check for medium load adjustment throught plug color. Pay attention, how the engine works, how you accelerate, and find the best position. The plug color will not show you all the truth.
    Last edited by HeM; 02-15-2019 at 11:54 AM.
    Aprilia RS50 1999. Bidalot RR 70 , Top Racing (Jasil) crankshaft, Motoforce PWK 24 carburetor , V-Force 3 reed valve , Polini Big Evoliution air filter , Top Performances intake manifold, Stage6 R/T digital internal rotor ignition PVL, Top Performances kevlar clutch, Metrakit Pro Race 3 exhaust , 13/47 gearing

  7. #22
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    It still looks rich. Buuut I think you should use a hotter plug. Looks too cold for me.

  8. #23
    apriliaforum Member aphasia's Avatar
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    I would try a hotter plug too. I run a 10 but a 9 should work well too.

    Sent from my LG-H850 using Tapatalk

  9. #24
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    Yeah mostly 9 is the best. Maybe on a 40 C summer day the 10 is better. Not always though

  10. #25
    apriliaforum prov-nov Doser's Avatar
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    Br9es in my hand. May be change Main Jet little smaller? I worry needle one step lower will be very much for next step. ��

  11. #26
    apriliaforum Member HeM's Avatar
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    Quote Originally Posted by Doser View Post
    May be change Main Jet little smaller? ��
    Try it. If it works worse, you can always go back to the same.
    Aprilia RS50 1999. Bidalot RR 70 , Top Racing (Jasil) crankshaft, Motoforce PWK 24 carburetor , V-Force 3 reed valve , Polini Big Evoliution air filter , Top Performances intake manifold, Stage6 R/T digital internal rotor ignition PVL, Top Performances kevlar clutch, Metrakit Pro Race 3 exhaust , 13/47 gearing

  12. #27
    apriliaforum prov-nov Doser's Avatar
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    Hello. Today take decision to move needle one step lower. And now it is first driving test without oil leakage from exhaust. Looking we on the right way. But needle already in lowest position, not possible receive leaner mix then now. I think we will drive some days and will look spark plug again.

  13. #28
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    Do you use Motul 710? If you use that oil in premix about 1:35-1:40 you should see the oil spitting out from the exhaust. Not a lot just a littlebit. Motul oils doesnt burn like others. Thats why they are better. I would use a richer mix, just to be sure.

  14. #29
    apriliaforum prov-nov Doser's Avatar
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    Yes, Motul 710. I also look piston too every time. Piston washed very well. So I think we have reach mix. I will chek all again after some days.

  15. #30
    apriliaforum Member aphasia's Avatar
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    If transition from idle onto main jet is smooth and colour of 9 plug looks ok then stick with current one. If not smaller main and use needle height to smooth the transition.?

    From earlier pictures of the plug and oil coming out of the pipe, I would say you would be safe to drop a jet size or two.

    Sent from my LG-H850 using Tapatalk

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