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Thread: Sick RS

  1. #1
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    Sick RS

    I have an RS250 which refuses to run properly unless the choke is on, even when warmed up. It constantly dies until the choke is on again and happily idles while choked.
    FYI: Rebuilt motor, carbs cleaned and new gaskets top and bottom, reeds good, no obvious problem with manifolds, battery charging correctly, rectifier changed, new coils and leads, new plugs. It seems to be both cylinders/carbs which need the choke. The tacho regularly misbehaves during the dying process which leads me to believe it is electrical. I seem to have exhausted all options for it being carb/inlet related. I have also checked the manifold equalization pipes for leaks and set the carb float heights per specs. The exhaust valve controller seems to be working correctly.

    Could it be a CDI problem perhaps? Any help would be greatly appreciated.

  2. #2
    apriliaforum expert rgvsean's Avatar
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    Quote Originally Posted by sepiltz View Post
    I have an RS250 which refuses to run properly unless the choke is on, even when warmed up. It constantly dies until the choke is on again and happily idles while choked.
    FYI: Rebuilt motor, carbs cleaned and new gaskets top and bottom, reeds good, no obvious problem with manifolds, battery charging correctly, rectifier changed, new coils and leads, new plugs. It seems to be both cylinders/carbs which need the choke. The tacho regularly misbehaves during the dying process which leads me to believe it is electrical. I seem to have exhausted all options for it being carb/inlet related. I have also checked the manifold equalization pipes for leaks and set the carb float heights per specs. The exhaust valve controller seems to be working correctly.

    Could it be a CDI problem perhaps? Any help would be greatly appreciated.
    it still sounds like a Pilot/Idle Circuit issue. I have had similar issue before after a carb clean.

    Turns out they still had a blockage and trying a different set of carbs proved it, so I knew I had to clean them again.

    Tacho issue may be a second fault so be careful thinking it's only one fault.

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  3. #3
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    Thanks for your input. I will look at carbs again. (Sigh.) A proper soak in expensive carb cleaner is called for I think.

  4. #4
    apriliaforum Junkie
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    Also have a look at the carb filters if you haven't already

  5. #5
    apriliaforum expert SoulDaddy's Avatar
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    Just had the same issue with a DR350 that I recently picked up. Owner told me he struggled with it and went through the carb more than once. I pulled the carb and took it to a long-time tech who pulled it apart in front of me and pointed out parts that were installed incorrectly. Said it happens a lot. So maybe it's just that simple.

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  6. #6
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    Problem Solved?

    Thanks for the advice on the tacho, it WAS a seperate problem. The carbs were cleaned again but to cut a long story short; don't remove the auxilliary air system on an RS unless it is a racebike or you are happy to buy new carbs. My bike has had it removed and this combined with raising the float height to manual specs appears to have caused the problem. Float height should be 12.5/13mm NOT 8mm. The bike still doesn't behave properly under 3,000 rpm and will die on a constant throttle but I don't believe it will cause an issue on a racetrack. If it does I guess I'm up for new carbs or re-installing the aux air.
    Anyone know if RGV carbs fit?

  7. #7
    apriliaforum expert mattology's Avatar
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    i deleted the pilot air jets but kept the main air jets per the kit manual, and the bike behaves beautifully...

    Get your confidence back with Aprilia.

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  8. #8
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    Quote Originally Posted by sepiltz View Post
    Thanks for the advice on the tacho, it WAS a seperate problem. The carbs were cleaned again but to cut a long story short; don't remove the auxilliary air system on an RS unless it is a racebike or you are happy to buy new carbs. My bike has had it removed and this combined with raising the float height to manual specs appears to have caused the problem. Float height should be 12.5/13mm NOT 8mm. The bike still doesn't behave properly under 3,000 rpm and will die on a constant throttle but I don't believe it will cause an issue on a racetrack. If it does I guess I'm up for new carbs or re-installing the aux air.
    Anyone know if RGV carbs fit?
    I need to go read the manual regarding the aux air system, what exactly it is. Is it installed on the cup (race only) bikes? as I've always adjusted float to the 8mm manual spec. RGV VJ22 carbs are supposedly bolt on for the RS250. Common on eBay in UK.

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  9. #9
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    Quote Originally Posted by mattology View Post
    i deleted the pilot air jets but kept the main air jets per the kit manual, and the bike behaves beautifully...
    What s this 'kit manual' and how do I get one?

  10. #10
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    Quote Originally Posted by crazybrit View Post
    I need to go read the manual regarding the aux air system, what exactly it is. Is it installed on the cup (race only) bikes? as I've always adjusted float to the 8mm manual spec. RGV VJ22 carbs are supposedly bolt on for the RS250. Common on eBay in UK.
    The aux. air system is on all bikes as standard. The manual explains it in the carb. section.
    Thanks for the carb info.

  11. #11
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    Latest update on the sick rs is that it appears to be fully recovered. I put a size bigger main jets in due to the mods made to the motor as a safety first measure (now 290/300) and it now appears to be running perfectly. Why this should be I can only imagine is some peculiarity of the carbs having no aux air system. Happy though. Can't wait to get to the track. Thanks for everyone's responses.

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