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Thread: Carb question

  1. #1

    Carb question

    I have a 1994 raider 700. I rebuilt the carbs when I got it due to hesitation when the throttle was pulled. I lowered the pop off pressure as recommended (now about 40psi). It runs great all the time unless it is idling. After a few minutes it dies and can't restart for more then 30 minutes. It gets a spark and I have a primer which I can see the fuel going in, but it won't start. I figure it has to be the carbs.

    Can anyone tell me if I raise the pop off pressure back to the factory setting can I use the lower fuel speed adjustment to keep the hesitation away, or is that the wrong way to think about this. I have read the Mikuni carb manual, and I am not sure why it would matter.

    Also anything else I should be checking. I am presuming its flooding badly. I took it out over the weekend ran fine for over an hour, brought back to dock, turned off. Waited about 5 minutes and it wouldn't restart. Could this be due to flooding?

    Any help would be great.


  2. #2
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    You should be able to cure the hesitation with the low speed adjustment screws. (you have dual carbs correct)?

    If you know you are getting fire and you can see fuel pumping into the carbs through the primer, it should atleast start up, it may not stay running but it should atleast fire up. If you think it might be flooding, have you tried starting it without the primer? Does it take 30 minutes to start when you first try to start it up for the day, or only after it has been running a while and dies? I only have to prime mine if it has been sitting over night.
    Last edited by 97GPSLEEPER; 03-28-2007 at 12:54 PM.

  3. #3
    It starts up first thing in the morning with just one or two pumps of the primer. The issue seems to be if it idles for more then a minute or two, the RPM's drop and it stalls and won't restart for at least 30 minutes no matter what I try (Holding open the throttle to vent, priming, shaking, eetc).

    I have run out of ideas, other then increasing the pop off back to factory and seeing if its just loading up from being too low a pressure. (The engine is stock).

  4. #4
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    I would try going back to the stock pop off pressure like you said. It is strange though, if this does not correct it, I would be out of ideas.

  5. #5
    RAIDER RUNNER BULLRAIDER's Avatar
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    Jeep , if you lower the popoff too much it will cause the n/s to dribble, causing a rich condition, I cant remember if you are running the stock flame arrestors or not, but you can simply wrap black electrical tape around the flame arrestor to choke off the air,NOT FULLY, just enough to make a restriction when you are idiling,` that is a way to check if you need more popoff, with out pulling the carbs......if it runs good ,you need more..if you are running the stock flame arrestors you need to go back to the stock popoff....hesitation can be cured elsewhere..

  6. #6
    Moderator DrewNJ's Avatar
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    Are you still running the stock oil injection?
    I know mine (WV700) used to load up when idling quite a bit from a bunch of oil. Running a hotter 7 plug instead of an 8 helps a lot.
    but-
    If it ran fine before and this has happened since you lowered pop off then I think you already know what needs to be done.
    Good Luck
    Doug

  7. #7
    Duke's Avatar
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    Quote Originally Posted by jeeprunnr View Post
    I have a 1994 raider 700. I rebuilt the carbs when I got it due to hesitation when the throttle was pulled. I lowered the pop off pressure as recommended (now about 40psi). It runs great all the time unless it is idling. After a few minutes it dies and can't restart for more then 30 minutes. It gets a spark and I have a primer which I can see the fuel going in, but it won't start. I figure it has to be the carbs.

    Can anyone tell me if I raise the pop off pressure back to the factory setting can I use the lower fuel speed adjustment to keep the hesitation away, or is that the wrong way to think about this. I have read the Mikuni carb manual, and I am not sure why it would matter.

    Also anything else I should be checking. I am presuming its flooding badly. I took it out over the weekend ran fine for over an hour, brought back to dock, turned off. Waited about 5 minutes and it wouldn't restart. Could this be due to flooding?

    Any help would be great.
    Don't do anything until you check your plugs after you run it and create this situation. If they are very wet and won't restart it may be to low of a pop off. I they are dry you have another problem. Don't presume anything just do a simple check and let us know.

  8. #8
    Net's been done, thanks for the input. Since I couldn't get on, I have switched back to the stock springs. I will take out and verify again with the original setup. I am running everything stock so far, (I want to understand this and have running good before I modify).

    If after I take out, and it does hesitate on acceleration, what is the way to correct this? I will try turning up the low speed screw. Up to how many turns is considered okay. The manual says 5/8s +- 1/4, is it okay to do more then this if necessary?

    If that doesn't correct what else should I try while out?

    Thanks.

  9. #9
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    It is O.K to adjust the screws more than the manual recommends, especially if it gets rid of the hesitation. How many hours are on the motor? Have you checked compression? As a motor gets more and more hours on it, its fuel requirements can change some due to the rings not sealing as well and the combustion is just not as efficient as it once was.

  10. #10
    Thanks for the info. The motor from what I am told has about 80 hours on it. I need to check the compression, but I appreciate the info on the rings and their needs.

    Is there any other way to adjust hesitation, or is the low speed screw the main/only way? I just want to be ready when I go out next time.

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