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Thread: Bro 500 GT ABS won't rev past 6200 rpm

  1. #1
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    Question Bro 500 GT ABS won't rev past 6200 rpm

    2006 Scarabeo GT ABS. First long trip on expressway I had a chance to open it up a little, and voila', nothing more. I can cruise all day long up to 75-77 mph, approx 6k rpm, but it won't rev more... except... Once in a while if I hold the throttle open it will start taking off again pulling strong up to about 6500 rpm. Just weird since it accelerates great then stops, almost like a rev limiter. Just installed new spark plug, did the valve lash, and today fixed the old fuel filter gas line. No change. On my second tank of BG44k injection cleaner....
    Last edited by Bullittfastback; 08-12-2019 at 10:38 PM.

  2. #2
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    Maybe it has rev limiter.

  3. #3
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    What's your top speed?

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    75-77 mph (GPS), 82-85 indicated

  5. #5
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    That is a little slow. Are you getting normal mileage? Normal temps? Normal exhaust note?

  6. #6
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    I don't really have a reference point for what's normal for exaust sound. Just bought it a month ago. Mileage seems ok, 55+ mpg. Replaced air cleaner also. On the freeway I can hold the throttle wide open and after about a mile or two it'll accelerate to 6500 rpms... If I let up a little it'll cut out again down to 6k. Acts like a rev limiter kicking in and out. Throttle linkage seems good, have full power range up to 6k. Bike has plenty of power. Next time I have the covers off I'm going to start checking all my connections... Specifically throttle position sensor... No dash lights on showing any problems either, although I don't know any additional way to check for fault codes

  7. #7
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    Won't rev past 6k smoothly on center stand either. Sounds like it starts missing badly.

  8. #8
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    Lets start with the basics like how many miles on the bike, last time belt along with the rollers in the variator were changed, are you using the recommended synthetic motorcycle oil and synthetic gear lube, age of tires, tire inflation, etc, etc. Could also be past due for a valve adjustment but thankfully that 4 valve head has individually adjustable rocker arms. It would be in your best interest to go onto the AF1 Stores website and download the service station manual for your bike and ensure that all the services required for the mileage on that bike have been done.

    https://www.af1racing.com/store/Scri...+Manual+500+4T

    https://www.af1racing.com/store/Scri...idProduct=5544

    https://www.af1racing.com/store/Scri...6+Scarabeo+500

    The Big Beo develops MAX HP at 7250 rpm.

    Belts are only good for about 6,000 miles and rollers depending on usage can wear out twice as fast. If the previous owner put heavier roller weights in the variator it will close too soon and limit rpm and top speed however it will also not reach full rpm if the clutch is stuck open and does not close up or if the clutch springs are weak allowing the belt to pull to the high gear position too soon. Variator and clutch maintenance along with how they are set up can really impact performance of the bike and prevent the engine from reaching full rpm.

    What your reporting is below even 250cc performance levels.

  9. #9
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    25k miles. Previous owner stated he changed belt at 19k. I rode it for about 2 weeks before I changed the oil, new air filter, new spark plug, installed 19gm x 8 Dr pulley sliders, new front tire, rear has decent tread, replaced fuel hose at fuel pump with new clamps, have run 3 tanks of fuel with BG 44k fuel injection cleaner, bled the brakes with new fluid...
    As I wrote in my last post, bike won't rev even on center stand. Sounds like a rev limiter or bad misfire once it hits about 6200 rpms. New sliders improved acceleration, but none of the things I've done have changed or improved the rev problem.

  10. #10
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    Has it been doing this since you bought it or is a recent development?

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    Well its likely time for a new belt and as ScaraBeowulf mentioned was it doing this when you bought it or has this started since you bought it?

    Decent tread is not a good indicator since it could have sat for years and be over a decade old already when motorcycle tires are past their prime and potentially unsafe after 3 or 4 years from date of manufacture.

    Its possible that the ignition pickup needs attention, etc however I would start by getting the service station manuals and go through the trouble shooting process outlined there for that particular year engine. 25,000 miles is about the time you'd expect for the first valve adjustment and its really time to bring the rest of the required scheduled services up to date before going too far astray. On a bike that old its even possible that the flexible intake that isolates the throttle body from engine vibration has started to leak. If this started since you did the valve lash adjustment you may need to revisit that since there is not that much room for deviation and each pair of valves needs to be set exactly the same and not too loose or your valve timing will be retarded.

  12. #12
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    Since I bought it about 2 months ago.

  13. #13
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    Start with the simple things like the spark plug wire and cap. Many times the cap itself backs out so that it is no longer screwed completely into the wire which can cause spark break down and loss of rpm.



    On my Sport City 250 I started having performance issues after the dealer did a service and it turns out that the screw on tip on the spark plug itself had come off and was stuck inside the cap however they did not pull it out and just pressed it back on so that the old tip was still inside and contacting the spark plug for a while. It died on me while I was hours away from home and the only way I was able to get it out was by screwing a spark plug into the tip stuck in the cap. Thankfully I had a spare spark plug and the factory tool kit with me.



    Did the seller have anything to say about it since it appears to be a pre-existing condition?
    Last edited by Rockynv; 09-15-2019 at 06:10 AM.

  14. #14
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    Unfortunately the seller failed to mention several things, started here hadn't ridden it in a year due to health problems. I did test ride it before I bought it, but that didn't include highway speeds where problem would have shown up. Like i stated previously, runs great up until that 6k rpm. When I replaced the plug, there wasn't much left of the center electrode from the old one, but who knows how old that plug was. Bike has 25k miles.

  15. #15
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    It is hard to imagine wearing out the center electrode in only 25,000 miles unless it has been running extremely lean/hot, pinging and such. Does the bikes condition indicate only 25,000 miles or much more? The engine should have been clean as a whistle inside at only 25,000 miles. What color was the old plug when you pulled it?

    Having been out of use for a year and coming from a potentially dubious seller you could also be experiencing sticky valves at high rpm so you may also need to add some Mystery Oil to the crankcase. If the plug was terribly carboned up there is also a chance that the catalytic muffler is clogged up. No Lambda Sensor though on the 2006 so you don't have to worry about that being fowled.

    I know it says regular gas in the specs however with a compression ratio of 10.5 to 1 your really should be running middle grade.

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