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Thread: valve compression

  1. #1
    apriliaforum newb
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    valve compression

    Hello guys, last week I hit 20k km so my bike went to the service garage for the valve clearance. I got a feedback from the garage that valve clearance are almost perfect (Intake 0.20 and outlet 0.25) but he mentioned one thing that the rear valve has smaller compression that the front one. If I am not wrong now, front one was on correct compression (12bar) and the rear one was only about 5bar. While the valve was opened he mechaniclally check decompressor by hand and it worked fine. Do you have any idea what could be possibly wrong that he measured this pressure?

    But why I`m writing this. Sometimes I got problems to start my motorbike correctly. I try to explain best I can now. I turn the key on, there is a check on the dashboard, once it is done I hit the starting button, it starts kicking the engine on, but in a very short while dashboard goes blank and starting stops, in this moment voltmeter on the battery shows only 6V, in a second engine goes slowly on and dashboard also turns back on. While riding the motorbike it doesn't feel good, once I even got URGENT SERVICE which disappeared after next start, while riding the bike it doesn't loose power but it doesn't run smooth. This do not happen all the time but after last year it happens often and often. Sometimes it helps to turn it of and back on again and it starts correctly.

    I have replaced battery with new one, didn't solve the problem.
    I have replaced fuses and cleaned bottom of the fuse box, didn't solve the problem too.
    I have clean contacts on the battery, problem not solved.

    As far as this happens so randomly it is hard to identify source. And I would like to ask you if any one of you would have any idea based on what I have written here.

    Bike is DD1200 ABS/ATC, made 2012, it have LeoVince SBK pipes and KN air filter in the box.

    thank you

  2. #2
    Honest always, feared often Micah / AF1 Racing's Avatar
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    Being Ride By Wire bikes you cannot really hold throttles wide open for compression test if they are attached. If this test was done with closed throttles on front and rear or open on front and rear that is a HUGE difference in compression. IF you think the test is accurate have them perform a "leak down test" on both cylinders to find out where the air is going and verify results of compression test.

    If bike runs fine and makes same amount of power basically as new then there has been a testing error, you would definitely feel a 50=% loss of compression on only 1 of 2 cylinders.
    Diminished expectations is the key to happiness in life.

    Micah Shoemaker
    AF1 Racing
    9900 IH35N
    Austin, TX 78753
    micah@af1racing.com
    @ShoemakerMicah
    @AF1Racingaustin

  3. #3
    apriliaforum prov-nov Paul666's Avatar
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    The valves I checked at mileage 25kkm and they were normal. My problem occurs when the motorcycle is warm and immediately after turning off I want to turn it on again.
    - I turn the key on
    - II press the start button
    - Dashboard turn off for 2-3 seconds
    - The motor turns on, after 1-2 sekconds dashboard turn on

    I cleaned the starter and the contacts. I have a new battery, 14V charging, battery voltage 12.85V. However, the problem sometimes occurs.

  4. #4
    apriliaforum newb
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    I was checking bike yesterday I had a seat off so I could see battery and cables. When I touch plus or minus cable they both are kind of hot after 10s of continuous starting. There was also smoke coming out close to starting relay so first try to replace this cheap relay. Next step i to check starter ..

  5. #5
    Honest always, feared often Micah / AF1 Racing's Avatar
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    If relay is smoking that is a pretty strong sign either the starter motor is drawing FAR more current than it should be (high engine friction, leaking exhaust valves etc) or the relay is JUNK. Cables should both get warm when passing HUGE amperage loads through them like on hot or cold extended cranking. Has a leak down test been done on motor recently?
    Diminished expectations is the key to happiness in life.

    Micah Shoemaker
    AF1 Racing
    9900 IH35N
    Austin, TX 78753
    micah@af1racing.com
    @ShoemakerMicah
    @AF1Racingaustin

  6. #6
    apriliaforum Junkie wthammond's Avatar
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    Will defer to Micah on the electrical and valve adjustment guidance. He's forgotten more about this stuff than I will ever know. What a couple folks seem to be describing, i.e. when bike is hot and tries to start, it bogs down, dash goes blank, then it starts on second attempt, sounds a lot like the 'hot start' issue that is well documented on the Capo 1200 which is essentially the same bike as the DD 1200. It doesn't appear to be a fatal flaw, just an annoying one. I tried a set of high capacity cables which did not help. I had AF1 deinstall them and go back to stock at the 12,000 mi service. Since then I replaced the battery with a different Yuasa model that has a higher capacity. It seems to largely solve the problem, only occurrence since I installed it. FWIW.
    __________________________________________________ __________________________________________________ ____

    Current: 2015 Caponord, 2015 Moto Guzzi V7 Special
    Gone: 2009 Aprilia Mana 850,
    2001 Aprilia Scarabeo 50,
    2002 Futura

  7. #7
    Honest always, feared often Micah / AF1 Racing's Avatar
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    A massively oversized Litium Battery sure as hell helps late model R1 Yamaha's...finally convinced buddy to try biggest one that he could fit, ZERO issues since then for his R1M
    Diminished expectations is the key to happiness in life.

    Micah Shoemaker
    AF1 Racing
    9900 IH35N
    Austin, TX 78753
    micah@af1racing.com
    @ShoemakerMicah
    @AF1Racingaustin

  8. #8
    apriliaforum Junkie wthammond's Avatar
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    Good to know. I was thinking to go Lithium before I put in the Yuasa but got scared off by the newness of the technology. Next battery will be though. Might stick one in the Guzzi V7, but that thing cranks like a mother as is.
    __________________________________________________ __________________________________________________ ____

    Current: 2015 Caponord, 2015 Moto Guzzi V7 Special
    Gone: 2009 Aprilia Mana 850,
    2001 Aprilia Scarabeo 50,
    2002 Futura

  9. #9
    Honest always, feared often Micah / AF1 Racing's Avatar
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    I have one in my Vespa even, IF they were cheaper I would have one in my car and airplane lol. I NEVER go with smallest or lightest, always the biggest friggin capacity that will fit in the battery slot but that is probably just OCD on my part. Seldom though have I ever thought, "wow is wish I had less cranking amps".
    Diminished expectations is the key to happiness in life.

    Micah Shoemaker
    AF1 Racing
    9900 IH35N
    Austin, TX 78753
    micah@af1racing.com
    @ShoemakerMicah
    @AF1Racingaustin

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