My Vf1000 frustrations

Discussion in 'Mechanics Garage' started by techno, Jan 27, 2007.

  1. donald branscom

    donald branscom New Member

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    Very doubtful because it is all electronic. They almost NEVER fail.
    Just because you do not understand the "black box" does not mean it is evil.
     
  2. donald branscom

    donald branscom New Member

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    The rev limiter is actuated by the TACHOMETER. It is the YELLOW wire going to the tach. VF1000R and VF1000F.
    If you remove the yellow wire from the tach, the revving is not limited. Simple.
     
  3. donald branscom

    donald branscom New Member

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    Let me help you.
    First lets take things off of the list that have nothing to do with the problem.
    The first SEVEN on the list are good things to do just as general maintenance. NUMBER Eight- "Balanced the carbs as best as possible" Do not know what that means.

    Remember this bike starts and runs and revs to 2500 rpm.
    It just does not rev up smoothly.

    Possible cause Either they were balanced or NOT balanced properly.
    Did you start by attaching the vacuum guage to the #4 carb first? Calibration??
    Then hook the vacuum guage to all four carbs because #4 cannot be adjusted. NEXT...You changed the engine from a 1984 to a 1985.
    What size were the main jets and idle jets on the 1984?
    What size are the main jets and idle jets on the 1985? Missing information. Question. When you changed engines, did you change carbs OR did the 1985 engine come with carbs?
    # NINE on your list. "Removed gas cap..." Based on the assumption that the carbs were not getting enough gas. If that WAS true it would stop running or not even start after the float bowls run dry because no additional gas would flow to the carbs.
    #10 "Airbox removed to check for obstruction."
    But you did not tell us if you were running it with NO airbox after checking it OR If you removed the airbox to check for a obstructions(tampon?) LOL, Then REPLACE the airbox and test run the bike. Needs to be answered because if it was run without the air filter it WOUD run very lean. Was it fully warmed p and off of the choke? No mentioned of RUN or CHOKE mode. Confusing.
    #11 "Run without exhaust cans" WAS there a difference? No mention of result. #12 "Check for rag in collector box" NOT sure HOW that could happen but it could easily be checked with a vacuum guage.
    #13 "Electrical issues"
    #14 Resister or non resister plugs. Makes no difference. The VF1000R and F models have resisters built into the spark plug caps.
    #15 Replacing the plug leads. What kind of wire??? Was it the right kind of wire? #16 "Swapped coils" Coils almost NEVER go bad. Can easily be checked with multi meter and procedure in the workshop manual. Measured by ohms. Needs a definitive answer.
    #17 "Pick ups on crank changed" Question< Were the gaps reset? What were the gaps?
    #18 "Wiring checked for obvious gaps?" Visual inspection is good. But for a more thorough inspection a meter needs to be used. Need to check for specific information on each component and connections.
    #19 You say you ran it without the fuse for the instruments(rev limiter)??
    # 20 "checked valve clearances" What were they? Did you change any of them?
    #21 " Checked cam positions in relationship to piston position." If a cam was 180ยบ off it wold run very poorly even at the lower rpm's and on this engine the valves may even run into the pistons. I have seen that problem on twin cylinder engines put together by beginners, but it would hardly even run. That is why it was at the dealer. The owner and all his friends could not figure it out. We fixed it in one hour. END of your list.

    OK...IF this problem came to me this is what I would do. This is the first thing. Since even if the compression was low or it had broken piston rings it would still run but just rattle. I would pull the carbs first. The carb balance procedure does not have a solid result given. I would find out if any of the jets are clogged. The idle jets are as small as a human hair. I would remove those and check to see if I can see daylight through them. Check the mains and WRITE DOWN what the jet sizes are and what they should be. Make sure all the chokes are fully opening and closing. Also the valve adjustment on the 1984 is not the same as the 1985 The 85-86 is .006 and the 1984 is .005 But honestly think about this- take a caliper and dial .001 now look at that. It is so small and what if the rocker arm is slightly loose on its shaft? If a valve is tight (usually exhaust) The engine does not want to idle even when everything else is right. There are a lot of gaps in this whole diagnosis of this motorcycle. It is scattered and jumps all over the place. No electrical values are given for anything. Checks must be done with the volt-ohm meter and procedure in the shop manual followed. This engine and symptoms described is a classic case of clogged idle jets. And remember if they are clogged and you take the carbs off and clean them and reinstall the carbs if there is junk OR moisture in the filter or lines you can still cause them to get clogged again in just a few minutes. I have had to clean idle jets twice before getting a result that sticks and that is after changing the fuel filter. The gas tank can be full of junk also. But the junk does not usually get through the tank filter and inline filter but WATER can get through OR clog up the jets. It only takes one drop of moisture.

    When you have 4 carbs this small those idle jets are Very very small.
    About that black box CDI. It makes spark.
    You can check if the plugs are firing.
     
  4. sidecar42

    sidecar42 New Member

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    The rev limiter is part of the CDI unit and is triggered by the rise in pickup voltage as the revs increase, which is interpreted by the programing of the electronics to kill the spark until the voltage (Revs) drops again to the preprogrammed level. The yellow wire is purely the pulse signal for the tacho. Very misleading information I'm afraid Donald. As for synching/balancing the carbs, the only truely accurate ways is mercury colums, gauges are to inaccurate as far as repeatability, you need to be reading all four simultaneously.
     
  5. donald branscom

    donald branscom New Member

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    That is a good explanation of the rev limiter except when you say" "(revs)drops again to the "preprogrammed level". There is no "program" it is not a computer.
    Just a circuit board. The needle of the tach has a place where the needle hits the redline and breaks the current to # 1 spark plug. I have taken a VF 1000 tachometer apart to actually find out where the yellow wire goes to exactly. That cost me $100.00. for that information. Electrical mechanical.

    It is NOT misleading information that I gave.

    The YELLOW wire is the wire that connects the tach, pulse generator, ignition unit, and coil together. You are right about that. It is shown on the wiring diagram.
    I WAS speaking of a mercury type unit for synching the carbs, like the Motion Pro or other brands. That is what I use to synch my carbs (Motion Pro) and it is the same engine.
     
  6. JamieDaugherty

    JamieDaugherty New Member

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    Are you certain that the rev limiter function gets it's input from the tach? That seems kind of weird. So you are saying that the spark box gets input from the pulse generators, formats the signal and drives the tach, then takes an input back from the tach and interprets that for the rev limit. It would seem like the spark box already got the engine speed data from the pulse generator. Have you actually tried cutting the yellow wire to see if te rev limiter is defeated?
     
  7. donald branscom

    donald branscom New Member

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    I do not even have the tach hooked up on my bike at all.
    Yellow wire capped off.
    Will rev all you want.

    But....i have not tried to blow it up either. Usually the valves will just float at high RPM, that will slow the engine down too.

    I am on a electronics expert, but when I see the yellow wire go to where needle is at redline inside the instrument, to me that means that when it gets to that spot it cuts the ignition to #1 cylinder. Slows the engine down. Or stops all the spark.

    If you have hit the rev limit on that bike, what do you hear or feel???
     
  8. JamieDaugherty

    JamieDaugherty New Member

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    It certainly isn't a mechanical contact, I can yell you that much. The tach doesn't have any way of sending back a signal to the spark box. I'd say you haven't hit the limiter yet. It just sounds like a stumble or a misfire (which it actually is).
     
  9. donald branscom

    donald branscom New Member

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    Look on page 19-10 of a VF1000R workshop manual and at the bottom of the page it shows how it works.
    The tachometer does signal the ignition control unit when the mechanical needle hits redline.

    Maybe I can dig out that tach and show you a photo.
    Here we go...
    [​IMG]
    The Yellow wire goes to a resister (look just to the right of the yellow wire labeled R1), and then it goes to a component that has
    10 soldered points. !0x 1000 =10,000 rpm.

    So i cannot explain all of the circuit but basically as the needle of the tach starts it's sweep around the dial it activates the circuits on the circuit board when it hits the 10,000 rpm limit it cuts off the ignition to #1 plug. That is where the yellow wire goes to (the coil for # 1 plug.

    Now I am going to give you a clue.

    The workshop manual says that if the tach does not work right that it has to be replaced. An d I am betting that if that tach is hooked to your ignition circuit and it is not functioning right it could affect the rpm if it cuts the ignition to #1 plug.

    Like i said I have no tach hooked up at all, and my engine will rev as far as you want. The way I see it is- it could be trouble. It effects the ignition circuit.
    [​IMG]
    Backside of tach.
     
    Last edited: Jan 1, 2011
  10. donald branscom

    donald branscom New Member

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    I would just buy a aftermarket tach designed for V4 engines and forget about all this nonsense. If you really have to have a tach.
    Why have a tach if you won't let off the throttle when it hits 10,000 rpm anyway.

    Fiat cars used to have a tach that said 8,500 rpm and many people believed that and blew up their engines. I can just listen to an engine and know when it is at its limit or is not pulling anymore.
     
  11. sidecar42

    sidecar42 New Member

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    Unfortunately then you have been miss informed, the larger of the two CDI's is the one containing the rev limiter, (have used various different tacho's on my race vehicles and the rev limiter still functions, none of these tacho's I have ever worked on had a rev limiter built in, which was also set slighty higher than the redline which is 10,500 on my VF1000F) The information I quoted on the function of the rev limiter was supplied by Mick Smith, former head of Honda Racing Australia and GP racer, he was in charge of Honda's racing efforts in Oz when the VF's came out. The CDI unit has an EPROM (erasable progammable read only memory) which gives the ignition unit advance curve parameters, rev limit etc.

     
  12. sidecar42

    sidecar42 New Member

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    Hello Jamie, Well put, yes I have removed and/or used different tacho's with no effect on the rev limit, having said that, I did once fit 750 CDI's (different advance and higher rev limit). Oh, it will cut both cylinders on that coil, not just #1, #3 will stop firing as well.

     
  13. donald branscom

    donald branscom New Member

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    So what you are saying SIDECAR is that the tachometer has nothing to do with limiting the revs, and is ONLY to display the rpms? Is that correct?
    I would like to know what other tachometers (brands), would work with this V4 engine.
    And does the yellow wire from the ignition control unit get hooked up other aftermarket tachometers?

    Just one more question. If the VF1000R from 1985-86 that has only ONE ignition control unit,have the rev limiter built into it too?

    Was Mick Smith, former head of Honda Racing Australia a mechanic or a CEO type?
    The HONDA website says"Over the last 24 years, Mick has taken on various roles with Honda in sales, marketing and service including Motorcycle Territory Manager for Victoria/Tasmania, and most recently Assistant National Service Manager."
    I am just wondering if he knows about tachometers and CDI rev limiting systems.
     
  14. donald branscom

    donald branscom New Member

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    "EPROM (erasable progammable read only memory) which gives the ignition unit advance curve parameters, rev limit etc."

    What does that mean exactly? Does that mean a computer can program it???
    OR does it mean the memory has to be erased first, then re programmed?
     
  15. sidecar42

    sidecar42 New Member

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    Hello Donald, I'm not completely ophay with EPROMS, I do have the equipment to do so, but I am still very much a novice, but they are programmed using a computer at manufacture, usually with information developed by the particular bike manufacturer, in very much the same way the EPROM in an EFI system is programmed.

     
  16. sidecar42

    sidecar42 New Member

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    Yes Donald, in this case the tach has nothing to do with rev limiting, yes the yellow wire is the pulse signal from the CDI to give the tacho it's input, and is connected to any tacho that's fitted, I have used tacho's of GPZ Kwaka, an RZ250/350 Yamaha (needed to be recalibrated due to the 2 stroke having 2 ignition pulses per rev, were as the VF only has 1 pulse per rev per coil) and a CBR1000F, so basically any tacho suitable for a four cylinder using 2 coils will or should give the correct reading. As for Mick Smith in the early 80's he worked as a mechanic in england for the Texaco Herron Suzuki Team, back when Jeremy Burgess (crew chief for Mick Doohan, Wayne Gardner and Valentino Rossi to name a few) was looking for a job as a mechanic, Smith ran the Oz Honda race team in a very hands on way being a former rider himself, and the last time I was at HRA, his office had more parts lying around it than I could dream of. The later VF's with single CDI box were very much the same, they just put every thing into one box

     
  17. invisible cities

    invisible cities New Member

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    Great info sidecar. On this note, do you know what type of life span the Honda VF series CDI boxes have? Can these be modified and/or rebuilt? Thx!
     
  18. invisible cities

    invisible cities New Member

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  19. duB

    duB New Member

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    We are talking here 25 years old electronic here. EPROM was erasable using ultraviolet but without using the erasing capablility, was more flexible to program (I mean write) than PROM. Later EEPROM was Electically Erasable and this is also old tech.
     
  20. JamieDaugherty

    JamieDaugherty New Member

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    Unfortunately the ignition map cannot be reprogrammed as it's permanently "burned in" to the chip. From what others have discovered, the map is incredibly simple. It only has two advance values, switching between them at a prescribed rpm. Clearly it's a crude system but Honda used a similar one until the early 90's.

    Yes, the R's also have a rev limiter. I've hit it many times.
     
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