Pulse generator

Discussion in '1st & 2nd Generation 1983-1989' started by a1gatorz, Mar 2, 2015.

  1. JasonWW

    JasonWW New Member

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    A1gatorz, as an example of Factory Service Manual mistakes, below are 3 pages from the Honda Manual for the 90-96 VFR750 bikes. It mentions PG resistance in 3 places. In the front under specs it says 200-400 ohm. Then in the Ignition section it says 450-550 on one page and 200-400 on the next page. See my point? Later revisions of the same manual usually catch those errors, but we don't always have those editions.

    Then we have Artee's book which showed only the 90 VFR750 being 200-400 ohm and all other years 86-89 and 91-97 as being 450-550 ohm. That's obviously wrong.

    [​IMG]

    The manuals for the older 83-85 VF750F-VF700F show the PG resistance at 450-550 ohm. The 86 VFR700-750 Manual says 450-550 ohm, as well. Both these early bikes used the 2 long trigger cranks.

    Then when the 87 bike come out the crank triggers switched to the 11 smaller units (which Rae-San says typically need a smaller resitance PG to sense them more accurately)

    I bet 450-550 is correct for the 86 VFR bikes and 200-400 is correct for 87-97 and maybe beyond.
     

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    Last edited: Mar 28, 2015
  2. JasonWW

    JasonWW New Member

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    I know the same part number starter clutch (the part that has the trigger teeth on it) is the same part number from 87-97. I bet I could wire up a 90-97 ignition box to run an 87-89 bike. The newer boxes are easier to find and cheaper as well. Plus being newer, they are probably more reliable than the older ones.

    (EDIT: I think the guys from Ignitech already have a programable box for the 90-97 VFR750 ($145). I bet it can work on the 87-89 as well)

    I don't know about the 86 bikes. You could probably swap the starter clutch and PG set from an 87-97 bike, ignore the cam sensor and use an 87-97 ignition box as well.

    They all seem to have the same 15* advance base timing. The advance curve starts about the same (1500-1800rpm) and ends about the same (3300-3800rpm) and the total advance is roughly the same at 37*-38*.
     
    Last edited: Mar 27, 2015
  3. JasonWW

    JasonWW New Member

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    Oh, A1gatorz, below are pics from the Honda Factory Service Manual showing the air gap specs on the 1st gen VF bikes. They definetely left it out of the newer bike manuals.
     

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  4. JasonWW

    JasonWW New Member

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    I've been talking to Rae-San and feel I have a good working knowledge of the 82-97 Honda V4 ignition systems. I'm working on a thread that will explain in detail how the pulse generators work, why the crank triggers are shaped they way they are, how the ignition boxes work (in theory) and explain the different firing orders.

    If anyone has seen a thread with similar content, let me know as I don't want to create diagrams, etc... if the information is already out there.

    I also wanted to mention that Rae-San does do ignition box repairs if yours starts acting up or you suspect it may have a problem. He said he could "refurbish" them. I'm not sure what that entails, but I'm sure it's cheaper than a new aftermarket ignition box.
     
  5. NormK

    NormK New Member

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    Jason, good work but I think a1gatorz has now given up.
     
  6. a1gatorz

    a1gatorz New Member

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    Not by a long shot ! Got to work to be able to play . Norm , followed your lead & all 4 coils working strong . Jason , ran all advised tests . At rest reading 12.1 - 12.6 at all black\white connections ig box & coils . Green wire resistance was very low at all grounds ig box & others . Testing while cranking very bad with just the battery . Below 8 volts at first then drops real fast in just a couple seconds . Down below 6 volts or less . My batteries old & have had to recharge over & over again in the last month due to all this crap I've been going through on the bike . Will I do any damage giving it a boost with one of those portable jump boxes ? Hoping to have some time into it this weekend ? Again thank you guys so much . Don't give up on me yet . OK ?
     
  7. NormK

    NormK New Member

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    Ok we are hanging with you, I would be reluctant to try the jump starter, could do some damage, but I think you have found your problem. See if you can borrow a car battery and jump start it from that. Below 8 volts and you are going to be up hill. My voltmeter will drop into the high 11's when cranking but as soon as it fires it will go up into the 13's
     
  8. a1gatorz

    a1gatorz New Member

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    Ok Norm . I've never had any luck getting jumpers on the bike battery myself with auto jumper cables . I have a good car battery . I guess I'll need a smaller bike specific set to hook up ? Or maybe its time I invested in a new quality battery ? Mine is barely holding a charge . Not to get off topic , but earlier you mentioned doing the relay to positive on coils ? Would you mind explaining that to me in a little more detail ? Does one relay feed all 4 coils ? Or do they require a relay per each coil ? 4 in total ? I have tried repeatedly to register on the superbike forum with no luck ? Even tried E-mailing them. Of course I'm not thinking on doing that mod until I've work out the issues I have now . Thanks !
     
  9. JasonWW

    JasonWW New Member

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    It's pretty hard to get big clamps on the small battery terminals. You can attach the ground clamp to the bikes frame (I do it right where the ground wire bolts down). For the positive, I can do a quick jump start by holding the clamp on the positive post while the other hand pushes the starter button. If I need to charge the battery I usually unbolt the battery hold down and tilt the battery out and I can then clamp it on to the positive.

    Anyway, it sounds like your bike battery is pretty low. Have you pulled it out and done a slow recharge for several hours? How have you been charging it up?

    About the relay Norm mentioned, I'm pretty sure they used a single 30-40 amp relay from the battery, fused it, and then to all 4 coil wires. Then used the original black/white wire as the relay signal. That way your kill switch, etc... still works.

    I don't like the idea of the relay as it should not be needed and adds complexity and extra stuff to the bike. If the coils voltage is more than 1/2 a volt less than the battery then I'd start cleaning plug connectors, fuses and ignition switch, kill switch contacts, etc... until I found the voltage drop and fixed it. If I still couldn't find the voltage drop then, as a last resort, I'd add the relay.
     
  10. NormK

    NormK New Member

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    Jason you are correct with how it is wired, the problem is we have are we are dealing with up to 30 year old switch gear and connectors, nice shiney 12 volts delivered straight to the coils can't be a bad thing. I have a pair of motorcycle jumper leads so that makes it much easier
     
  11. marcuch

    marcuch New Member

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    Greetings Gentlemen, I'm new to the VFR family. My history is with Hondas of the 70s, of which I still own a number of them. The VFR700 is so much more complicated than my CB750ks. I've read through this thread and in summary it sounds like I'm SOL if in fact my 1987 VFR700F2's Spark Generator is toast. I tested it like the shop manual instructs you to do and I have "OL" across both the wire pairs. I could be testing something wrong but the instructions are pretty straight forward.

    Since the last post was a couple years ago, I thought it would hurt to ask if anything has changed with someone making an aftermarket Spark Generator. It's hard to believe these go bad. It's also hard to believe that both sets of wires leading to the 2 spark generators are open. Strange. I'll keep checking eBay. I hate to part the bike out.

    Any help/advice would be appreciated. Thanks in advance!
     
  12. JasonWW

    JasonWW New Member

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    Maybe you could start a new post with all the details and then post a link to the new thread here so we can find it. I'll try and help you out.
     
  13. marcuch

    marcuch New Member

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  14. JasonWW

    JasonWW New Member

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  15. marcuch

    marcuch New Member

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    Thanks...I was a little challenged creating a new thread. If possible, please have someone move it to the right category. Thanks again!
     
  16. Ascalon

    Ascalon New Member

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    I'm struggling with this issue myself at the moment on an '87 VF1000 FF.

    Same kind of symptoms, after running for about 15-20 minutes, dropping one, then two, then appearing to die from fuel starvation.

    It was suggested to me that it might be the pulse gen coil for cylinders 2 and 4, which is also responsible for the signal to the fuel cut off relay.

    I've just replaced the P/G assembly with another one from a spare engine I had, but have had not had a chance to fire it up yet as I only got it oil tight last night.

    The FF model is the one with two P/G and two ignition boxes, so at least I can swap them to see if the issue follows, for further troubleshooting.

    Now, when I took out the old ones, the measurement was fine, well within the 450-550 Ohm range, but someone from another forum suggested that the main failure on these is breakdown in the windings that is exacerbated by heat, hence the failure after a while running. So, they may well seem fine at room temperature, but then shit themselves at running temps.

    I am currently looking into the possibility of getting the coils rewound and the old assembly rebuilt, as even if my spare works, I'm still relying on a thirty year old electrical component that has already done its job.
     
  17. JasonWW

    JasonWW New Member

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    I've forgotten everything in this thread, so I'll try and start from the beginning.

    Usually if one of your pulse generators becomes open after it's heated up you can usually tell just by letting the engine set. It will cool down and then it will run fine again until it gets hot. Is that happening to you?

    You can also test the coils by measuring them while using a heat gun or hair dryer to get them nice and hot. If the circuit goes open after heating them, then you know it's bad.

    The pulse generators have nothing to do with the fuel pump relay. If you have a wiring schematic for your model, I dont, you can trace the relay wires to see if the signal comes from either the spark box or an ignition coil.

    Ignition coils are outside the engine and connect to the spark plugs.

    Pulse generators are small and inside the engine providing a signal from the crankshaft to the spark box.
     
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