Pulse generator

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

  1. a1gatorz

    a1gatorz New Member

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    Hi , hoping someone hear may be able to help me out ? I own a 1987 VFR700F2 that apparently the pulse generator has gone bad .My manual states that checking the resistance on pulse generator plug it should be between 450-550 ohms on both sets . Mine is reading 291 on one set & 302 ohms on the other set , making them both fail miserably . The Honda part # for my bike is 30300-ML7-921 . I have called all local Northern California Honda shops with no luck of getting a new replacement . Not that I could afford one anyways ! So, whats a guy supposed to do now ? If anyone out there may know of one available , PLEASE, PLEASE let me know . THANK YOU ALL !!!!!!!!!!!!
     
  2. desktopdave

    desktopdave New Member

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    Those are some pretty low readings. Are the sensors clear of any metallic debris?

    Most dealers won't stock parts for our bikes, other than common stuff like bolts, brakes or chains. Back when I still went to dealers I usually got overcharged even if they could get the part. I hate to say it, but I'd suggest eBay from a reputable seller. It's your best chance of finding the correct part. Be aware that the "spark box" (ignition computer) can also cause you some troubles on these bikes. I'm also told that the first year '86 VFR has some differences from your '87 model. I'm not sure if that extends to the pulse generators but the spark boxes are definitely different.

    Maybe something like this? I know it's across the pond, but it seems like it's worth the chance to me. I've bought & sold stuff to Europe many times before.

    Nearly identical pulse generators are installed on thousands of Hondas. They might have a bunch of other ones that are different part numbers based on wire lengths, bracket type or something like that. I have a bunch of sets from older V4s...makes me wonder if they cross-ref.
     
    Last edited: Mar 2, 2015
  3. a1gatorz

    a1gatorz New Member

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    Thanks for the info . I have two spark boxes . Both seem fine . The link you gave me is exactly what I am looking for , thank you . When you ask me about any metallic debris ? I assume your meaning inside the engine casings ? I have not opened up the casings yet . So would these debris be floating in the engine oil ?
     
  4. desktopdave

    desktopdave New Member

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    Glad I could help, although I wished it was cheaper & closer. You can usually cross-reference parts from Honda schematics available at many online parts sites like BikeBandit, RevZilla, etc. Here's an example:

    I pulled up the page for an '87 VFR750F2 A here.
    There's a schematic diagram for the pulse generator here. I clicked on the Pulse Generator link to get more info and it tells me that PN 30300-ML7-921 is (unfortunately) obsolete and (more unfortunately) only used on the '87 VFR700F2 models. I'd still think you could adapt other models to your bike. The only likely difference between all other Honda is the mounting bracket or wire length. But if you want a plug-and-play replacement, eBay is the only relatively common source unless you get lucky at a local bike salvage yard.

    Metallic debris won't be floating in engine oil - it'll settle in the bottom of the oil pan and side cases. Not much oil will work into the side case where the pickups are unless the motor has seen a lot of abuse. It's possible if the previous owners raced the bike or were really hard on the gearbox & clutch. That tends to put finely-grated parts of the gear dogs into the engine sump. Those can work their way over to the magnetic pickups, stick to the sensor heads, and interfere with the crank signal.

    Have an oil pan ready when you pull the sidecover - you'll find a few tsp of oil sitting in there.
     
  5. squirrelman

    squirrelman Member

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    Thanks, Dave, that's seriously brilliant info-data for our site !
     
  6. JasonWW

    JasonWW New Member

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    How can you have 2 spark boxes? The 2nd gen 86-89 have a single spark box in the tail section. Are you refering to something else?

    The 1st gen bikes with the 360* crank used 2 spark boxes.

    The pulse generators are again different from 86 to 87-89 (as well as the spark boxes). So don't buy from an 86 bike, only 87-89 and you'll be okay.
     
  7. JasonWW

    JasonWW New Member

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    Something doesn't sound right here. Are you sure your 87 is supposed to be 450-550? That's what the 86 bikes are and I could swear the 87-89 bikes were supposed to be a lower value around 300 or so. Are you using an 87-89 service manual? I could be wrong, but I thought the resistances were different.

    My 86 book shows the pulse generator resistance from 450-550 ohms. (Between yellow and yellow/white and then the other blue and blue/white wires)

    Then it shows the cam pulse generator resistance from 405-495 ohms. (2 wires, white/black and yellow/black) Is this the unit up by the camshaft?
     
    Last edited: Mar 5, 2015
  8. artee

    artee New Member

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    [​IMG]
    Going off whats on here any 87 -89 will do. 86 may work but are a physically different fit. Unless you pull them off the mount and refit to the 87 mount.
    get those 700 from Ireland for that price

    Roger
     
  9. JasonWW

    JasonWW New Member

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    I don't think that would be easy. From what I've read, the 86 sensors might fit the 87-89 engines, but you'd need to drill and tap the 4th mounting hole. See the pics below.

    [​IMG]

    [​IMG]
     
  10. JasonWW

    JasonWW New Member

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    Is that a book for VFR750's? So it's the '90 model that is the oddball 200-400 ohm pulse generator? Good to know. I guess a1gatorz are bad.

    Interesting timing info, too.

    I see now, the 86 model is the only one with the cam pulse generator even though all the parts schematics show them on the 87-89. It's odd, you'd think they would change the pictures.
     
  11. desktopdave

    desktopdave New Member

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    First time I saw that cam pulse generator I thought it was a coolant sensor. :lol:

    Jason (& Artee too), those pictures are great. It does seem that Honda just changed the brackets but they changed them a lot more than I'd expected. I'll have to pull the cases off mine to see what's going on and actually get us some good data.

    The early VFR (FG model) is an oddball. Two units bolted directly to the block with high offset brackets, like all the early 80s V4 models. The '87-on models got short stub brackets screwed into a larger bracket then bolted into the block. I still suspect those pickups might be electrically identical, but since they can't be disassembled it's academic. In that case, I'm wondering if the early 80s VF or CB units might be persuaded to fit a VFR. I'd suppose they're pretty similar, Honda tends to be very methodical with their machines.

    Interesting info about the later spark box too. I'd be willing to bet the larger one-piece spark control unit is a single board version of the earlier dual units. The '86 box looks different than the later ones too - similar box but with a few more connectors. When I roll the bike out to fire it up this spring I'll try to do some quick testing to verify my theory. I held onto a few of the older V4 spark control units just in case.

    It's not hoarding if you're keeping them for experiments, right? :black_eyed: It's always a good thing to have some spares. Those spark boxes are getting rarer every day, it seems.
     
    Last edited: Mar 5, 2015
  12. desktopdave

    desktopdave New Member

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    I think he's referring to the ignition pickups as spark boxes...not the TCU/spark box/amplifier (or any of the other 25 words we use to describe them :lol:). OP - we need clarification! :wink:
     
  13. JasonWW

    JasonWW New Member

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    Hold on there. I think your mixed up by what F1 and F2 means. This refers to the dash package, not the year. The F, not F1, had the round gauges. The F2 had the square gauges. For instance, my 86 bike is an F2. There was no F3.
    Can't be. He said he has 2 and both seem fine. Then he said his pulse generators measured below spec. So I'm not sure what 2 things he meant that seemed fine. (he has a spare ignition box from a donor bike)

    Some members over on Biker Oracle are offering him some used parts for cheap as there doesn't seem to be any on USA ebay right now.

    A1gatorz, take a look at this on eBay UK.
    http://www.ebay.co.uk/itm/Honda-VFR...pt=UK_Motorcycle_Parts_13&hash=item3aa4190325
     
    Last edited: Mar 25, 2015
  14. artee

    artee New Member

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    Oi.... those are my piccies.
    So 86 wont fit.
    The one with the writing on is of my 700.
    The other one is a Jap spec rc07 engine, yes rc07..... I dont know why they gave the 86 vfr750 the Sabre engine number?

    Roger
     
  15. desktopdave

    desktopdave New Member

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    You're right - I wasn't checking my info. I figured Honda just changed that "F" identifier every model year. I should have referred to the letter code instead (FG, FH, etc.), that would have been much more accurate. Previous post updated!
     
  16. artee

    artee New Member

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    There are three types of ignition box.
    The 86 is unique to the 86
    The 87 is unique to the 87
    The 88/89 models share the same box
    They all have different plugs and fittings

    Roger
     
  17. artee

    artee New Member

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    If anyone has problems with shipping, they could send them to me in the Uk and I could send it on to you.

    Roger
     
  18. JasonWW

    JasonWW New Member

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    I dug up those pics from an old thread. Good pics

    So do you know what's different with the ignition boxes?

    As far as I know, if you need a replacement engine for your 86, then you have to get an 86. Are the other 3 years engines all swappable with each other?
     
  19. artee

    artee New Member

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    Your welcome to the pics.
    As far as I know the 86 box has three plugs, two multis and a single bullit.
    The 87 has two red multi connectors
    The 88/89 has red and white multi connectors.
    I toyed with the idea of fitting the 86 rc07 engine in the 700, but couldnt see the benefit of 50cc.
    I was going to swap the starter clutches over and see what happens. However I have now got a complete 86 project going. I had to use the rc07 pulser units on the project bike to get it running.

    Roger
     
  20. artee

    artee New Member

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    I do think the engines are interchangeable to some respect that, you could run an 86 without the cam pulse unit if you fit a later starter clutch and pulser units to match. Thus alleviating the need for the cam sensor.

    Roger
     
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