Bringing my Brothers 83 VF750 back to life

Discussion in '1st & 2nd Generation 1983-1989' started by MyBrothersVF750F, Jun 4, 2020.

  1. MyBrothersVF750F

    MyBrothersVF750F New Member

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    My brother is in a very tough situation health wise and I've jumped in to do as much as I can to help.
    One of the tasks is to become caretaker of his beloved Interceptor. It's been sitting in his garage since at least 1995- tabs expired March of that year. She's got 21K on the odo and is in very good condition considering a 25 year sleep.
    It will end up being his Son's motorcycle at some point so I've brought it home and done the following:

    Complete hydraulic systems rebuilds, new brake pads all around.
    Cleaned and flushed the tank with fresh non ethanol fuel, carbs had been drained early on (thank heavens!)
    Replaced fuel pump and filter.
    Flushed and refilled coolant.
    Set Valves, replaced spark plugs.
    Replaced both spark boxes with new V4spark units.
    Both coils test within specs as do the inducers.
    New battery.

    I've tried to start it a couple of times with no joy... it's getting fuel, turns over well and builds oil and coolant pressures.
    All electrics work on it except the obvious no spark at the plugs.
    I'm stymied at this point, I've considering replacing the inducers but since there's no spark to either coil I don't believe that will make any difference except to my pocketbook.

    My question to the forum is what would you check next?

    Thanks in advance!!!
     
    Last edited: Jun 5, 2020
  2. Captain 80s

    Captain 80s Member

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    Jump the kill switch?
     
  3. Allyance

    Allyance Insider

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    Check the wires and connectors on the coils just above carbs. Check all connectors and switches. Good luck with it, I have had mine since new.
     
  4. squirrelman

    squirrelman Member

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    cleen connecdions on coils, check pulser coil resisdnces. flip kill swidch on/off few dimes.
     
  5. MyBrothersVF750F

    MyBrothersVF750F New Member

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    Thanks!
    I did check as many connections as I could find, I didn't think about the kill switch...

    I had a 1982 CB900F that I bought new, he had a 76 CB360T. He soon got tired of me disappearing into the distance on him so he bought this to keep up on.
    We put thousands of miles on those two bikes together. I'm anxious to hear it run again!
     
  6. MyBrothersVF750F

    MyBrothersVF750F New Member

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    I still need to try jumping the kill switch, I did work it on and off several times and rechecked all the coil connections.
    Here's the numbers for the resistance checks:
    Resistance tests on both coil primary's reads 2.9 ohm (manual says 2.8).
    Resistance on the secondary's are 26.65k ohms for the 1/2 coil and 24.82k on the 3/4 coil- well with the manual's range of 21-28K.
    Inducer resistance on the 1/3 side is 482 ohms, 2/4 shows 467 ohms- manual specifies 480 ohm.

    Tried the old standard of pulling spark plugs, connecting the lead and holding the plug on ground- no spark.
    It's got to be upstream from the coils, etc.
    I'll pull the right side handlebar controls apart and see if there's any issues.

    Is there any other common point of ignition failure that has been noted on this machine?
     

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    Last edited: Jun 5, 2020
  7. MyBrothersVF750F

    MyBrothersVF750F New Member

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    Here's an update to this thread... life events took this project down the priority list up until the last week.
    I took the kill switch apart and cleaned the contacts, it tested fine before and after.
    I had called and set up an appointment to take it into an independent mechanic and decided- one more try!

    I turned on the fuel, pulled the choke to full on and cranked for about 5 seconds, waited 10 seconds and repeated... during the 4th try she started popping and making good noises!
    after a bit of time at idle on full choke I was able to get it to rev- it won't run at all unless the choke is full on, and once it warmed up I could gain some rpms with the choke off... she will not idle though. It's obvious to me that the slow speed circuit is clogged so I've got 4 carburetor rebuild kits on the way.
    My plan is to pull the carbs as a unit and do as much rebuilding, cleaning and blowing out passages as possible without separating the carbs from each other.

    I'm excited at the prospect of getting her back out on the road after 25 years of sitting, that's tempered with the heartache of my big brother's passing 3 months ago... wish I could share the good news and great sounds of his favorite motorcycle with him...
     
    duccmann likes this.
  8. Diving Pete

    Diving Pete Member

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    do yourself a favour and also flush the tank & lines - no point getting more crap back into the carbs... and also worth buying new carb rubbers - the old ones will be as stiff as hell.
     
    Last edited: Jan 17, 2021
  9. Diving Pete

    Diving Pete Member

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    oh, and lovely bike - good luck on your quest..
     
  10. duccmann

    duccmann Member

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    So sorry to hear about your brother.
    Had a new red one back in 84


    Sent from my iPhone using Tapatalk
     
  11. MyBrothersVF750F

    MyBrothersVF750F New Member

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    Thanks duccmann, I appreciate that.

    I also appreciate the help I've had here!

    One of the first things I did was a tank flush and CLR cleaning, new gas filter and I replaced the gas lines- 27 years is too long for me to trust them.

    When you say the carb "rubbers" I assume you mean the intake to carb insulator?
    "INSULATOR B, CARBURETOR
    16212-MB0-770"

    I'll get 4 of those ordered too!
     
  12. Diving Pete

    Diving Pete Member

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    Yes that's the part... now a little tip is to put a smear of red rubber grease on them to aid fitting of the carbs. My way is to install the insulators onto the engine, smear a touch of red rubber grease in the tops of them & then place the fronts a touch in before getting the rear in & pressing firmly. It will be more obvious when you do it, but this can be a real pain in the butt.

    The carbs will likely require ultrasonic cleaning.
     
  13. MyBrothersVF750F

    MyBrothersVF750F New Member

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    Thanks again!
    I saw a youtube video of a partial teardown (slides, float bowl, floats and all jets removed) then several hours in an ultrasound tank using a cleaning solution of 50/50 simple green and water. He left the carb linkages alone and left them attached to the metal air box.
    I'm checking around the area to see if someone had a large enough tank to immerse the carb assembly and give it a thorough cleaning. I'm still waiting on the carb rebuild kits and the intake insulators to arrive.

    I also checked prices on a 5 to 8 gallon ultrasonic cleaning tanks- $1200 and up is more than I want to spend tho!
    Great tip on refitting the insulators and carbs!!
    I've used Sil-glide in the past on some difficult seals and will use it again...
     
  14. MyBrothersVF750F

    MyBrothersVF750F New Member

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    I have access to 87 or 91 grade non ethanol fuel, I use the 87 in small engines, a 71 Bonneville with a '66 motor, a 72 Porsche and I even treat my '13 Ram with a full tank now and then, it runs better on the real stuff too!

    Should I go up to the 91 with a 10.5/1 compression on the Interceptor?

    Also, I looked carefully at the cam shaft lobes and wear surfaces when I was setting valves and did not see anything more than normal wear (21,600 on the odo).
    Is there a good synthetic anyone can recommend for additional protection that plays nice with wet clutches?

    Thanks!!
     
  15. Captain 80s

    Captain 80s Member

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    87 would be fine, but I would run 91 to be safe. But out on the road you can take what you can get.

    I personally wouldn't change up on oil. Everything has run in and is used to conventional 10/40 oil I'm sure. I have witnessed older engines that didn't like the switch to synthetic, as they leaked in places they didn't before. Could be completely anecdotal, but I've seen it a few times. And while you can find a synthetic that is just fine with a wet clutch, your actual used clutch might not like it so much.

    Just keep it clean and consistent imo.
     
  16. MyBrothersVF750F

    MyBrothersVF750F New Member

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    Update:
    After the carb tear down, cleaning and rebuilds the bike runs fantastic!
    I need to get in some miles wearing the new tire coatings off and seating the brake pads, I'm pleased to get to do so- catching some sights and sounds for my Nephew and there maybe a Youtube video in the works...

    Thanks again for the suggestions and help on this! IMG_6251.jpg IMG_6250.jpg
     
    Captain 80s and Viffer J like this.
  17. Brian Rodgers

    Brian Rodgers New Member

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    Great job !!
     
  18. Hellapet

    Hellapet New Member

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    Great to see a bike like that brought back to life. I bet it sounds amazing! Would love to see a youtube video too if you get around to it.
     
  19. MyBrothersVF750F

    MyBrothersVF750F New Member

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    It's a beauty and ran perfect until yesterday... took it on a 20 minute cruise up to a buddy's house and worked on a gazebo build project.
    When I went to start it and leave I turned on the key, pulled the choke on and hit the starter button. There was a instant where the starter engaged then an electrical "pop" sound, then no lights, no starter... seemed completely dead. Check the main fuse first, it was still good, checked all other fuses... all good.
    Checked battery voltage (new battery about a year ago, kept on trickle charge) and it showed 12.42 volts.
    After letting it sit a while. turned the key back on and the lights and gauges came back on... faintly at first, the starter solenoid buzzed, but no start.
    Buddy gave me a ride home, got my truck, loaded up the bike and brought her home again.
    This all happened yesterday, I have not done any more trouble shooting yet.

    Any body else have a similar failure?
    Where would you start looking for the issue?
    I thought about the starter solenoid, but it doesn't make sense the it would go completely dead, then come back to a degree... ignition switch failure??
     
  20. raYzerman

    raYzerman Member

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    Main battery ground to engine or frame?
     
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