'86 VFR700 lost spark and bogging

Discussion in '1st & 2nd Generation 1983-1989' started by Darryll, Jun 15, 2020.

  1. Darryll

    Darryll New Member

    Country:
    United States
    Joined:
    Oct 16, 2017
    Messages:
    5
    Likes Received:
    0
    Trophy Points:
    1
    I bought an 86 VFR700 in 2018 with 22kmi on it that had not been running for years. I had the carbs professionally then reinstalled them and started it to make sure I wanted to keep putting money and time into it. It only ran on the back two cylinders, troubleshooting showed it needed two coils. I bought two off of ebay installed them and with new plugs and it has run for over 500 miles in the last few years. For winterization I have drained the tank, use non-ethanol premium, put stabilizer in the gas and run it to make sure it gets in the filter and carbs. I am running K&N filter and Kerker exhausts…oh she snorts so nice! Before/After
    Left.JPG CL ad.jpg

    I’ve driven it more this spring than ever but this weekend it started with less choke than usual trying to be quiet in my subdivision (about 1500 rpm). Within 1 block it stalled. I thought I just reduced the choke too soon so I left it on ½ way and it ran fine at 30 mph. I drove 10 miles going 55-65 then all of a sudden it started bogging down and the throttle wasn’t as responsive as normal. I pulled off the road and it would not idle unless I kept choke on. I was able to turn choke off after riding 1/4mi at 30mph it even idled at a lengthly traffic light. I accelerated on the highway and it soon started bogging again. It seemed like it was pulling normal at full throttle but when I let off it bogged down and wouldn’t idle without at least ½ choke.


    Next I found a good place to stop and pulled off the side cover and started troubleshooting with no tools. After it had cooled down I idled at ½ choke. I noticed that the front right exhaust was cold so started playing with the coil but had no tools. I removed the spark plug wire from the coil replaced it and pulled spade connectors off to made sure they were making contact. After doing this it idled without choke and the exhaust was hot. I didn’t make it down the road a mile before it started acting up again.


    I brought it home on trailer and it runs with choke but the front right (#4) is not firing. When I increase throttle sometimes it responds well and other times it bogs. I removed the coil and checked resistance on primary (3.5 ohms) just out of spec? but exactly like the front left coil. The secondary is within spec. When running with plug removed and grounded the plug sparks white not blue. Tested pulse generator and cam pulse generator are within spec. Battery is new and shows 12.67 V.


    What would you do next?
     
  2. squirrelman

    squirrelman Member

    Country:
    United States
    Joined:
    Jul 27, 2006
    Messages:
    8,317
    Likes Received:
    286
    Trophy Points:
    98
    Location:
    Buffalo, NY
    Map
    crbz.
     
    Last edited: Jun 17, 2020
  3. Darryll

    Darryll New Member

    Country:
    United States
    Joined:
    Oct 16, 2017
    Messages:
    5
    Likes Received:
    0
    Trophy Points:
    1
    I've found that the front right carb doesn't have much gas in the bowl and it refills slowly. Less than a 1/2 ounce also drained out of the front left and the back bowls had about an ounce each. The fuel pump works fine and I have a filter inline.

    I really don't want to pull them again and wanted to know if you have any suggestions for solving this issue?
    Would it damage anything if I blow compressed air into the drain holes in float bowls?
     
  4. Paul Myers

    Paul Myers New Member

    Country:
    Canada
    Joined:
    Jan 26, 2020
    Messages:
    43
    Likes Received:
    6
    Trophy Points:
    8
    Location:
    Kingston, Ontario
    Map
    Ok silly question but I've got to ask - you have verified there is enough fuel in the tank and it is not ready to be switched to reserve or empty. Probably have but we all have not done the simple thing first sometimes so thought I'd just get that out of the way.

    You said you had a filter in line but have you checked it is not loaded up and restricting fuel flow? I'd pull the fuel line off at the filter outlet put on a temporary hose to a container and check flow from the pump/filter.

    You could also blow compressed air down the main fuel supply to the carbs with the drains open.

    Check for water in the fuel. Possibly add some fuel line antifreeze just to tie up any free water. Or just drain the tank into a suitable container and decant it.

    You can add Xylene to the fuel which will clean out varnish. This is an old racers trick to increase octane but it also cleans the fuel system. You should not go above 30% xylene and 10-15% should do it but there needs to be at least some flow to get it to clean. It is available at paint stores. Possibly open the carb drains and let fuel flow through. Not sure I would let the bike sit for a long time with it in the fuel system. I add it once or twice a year just to clean out the system but try to do it before I know I am going to burn the tank down fairly quickly.
     
  5. raYzerman

    raYzerman Insider

    Country:
    Canada
    Joined:
    Dec 3, 2019
    Messages:
    491
    Likes Received:
    167
    Trophy Points:
    73
    Location:
    Millgrove, ON
    Map
    Xylene is a harsh solvent that has an effect on some deposits, but won't necessarily dissolve gummy deposits that are built up from gasoline/ethanol evaporating. In that case a slow acting solvent works. If you use fuel with ethanol, after a week or so, it reaches its saturation point (~5%) with water and can't absorb any more, water can start to accumulate at the bottom of the tank. The solution there is naptha and isopropanol, conveniently packaged in a product called Seafoam. It only takes 3-4 ounces in a tankful to work on water (not sounding like water is your problem though), but use it regularly and gummy deposits will be dissolved.
     
  6. Dr.Инженер

    Dr.Инженер New Member

    Country:
    United States
    Joined:
    May 11, 2019
    Messages:
    66
    Likes Received:
    18
    Trophy Points:
    23
    Location:
    Tennessee
    If what your saying is true about everything else checks out. Then SquirrelMan is right, Carbs!
     
  7. Darryll

    Darryll New Member

    Country:
    United States
    Joined:
    Oct 16, 2017
    Messages:
    5
    Likes Received:
    0
    Trophy Points:
    1
    Hey guys, thanks for the quick replies. The T.S. on the road included switching to Reserve and filling tank completely. I left that out because it was starting to get like a book already.

    I have some xylene and I'll get some seafoam but it just doesn't make sense to me that the bike is running great then all of a sudden craps out. I've never had this problem with the older Honda Twins I've owned but there are some obvious differences. I've also never had this type of problem for years with gas in boat, lawnmowers, crap chinese weed wackers and dozens of Hondas. Are VFR owners cleaning carbs every two years?

    Before dissembling I did use a syringe in front right float bowl drain to pull fuel. It did start flowing better. Took it for a short ride, ran ok for one block and started bogging again. Flow was better but not solid stream.

    IMG_7446.JPG

    I've got it apart and will try these next:
    Confirm pump flow rate (I've seen here that pump isn't absolutely necessary)
    Flush hoses and carb bowls with solvent/sea-foam
    Confirm fuel filter flow (it's also probably Chinese crap)
     
  8. raYzerman

    raYzerman Insider

    Country:
    Canada
    Joined:
    Dec 3, 2019
    Messages:
    491
    Likes Received:
    167
    Trophy Points:
    73
    Location:
    Millgrove, ON
    Map
    While Seafoam is mechanic in a can, might be possible one float needle is sticking... in the end, there is no substitute for removing the carbs and cleaning things up.
     
    straycat and Dr.Инженер like this.
  9. Colddevil

    Colddevil New Member

    Country:
    United States
    Joined:
    Apr 2, 2008
    Messages:
    155
    Likes Received:
    28
    Trophy Points:
    28
    Location:
    Wisconsin
    Map
    I think damaging a component is the only thing that could actually happen from blowing compressed air into the bowls through the drain hole. From reading your explanations, I think it may be that the float valve is getting hung up and caught on Cyl #4 restricting or eliminating flow. If you do pull the carburetor back off, I'd be checking the pin, float, needle valve, and needle seat for any damage. I've had a similar thing happen due to a bent pin before on a Honda twin.

    As suggested previously, check that the fuel filter isn't completely clogged. Lastly, check that the primary battery terminal connections are tightened well. While that's usually an all-or-nothing thing, it takes 15 seconds if you've got access.
     
    raYzerman likes this.
  10. straycat

    straycat New Member

    Country:
    Canada
    Joined:
    Jun 27, 2017
    Messages:
    386
    Likes Received:
    119
    Trophy Points:
    43
    be very careful spraying solvents into Carbs that are still assembled. Some Carb cleaners for example will melt the rubber diaphragms in your carbs
     
    raYzerman likes this.
  11. squirrelman

    squirrelman Member

    Country:
    United States
    Joined:
    Jul 27, 2006
    Messages:
    8,317
    Likes Received:
    286
    Trophy Points:
    98
    Location:
    Buffalo, NY
    Map
    air in fuel line OK, crbz kin be damged bi chemicelz....avoid dem all.
     
    straycat likes this.
  12. Darryll

    Darryll New Member

    Country:
    United States
    Joined:
    Oct 16, 2017
    Messages:
    5
    Likes Received:
    0
    Trophy Points:
    1
    Ok...with tank/pump/filter removed I poured 4 oz Sea Foam into the carb bowls thru hose, soaked over an 1 hr, emptied them thru drains, then poured 6-8oz gas into them and drained them again. Each bowl had about an ounce of Sea Foam in them and it seemed like fuel was flowing well too. Added more gas and ran it for a couple minutes. It hit flat spot at about 3k rpm once but other than that seemed to be running well choked, idling and up to 5k rpm. All cylinders producing about same heat at header. Drained tank completely and found crud/rust in fuel filter shown in pic. When reassembled next week I'll test further and report.

    Thanks for all the comments/suggestions!
     

    Attached Files:

  13. raYzerman

    raYzerman Insider

    Country:
    Canada
    Joined:
    Dec 3, 2019
    Messages:
    491
    Likes Received:
    167
    Trophy Points:
    73
    Location:
    Millgrove, ON
    Map
    Looks like new filter in order... it would be beneficial to put Seafoam in the fuel for a couple of tanks also.
     
  14. squirrelman

    squirrelman Member

    Country:
    United States
    Joined:
    Jul 27, 2006
    Messages:
    8,317
    Likes Received:
    286
    Trophy Points:
    98
    Location:
    Buffalo, NY
    Map
    u need clean zmall filderz above fload needlez
     
    straycat likes this.
  15. Darryll

    Darryll New Member

    Country:
    United States
    Joined:
    Oct 16, 2017
    Messages:
    5
    Likes Received:
    0
    Trophy Points:
    1
    OH, I've never seen a filter on the float bowl valve! Thats one disadvantage of having someone else rebuilding your carbs. s-l1600.jpg
    Thank You Squirrelman s-l1600.jpg
     
  16. ddflying

    ddflying New Member

    Country:
    United States
    Joined:
    Jan 19, 2017
    Messages:
    2
    Likes Received:
    0
    Trophy Points:
    1
    Too clarify the issue I have been going through, I never lost the spark on #4 (front right) but only observed that the #4 header pipe was found to be cold as I was first troubleshooting my problem on the road.

    As I isolated the problem I found out that the #4 cylinder was the just the first to lose power but when I evaluated fuel flow on all cylinders I found out I had a entire fuel flow issue. None of the float bowls were getting gas. So as I isolated the problem I eventually found out that the problem was actually in the pump. The pump wasn't operating correctly because when I applied power directly to it. It would just click once. If I separated the contact points in the pump with the slightest pressure it would start pumping continuously. I was able to carefully bend the contact point mounting bracket so there was less pressure on the points and it started running continuously with 12v applied directly to the motor.

    It has run for about a half hour and dozens of miles. Hopefully this continues!

    Something I can't explain is that when I initially turn on the ignition the fuel pump has always only clicked once. It doesn't matter if the fuel system is full or no fuel is in the lines/bowls??? If someone can explain the design/function of the pump better it might be helpful? I would expect the pump to run continuously until pressure builds up and then only pump as needed to maintain pressure. Maybe on start up the fuel stop relay only applies voltage to confirm motor presence but since the CDI doesn't sense rpm from tach maybe it keeps it from running?
     
  17. squirrelman

    squirrelman Member

    Country:
    United States
    Joined:
    Jul 27, 2006
    Messages:
    8,317
    Likes Received:
    286
    Trophy Points:
    98
    Location:
    Buffalo, NY
    Map
    more problems are due 2 relay than 2 pump.
     
  18. Paul Myers

    Paul Myers New Member

    Country:
    Canada
    Joined:
    Jan 26, 2020
    Messages:
    43
    Likes Received:
    6
    Trophy Points:
    8
    Location:
    Kingston, Ontario
    Map
    Hmm I'm thinking that's going to be one of those timeless quotes "confucius said"
     
  19. Captain 80s

    Captain 80s Member

    Country:
    United States
    Joined:
    Apr 25, 2009
    Messages:
    1,913
    Likes Received:
    376
    Trophy Points:
    128
    Location:
    Edmonds, WA
    Map
    The motor has to be being cranked or running for the fuel pump to operate. They never "prime" when the key is turned on unless the relay has been bypassed. It is a safety feature if the bike has been wrecked and a fuel line compromised. It won't just continue to pump fuel with the key on. Many people just eliminate the relay when it goes bad. I wire a parallel switch so I can prime the system after storage and I can still get home WHEN the relay fails. I also carry a jumper wire in every tank bag.
     
  20. sixdog

    sixdog New Member

    Country:
    United States
    Joined:
    Sep 5, 2010
    Messages:
    191
    Likes Received:
    38
    Trophy Points:
    43
    Location:
    Westchester, CA
    Map
    My 'jumper wire " saved my ars a couple of years ago when I was 120 miles away from home....
     
Related Topics

Share This Page