Just bought a '95 vfr, having some surging issues, also a lot of burbling/popping

Discussion in '3rd & 4th Generation 1990-1997' started by NateV8, May 9, 2022.

  1. NateV8

    NateV8 New Member

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    Bought a '95 vfr with 30k km on it. It's so clean but having some issues with the carbs. It surges a lot, I generally cruise in town around 4k rpm but it doesn't matter what rpm it's at that it surges. When accelerating very slowly the Rpms increase in surges. While cruising and surging it also kind of burbles at the same time. When decelerating it burbles and pops a lot. It has a k&n filter and a black widow slip on that with baffle removed (baffle was pitch black). The PO changed the Jets, he races bikes and used a company that matches jets to the cc and mods. I'm not sure what the jet size is but it smells rich.

    From research from the '94 vfr I had, there wasn't much gain in jet changes so I'm wondering if it's very rich right now. The popping isn't loud and the burbling and popping kind of mix together on decel. It idles just fine, starts well enough with choke on. The surging is very annoying. I removed the baffle to try and lean it out a bit, I really noticed the burbling and popping after removing the baffle. It does smell strongly of gas but it's a carved 4th gen, maybe they always do? It's been a few years since i owned one. It pulls great at WOT from 7-11k rpm
     
  2. Captain 80s

    Captain 80s Member

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    Sure sounds rich. Time to pull the carbs and document what was done to it and bring it back to something reasonable.

    A K&N and a slip-on shouldn't require radical jetting to run good assuming everything else is in correct working order.

    You can tape off half of the air filter and see if it gets better or worse for a quick clue.
     
  3. squirrelman

    squirrelman Member

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    when i first got my '97 (around 2000) it surged alot at small throttle openings and was too lean, so a turn and a half open on the mixture screws fixed it nicely. everyone knows the bikes were too lean from the factory to meet epa emissions requirements.

    11-28-16_004.JPG.afb248fad26d294b99421ca170c171bf.JPG
     
    Last edited: May 9, 2022
  4. NateV8

    NateV8 New Member

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    Jet size is 130/132.5. elevation here is sea level so I suppose that's fine. The surging is very annoying though. I'll see what the range of the surging is
     
  5. NateV8

    NateV8 New Member

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    So at highway speeds at 4-6 k rpm I don't notice surging, probably because I'm in 6th, but in low gears I notice it most under 5k and it lessens at 6k and up. When I'm in low gear low rpm it also burbles and pops while trying to maintain steady throttle, I don't know if it's because of the surging as the surge ends it's like decelerating. Pulls like a freight train at 7k and above.
     
  6. Captain 80s

    Captain 80s Member

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    Again... kinda sounds like somebody's work needs to be checked.

    Did they put in different needles?

    Where are the pilot screws set at?

    What pilot jets were used?

    Are the carbs installed properly? Fully seated? Did they tear a boot? All clamps tightened?


    Too many what ifs for me, but I don't mind pulling V4 carbs. I never trust "what the guy said" or "what the piece of paper says".

    The previous owner of my ST was told, and then told me, ,"rejetted and all coolant orings replaced." How about pilot screws jacked way out and NOTHING else touched.
     
  7. NateV8

    NateV8 New Member

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    Needles are stock but have been adjusted, the pilot Jets are 42 if that helps. I believe he did not rip or tear anything and installed everything correctly. He doesn't remember his settings though as he tore it all apart and replaced many parts 2 years ago. He owns 19 bikes and from what I saw of them and when we talked, I am not concerned. He said it's hard to remember all the settings with 19 bikes lol. I'm still messaging him about stuff and he replies honestly. But that being said I do believe he didn't tune it for cruising.

    Would the pilot Jets be the cause of my surging? Surging is caused from lean or rich condition? I'm assuming the bike runs rich currently

    He mentioned that I should try adjusting the needle when I mentioned that it surges around 4-5k rpm
     
  8. NateV8

    NateV8 New Member

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    To further add he used a jet and kit and followed the instructions as per the kit. The kit is from 6sigma. It says to use the 132.5 on the front, 130 on the rear, adjust the needle 1 position towards pointed end or install shims if not adjustable. For mixture screw it says to back out 2 turns or best idle
     
  9. squirrelman

    squirrelman Member

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    your assumption may be incorrect, and tuning is never based upon assumptions !

    have you checked the plugs' colors ? capt80s suggested you cover part of the air filter as a test. what are the mixture screws set at ?
    an easy rich/lean test would be to open or close the mixture screws about 1/2 to 3/4 turn to see the results..........................but you need the special D-shaped tool for that (comes in a jetkit ). :(

    both factorypro and K&N/dynojet provide tuning info you can download and study.

    the guy who says he put in a jetkit and you bought the bike from.......wouldn't he have fixed the surging if he knew what he was doing ?
     
    Last edited: May 10, 2022
  10. jethro

    jethro New Member

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    Being lean is what causes surging. Alot of suggestions above that need to be done and diagnosed.
     
  11. NateV8

    NateV8 New Member

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    Yes the kit came with the d shaped tool. I wonder if I caused the issue by removing the exhaust baffle. I thought it was rich so I removed the baffle because I read removing the baffle can lean it out (it was also mainly because I wanted more sound lol) . I will put the baffle back in and see if it still surges. If it does stop does that mean I would have to richen the mixture if I want to remove the baffle?
     
  12. NateV8

    NateV8 New Member

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    After a run with the exhaust baffle back in, the burbling and popping was dramatically reduced and the surging was reduced by about 50% I'd say. So it seems that it is running lean. I also noticed WOT didn't pull as hard with the baffle in but that makes sense. So I'm going to remove the baffle and start with a half turn out. I will count the turns it's at currently before turning it out more
     
  13. Captain 80s

    Captain 80s Member

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    With the jetting changes described, that bike should run tits even with the baffle out.

    Jus sayin
     
  14. NateV8

    NateV8 New Member

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    Sorry for the long delay. I finally had some time to look at the bike and the mixture screws are slotted, I bought the pro motion 90° driver and I checked all the screws. They were 2 turns out. Found my lean problem. So I changed them to 2.5 turns out. I'll see how it runs with the baffle out. I went on a good run today and it surges a small amount the with baffle in. If the surging with the baffle out is comparible to today's run with the baffle in I will turn the screws out another 1/4 turn
     
  15. NateV8

    NateV8 New Member

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    Alright so test ride was a success. Last time I took the baffle out it surged like crazy and constant backfiring/burbling even while cruising it was burbling. Now I think it surged just a hair? I'd have to go out again for a longer ride. The burning is gone and it pops a few times when you get on it and then cut the throttle which is normal. It also pulls noticeably harder and keeps pulling to redline. I did a lot of pulls today and I noticed the difference first pull.

    My idle dropped just slightly when warmed up so I'll bump it up a bit.
     
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