Strange Cobra Phenomenon

Discussion in 'Exhaust' started by Lotsokids, May 8, 2017.

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  1. May 8, 2017 #1

    Lotsokids

    Lotsokids

    Lotsokids

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    I purchased my V-Max here in Hungary a couple years ago with a custom VERY LOUD exhaust system. I have since purchased a Cobra 4-into-4 system for a quieter daily ride to work. In a different post, I've had a chronic problem with #3 cylinder popping and sputtering.
    I recently returned from last weekend's drag races where I beat my best 1/4 mile time... 3 times! My best was my final run - 11.52 seconds... with the custom exhaust installed. That beast was pulling HARD at the track.

    HERE'S A VIDEO FROM THE TRACK

    A LITTLE REV IN A PARKING GARAGE

    Yesterday, I reinstalled the Cobras again. On the ride to work and back today, there was more sputtering and hesitation from #3 cylinder. I have true 4-into-4, so it's easy to identify.

    WHY DOES MY #3 CYLINDER DISLIKE THE COBRAS? This is really strange.

    It sounds like a Top-Fuel dragster with the custom exhaust, but sounds like crap with the Cobras. :confused2:

    Custom:

    [​IMG]

    Cobras:

    [​IMG]
     
  2. May 8, 2017 #2

    Fire-medic

    Fire-medic

    Fire-medic

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    Well, #3 is the 'problem child' cylinder which often has issues with the conn rod big end getting wiped-out. That's the opposite end of the cyl from the combustion chamber though, and I doubt one would have anything to do w/the other.

    Maybe you could scope the cyl & see if there is a carbon build-up in the head? A 'hot spot' could cause preignition, and could be due to something like a carbon build-up or a 'spur' of metal becoming a de-facto glow plug, though I think it would happen whatever exhaust you have on there.

    I'm surprised that you are running the Cobra and that your perception is it's making the engine pull well. The reports from people running the Cobra 4/4 are that it costs them significant HP, often dropping them into double digits at the rear wheel, i.e., below 99RWHP. Since a standard VMax is usually in the neighborhood of 110 RWHP without any mods, that represents a ~10% decrease in power. Most of us would be tickled-pink to make an additional 10%, which is why I'm surprised you went with a system known to decrease power by 10%. As I'm sure you know a 4/4 gives no scavenging effect. They do look 'pretty' and we all know a certain Bar & Shield (TM) brand that has for generations relied on the appearance factor to substitute for performance. Then again, not everyone is looking for a 14,000 rpm (for a 600 cc supersports) ride to the corner store, or during their daily commute. Torque and comfort can be acceptable substitutes for that 20% at the top of the powerband, and are much-more accessible, more-often.

    My thought is that if your coil is functioning correctly for that cyl, that you have some partial obstruction in the carb passages, and it won't go-away without a disassembly and thorough cleaning. I don't recall if you've changed plugs recently, but you might switch plugs cyl to cyl, and see if the 'pop' follows to the new location. Plugs are cheap. I once drove myself crazy trying to determine the cause of a miss in my KZ1000J, and my friend, a professional mechanic, asked me if I had changed my plugs. I replied in the affirmative. He switched the plug out on the offending cyl, and the miss disappeared. A faulty plug! Sometimes the easiest explanation is the one most-easily overlooked.

    I had a similar episode with a headlight bulb, much later, and again, a faulty product shortly after being put to use. http://www.vmaxforum.net/showthread.php?t=31075&highlight=chasing+tail

    An old stereo salesman trick is to slightly increase the volume on an A-B comparison of two speaker systems where the volume is higher on the line/product where you derive the most profit, because to most people, the louder system is perceived to be 'better.'

    Too-bad the UFO Quadzilla isn't quiet enough to meet your requirements.
     
  3. May 9, 2017 #3

    Lotsokids

    Lotsokids

    Lotsokids

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    I think you misunderstood. The opposite is true. My CUSTOM (not Cobra) exhaust sounds good and the engine performs well and pulls hard with my CUSTOM exhaust installed.

    I understand the power loss with the Cobras and true 4-into-4. I only install the Cobras so I don't wake up the whole village when I go to work in the morning. But When I installed the COBRAS, that's when #3 started sputtering and hesitating.

    I will check / replace the #3 spark plug soon.
     
  4. May 9, 2017 #4

    Fire-medic

    Fire-medic

    Fire-medic

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    Cobra? This is a Cobra! Not a kit car. From a car show in south FL this past weekend.
     

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  5. Jun 27, 2017 #5

    carrizog60

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    links dont work unfortunally...
    maybe your a/f mixture for that cylinder is at the edge with the custom exhaust and when you install the cobras they start acting?
     
  6. Jul 22, 2018 #6

    lilredrooster

    lilredrooster

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    G`day LOKids,

    Just wondered what ever happened with your Phenomenon?

    What was the conclusion?

    Enjoy the Ride...... Ride Safe..... :thumbs up:
     
  7. Jul 23, 2018 #7

    sdt354

    sdt354

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    Got an exhaust leak at #3 with the Cobras? Just saying.
     
  8. Jul 24, 2018 #8

    Lotsokids

    Lotsokids

    Lotsokids

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    Sold the bike last year and moved to the US.
    Never found the problem.
    Bought another V-Max when I arrived here, and no problems that I experienced in Hungary. No high-speed wobble. No #3 exhaust problems.
    I suppose we'll never know. :confused2:
     
  9. Jul 24, 2018 #9

    lilredrooster

    lilredrooster

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    G`day LOKids,

    Hope All is Well in your World, enjoyed reading about your drag racing exploits, very entertaining.... Many Thanks for your reply, very, very much appreciated, was hoping to pick your brains again if you don`t mind sharing.....
    I should firstly explain that i am from Australia and my interest stems out of curiosity with your custom 4/4 exhausts and how they compared with the Cobras as I have the Cobras on my own bike....

    I am thinking you sold your old VMax in Hungary and left the Cobras (street use) on it, if I remember correctly, you later brought the custom 4/4 exhausts (race/track use) back to the USA with you?

    The Hungarian Vmax that you used with both the cobras and the custom 4/4 mufflers, did it have the standard yamaha front headers fitted? I am assuming it did?

    Was the engine stock/standard other than the pipes?

    Did you notice a significant drop in performance in this Vmax with the cobras fitted compared to the custom 4/4 pipes fitted?

    Do you have any horsepower/dyno readings for either the Cobra 4/4 pipes or the custom 4/4 pipes at all from either country?

    Ride Safe...... Enjoy the Ride..... :thumbs up:
     
  10. Jul 24, 2018 #10

    Lotsokids

    Lotsokids

    Lotsokids

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    Answers:

    Yes, I left the Cobras on the Hungarian V-Max and brought the custom pipes back to the US with me. I bought another set of Cobras here, so I have the same options as I did in Hungary. Cobras for everyday use, and the louder custom set for weekends or when I feel rowdy. :biglaugh:

    I did not FEEL any major power gain or loss by using either system. I have stock down pipes (standard front headers).

    A couple months ago, I had my V-Max dyno'd with the custom pipes on - 109.9 HP at the wheel. No dyno in Hungary - only 11.52 1/4 mile time. Neither bike here or in Hungary had any engine mods. Only the exhaust pipes.

    Attached is my OKC V-Max I currently ride and love.
     

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  11. Jul 24, 2018 #11

    lilredrooster

    lilredrooster

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    G`day LOKids,

    Thank-you so much for your reply, really appreciate your help, very interesting and very helpful answers... :eclipsee_gold_cup: :clapping:

    Grrrrreat looking Bike, hope you both enjoy more 1/4 mile action USA style now you are back on home turf ..... :hippy biker:

    Enjoy the Ride..... Ride Safe..... Cheers... :icon_jook:
     

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