Announcement

Collapse
No announcement yet.

Bogging from about 3500 up

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Bogging from about 3500 up

    Still trying to get "Big Red" back to the way she ran before I parted with her. Initially my brother (another XSive) and I tore down the carbs, set the floats, cleaned everything possible, and reassembled them. Also tore down all three brakes and thoroughly went through them. New battery and tires were mounted.

    She fired up and ran fairly well with only very minor "missing". Accelleration was strong throughout the power band. We hadn't changed the oil yet (was on a limited timeframe before I had to return home). He suspected the few hiccups would pass once she streched out and breathed again.

    Upon returning home, I rode her about 50 miles without incident while procuring the necessary lubricants, safety inspection, licensing, etc.

    Header, centerstand, and sidestand were repainted. The K&N's were cleaned and re-oiled as per their directions and with their products. Brand new NKG BP6ES plugs were installed (gapped at .030"). Mid and rear gear oil was replaced with Bel-Ray Gear Saver SAE 90 hypoid gear oil. I haven't replaced the fork oil yet but have 10W Bel-Ray High Performance Fork Oil ready. Engine oil and filter (EMGO) was replaced with the reccommended Yamalube SAE 20W-40/API SJ.

    She starts up and idles fine. Accelleration is fine as long as it stays below 3500 RPMs. Rolling hard on the throttle she bogs down bad starting at about 3500 to 4000 RPMs and can't get to red line. I can't for the life of me think what I could've done since returning home (didn't do that during the 50 miles since I got home) to cause such a loss of power. The air cleaners were filthy and after cleaning and oiling should be breathing much better. The plugs are carbon fouled (sooty black halfway around and nice dark gray/brown the other half).

    She was rejetted (mains only) over 20 years ago when the header and K&N's were installed and ran mid to low 12s in the 1/4 mile. Sorry, I don't remember if they are 140 or 142.5s from the stock 137.5s. Wish I'd paid more attention to them when we had the carbs apart last week. Guess I'll find out soon enough, huh?

    Any ideas or suggestions are welcome.
    Last edited by JohnSg; 07-06-2004, 09:36 AM.

  • #2
    Bogs down above 3500

    John, take the K&N's off for a quick run up the road. Just an experiment. Possibly they are acting like a choke restricting the air inflow enough to cause excessively rich at higher RPM.
    Ken/Sooke

    Comment


    • #3
      Ken, looks like you hit the nail on the head. I just pulled the K&N's like you suggested and it ran just like before. I must've put too much oil on the air cleaners. Time to reclean them! Thank you too much!

      Comment


      • #4
        Individual Air Filters

        John, are these true K&N's or after market copies? If they are aftermarket check to see if they have a large rubber shoulder where they couple onto the carburetor air horns. If they have the large shoulder then they are junk. This big rubber collar blocks off several of the balance passages in the mouth of the carbs. It is also smaller in diameter than the actual throat of the carbs. This causes a choke affect at higher engine/air intake speeds. This causes the vacuum in the venturi area to get too high causing things to go away to rich. High engine speed and HP go in the toilet as the intake charge goes rich.
        Ken/Sooke

        Comment


        • #5
          Ken, they are real K&N's and have a very large unrestricted opening, larger than the carb shoulder that they slip onto. After cleaning them again of the eXSess oil and reinstalling them, she ran fine. The only problem I have with the K&N's is I'm using regular hose clamps to hold them on and they are much too wide. I have OEM clamps on order from Speed and Sport (YamaTopDog.com) and eventually plan on putting the stock airbox back on. It would be XSellent if I could find NOS OEM XSaust pipes for her.

          Comment

          Working...
          X