86 VFR issues

Discussion in '1st & 2nd Generation 1983-1989' started by Guest, Jul 5, 2004.

  1. Guest

    Guest Guest

    I have purchased an 86 vfr 700 that I ride alot. It has a yosh pipe and header.
    The bike surges and bucks while holding a constant RPM at all RPM's, although not as bad when cold. When I got the bike it would'nt run very well, so, I pulled the tank and found that the carbs had been messed with. After fixing the enricheners and bolting the carbs together as a unit, including the air pan, (the only right way to put them on) I put them back on and synced them. The bike never seems to be "smooth" and has a huge flat spot when you roll back on the throttle after shifting or running at WOT. I have replaced the fuel filter, and will set the floats next (if I can find the specs somewhere). After that I will move to jetting for my alttitude of 4500' elevation+pipe. I also added a new K & N filter and taped up the "holes" someone put in the airbox lid, and it made no difference.

    Anybody deal with this before? Anyone have the carb float specs or jetting recommendations?

    Sorry my post is so long, I'm just frustrated. Thanks guys
     
  2. Guest

    Guest Guest

    Well, I figured it out. I used an EGA machine from a friends shop and determined I am really lean from just above idle untill the needle leaves the jet at about 7,000 to 10,000 rpm(holding it there and letting it stabilize). I am not sure if the needles are adjustable, if not I will shim them when I tear off the carbs this weekend. In theroy this will enrichen the midrange/part thottle without adding to fuel to a good upper RPM/WOT fuel curve. If the problem persists, then I may throw some main jet at it. Stock the 86 700f has 118 mains, and 38 slow jets; I will increase the main to 120, and the slow to 40 and see what happens. If anybody cares to hear the results (such as those planning a pipe/header install), post up. Otherwise, I will stop wasting board space.
     
  3. Guest

    Guest Guest

    hello i am I bought a 1987 VFR 700 with a yosh pipe on it!The bike sat for 5 years and i changed the gas and have taken the carbs apart (about 5 times now)installed a after market filter and still have contant carb promblems i know that the mains were 118 but could not find out what the dyno stage 1 kits jet sizes where. I never adjusted the carbs and figured it just needed bigger jets .PLEASE let me know what you came up with!
     
  4. Guest

    Guest Guest

    Well, it was a long ass road, thats for sure. Anyways, I found that the stocks were 118's, but you should be around 125's (keep in mind I am at 4500' elevation, if your at sea level it may need more jet) with a pipe on it according to what research I have done. I bought the jets from chapperal or whatever for 2.99 each(x4 obviously), mine took the round jets for the keinin or whatever carbs they are. I have started with the #3 position on the needles, which were all bent thanks to the hack that tried to rejet the bike before me. If it works out to be the right needle position I will let you know here.
    The main thing is the float levels, your honda dealer should still be able to get that info for you, or I will post it here if you can't find it. All of my float levels were off by as much as 5mm, which is a ton on a bike. This would explain the surging and the flatspot when I roll back on the throttle after a WOT burn or during hard cornering. Check your needles to make sure you or someone else did'nt force them in and bend them. The trick is to gently guide them in when you assemble the carbs. I also fixed my enricheners as winter is only a couple of months away, remember to check yours to see that they all open as the linkage is tricky as well.
    Finnaly, the trick to putting the carbs back on the right way is to assemble the carbs, air pan, and enrichener linkage as a unit. Don't leave the bolts out that tie the carbs together and try to put on the carbs that way. Thats how mine were and it sucked. Then start on the rear manifolds, with lubrication on the rubber and carbs, and gently work it back and fourth untill the rear, then the front bank "pop"in.
    I have not yet been able to test the bike now that the carbs are set up correctly. It kills me not to be able to ride it yet, but my motorcycle mechanic friend (who taught me all of this) is out of town untill next week. I will let you know the results as soon as I go for a ride, untill then I am bitting my damn teeth.....or maybe I'll buy a Busa to keep me occupied untill then.
     
  5. Guest

    Guest Guest

    good info !my 87 has stock 118 .I looked at the needels and didnt see any adjustment .when you take out the diapham i just see a plastic screw when unscrew it the needel falls out for replacement is that hoe the 86 is?
     
  6. Guest

    Guest Guest

    My needles have 6 positions on them for depth adjustment into the jets. Do you have the Kenin carbs?
     
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