Carb Vent lines???

Discussion in 'Thumpers' started by buffallodan, Jul 1, 2006.

  1. buffallodan

    buffallodan Long timer

    Nov 18, 2004
    Frankfort Kentucky
  2. Countdown

    Countdown Long timer

    Oct 20, 2003
    Carson City/Ridgecrest
    As I wrote in another thread, I think that one vent hose on each side should go down to drain any liquid gas that comes out the vent when bike is on its side. Second hose on each side should go up under tank to break vacuum when lower hose goes under deep watter. Bikes with all hoses down tend to stall in deep water.

    The vent is a pressure vent and does not need any air flow except to equalize pressure.
  3. rmhrc628

    rmhrc628 Long timer

    Feb 6, 2006
    OK this is what you should do:

    One hose from eother side goes north and gets routed up near the tank. The other 2 stay low.

    I did the left hand side as the way FCRs route their hoses, they have one from each side passing through on opposite sides
  4. Xfool

    Xfool Been here awhile

    Jul 21, 2005
    Thousand Oaks, CA
    Alpiv: Great pics!:clap

    Right side: route hose 3 up under tank to somewhere around the coil for vent.
    Route hose 4 down to rear swing arm as drain.

    Left side: route hose 1 up.
    Route hose 2 down since it is already pointed that way.

    The idea is to have at least one vent line high so that the carb bowl is always vented to atmosphere and one vent line low so that fuel spilling or boiling into the vents can drain. If all of the vents go down, when crossing deep water, the water flows up the vents pressurizing the carb bowl and flooding your bike with fuel. Learned that from the ktm race team.

    I also found out there are internal vent passages in the carb bowl that allow the bowl to drain when overfilled. If you drop your bike, fuel will be coming out the carb bowl drain line even though the valve is closed – so that kink in the carb bowl drain line on top of the starter motor is a potential problem.:eek1

    To reduce the number of lines running around the bike I used some of the tees from the canisterectomy and joined hoses 1 and 3 above the carb on the frame backbone into a single vent line that runs up near the coil. Leave some slack in lines 1 and 3 so you can rotate the carb around to get to the bottom of the carb bowl for future jet changes and pilot screw adjustments. The vent line should have a continuous upward slope with no loops or woop-de-doos so that any liquid in the line will drain back into the carb bowl.

    Used another tee to join the drain lines 2 and 4 below and behind the carb into a single drain line back below the rear swing arm. The drain line should have a continuous downward slope so no liquid collects.
  5. Chadleys1

    Chadleys1 working on it

    Sep 26, 2005
    Toledo Bend Country Louisiana
    You summed it up perfectly, Xfool.
    I use these on my TE610, and have never had a surging idle or sputtering after crashing or anything like that, since. The bike has been upside down in a ditch for a few seconds, and everything drained out fine and it started right up.
  6. Ruffus

    Ruffus Dirty Old Mudder

    Jan 22, 2006
    Fort Erie,Ontario
    That rerouting looks like a great idea, I'll have to do the same, a couple years ago I read in one of the mags (Dirtbike?) that when you hit deep water, it super cools your engine causing it to run really rich & starts blubbering, needing quick clutch & throttle work to keep it running???? Don't know how true that is, but it's something to keep in mind aside from venthose routing, I'd like to hear how much of a difference the rerouting did in deep water crossing's :ear :thumb