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Sachs 150 stalling after full throttle plz help!

Discussion in 'Technical and Troubleshooting Torque' started by Jase1, Jul 17, 2012.

  1. Hi guys

    This issue is driving me nuts!
    What happens is the bike starts to hesitate and bog down after roughly 5 seconds or more of full throttle. Ill then have to back off the throttle and itll be ok while just cruising, but if i then stop then engine will stall for sure, and it wont start back up straight away unless I apply full choke.

    Even if i back the throttle off before it starts hesitating it will almost always stall as i pull up the to the lights etc which is annoying and embarrasing as i cant start it back up straight away. If i apply full choke it will start immediately, so obviously its a fuel problem. Could someone tell me where the mixture screw is on the carb on this bike? Presumably its a mixture issue?

    Btw unless i go full throttle for more than a few seconds, the bike runs fine and never misses a beat. The problem occurs whether hot or cold! And it's a 2007 model.

    Plz help! I know a fair but about cars but mainly fuel injected, and im fairly nift with a spanner so if someone could just explain to me what they think is going on with the fuel i should be able to tune it up. Is it gradually flooding? Or running leann? Maybe the carb cannot get enough fuel and is being starved? But then why would it start on throttle close?
  2. Start with the basic stuff first...

    1] fuel filter...most bikes have a simple fuel filter incorporated in the tap assembly. Some have a small bowl containing a screen that can be unscrewed with the tap in place and others will require removing the tank and draining, followed by removing the tap assembly from the tank

    2] check the vent in the tank cap is not blocked

    3] check for kinks, tight bends, folds in the fuel line between the tank and carb

    4] check the carb float and valve assembly and set float height.
  3. try it will a full tank of fuel
  4. Did 1 2 and 3 t no avail. Also filled the tank to full with no difference.

    However number 4, do i have to remove and completely dismantle the carb for this?

    Also, does it sound like it's starving for fuel to you or over fueling? I may have to remove my wideband o2 sensor kit from my skyline and install it on the bike.

    So far i havent been able to work out what would cause the bike to stall on throttle close. Like if its running out of fuel during the full throttle run, why would this cause the bike to stall on throttle close when it needs the least amount of fuel?
  5. Ok so ive semi fixed it.

    Took the fuel hose off the carb and discovered only a slow trickle/drip of fuel coming from the fuel tap. I knew this was the problem straight away. I then turned the tap to reserve and voila i had full fuel flow. So just by turning the tap ive eliminated the stalling problem.

    But now the issue of the blocked tap. I installed a big fck-off fuel filter inline to stop any crud getting to the carb. I undid the bottom of the tap and was horrified at the amount of crap that was sitting in the bottom. Still didnt fix the flow problem though.

    So whats the next step? Remove the tank? Or drain the tanlk and just unbolt the tap from the bottom? Is there a filter in the tank? Im trying to visualise how the primary flow could become blocked but not the reserve, cant really picture the mechanics of it.
  6. The tap can have a gauze filter on the inlet. Remove the tap from the tank, clean any filter, flush the tap on normal and reserve positions to remove any crap stuck inside it. Flush out the tank to get all the loose crap out. It sounds like something is stuck in the tap and partly blocking the flow in the normal position.
  7. Remove the tap from the tank.

    3 possibilities here..

    1] there's something blocking the main pickup tube. Blowing it back into the tank will only see the problem reoccur sometime in the future.

    2] some tap assemblies have a gauze cover over the pickup tubes which may be blocked.

    3] out of left field...how many hoses / lines connect to the tap?
    1 line....back to 1 or 2.
    2 lines....is the second line a vacuum line ? in this case check that the diaphram in the tap is opening properly...ie not damaged.

    If its all too hard....leave it on reserve and use the trip meter as a virtual fuel gauge.

    Ref #4....yes checking float and float valve is a major part of servicing the carb..remove and dis/re assemble.