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Discussion Starter #1 (Edited)
[Total mechanic newbie, Suzuki Symply2 150 scooter]

Could anyone help me diagnosing this issue?

  • Scooter starts and idles perfectly
  • As soon as I open the throttle past 1/4 engine splutters and backfires
  • If I disconnect the air intake on the carb totally (?!) then she runs like a dream

I've already:
  • Checked the spark plug
  • Checked the automatic choke
  • Checked (and removed to test) air filter
  • Tried to adjust the mixture, however regardless of where the screw position is, it makes absolutely no difference -- to idle or running.
  • Sprayed carb-cleaner into carb while engine running

The air intake pipe is really fat; I can't imagine that -- with air filter removed -- simply disconnecting the pipe from the carb increases the air flow much, however it definitely fixes the issue. I see there are some other pipes coming off the air intake pipe...what goes on here? Could they be the reason? Otherwise, any other suggestions of where I can look?

Super Moderator
12,830 Posts
Are you saying that it acts differently with the air cleaner element removed......versus with the whole intake assembly removed ??

Seems that IS what you are saying; if so a careful inspection is in order to see if the boot is putting a bind on something else or pinching a hose.
After that, I'd say to take each hose off one at a time and plug it (like with a golf tee) and see which one makes a difference.

My guess would be that one of those smaller hoses is kinked when everything is in it's normal position.

Regardless, a healthy dose of carb cleaner in the gas tank is a good idea. Berrymans B12 Chemtool is good.

P.S. If this is a 2 cycle engine, replace the spark plug. Just because.
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