I just finished a tune-up on a 400ex I just bought, But at low idle it does a sucking noise every 3 to 5 seconds. Anyone have any idea what this could be. Thanks in advance.

 

also the bike wont idle by itself I have to slightly give it some throttle so it stays on.

 

Take a can of carb clean and spay around the boots to your carb ... Check the boot from your motor to the carb if there is a Vac. leak the motor will idle when you are spaying it . That will tell you if you have a Vac. leak

 

Also what do you mean by a tune up ? What did you do to the bike ?

 

i changed the oil and oil filter, i changed the spark plug and gapped it to the right size. And I also drained out some old gas in had in the tank for a couple of months, and put in new 93 octane gas.

I just bought the quad from my friend it had a busted real axle carrier, and I just ordered a rad tapered carrier for it. And im trying to get the engine running fine by the time the part gets to my house.

 

What does the noise sound like ?

 

its sound like a hicupping noise at low throttle. And it sometimes backfires at high throttle

 

Where does it back fire out the exhaust or the carb. That might help if you can tell me where it's backfiring from ..

 

Did it backfire before you did the tune up on it ?

 

it backfires out of the exhaust and and it hiccups out of the carb. It also did this before the tune-up. Me and my dad just finished cleaning the carb. It was perfect for the first 5 mins. then started doing the same hiccup.