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99 big bear 350 new carb install


Colasonojon9

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I purchased and installed new zoom zoom carb on my 99 big bear 350. It starts alot easier where it used to start once or twice then you would have to wait awhile. But it needs at least half choke to run if you cut off choke it slows idle all the ways down until it dies. I tried turning in idle screw but just makes it harder to start. Also with half choke on i put in gear and it will go if you barely hit throttle anything past that it cuts out, any ideas?

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It  sounds like it is starving for  fuel..  I'd start  by  adjusting  the  idle  air screw.  Start  at  about  1  1/2  to  2  turns out from seated.  and  try  in 1/4 turn  adjustments  out  or  in  to  see  if that  cures the   idle  and accelerate from  idle  problem ..  also  check  for  air ( vacuum)  leaks.  If  that  doesn't  do  it  then    I'd  suggest   taking the  carb  apart  and recheck  float  height and  carb jets  and  passages  for  blockages. . Even a brand new  carb  could  hacve  some  manufacturing  debris in  it ,  and  rebuilt  could  have  a missed blockage or float  height set  wrong .

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Thats where i was thinking of starting, the mixture screw i mean. Gonna count how many out the screw is from the factory first. Just so i can reset if need be. I also bought new screw for intake boot incase vaccume leak there. Didnt have an air box on idk if thats considered an air leak being after the carb an all but i got one now havnt started with it yet. Just trying to give all the details

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20 hours ago, davefrombc said:

It  sounds like it is starving for  fuel..  I'd start  by  adjusting  the  idle  air screw.  Start  at  about  1  1/2  to  2  turns out from seated.  and  try  in 1/4 turn  adjustments  out  or  in  to  see  if that  cures the   idle  and accelerate from  idle  problem ..  also  check  for  air ( vacuum)  leaks.  If  that  doesn't  do  it  then    I'd  suggest   taking the  carb  apart  and recheck  float  height and  carb jets  and  passages  for  blockages. . Even a brand new  carb  could  hacve  some  manufacturing  debris in  it ,  and  rebuilt  could  have  a missed blockage or float  height set  wrong .

Okay I just wanted to get a good idea where everything was this morning so I started with the timing checked it, it looks like it's about 1/16 or 1/8 off is it as simple as removing the center bolt in the Top Gear and then turning the gear without turning the chain that far and bolting it back up

IMG-20171124-WA0003.jpeg

IMG-20171124-WA0000.jpeg

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I  haven't  had  to  mess with  the  ignition and  cam  timing  on a  quad  motor so  I  cannot be sure ,  but I believe  the  sprockets are  keyed to the  shafts  and  are  not adjustable.  I  believe  about the  only  thing that  could take  them  partially  off  center  would be  wear  on the   sprocket teeth  and  chain stretch..   Neither  should  have a  great effect  on the  timing and  how  the  engine  responds..  If  the  chain  jumped  a  tooth or  more due  to  wear  and  a  loose  slack  adjuster, I  believe  the  timing  would be  much  farther  out and the  motor  would  be  greatly effected  at  all speeds from  idle  up.

I  don't  believe  that  is  your  problem. The  most likely  is fuel  problems , with  a  much  less likely possibility  of weak  spark.

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17 minutes ago, davefrombc said:

I  haven't  had  to  mess with  the  ignition and  cam  timing  on a  quad  motor so  I  cannot be sure ,  but I believe  the  sprockets are  keyed to the  shafts  and  are  not adjustable.  I  believe  about the  only  thing that  could take  them  partially  off  center  would be  wear  on the   sprocket teeth  and  chain stretch..   Neither  should  have a  great effect  on the  timing and  how  the  engine  responds..  If  the  chain  jumped  a  tooth or  more due  to  wear  and  a  loose  slack  adjuster, I  believe  the  timing  would be  much  farther  out and the  motor  would  be  greatly effected  at  all speeds from  idle  up.

I  don't  believe  that  is  your  problem. The  most likely  is fuel  problems , with  a  much  less likely possibility  of weak  spark.

 okay that's good to hear I was rather gun-shy about messing with it anyway I like to know exactly what I'm doing before I go messing with something and the chain is very tight so I doubt it could have slipped anyway never know though. Of course my starter had to go out and I'm having a little difficulty pull starting so kind of at a standstill thanks much appreciated

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  • 2 weeks later...

Just to touch base ended up ordering the stock pilot jet for the brand new carburetor size 42.5 at least 2 sizes bigger than what was in carb brand new i can actually drive now still trying to tune carb in after about 20 mins of riding it wants to shut off and not start but this could either be float level or electrical heat problem ill keep you guys posted

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