Yamaha 05 YFZ450 Misses out & pops loud

[locodave69YFZ450]

Basiclly stock with pipe & jet kit ran find all last year & now all of the sudden it misses out & pops alot especially off idle !! I am not sure whats going on starts & runs fine after warm up try & ride it sounds like some one shooting the big gun ???? :bonk:

[450plumber]

pilot jet ? valves ?

[chim-chim7]

Basiclly stock with pipe & jet kit ran find all last year & now all of the sudden it misses out & pops alot especially off idle !! I am not sure whats going on starts & runs fine after warm up try & ride it sounds like some one shooting the big gun ???? :bonk:

We need more info. How long did it sit? Was there gas in the carburator when it was sitting? Is your gas in the tank fresh? Is this the first time you have ridden it since it's been sitting? How many hours on the engine? When was the last time the valves were inspected/adjusted?

[NYMXer]

W/O more info, I'd say you have a dirty pilot jet from letting the quad sit w/ gas in the carb for too long.

[locodave69YFZ450]

we have been riding the Quad all year & the fuel is fresh & run race fuel thru it !! This just started happening over the last couple of weekends & getting worst ! We replaced the throttle sensor but didnt help & yesterday it did not want to even idle ????

[locodave69YFZ450]

fresh gas only sits during the week ride almost every weekend ! Valves have never been adjusted ???

[NYMXer]

An 05 might need valve adjustment, so check that.

I would do all the simple things first like drain out the fuel bowl, clean the air filter, check for a short or air leak, check plug cap, plug, etc.

It sure does sound like a carb related problem though.

[locodave69YFZ450]

An 05 might need valve adjustment, so check that.

I would do all the simple things first like drain out the fuel bowl, clean the air filter, check for a short or air leak, check plug cap, plug, etc.

It sure does sound like a carb related problem though.

OK THANKS EVERYONE !! I will let you know !! Dave:banghead:

[locodave69YFZ450]

Thanks for all your help the valves were near perfect & the problem was a missing o-ring on the air inlet screw on the carb !!! Weeeeeeeeeeeeeeeee

***************** thanks again !!!

[NYMXer]

You said it was running fine and then 'all of a sudden'.......O rings don't go AWOL all of a sudden. Did you take out the fuel screw for any reason?

Glad you found the problem.

[locodave69YFZ450]

You said it was running fine and then 'all of a sudden'.......O rings don't go AWOL all of a sudden. Did you take out the fuel screw for any reason?

Glad you found the problem.

Oh yeah we changed the screw to an a/m screw & must have pinched the o-ring & had checked that like twice before seeing it !! lol Anyway never forget the basics. Thanks Dave