04 crf450 backfiring

[oglejust]

i just bought an 04 crf450r thats brand new, it had never had gas in it b4 yesterday other than wat the factory put thru it, the bike pops and crackles really bad when u chop the throttle, its wat i believe to be a lean condition on the pilot jet, so i took the jet out and made sure it was a 42, and blew it out with air, also blew out the bottom of the carb with air.. still does it. it runs good at rpms also. any ideas?

[AgentSmith]

Open up the fuel screw, 1/8 of a turn at a time and retest.

[oglejust]

2 1/2 turns out and it still does it

[AgentSmith]

The CRF450R responds well to a 45 pilot. I would swap the 42 out for a 45.

[oglejust]

well thats my luck, have sunday and monday off and i cant even ride... wat a bummer. ill try the 45, thanks

[AgentSmith]

Originally Posted by oglejust

well thats my luck, have sunday and monday off and i cant even ride... wat a bummer. ill try the 45, thanks

Try pulling the pilot jet out and run small gauge wire through all the orifices. Might be partially clogged.

Keep in mind many different bikes use the Keihin carb, KTM, Yamaha, etc. They may have the jet you need.

[oglejust]

well i found a jet i can use for the weekend, i pulled the pilot out of my old 85 cr 250 and its the same type but its a #60.. it fixed it, of course its a little rich but im gonna order the 45 tuesday. thanks for the help guys

[oglejust]

ok well i got my #45 pilot and it pops with it, it has a tiny bit of popping with the 60 but its not too bad, i also lifted the needle by lowering the clip 1 position and it didnt help, seems like i only have a pilot problem but y isnt the 60 taking care of it?!?! its only suppose to have a 42.. theres got 2 be a bigger problem somewhere any ideas?

[AgentSmith]

Could be an air leak at the header/exhaust port connection.

Could be something obstructing the passageway that the fuel screw controls.

[dogger315]

Could be an air leak at the header/exhaust port connection.

I agree. Unbolt the head pipe from the cylinder and run a bead of Permatex
Hi-Temp Copper to really seal it up. I have had to do this on more than one
CRF. Stay with the 45 pilot and see if that takes care of it.

If the problem persist, it can probably be narrowed down to varnish from
old gas in the pilot circuit like AgentSmith said. A soak in carb cleaner
followed by any kind of stiff bristle brush you can get to fit. In fact, it
wouldn't hurt to "hit" all the passages while you have it apart. A dose of
compressed air should finish the job.

Let me know one way or the other.

dogger

[VET393]

JD jetting kit

[oglejust]

ill try to seal the header with that stuff, i hope thats it. i dont see what a jet kits gonna do if ive already rejetted