Just bought a 02 Yamaha yzf426...popping?

[blanc]

Hi All,
We just bought a very clean Yamaha yzf426, we ran grasstrack style track over weekend and rode it very hard for roughly 40minutes, it ran like a champ. However all of a sudden it started popping when shutting off the power, and then completley died. It would then only start on choke!!! WTF?
We let it cool down and then tried her again, the problem still persists now even cold. The airfilter was spottless, Why would this happen and what could be done to resolve this. Very dissapointing when just bought a new bike!
Boy Im glad now my Dad bought the Yamaha and I bought the Honda!!

Also any way of lowering the bike, hes only has a 30" leg?
Tks All
Steve

 

[Agie rider 76]

I would look for any leaks in the exhaust, letting air in.

 

[SirHilton17]

Clean the carb...
Maybe one of the jets is pluged

 

[blanc]

Checked both, no leakes.

 

[Tyler3386]

Did you check the exhaust gasket?

 

[Masterphil]

If it would only start when choked, it sounds like the pilot circuit is blocked creating a very lean condition. Have you ripped the carb apart yet? Check the plug, it might need changed as well.

 

[rasta]

426 popping

check to see if the fuel mixture screw fell out, it happend to mine all it did was pop before and after it fell out.

 

[LaRider20]

My CRF450 started poping on decelaration. It turned out to be a cracked head pipe. It's not always easy to find either.

Troy

 

[blanc]

I pulled the carp apart and thuroughly cleaned it with carb cleaner, cleaned the filter and box, neither of which where dirty at all. It has a 162 main jet in her, It has solved the problem fo now, and believe me I hav no idea how as she didnt have even a spec of dirt anywhere, however she still feels very hot and i suspect shell do it again. Any Ideas? Tks Steve

 

[Matt90GT]

blow the pilot jet out with compressed air. You got dirt in your tank. I would suggest to flush your tank out, then clean the carb especially the pilot.

 

[a454elk]

Those pilot circuits are really hard to get all the dirt out, and it only takes a little speck to mess up the circuit. It's the same problem I had with my WR400, the idle circuit got clogged and it took a ton of work to clear it. It made was popping as well and ran a little lean due to the blockage. I seem to think it's the same issue, especially if race gas was run through it.