2000 WR400F Questions?

My WR400F has been popping ever since I bought it when I rev it up and let off the gas the rpms slow down and the muffler makes a popping sound. It must be the jetting but I don't know what jets to use or how to put them in the carburetor. What size jets and should I use? Will that fix the problem? Also my rear tire is pretty worn in the middle section so I will probably be buying a new rear tire. My tire do you recommend for trail riding and good traction or good all-around tire. I found a dunlop D739 for $58.20 + $12.50 shipping on EBAY. Is that a good tire? It's suggested retail is $97.00!

Hey I have the same bike! As for the popping do ya have a differnt exuast or any mods? also what altitude do you ride at? I have the Dunlup on mine an it works pretty well. but for the most part I ride in sand an the woods. I dont like the tires on hardpack firelanes too slippery. You didnt by chance take out the restricter plate from the muffler did ya? That may make it pop.

It's the stock exhaust. Well I have the baja baffle on the end of the muffler and the K&N Air Filter with the airbox lid removed. But the bike has always made the backfiring sound before the K&N air filter and airbox lid removed. The guy I bought it from just put baja baffle on it. I don't know what altitude i'm at. i Figure I can play with the fuel mixture screw or change the jetting until it stops backfiring.

If you want to get the bike to run properly get the JD Jetting kit with an after market exhaust. The JD kit has multi tapered needles that make the bike crisp on throttle response. The kit comes with installation instructions and it's really easy to do. Good luck!

That would be way too much money to spend. They R.I.P. people off with the aftermarket exhaust systems! I'll probably re-jet it and it will not backfire anymore.

That would be way too much money to spend. They R.I.P. people off with the aftermarket exhaust systems! I'll probably re-jet it and it will not backfire anymore.

It appears that you had your answer before you even asked it. :applause::eek:

Perhaps a lobotomy is the best option.

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