5 replies to this topic
  • RIP051

Posted December 03, 2010 - 08:05 PM


i have an 05 wr 450
i have done the grey wire mod
put in the yz cam and checked valve clearence
gytr titanium exhaust and silancer
gytr fuel screw
i had a 165 mj and went up to a 182 my headpipe is glowing and bike backfires when i let off of the throttle
im at sea level
any helpful tips???


Posted December 03, 2010 - 08:29 PM


You're too lean on the pilot jet. Increasing the main will not help. What pilot jet and needle is in the carb?

  • William1

Posted December 04, 2010 - 04:33 AM


First, letting the bike sit there and idle, any bikes headpipe will glow. It needs airflow.
Pilot may or may not be good. Easy to check:
Fuel Screw/Pilot Jet
Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.
Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.
*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***
Turn the screw in until the idle becomes rough or the bike stalls.
if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.
If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.
Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.
If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.
If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.
If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

Lastly, a 182 main is way too big. put the 165 back. Even that is a tad large.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • RIP051

Posted December 05, 2010 - 12:03 PM


went to a 175 mj and a 50 pilot fuel screw 1 turn out... runs great


Posted December 05, 2010 - 04:29 PM


went to a 175 mj and a 50 pilot fuel screw 1 turn out... runs great

Glad you got it running. Those numbers still seem a little fat as evidenced by the screw only being 1 turn out. You could probably drop to a 48 pilot (2 turns out) and a 165'ish main.

  • GCannon

Posted December 06, 2010 - 04:52 PM


went to a 175 mj and a 50 pilot fuel screw 1 turn out... runs great

Still seems a bit rich!


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.