Jump to content
Sign in to follow this  

bike wont idle down

Recommended Posts

i have a 04 yzf450 bike runs great but it seems that when the bike warms up when on a ride the bike wont idle down but if i rev the bike a couple times it kicks down and the throttle feels good and does'nt stick any idea's thanks

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

ok i will try that but i just went though all those steps when the bike had decel poping only thing i can think of is that may have put to big of a pilot jet in maybe i will try going down a size thanks

Share this post


Link to post
Share on other sites

You cannot 'jet away' decel popping. The pilot circuit is for idling. You may find the fuel screw has a very narrow point between a good idle and a occassional fast idle. You must ride, adjust, ride, adjust. Do not just fire the bike up in the driveway and atempt to get it right sitting there.

Decel popping, if it suddenly started, is usually a leak in the exhaust or worn out packing.

If you just put a pipe on, the more open the pipe, the worse the popping will be.

If it is a woods bike, it is possible the ACV (Automatic Coast Valve) is not working correctly.

If it has done it since new and it is a MX bike, live with it. The solution is to ride faster.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×