Throttle after throttle stop and grey wire

Last night my brother and I did the throttle stop mod and the grey wire mod on my 05 WR450F. I also punched some holes in the closed side of the air filter.

After we got it all put back together and started it up it idled fine and rev'd up fine, but after reving it up it would idle really high then slowly come down to normal idle. Not sure what the rpms are but I would geuss if it idled at 1k it would hold between 2 - 3k rpms before gettting back to normal idle.

We also put in a 170 main jet to help richen it up since we ride at sea level most of the time. The exhaust pipe was glowing orange within 1 minute of startup, does this mean it is idling lean and if so what is the jet that I need to replace to make it richer at idle? I am going to order the JD jet kit when my next paycheck rolls around, will this kit have all the jets required for this?

Thank you in advance for your help.

Start with the fuel screw. Turn it out 1/8 turns at a time until the hanging idle goes away. If you end up more than 2 or 2 1/2 turns out then you need to go to a larger pilot (slow) jet and then go back to the fuel screw. Rule of thumb, more than 2 1/2 turns out change pilot larger, less than 1 1/2 turn out change pilot smaller. Hope this helps.


Thanks for the advice Josh. I have been wrenching on cars for quite some time but am a newbie to the motorcycle world and tuning is the only thing that has me asking questions, for the most part. Is this what the Zip Ty screw is used for? I think I am going to order one of those along with the JD kit.

Yes, definately worth the money in my book. You will have to punch out the plug that Yamaha put over the fuel screw. Your manual should show where it is, but you will see a place on the carb bowl near the access plug for the main and pilot jets that looks like it should have a screw in it. You can either remove the bowl and punch out the plug from the inside or you can drill a hole in it and pull the plug out. Just don't use too large a drill or you could dammage the bowl. When you put your Zip Ty screw in there be sure to keep the OEM spring and o-ring and put it on the new screw. Hope this helps.


You would more than likely be running lean on the pilot and needle as well.

Throw in a 48 pilot.

You have your idle knob would too far in (black knob on side of carby). Wind it out

and it will idle properly.

JD kit only comes with mains and needle. I am waiting for mine to turn up too!

Thanks for the help guys. Where can I find pilot jets? Is there a kit for these?

Yamaha dealer sells you FCR39 carb jets:


4MX-14948-06-00 .JET, SLOW (#48) AP 1

4MX-14948-04-00 .JET, SLOW (#42) STD 1

4MX-14948-05-00 .JET, SLOW (#45) AP 1

4MX-14948-07-00 .JET, SLOW (#50) AP 1

4MX-14948-01-00 .JET, SLOW (#35) AP 1

4MX-14948-02-00 .JET, SLOW (#38) AP 1

4MX-14948-03-00 .JET, SLOW (#40) AP 1

You shoul be able to get them easily off your yamaha dealer. you can get a GYTR kit with main jets, pilot jets and needle but I would just get what jets you want to try. They are cheap enough.

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