Jump to content
Sign in to follow this  

450 exc jetting

Recommended Posts

Just purchased an 05 450 exc and have three rides on it. At assembly the dealer put a 52 pilot jet in, left everything else stock. The bike was stumbling at low rpms and hard to start when hot. Checked with dealer and he replaced the 52 with a 50. The bike is easier to start when hot but still has an off idle bog. I have read several threads on TT regarding the JD kit so I ordered it and will install this weekend.

My dealer's rational for going to the richer jet was that stock jetting was way too lean. When I took delivery of my bike I rode an 05 450 exc demo that he brought back from the dealer show in Reno. The bike popped like crazy and the head pipe was blue almost all the way back to the silencer.

According to the instructions with the JD kit, for my altitude (3000 - 6000 ft.), I am to replace the stock main (#178) with a #170 and place the blue needle in the second position. Nothing is mentioned regarding the pilot jet so I assume I should return to the stock #42. My question is, if with stock setting the jetting is very lean how is it not going to be lean with the settings indicated by JD. Is the needle position going to richen it up? I am not doughting the experts as I am a jetting rookie, I am just trying to understand how this works.

Share this post


Link to post
Share on other sites

The stock needle is lean, but not the pilot jet and main jet. The recommended kit main jet (170) is used to match the richer kit needle profile at your altitude.

The stock #42 pilot gives a good range of adjustment for altitude changes with the fuel screw while using the jetting kit. Given your concerns, run the blue marked needle in the 3rd from top clip position and the #170 main jet. This is a very common clip position for a wide range of conditions.

Thanks,

James

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  

×