start point for jetting 2007 450ER

[speedracer350X]

I have a Sparks racing full system, w/spark arres. and quiet tip. Probably going to run a no/modified lid w a foam filter for now. Looking at a few jet kits, I'd like to stick with Kehein jets, saw a few kits on e-bay and other places that have them. Should I also switch the needle? Also, I know the stock main is a#120, some of these kits start with a #158 main and go higher to #180. Do the mains really need to be that large? Thanks for any advice in advance.

[coryatver]

With a full exhust and lid removed it needs about a 165 main. The stock jetting is way lean becuase it is so choked up stock a bird couldn't breath through the intake. You should get an adjustable needle. I think you can buy the one that comes in the hrc kit and a 48 pilot.

[WOLFPACK]

The recommended jetting for the Sparks exhaust at sea level, 75 degrees with airbox lid removed is 175 main, NCVQ needle, stock pilot and 2.5 out on the air screw.

This is the exact same jetting spec recommend for the YFZ except we went with a 45 pilot.

I did one exactly like this for a customer last week and it ran perfectly. I ended up going with 2.25 out on the airscrew but it probably would have been fine either way.

No one has the exact spec for what your trying to do because it isn't normal the leave the lid on as that isn't the most power gain.

If you have a fax i can send you a jetting chart from Keihin that may help you fugure out your problem.

A jet kit for your bike is $20. and includes the needle and 165, 170, 175 jets and instructions.

[d3ktrix]

Also if you don't change the pilot jet and leak jet you will get a lean bog off idle when you stab the throttle.

Stock pilot on the 07 is a 42. Most likely needs to be bumped up to a 45 or 48.

This is the settings I use in most of my friends 06+ bikes. Piped/No Lid
Could help you as a starting point.

165MJ
HRC Needle middle clip
45 pilot
#55 leak jet

Jets are Keihin sizes.

[speedracer350X]

Yes, I also think I'm going to change the pilot jet also, get rid of that low end bog and stutter every time you blip the throttle if you're not into it a little. Like I said in my post, I'll probably run a no lid with an outerwears cover, or cut a hole in my lid and cover it with outerwear material, I understand from a few forums and such that these particular machines are really corked up from factory. Thanks again for all the advice!! Alson think I'm going to get an adj. fuel screw from R@D like I saw in quad mag. Seems a lot better than trying to adjust the damn thing, they're always in such a hard to reach place.