XR650L - Jetting Question

I'm a newbie, this is an unreal site. Thanks in advance.

I have two jetting/tuning questions:

I have a '04 XR650L and have uncorked just about everything. Spending mega bucks...motard...Sick! :)

1.) Redrilling the holes in the carb slide to 5/32; what is the purpose? Pros? Cons? I don't remember this being mentioned in my BajaD jet kit instructions. Should I do this?

2.) After the uncorking, the power and feel is unreal, good! However, I find that at a stop, the idol tends to slowly drop drop drop and sometimes shuts me down. Thus, I am always having to keep the throttle moving around at stops... Any ideas here?


If you bought the newer BD kit which you most likely did being an '04' then drilling is not needed. BD now includes a softer spring in the kit which takes the place of the 5/32 hole you had to drill in the old days. The reason for all this is because the L has a CV type carburetor.

My friend has the L with a BD kit installed and it performs great. Did you have an aftermarket exhaust? My thoughts on the idle down problem are that you need to adjust your fuel screw. The L has a tab on it to prevent to much adjustment, so I would grind it off. Chances are that you are burning to lean at idle so I would open that fuel screw up a half turn. See if that make a difference for you. Do you know the procedure to adjust your fuel screw properly?

Hi Grimmer,

Great information.

So I don't need to drill out the holes. Great! :)

I do have a full system (can & header). I'm running a T4 Race with a BigGun header (Loud & Flowing). I did cut the FM tab, and now have it set to 3.5 turns out (BajaD recomm 2.5 out). I don't know of any procedure to follow (feel and gut?). Do you think I should move the jet pin up (4 notches) instead?

Sorry I don't know all the correct names to all the parts, but I learn fast and I am technical...

The bike screams, however I am in the tweaking period.



You are having a idle problem right?Well it sounds like you have the mixture screw too far out.Try warming up the bike, adjust the idle speed to about 1000-1200 rpm,then back the mixture screw out (starting at 1.5 turns out)till it reaches the highest rpm.Do it slowly and stop every 1/4 turn to allow the idle to stabilize.You probably will have to adjust the idle speed screw to fine tune your final idle rpm setting.Stock idle is 1300 rpm but i run mine as low as possible.Good luck :)

Hi MotoChris521,

This is super! I'll play with the adjustments over the weekend... However, I have a stupid question; how do I know where I am with regards to RPMs? Is there a trick to figuring that out without a tach?

Mahalo, TZAR


Yeah i know without a tach you cant get exac :lol:I do it but feel(sound?)I've owned 6 XR600/650 L/R's and the longer you own your bike you'll get the "feel" of it.Try turning the idle speed down to where it almost stalls then back up to where it is stable.Then try the mixture screw.You'll hav e to back and forth between the two ,but remember your trying to reach the highestspeed from the mixture screw(bike fully warmed up) :)

Hi MotoChris521,

Thanks for all your help here. Did a bunch of riding today. Let me tell you what I did (before I went for my spin):

1.) I opened the carb and drilled the holes in the slide. This didnt really seem to make a diff.

2.) I moved my DJ needle from position 3 to position 4 (closer to the pointed end). I assume this is to make it richer???

3.) I have the fuel mixture knob (initialy at 2 out), now 3 full turns out. Played with it throught out the day (more, less etc...)

My results:

** The throttle response was about the same...unchanged.

** The engine runs strong.

** If I run hard in second and quickly let off the throttle, it has a few "mini" pops (snappy) at the end of the rev-down. This is also occuring in third (intermittantly), but not happening in first, fourth, or fifth... If I lean up the fuel mixture 2.0-2.5 out, I get more pops...

** The idol is still dropping (intermittantly now) when I come to a stop. Quandry!

** When I richen the fuel mixture it does not idle faster as every one states; it idles slower... Thus, I proceed to richen it, and bring up the idle knob...

** One last thing; It seems as though I hit a ceiling when I push it in second, third, and fourth; it has this feeling of it not being able to go any more... Is this the way it supposed to be? Remember I used to race sport bikes...

??? On a unrelated note; what would I expect if I placed a more restrictive end-cap on my T4. I currently have it wide open?

Hope my feedback helps. Thanks again.

BTW, I went to our only race track to see some sport bikes race (track day). There was a CRF450 motard smoking the R6/R1's, TZ's, RC51, GXR's... He is the "only" motard racer in Hawaii... Cool!

Mahalo, TZAR


Hi MotoChris521 (Sunday),

Sunday I hit the roads again. Let me tell you what I did (before I went for my spin):

1.) I moved the fuel mixture knob to 2.5 turns out.

My results:

- This (leaning up the fuel mixture) seemed to normalize the idle problem. Yes!

- Still some minor pops (2nd & 3rd gear) upon rev down.

- I still want to play with the needle and main jet. I think I can draw a bit more power out of the bike. I think I need to richen the mid range on up... What do you think? I am considering moving the needle up (closer to the point...currently at position 4 using DJ needle). Or, what do you think of using and shimming the factory needle (diff shape...)? Also, I was considing going to a larger main jet (currently at 165), maybe a 168 or 170? Do these exist? Any suggestions would be greatly appreciated.

Mahalo, TC



I also am running a T-4 on my bike,for maximum power i would stay with the open end.(i tried the Quiet core and even modified it with different size openings and it does cut down the power,but makes it quieter)Whats your elevation,sea level?What pilot jet are you using,I recommend a 55 pilot.I have a 170 main.It runs fine with that in it.(you can either order it from your dealer<aftermarket>or thru Chaparral.Did you modify your airbox/airfilter ? Smog removal?I tried both ways on the needle,resimmed stock & dynojet(didn't notice much difference.Let me know :)

Hi MotoChris521,

Thanks! I am in Hawaii, below? I'm running a 55-pilot with a 165-main. I may order a 170-main just to see what it does... Air box is wide open w/Uni, and the smog junk is gone. Thanks for the scoop on the needle; however I still may try it at 5 clicks out.

I am still awaiting my motard wheels (late next week?). I'll have to send you a few pics. I spent a ton $$$. I wish I had gone with a CRF450 or XR650R for this project.

How is your bike setup?

Mahalo, TZAR



My bike is set-up for off-road.IMS 4 gallon tank,renthal bars(cr-hi)works connection glide plate,IMS pro pegs & shifter,14/48 gearing(renthal)DID O ring chain,Pro-Circuit T-4,twin-air,IMS smog kit,Dunlop 756's,rim locks,H-D brigestone tubes,Carb(55 pilot-170 main-DJ needle-3rd notch)and i removed everything else to save weight(push throttle cable,reflectors,chain gaurd & bracket,tool bag.I thinking about a header pipe,any problems with lining up your BigGun to your T-4?I'd send you a picture of my bike,but i dont know how other than regular email. L8tr :)

Howzit MotoChris521,

I ordered the 170 and 175 main jets; the shipping cost more than the jets... :D

As for the BigGun header: it fit perfect. I did have to get a new exhaust bracket, but you can get that at a local hardware or marine store, buy SSteel. Also, I needed to put a small section of heat reflective tape (lower air box) where the pipe threads thru the lower airbox and frame. Otherwise, it was easy! BTW, it does not include a leg/heat shield. I got the header from WB for about $179+s/h.

I'm supposed to receive my front wheel Wednesday, and rear wheel possibly Friday...unreal!

Mahalo, TZAR


TZAR, you are definately going to have to get some pictures of this road shredder of your. Sounds like it's getting pretty nice. I would love to hear how exhaust settup works. I am still using the stock with a highly modified insert. Can't wait to through that whole thing in the garage and replace it with a thumper. Must see some pics man!! :)

Hi everyone and especially MotoChris521,

Thanks again for all your help with this. I'm now running a 55-pilot with a 170-main. And the bike absolutely SCREAMS! I also picked up a 175-main and may experiment with that in a few weeks.

My motard wheels should arrive by end of week; and when I figure it out, I'll post some pics.

Wanted to THANK everyone for all the support and great insights. I hope I can return the favor as time goes.


TZAR (Hawaii)


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