XR650L -> Where to start!

4Strokes.com Honda Tech: XR650L Carburetor Modifications - By Dave Closs & Brian Jackson

Below is a republished article of Dave Closs and Brian Jackson's Honda XR650L carburetor modifications that was posted in the 4Strokes.com forums. These carburetor modifications will correct the stock lean condition, thus allowing the motor to run much cooler. Also, the low and mid range power is increased substantially and the throttle response is liquid smooth compared to stock. Brian considers this almost mandatory for any XR650L.

These modifications should work on 1993-2004 Honda XR650L model years, but may also work on other models and years that use the 42.5mm diaphragm-type CV Keihin carburetor.

Important Note: These XR650L carburetor modifications work in conjunction with a free-flowing aftermarket style air filter and removed airbox snorkel. These mods might actually make your bike run worse without replacing the air filter and pulling the snorkel.

Be clean as possible. Clean the carburetor exterior really well before removing it so nothing gets into the intake manifold or head. Always clean out all metal shavings and dust from the carburetor before reassembly. Before starting any work run your carburetor dry of gas. Do this by running the engine with the fuel petcock valve off until it dies (runs out of fuel).

Make sure the fuel petcock valve is set to off. Disconnect the fuel line at the carburetor and remove the seat and fuel tank.

Remove the throttle cables, hoses, choke cable, fuel line, rear brake reservoir and its bracket. Make sure to note all connections so you can put things back to where they were.



Loosen the hose clamps on either end of the carburetor.

Squeeze the intake tube (from the airbox to the carburetor) back and out of the way. You can pull the carburetor out of the frame now to the right side quite easily. Cover the intake to the head with at least a clean towel. Make sure not even dust gets in there.

Remove the top and bottom plates of the carburetor by removing 4 screws on each end. (Figure 3)


Remove mixture screw now that it can be turned. (Figure 4)


Grind off the tab on the mixture screw as shown in figure 5 and 6, or as Dave did, grind the tab off the carb body instead of the mixture screw. See figure 7 for the tab on the carb.



Reinstall by turning all the way to the bottom, lightly seating it and then backing it out appropriately. (Most seem to think 2-1/4 to 2-1/2 will run best.) (Figure 7)


Remove the large spring and slide from the top of the carb under the top cover.

The Needle: When removing the slide, the needle is held into the bottom of the slide by a little yellow widget that you press down on and turn a little with a screwdriver or an 8mm socket. When you remove the little yellow widget, the needle comes right out. Notice the needle sits in a small recess. Find a small washer that meets the following: 0.020-0.030" thick and fits fairly snugly over the needle at the thickest part at the top.



Just put the washer on the needle and slide it up to the top, as shown in the photo to the right. The needle will be raised by the thickness of the washer. If you don't already have a washer that works in this application, check your local hardware store. Some folks have found a similar washer in a kit from Radio Shack.

In the bottom of the slide, drill out the two existing holes to 5/32” per the photo. (Figure 9)



Reinstall with washer, as removed earlier. Make sure to seat the slide bowl (terminology?) properly and align the tab correctly. (Figure 3)


On the bottom of the carb, remove the plastic piece (slosh baffle) that is partially covering the pilot/slow jet. (Figure 10) Note: If you use the longer style pilot/slow jet, you will need to clearance the slosh baffle to accommodate it.


Gently unscrew the brass jets. The longer larger one is the main jet and the shorter flush-mount one on the pilot or slow jet. Gently screw in the new jets. (Figure 11)


Place the plastic piece back over the main jet and install the carburetor bowl. (Figure 10)


That’s the end of the carburetor modifications. Check for smooth operation of everything, clean well with carburetor cleaner, and reinstall the carburetor on the bike. After installation, recheck the operation of the throttle and adjust of necessary.

Jetting Suggestions: With the stock exhaust at sea level and no gasohol, the jetting should be around 55/158. Jet leaner for higher altitude, richer for gasohol, or richer for aftermarket exhaust.

The nipple on right side of carb (same side as choke insert port) and nipple at very bottom are vent/drain ports and were left unplugged using existing vent tubing. The front (outlet or cylinder head side) of carb has 3 vacuum nipples. 2 on top pointing up and one near the bottom pointing down. I plugged the one near bottom pointing down and the right side (closest to choke insert port). I routed hose from the upper nipple closest to throttle linkage up and around using existing metal eyeletts to the vacuum diaphram on left side behind throttle linkage. Rubber plug included in kit is for the airbox bottom. After removing all smog "stuff" including vapor canister, carb beather canister and diaphram, I cut existing breather hose to fit. Airbox upper large nipple to vac canister top, and vac canister side and bottom to T fitting and then to case breather.










All this and more found here----> http://www.4strokes.com/tech/honda/


Add a JE 10.5:1 piston (stock bore), WB All-Around Camshaft, 41mm Flat slide Mikuni Carb, port the cylinder head and installed

a Pro Meg E-Series Exhaust and you can get 50hp, 41 foot pounds torque, out of your XR650L!! Still running pump gas. Just as reliable as ever! Now you have a real XR650!

WOW, Thats a lot of stuff to do to make a L go better...... :)

It would be better to get a XR650R and uncork it, install a pumper carb and dual sport it IMHO and you'd have 10 times the bike...... :)

yeah me too

hehe jk peace bro!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!#1 thats me HA! toodles...

&%$#@! mate HA! toodles...

Come on guy's be nice! :) If you can't beat them join them. Here is the step by step to remove the smog stuff. Writen by and for true "L" guy's (there must have been a big sale on XR650l's in California??


1) Left side. We'll remove the smog pump and evaporative charcoal canister. Green: These two 10mm nuts allow removal of the smog pump. Red: Smog pump Blue: Evaporative charcoal canister


2) This is the goal. The finished product.


3) Red: Remove these 5mm bolts then install the IMS block-off plates in there place. Blue: Front view of smog pump.


4) Remove the 5mm allen-head bolts and pull off the steel tubing from each side of head. Install the two block-off plates reusing hardware. I put liquid gasket on the plates before installing them.


5) Red: Right-side smog block-off plate location. Remove the two bolts and install the block-off plates re-using original hardware. Blue: Left-side smog block-off plate location.


6) Right-front smog block-off plate location. Photo taken from behind front wheel.


7) IMS Smog Block-Off Kit.


8) First step is to remove the metal smog tubes from the front of the cylinder head. Left side shown. A T-handle allen wrench or socket is needed here.


9) Both bolts removed from left side of cylinder head. Both sides must be unbolted to remove the smog tubes.


10) The four allen-head bolts are removed and the smog tubes are free from the head.


11) The smog tubes and air pump have been removed as one unit. Remove four allen-head bolts and two 10mm nuts for the assembly.


12) Install the left-side smog block-off plate. I used hi-temp liquid gasket maker to seal it all up.


13) This is the smog pump bracket located under the pump itself. Remove it by removing the two 10mm bolts.


14) Right side smog block-off plate installed.


15) Next is the removal of the charcoal canister. The smog pump hose will be shortened and attached to the trany case.


16) To remove the charcoal canister, slide it up and off the metal mounting strap.


17) The trany vent is located just under the carb on top of the trany. Pull off the hose from the charcoal canister and smog pump, cut to length, and reattach. The hose will run between the trany vent and airbox.


18) Red: Pull off the top airbox vent hose. Blue: Pull off the airbox vent hose connector. Green: Insert the large rubber plug into the hole that you just created.


19) Large rubber plug inserted.


20) The evaporative charcoal canister and all of its hoses detached.


21) The last step is the carb vent hoses, which may differ per model year. Remove hose and plug the T-connector. Remove smog pump from bike.


22) Close-up of other end of hose at the T-connector.


23) Rubber cap from smog block-off kit installed.


24) Vent hose routing.


25) Close-up of vent hose connected at transmission.


26) All smog equipment that was removed.


27) Smog equipment laid out as it was bolted on the bike.


28) 1995 Honda XR650L with smog equipment removed. Best Bike in the WORLD!


More reading for time spent at Starbucks.

More reading for time spent at Starbucks.


Reading all of that stuff is what helped sway me even farther towards the R back when I was shopping. Not that I hadn't already made up my mind that is.

Yo do all that work and what do ya got when you're finished?

An XR650L?


The carburetor page is good stuff and is needed if you have any CV type carburetor. ( if you have the money a pumper carburetor would be much better) Same drill if you have a KLX300R.

This is a XR600, XR650"L" and XR650"R" group can't we all get along!!

The XR650"L" can really put out some Horsepower if you changed the 8:1 piston to a 10.25:1, porformance Cam, Pumper carburetor, Header/muffler, plastic gas tank. Stripped all the junk off it. You would have a 15 pound slimmer bike and 48~50hp to the rear wheel. It would weigh the same as a XR650R with electric start and put out more horsepower then a stock uncorked XR650R.

It's really not that much stuff but, the "L" guy's that wrote it way over did it for "R" type guy's. One of the guy's calls this a Vacuum canister 6Gearbox2Airbox.jpg and another calls it a Carcoal filter (I have called it that). Crankcase filter, helps remove the oil from the vented case pressure before it goes to the air box. It is not needed (weight) but doesn't hurt. A straight tube to the air box like the XR650R uses, is fine.

On most "R" talk we would have just said,"remove the smog pump and install the block off" So, for Office type "L" guy's it's spelled out with a little more step by step.

I like the part, loosen the bolt now take it out. "Picture" now go to the next bolt and loosen it, then take it out "picture" Etc. etc....... Oh, no I am slipping back into a "R" "R"ider :)

More appLes to oRanges.

The 650L is more like the now defunct 600R than any modern water-cooled Thumper. This reprint of the L mods just shows how detuned the motor is compared to the old RFVC 600R.

If you are the owner of only one bike and that happens to be an L (as was my situation), this is what it takes to get rid of the inherent performance issues, plus a few more items like the ones listed in BWB's earlier post.

The L is not and never will be the king of Baja. But is a decent all-purpose (Honda) bike that's still street legal in here in the people's republic of california.

My L will most likely never win baha ;) But it will get me across Austin fast with the front wheel on the ground only 80% of the time :D;):banana::banana::D:D:D:D:worthy::D Thats good enough for me :):):D

Yeah, jees, here's an article (much of it based on stuff I wrote over at 4strokes) for the L folks, and the R guys (and some other folks) show up and start their crap. What the heck is wrong with you guys?


I think you guys just don't get it.

XRKING.. :):D Its the Lame idiots that cause problems and act like jackasses, Not the bikes........ :)

Well I try not to act lame, but I had a bad injury at work (fell off a pole?) and have all the time in the world to sit at the computer. Hum, I guess I can get thousands of posts now. Just like you guys :) Your nothin but computer nerds - I'll bet you don't even have "R's", you just wish you did.

Is this personal enough? O its only cyberspace.....quit crying FRANKSTR and BWB63. You guys are babies. :)

my 'L' doesn't give an 'R' any competition, true enough, ... but I can still dump on the Kaw KLRs, anyway .....

Just what do you mean by "meat up?" :) spell


All right Bruce this does it!!!!!! I'm shipping my bike piece by piece to you and your putting back together with all of the affor-mentioned bits. (most of which has already been done)(Thanks Dave) You can have the cam and the piston shipped directly to your house. Loan me a 400 to ride when I come out my butt. You're fixing my L!!!!! :):D

Looks like this never ends eh? :) I mean this stuff starts now in every thread here - that is slowly getting lame...

Slowly getting lame?


I think if anyone rode with Tortue, or myself, or a few other guys that'd dispell the notion that the L is a poser bike. Would a poser bike make it through the roughest part of 5MOH? I don't think so!

Plenty of putt-putt guys on the bike, though. It's a lot of different bikes to a lot of different people!


Slowly getting lame?


I think if anyone rode with Tortue, or myself, or a few other guys that'd dispell the notion that the L is a poser bike. Would a poser bike make it through the roughest part of 5MOH? I don't think so!

Plenty of putt-putt guys on the bike, though. It's a lot of different bikes to a lot of different people!


There has never been a poser bike. Well, if a poser owns a bike then that bike is a poser's bike as in belonging to a poser. Bikes don't pose, people do. I have been a poser for almost two months! I pose next to my bike with my cast on. I pose for a picture sitting in a chair while everyone else is riding.

A poser is someone that looks like they can ride put can't. I just got off the poser list and am ready to pose on the bike in the air!

Where some lost track with all this silliness is they spout off what bike is better or can do what better and do not have a clue what they are talking about, that is a poser. I have seen guys thrashing a Husky, KTM, Husaberg 650 or such and they have never even seen one more less rode one. They just repeat what they saw someone else write.

The XR650L can be a great bike, way more then it is stock and that goes for a stock XR650R. It's awesome that some push there XR650R's around and some push there XR650L's around.

In the tighter rough almost impassable stuff the XR650R will do better then the XR650L and the KTM 525 will do better then the XR650R. There are times when a CRF250 will do better the all of them. That is not the point of any of it. It's when you get guy's bent because someone states a fact and then it's taken like it was against there precious bike and the world comes to an end. It's not who fast you ride or don't ride ether. It's when you pose like you can rip up the world and then cry "My 1992 'XR50' is the best bike in the world, and can smoke any water cooled bike on the planet!" Sure sign of a poser :)

I think that is where Starbucks came in. Drinking coffie posing by there bikes watching the school children go by. XR650L guy's are not the only ones that get this. When your out with a bunch of riders, riding "Cut throat" and they are on KTM 525's and CRF450's. It's on buddy, it's a fight to keep in the lead so you can have breathing room because once you get cut, you know that the smaller bike is going to go where the weight of the XR650R is going to work against me. That is a fact I except. The roost is real and the facts are in my face at that moment. Chevy's RULE!!!!! :)

I had a bad injury at work (fell off a pole?)

Which club do you work at, the Spearmint Rhino?



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