XR650L new Biggun exhaust/pipe, should I rejet?

7 replies to this topic
  • flakrat

Posted April 16, 2003 - 11:21 AM


Howdy y'all,
I have a stock XR650L 2001 that I bought new, here in Texas (i.e. not
a Kalifornia modded bike).
I just put a Biggun Race exhaust and head pipe on.
The bike starts fine, and seems to run well (it's only been installed
for a couple days now). I can definitely notice the additional power
(I have to shift a lot sooner as I accelerate :-)
I also got a stage 1 dynojet kit with the order.
I'd like to install that, but, I've not messed with a carb in over ten
years and the bike shop says it'll cost 2 labor hours to rejet.
Soo... I'd like to try and do it myself.
My question, anyone know of a good resource on rejetting the stock
carb on the XR650L or any suggestions or warnings?
Austin, Texas

  • Keo

Posted April 16, 2003 - 01:19 PM


I'm sure you will agree that $50 is alot for a book, but I finally broke down and bought the official Honda service manual for my "R" model. It has been the best money I have spent on my bike so far. IMHO, you can skip the Clymer/Haynes manuals and go right for this one. It basically gives detailed instructions on how to take apart every nut and bolt on the bike and put them back together. I used mine to work on my carb a month or so ago. I feel like I have about average mechanical ability, and I easily disassembled and reassembled the carb in one night. I guess I did ok since I rode it to work the next morning....lol. It was the first bike carb I had ever worked on.

I would bet that once you open up the intake side of the bike and drop that jet kit in, you will see a BIG difference, even from what you have now. Hope this helps!


  • jstevens

Posted April 16, 2003 - 02:05 PM


Yes, you need to ReJet! it's the best upgrade. I was lucky and had a friend help me with my jetting (I.E. he basically did it for me) All I can say is get the Honda Service Manual for $50.00 bucks. That along with the instructions inside the Dyno Jet kit will tell you everything. Don't worry you really won't break anything, you just have to basically unhook all of the hoses, move the brake fluid resorvor out of the way, and take the carb out sideways (because your limited on space inside the frame). Not a big deal in hined site.
When I did mine there where some older posts where the guys detailed the steps involved. Keep in mind most of the posts I saw were for the older jet kit which required you to drill out the holes in the bottom of the carb. You don't have to do any of that anymore with the DJet Stage 1 kits.

Good luck when you finished report back your thoughts. :)

  • flakrat

Posted April 17, 2003 - 05:57 AM


Cool, good advice y'all.
I'm about to call the Honda dealer to see if the have the Service Manual.
A couple bits of advice that I got off of the xrlug Yahoo group were to take the tank off to make getting at the carb easier, and replace the phillips screws on the float bowl with allen heads.


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  • smashinz2002

Posted April 17, 2003 - 06:00 PM


Go buy a genuine Honda Service Manual so you can know everything about your bike!
And YES!!! You MUST rejet with the aftermarket pipe. Running an aftermarket pipe with the absurdly lean stock jetting is a waste of your money on the pipe. Make absolutely sure that you have the necessary mods done to allow more air into the engine (airbox and intake). The whole idea is to get more air into, and out of, the engine, at a faster rate. This equals more power. Simple as that.
Note that when you rejet the carb, you must also reset the needle position appropriately. You will need the shop manual if you are not sure of how to do this. For example, if you richen the main considerably, which you will need to do, then you have to change the needle position to compensate. But I don't know if the L model has a fixed needle or what, since I bet it's got a CV carb, which you can't change the needle position? Don't know much about those kinds of carbs.
PS. Baja designs or XR's only or somebody like that, has the carb kit for the L version. I remember reading about it.

  • motometal

Posted April 20, 2003 - 02:44 AM


just because you richen in one area of the circuit doesn't necessarilly mean you must richen needle, main, pilot, etc.

the fuel delivery of a carb is not linear. Chances are you are leaner in some areas than others.

For more help on jetting specifics, try reading more on the internet, do searches.

  • BadKarma00

Posted April 22, 2003 - 06:09 AM


Hi Everyone I just discovered TT. Good sight. I have been on some of the other boards for a long time and I like this one pretty well. I would suggest at the very least check your jetting, it is not as devistating on a 4 stroke as on a 2 stroke but still pretty critical. Try Ericgorr.com. There are some articles on there that may help you get started.

  • seebee

Posted April 22, 2003 - 07:44 AM


Flakrat, I had never seen a CV carb before I got this bike and with the Dyno jet kit instructions and the exploded diagram in the Honda service manual it was a breeze and took about an hour. You need to re-jet to bring the heat of the air-cooled motor down to a reasonable level. You also need to do the Airbox mods like everyone else stated.


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