XL600R pilot jet sizes

8 replies to this topic
  • Motosprtman

Posted January 15, 2008 - 10:05 AM


What size of pilot jet to you bump up to on a XL600R and also how many turns out on the air screw. (sea level)

  • pwrpapa

Posted January 15, 2008 - 06:19 PM


I'm running a 62 an two turns out on the screw. My 83 came with a 55 slow jet.

  • Motosprtman

Posted January 16, 2008 - 06:08 AM


I'm running a 62 an two turns out on the screw. My 83 came with a 55 slow jet.

I was looking in my clymers last night (forgot I had it) and it said the 86 came with a 65 pilot, which is as big as you can go! according to the sources I have looked at. Like Jets R us dot com and the Honda parts schematics online. I bought a Dynojet kit to install in it - and as I did with my XR650L, I thought I would install the DJ main jets and needle (s) and bump up the pilot, apparently it is as big as it can be in stock trim! (65 pilot) so........... guess I will install the Dynojets etc and see what happens... it is running a supertrapp on it.

  • HawkGT

Posted January 16, 2008 - 08:59 AM


What style pilot jet is it?

Series 21
Posted Image

or Series 26
Posted Image

In many carbs they can be used interchangeably--they are identical other than overall length. Whatever the case, Series 21's are manufactured up to a 98 and Series 26's are manufactured up to an 80. Motorcyclecarbs lists both sizes up to 80.

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  • Motosprtman

Posted January 16, 2008 - 01:05 PM


Looks like a series 21 to me (item #47 on the schematic)


so what size should I bump it up to ?

  • HawkGT

Posted January 16, 2008 - 05:15 PM


I have no idea what size your bike needs. Are there modifications or running issues that lead you to believe the jetting is incorrect as-is? Whatever the case, the behavior of the fuel screw is a good indicator on whether the pilot jet is the correct size. The pilot jet and fuel screw work together to form the pilot circuit. Think of the fuel screw as a "fine adjustment" for the pilot jet size. You may already understand that relationship.

On most carbs, normal fuel screw settings are between about 1 and about 2.5 to 3 turns out when a correctly sized pilot jet is in use. IN is leaner. OUT is richer. The normal procedure for finding the correct fuel screw setting is to warm up the engine fully, set a slightly fast idle (slightly fast idle speeds make changes in idle speed easier to hear), and then adjust the fuel screw in or out until the highest and smoothest idle is found. Move the screw in 1/8 increments and wait a few seconds for the idle speed to react. Listen very carefully. 100rpm changes can be difficult to pick up but that's the kind of change you're listening for. Hooking up a tach is better and you can also use the normal idle speed.

If the best idle is found at or below 1 turn out on the fuel screw, the pilot jet is too large. Change to a smaller pilot jet and redo the procedure. On most carbs the engine should die with the fuel screw all the way in--unless the pilot jet is way too big. If the highest, smoothest idle speed is found at or beyond 3 turns out (or the fuel screw does not seem to react at all as it's screwed outward), the pilot jet is too small and should be replaced with a larger jet.

BTW, I'm assuming this is an '84+ since you say the stock pilot jet is a 65. The early model had different carbs, a 55 pilot jet, and used an air screw instead of a fuel screw. Air screws and fuel screws work opposite one another. IN is leaner on a fuel screw. IN is richer on an air screw.

Sometimes the hardest part of the whole procedure is just gaining access to the fuel screw while the bike is running. If it's on the side of the carb body that's good. If it's on the bottom of the carb body, a 90 degree screw driver is sometimes needed.

Hope that all made sense and at least helps a little. Surely someone with the same model/year bike will come along and share their experience.

  • Motosprtman

Posted January 17, 2008 - 06:28 AM


Thanks for the great information and detailed answer Hawk. I pulled the plug on the XL600 to change it and it is running lean, as the center electrode is white. I have not had the bike long and want to make it run as good as possible. Someone installed a Super Trapp - but I suspect they never rejetted, hence the lean indication on the plug. So I bought a Dynojet kit and want to rejet it - same as the XR650L, where the needle is changed and the main and pilot jets. The XL600R right now runs fine, but starts a bit hard, I am thinking a fatter pilot will aid in the cold starts and throttle respsonse off idle.

  • HawkGT

Posted January 17, 2008 - 08:58 AM


In that case, if you don't want to mess with any testing procedures: I'd call it reasonable to just go up one size on the pilot and set the fuel screw at 2 turns out. Then see how she runs. If starting improves and throttle response seems better, call it good or fine tune some more.

  • Motosprtman

Posted January 17, 2008 - 01:46 PM


Yea I think that I will install the DJ kit (which as you know contains bigger mains and new needles) and while I have it apart I think I will bump up one on the pilot to a 70 for Sh*ts and grins and run the air screw out 2 turns. Will advise on how it runs!

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