Xr650l jetting help!

[Xr702]

Hi, I just picked up a xr650l. It's been about two weeks in and its amazing. Surpassed everything I hoped it would be. I've already racked up around 400 miles and no major issues. For a 1997, it's been taken great care of. I got a great deal. However, I was hoping to learn from wiser minds about jetting. It stutters when I have to throttle wide open. Maybe it's running to lean at higher rpms? It would be nice if I could see pics of exactly how to adjust the jets and where the adjustments are. I've searched everywhere and can't find a good guide on how to do it. If you have a link to where I might find out it would be much appreciated as well. Thanks and keep on thumpn!

[Hollerhead]

Jets aren't adjustable (at least the one(s) that are probably causing you a problem).  You must disassemble the carb to access and replace with new, different sized, jets.  You should get a service manual and do some studying if you want to tackle the job yourself.  I can probably dig you up some pictures of what you would be facing.

 

You should first establish what you have and then there is plenty of folks that can help quickly.

Edited December 31, 2016 by hollerhead

[Xr702]

Jets aren't adjustable (at least the one(s) that are probably causing you a problem). You must disassemble the carb to access and replace with new, different sized, jets. You should get a service manual and do some studying if you want to tackle the job yourself. I can probably dig you up some pictures of what you would be facing.

You should first establish what you have and then there is plenty of folks that can help quickly.

So I can't tinker with the air fuel mixture?

[Hollerhead]

So I can't tinker with the air fuel mixture?

Only the idle mixture can be tinkered with by turning a screw.  Once the throttle is touched and the butterfly opens the idle mixture screw is essentially non-functioning.

[baldy110]

By changing jets you are tinkering with the A/F mixture. Do a search here for "Dave's mods" that will pretty much explain what and how.

[ScottRNelson]

Give us a hint as to what altitude you're running at.

 

I live at basically sea level and a 155 main jet is optimal for a stock motor.  I had a 158 in there and was going to drop it back to a 155, but had the motor rebuilt with a higher compression piston and I'm keeping the 158 for the richer mixture to help avoid detonation when it gets hot.

 

If you have the stock metering needle in there, you can make the mid-range a bit richer by putting a shim under it.  I have the Factory Pro needle with five clip positions, so it's easier to adjust.  But I haven't felt the need to change from the middle position on that.

 

I'm pretty sure that I have a 55 pilot jet and probably should use a 58, but I don't normally notice any issues at all at small throttle openings.  I could adjust the mixture screw a bit more to affect that anyway.

 

Just don't go buy a DynoJet kit.  They use different jet numbers and are supposed to be a bit harder to get right.  If you don't want to just buy the jets from a dealer or from jetsrus.com, at least go with a quality kit that uses the right parts, like FactoryPro (CRB-H74-1.1-TI).

[Xr702]

Give us a hint as to what altitude you're running at.

 

I live at basically sea level and a 155 main jet is optimal for a stock motor.  I had a 158 in there and was going to drop it back to a 155, but had the motor rebuilt with a higher compression piston and I'm keeping the 158 for the richer mixture to help avoid detonation when it gets hot.

 

If you have the stock metering needle in there, you can make the mid-range a bit richer by putting a shim under it.  I have the Factory Pro needle with five clip positions, so it's easier to adjust.  But I haven't felt the need to change from the middle position on that.

 

I'm pretty sure that I have a 55 pilot jet and probably should use a 58, but I don't normally notice any issues at all at small throttle openings.  I could adjust the mixture screw a bit more to affect that anyway.

 

Just don't go buy a DynoJet kit.  They use different jet numbers and are supposed to be a bit harder to get right.  If you don't want to just buy the jets from a dealer or from jetsrus.com, at least go with a quality kit that uses the right parts, like FactoryPro (CRB-H74-1.1-TI).

Thanks! I'm pretty new to all of this but appreciate your input. So I can adjust the main needle and it will affect a wide open throttle?

[Xr702]

I've read a bit and came across the CDI acting as a rev limiter of sorts. Not sure if its true but would explain the stuttering at higher rpms. I know the xr is not ment to be reved so high but its a bit unsettling with highway cursing in mind. 70-75 is max with throttle wide open. Im lucky if i dont get the jerk from a misfire tho

[ScottRNelson]

Thanks! I'm pretty new to all of this but appreciate your input. So I can adjust the main needle and it will affect a wide open throttle?

No, it's the main jet that affects wide open throttle.  The metering needle is for half to three quarters throttle.

 

And I've never noticed any sort of "rev limiter" on my bike.  I hit it way too often on my KTM, and the Ducati that I owned before that, so I'm familiar with that sort of thing on motorcycles.

 

And you still haven't told us the altitude where you live.  Give us the information that will let us help you properly.

[Xr702]

No, it's the main jet that affects wide open throttle. The metering needle is for half to three quarters throttle.

And I've never noticed any sort of "rev limiter" on my bike. I hit it way too often on my KTM, and the Ducati that I owned before that, so I'm familiar with that sort of thing on motorcycles.

And you still haven't told us the altitude where you live. Give us the information that will let us help you properly.

Sorry, I'm in Las Vegas. I'll take it up to high altitudes up at mnt Charleston occasionally but I haven't noticed anything different.

[Xr702]

Sorry, I'm in Las Vegas. I'll take it up to high altitudes up at mnt Charleston occasionally but I haven't noticed anything different.

Maybe I should run higher octane gas?

[ScottRNelson]

Sorry, I'm in Las Vegas. I'll take it up to high altitudes up at mnt Charleston occasionally but I haven't noticed anything different.

 

Las Vegas - I would definitely go with a 155 main jet.

 

Maybe I should run higher octane gas?

I have higher compression than stock and mine runs fine with the 87 octane stuff we get here in California.  Unless you are experiencing detonation, higher octane does nothing to improve things.

 

Do you know what jets are in there now?

 

After I purchased my XR650L, it ran okay, but I had to know what was in there.  So I bought a Factory Pro jet kit - since they've worked well for me on other bikes - and updated all of the jets.  I'm not sure I actually changed the sizes of anything, but after that I KNEW what was in there and it ran well, because all parts in the carburetor were top quality.

 

One way to tell if you're too rich or too lean is to fool around with how much air can get to the carburetor.  Take off the left side cover and you'll let more air in there.  If it runs better, it was too rich.  If it's worse, too lean.  You can then use duct tape to block off more air to get a lean bike to run better.  I find that to be easier than trying to read sparkplugs.

 

Also, if the jetting is too rich, supposedly you can back off the throttle a tiny bit when it starts to cut out at full throttle and it should run better.  I read that somewhere in the writings of Kevin Cameron, although I've never tested it myself.

 

My bike, with stock gearing, tops out at 95 mph and runs cleanly while holding the throttle wide open.  I tested that at sea level a couple of years ago.

 

I would strongly suggest pulling the carburetor out and verifying exactly what is in there before trying anything else.

[Xr702]

Las Vegas - I would definitely go with a 155 main jet.

I have higher compression than stock and mine runs fine with the 87 octane stuff we get here in California. Unless you are experiencing detonation, higher octane does nothing to improve things.

Do you know what jets are in there now?

After I purchased my XR650L, it ran okay, but I had to know what was in there. So I bought a Factory Pro jet kit - since they've worked well for me on other bikes - and updated all of the jets. I'm not sure I actually changed the sizes of anything, but after that I KNEW what was in there and it ran well, because all parts in the carburetor were top quality.

One way to tell if you're too rich or too lean is to fool around with how much air can get to the carburetor. Take off the left side cover and you'll let more air in there. If it runs better, it was too rich. If it's worse, too lean. You can then use duct tape to block off more air to get a lean bike to run better. I find that to be easier than trying to read sparkplugs.

Also, if the jetting is too rich, supposedly you can back off the throttle a tiny bit when it starts to cut out at full throttle and it should run better. I read that somewhere in the writings of Kevin Cameron, although I've never tested it myself.

My bike, with stock gearing, tops out at 95 mph and runs cleanly while holding the throttle wide open. I tested that at sea level a couple of years ago.

I would strongly suggest pulling the carburetor out and verifying exactly what is in there before trying anything else.

I really want to see what going on with the carb. The bike has had some mods done before I got it.

Smog removed and blocked

Oil separator is gone

So im really curious to see inside the motor/carb

As this is my first bike and never ridden anything this powerful I don't know the power of it stock.

I'm in the dark a bit but these bike are awesome and know I made a good choice

[Conifer_Mike]

My bet would be that you have a DIRTY main jet, causing lean conditions and you merely need a good cleaning.  Based upon the age, I would order a new carburetor bowl gasket before tearing it apart.  Write down the sizes of the main jet and pilot jet before you slap it back together. Take a look at the needle to see if it is stock (smooth, no clips) or aftermarket.

 

Another suspect would be your air filter.  A clogged paper filter causes rich symptoms.  A bone dry foam filter would run lean and more importantly could suck dirt into your engine.

[ScottRNelson]

My bet would be that you have a DIRTY main jet...

It's easier to just put a new one in there that you know is going to work correctly.

[JoeRC51]

I've NEVER had a jet I had to replace because I couldn't clean it.

[ScottRNelson]

I've NEVER had a jet I had to replace because I couldn't clean it.

But how do you know for sure that a previous owner hasn't stuck a wire through it or something else that changed the size or shape of the orifice?

[JoeRC51]

Poking a wire thru a jet isn't going to do anything but unclog it. Brass is pretty hard. Using a drill , yes , you've got a bigger jet now.