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XR650L Jetting help.

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Hey TT,

 

I need some advice on what jets I should be using in my 2005 XR650L. Here's a run-down on what parts it has.

 

- UNI Filter

- Snorkel removed

- Dave's mods

- Vance & Hines XCR Slip On Exhaust

- Most riding will be in elevation of 2000-3000ft

 

I run only premium gas, 80% on road, in a hot climate. Winter temps around 60-70 degrees with summer temps 90-110. Occasional rides to cold climates or higher / lower elevations.

 

Based on this information, what jetting setup would be suggested? I don't have any way to test fuel-air ratio so I'll have to rely on the experts here haha.

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SInce "Dave's Mod" includes new jets, what did you use?

 

Does it seem to run okay with the current jets?

If not, is it better when cold or when warm?

 

I'm guessing by the altitude that it might run better cold, then load up a bit when warm.  In that case you would go one size smaller on the main jet.

 

I know that mine is a bit on the rich side, especially at altitude, but overall I like how it behaves, so haven't felt the need to change the jetting on it.

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Hey Scott, thanks for the reply.

 

I haven't actually performed all of the above modifications yet. Currently, it has the UNI filter and snorkel removed. Exhaust is stock right now. I was waiting on that so that I don't end up dangerously lean, I ride the bike every day as a commuter so I don't want to cause any harm.

 

The previous owner re-jetted the bike, but I'm not sure to what sizes. He jetted it for ~6000ft (I bought it when I lived in high Colorado, but have since relocated to Arizona).

 

It seems to run ok, though in my perception it seems to pull a little weaker then I remember. Could just be my own confirmation bias. It actually seems to improve a little bit as the machine warms up. Often times running at 1/4 to 1/2 choke seems to help until the engine is at full operating temperature. I would assume that means I'm lean, and the Dave's Mods and Exhaust will only make that worse so I need to go up in jet size a decent amount. I just don't have a ton of experience with this, so I'm trying to make sure I get as close to the right stuff as I can the first try.

 

I would prefer to end up a little bit rich, rather than lean.

 

Thanks.

 

EDIT: I'm willing to order a couple sizes of each to make sure I get what I need, I just don't have a starting point. Also, are there any other fuel / air system adjustments or modifications that would be recommended for the setup I'll be using?

Edited by Von_H

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I use keihin 55 / 158, the snorkel is still installed, uni filter, Dave's mods, desmogged, Staintune exhaust, regular fuel,  elevation 1850 ASL. I find the bike runs just a tad on the rich side, no backfire on decel, a wee bit of soot on the inside of the tail pipe. I like the way it runs, starts up nicely in below freezing temps with 10w30 HDEO, excellent throttle response and no flat spots anywhere.

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The most important part of Dave's Mod is the jetting and the setting of the idle mixture screw.  You didn't really do Dave's Mod if you didn't do those, you just fiddled with the intake a bit.

 

My bike has "Dave's Mod" minus drilling the two holes in the slide, which I didn't feel was necessary.  Dave's Mod makes the bike quite a bit richer than stock.

 

The 1994 XR650L that I bought in August was way lean.  I could barely live with it for the first 15 minutes after starting it, then it was mostly okay.  It ran pretty good above 6000 feet, though.  I changed the jetting to richer and opened the mixture screw to 2 1/4 turns and it made a huge difference.

 

On a bike with all of the smog stuff removed, I can take the carburetor out, make all of the changes, and have it all back together in under an hour, including removing seat, tank, and side covers.  If all of the smog stuff is in place it takes quite a bit longer and is significantly more frustrating.

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Thanks for the example Paul, that should get me in the ballpark.

 

What I meant to say is that I haven't actually performed the Dave's Mods either yet. The carburetor is stock aside from the previous owners re-jetting. The mods and exhaust are planned changes, that I'm waiting on until I can get the jetting sorted out in advance. The bike is de-smogged as well, I suppose I should have mentioned that. I guess I'll re-summarize.

 

- 2005 XR650L

- Snorkel Removed

- UNI Filter Installed

- De-Smogged

- Jetted for ~6000ft

- Dave's Mods (Not done yet)

- Vance & Hines XCR Exhaust (Not installed yet).

 

My riding will be in the 2000-3000ft range, mostly warm temperatures.

 

Given this information, how do you anticipate the jetting should be set, taking all of the above into consideration. Sorry if I wasn't clear enough.

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Thanks for the example Paul, that should get me in the ballpark.

 

What I meant to say is that I haven't actually performed the Dave's Mods either yet. The carburetor is stock aside from the previous owners re-jetting. The mods and exhaust are planned changes, that I'm waiting on until I can get the jetting sorted out in advance. The bike is de-smogged as well, I suppose I should have mentioned that. I guess I'll re-summarize.

 

- 2005 XR650L

- Snorkel Removed

- UNI Filter Installed

- De-Smogged

- Jetted for ~6000ft

- Dave's Mods (Not done yet)

- Vance & Hines XCR Exhaust (Not installed yet).

 

My riding will be in the 2000-3000ft range, mostly warm temperatures.

 

Given this information, how do you anticipate the jetting should be set, taking all of the above into consideration. Sorry if I wasn't clear enough.

I would try the 55/158 once you have everything done, at least as a starting point.

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Some pigs find 55/158 to be pretty rich, some don't, each one seems to have its own sweet spot.

 

Only way to tell if your jetting is optimum for your needs is to make sure every combination othert than what you are running is worse.

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So you're saying I should maybe buy 55/158 and also maybe a 52/155, in case it's too rich??

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I'm not sure you should buy a hatfull of jets now, or sure you shouldn't... that's the way it is with jetting.

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So you're saying I should maybe buy 55/158 and also maybe a 52/155, in case it's too rich??

That's what I would recommend.  You should be able to get it right if you had all of those.

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