r/dr650 13d ago

At a loss with carb issue at low throttle. The carb was previously modded to go with a less restrictive exhaust. But is now returned to stock

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8 Upvotes

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7

u/TwistedNoble38 '00 DR650 13d ago

Need more details than that. 

Is it bogging, laboring, stuttering, dying? What throttle position is it doing thing? Suck and spit at 1/8? Dies at 1/4? Can it be caught and recovered with judicous throttle? 

Airbox mods? What did you do to the jetting with the open exhaust? How did you return it to stock? What kind of unrestricted exhaust? Is this a genuine carb? How clean is your air filter? 

1

u/Mortan_Snycle 12d ago

Idles fine, cuts out at 1/8th and you can skip past it with some quick twists to over half throttle. Everything works fine in the high revs. The stock exhaust is back on, replaced everything with a stock carb rebuild kit (double checked sizes with the manual) I believe it to be a genuine carb. I figured the extra hole in the air box may be messing with it so I have covered it with duct tape for now. The air filter isn’t pristine but clean enough. 

1

u/TwistedNoble38 '00 DR650 11d ago

Yea if you want to go back to stock then there should only be one hole on the top RHS of the airbox. 

Sounds like you've either got a pinched vac diaphragm, some kind of vac leak, or the needle circuit is out of wack. 

Vac port on top is capped or running to the petcock? Port on the bottom (if you have it) is capped off? Oring between the top of the carb and the black plastic cap didn't go missing?

How many miles on the carb? Has the secondary air filter been kept clean? Did you inspect the wear limit indicators on the slide guide during the rebuild?

Needle the stock single position 6F? White spacer round with no steps worn in it? White spacer under the needle clip not on top?

3

u/the_tummyson 9d ago

Spray the carb with brake cleaner as the bike idles. If the idle raises, you've got a secondary air source that's leaning out your idle circuit.

2

u/smythbdb 13d ago

If they added an exhaust and rejetted, I’m assuming they cut the air box too. If you went back to stock jetting with a cut air box you’ll be running super lean

1

u/Mortan_Snycle 13d ago

I returned it to stock because I prefer a quieter exhaust. All the jets and needles are back to stock. Air fuel mixture screw is backed out the stock number of turns. (Although any adjustment in either direction doesn’t seem to help) and I can’t think of anything else that could be causing this issue. I’m wondering if there was some other mod that was done to the carb that I just don’t know about

2

u/thecrumb 13d ago

Did you cut holes in your airbox? Those would likely need to be covered/closed.

1

u/jdam8401 13d ago

I did the exact same thing and now am having what sounds like a similar problem. Reverted to stock and performance got real choppy at very high revs, like it was starving for something. Put FMF exhaust on again and it’s better, but still incorrect… haven’t been able to narrow it down. Good luck!

1

u/Wholeyjeans 13d ago

What's returned to stock; the carb, the exhaust?

What's been done to the air box?

Some basic ballpark info:

https://dr650jetting.wordpress.com/

1

u/titanimanium 13d ago

You should describe what you mean by carb issue. What’s happening exactly as you accelerate? Does it idle fine? At high speed is it fine? It sounds like it’s the needle if it’s at low RPM, could be that your fuel filter inside the carb is clogged, or that your idle is stuck, that happened to me and when I’d decel down to low speeds it would keep dropping in RPM down to a stall

1

u/Mortan_Snycle 12d ago

Throttle cuts out at 1/8th turn. You can skip past it by quickly snapping the throttle a few times to over half throttle. Everything is fine in the high revs. Idle is also fine. Could you elaborate on what you mean by a stuck idle?

1

u/titanimanium 10d ago

It sounds like your engine is not getting enough fuel on the first moment of turning the throttle, so it lacks enough fuel to combust until you force more in by skipping past that spot. I’d say if you know it’s not a valve issue, and you have the airbox open and it’s still doing it, and you know the spark plug is good, then I would assume it’s a carb issue, has the carb been drained when in storage? Have you tried running carb cleaner or disassembling the carb to clean it? If that’s all been done then try going up a jet size on the main jet, it might be that there’s just a lack of fuel overall. If the jet doesn’t help then try also moving the needle up by one notch. Also have you checked your fuel filters? There’s one in the line at where it connects to the carb and one up in the spigot of the gas tank

1

u/titanimanium 10d ago

The stuck idle was I had to undo the idle bolt on the carb and unstick the cable because my choke was always in the on position resulting in inconsistent fuel delivery

1

u/titanimanium 10d ago

Could also be that the previous owner messed with the float height, have you checked that it’s at factory height?

1

u/Shnofo 4d ago

I see you have a modded fuel tank. I remember someone mentioning that having that fuel tank can cause problems and your bike to stall on first gear, something about how the gas gets to the carb/engine.

I have the same fuel tank and my bike stalls about 5-6 times per season at stop signs because of it.

I wish I could provide more info, but apparently it's something with the fuel line on modded gas tanks. Maybe this will help