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Old 01-30-2004, 06:05 PM   #1
Bicycle Phil OP
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DR 650 backfire

I just test rode a 2001 DR 650, 5700mi, with a Supertrapp pipe and the carb has been jetted. With the bike in gear, clutch let out, and decelerating(throttle off) the bike was backfiring. Not a loud backfire. Your basic pup pup pup. Is this a potential problem, can it be tuned to eliminate the backfire? Otherwise all other functions of the bike seemed to be in order. Comments and suggestions from those who know are appreciated.
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Old 01-30-2004, 06:24 PM   #2
Rocket Ron
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The only time my 98 DR 650 ever backfired was when the power source coil was going out. Easy fix but don't buy the wiring harness from Suzuki. The coil can be found by it's self. I found mine at Ricky Stater, in El Cajon, Ca. He Told me that a Yamaha coil also works. (Forget which model. )

I have never changed the pipe on my bike so I can't coment about any back fires that may be coming from the pipe.
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Old 01-30-2004, 09:08 PM   #3
P7HVN
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That's pretty common on big singles with aftermarket pipes. Can be reduced by jetting changes.
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Old 02-01-2004, 04:25 PM   #4
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The backfiring on deccelaration is a fair sign that the bike is running a tad rich (which is infinately better than it running lean). If this is the case then I wouldn't think it is too much of a problem.
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Old 02-01-2004, 04:43 PM   #5
Drif10
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Not an issue at all. According to Mikuni's own website, this is normal for tuned engines.

See section #4
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Old 02-01-2004, 06:56 PM   #6
Bicycle Phil OP
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DR 650 backfire

Thanks for the responses and info.
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Old 02-02-2004, 12:49 AM   #7
Possu
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I am under the impression that backfiring when decelerating was due to running lean, not rich?

This happened occasionally with my DR600. Try screwing the pilot mixture screw out in 1/8 turn increments. If the pilot mixture is on the engine side of the carb , then it's controlling fuel, screwing it out will increase fuel & vice versa.

Adjusting this screw is only for throttle reponse from a closed throttle , up to about 1/4 throttle max. After that, it's down to needle height & then main jet from 3/4 to full throttle.

BTW, if adjusting the mixture screw, it may be worth your while to remove it first & then grease it prior to replacing it. I've had Suzuki's in the past where it's seized in place. As they're normally recessed in to the underside of the carb body, they're difficult to unseize & it's easy to do damage. Watch out for the spring.

If you remove it, first screw it in slowly, counting the number of turns until it stops - do not screw it tight. When you replace it, screw it home gently, then screw it out to the original setting plus 1/8 turn. Keep adjusting until it backfires no more.

Also check your air filter - my DR used to backfire through the carb sometimes, burning a hole in the air filter!

Steve
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Old 02-02-2004, 09:29 PM   #8
murgatroid42
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Stock Honda XR650L's like mine (the air-cooled engine), notoriously backfire, pup pup pup, as you call it. It's considered a "feature", not a problem.
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Old 09-23-2007, 03:02 AM   #9
stevh0
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I have the exact problem on my Dr600 ,

Turning the mixture screw makes an off idle change but not much.

It seems to me my bike only pings in 4th and 5th when riding 2 up ..

would raising the needle a notch cure this ?

Steve
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Old 09-23-2007, 10:11 AM   #10
CaptTurbo
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I agree with Possu Steve. Popping on decell is a lean condition. Play with the mixture screw and see if you can reduce the problem. I don't think it's a big deal to worry about in any event unless it's more the a mild pop you're hearing.
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Old 09-23-2007, 10:17 AM   #11
stevh0
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I will hear a decent backfire - but only sometimes on the compression kickback .

The scenario goes like this .


The bike starts when hot usually 1st or second kick with no throttle and then it would idle .

if i go ride and get to an intersection where i would have to sit for a couple of seconds, it would only sometimes have a mild pop and die .. but then 1 or 2 kicks and it runs again ..

im really starting to dislike the bike ...
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Old 09-23-2007, 10:18 AM   #12
stevh0
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is the std mufler not prone to backfiring a little .. or the little soft pup pup ..

i hate the std mufler so much...ewww :(
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Old 09-23-2007, 10:25 AM   #13
CaptTurbo
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Quote:
Originally Posted by stevh0
is the std mufler not prone to backfiring a little .. or the little soft pup pup ..

i hate the std mufler so much...ewww :(
I (for the moment) still have a bone stock '07 with the snorkle removed. The stock setup does have some gentle popping on engine braking. I'm at sea level and believe that this is normal. I just bought a second hand DJ kit and was planning to fatten the jetting to the DJ 150 and darned if that jet isn't the one that was missing from the kit. I'll be trying the DJ155 and hope that it will work with the stock pipe.
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Old 09-23-2007, 10:30 AM   #14
stevh0
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how about just drilling out the jets myself?
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Old 09-23-2007, 10:31 AM   #15
racer 07
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Phil

As said above, back the mixture screw out 1/4 turn at a time and it will go away. Usually Super Traps wind up with the static idle a little rich.
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