Backfiring issues...

[Sixgill]

OK well i got a big box of goddies and like a really smart person i threw them all on at once so i dont really know where to begin with solving the backfiring issue...

Modded the air box (read cut big hole in top as per keintech)
Dynojet kit (160main, 4th slot on the needle, 2.5turs out on the screw)
Moose air filter (oiled)
Leo Vince exhaust (damn its loud)
14 tooth sprocket

It accelerates like a cham,p no hesitation at all, idle has gotten a little faster when its warm, you dont need the choke at all any more.

When you let off the throttle it pops/backfires. I am assuming way too much fuel...

Im at sea level.

Any advice as to how to attack the backfiring would be appreciated.

thanks in advance.

 

[Kuzzy]

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I notice on my klr the lower the octane number fuel I use the more pops and farts I hear. Could just be a lot louder with that new pipe.

 

[Sixgill]

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yeah the pipe is crazy loud.

but if i kepp the throttle cracked a smidgen on decell the pop/fart stops....

 

[joker650]

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Sixgill wrote:

yeah the pipe is crazy loud.

but if i kepp the throttle cracked a smidgen on decell the pop/fart stops....

Richen up the idle screw. If that doesn't fix it, then most likley an exhaust leak at the hedder pipe. You may not hear the leak when under load.



Keep us posted:tup:

 

[Island Hopper]

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Sounds like your running rich, what was the stock carb formula you replaced? Probably the ideal setting is halfway between. Adventure Rider has some good stuff on carb tuning: adventure rider- thumpers- thread index LC-4- factory cv carb tuning. Some good info in those threads should help you out.

 

[Buck]

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joker650 wrote:

Sixgill wrote:

yeah the pipe is crazy loud.

but if i kepp the throttle cracked a smidgen on decell the pop/fart stops....

Richen up the idle screw. If that doesn't fix it, then most likley an exhaust leak at the hedder pipe. You may not hear the leak when under load.



Keep us posted:tup:

Agreed. I did the same mods. Experiment with the idle mix screw. Mine backfired on decel when too lean. Did you install the mixture thumbscrew for easy adjustment?

 

[Sixgill]

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the extralong fuel adjustment screw is on the way along with my replacement rear spring...

im not sure i can richen up the scew much more that i allready have it... its 2.5 turns out right now.

So as for now i am going to adjust the screw by turning it all the way in and then backing it out as descrided here:
http://www.thumpertalk.com/forum/showthread.php?t=327405

as of yet i havent touched the float level.

i will check the exhaust for leaks, just not sure the best way to do this...

 

[Island Hopper]

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When you stated you do not need the choke anymore that suggests to me that your engine is too rich down low, but I could be wrong, wouldn't be the first time.

 

[Payback]

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hey guys,
my bike has been doing the same thing , I get off the throttle and it'll crack and pop, not terribly , but more than it should. I'll try the idle screw first except me being a newb to mechanics, which way do you turn the screw to richen the fuel ???? clockwise or counter , com'on I've got to learn sometime!!!
my bike is stock engine wise it's a 2001 DR 650

thanks from the newb

 

[scotty905]

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This is taken from http://www.bigcee.com/klr650faq.html

Why does the bike pop on deceleration?
The bike is jetted very lean from the factory. You can enrich the idle mixture by removing the pilot screw cap and backing the screw out 1/2 to 3/4 turn from its factory setting. (The pilot screw is located on the engine side of the carb, in front of the bowl, on the bottom. It is underneath a plug, which must be drilled through to remove.) Note that it may be illegal to tamper with carb settings in your state. Note that this symptom can also indicate an exhaust leak, so check all of the exhaust connections first

 

[Payback]

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i'm pretty sure my idle screw is out all the way.

I did notice that when I have the choke on while riding, the decel noises stop, what does that mean??? it does not have to be on all the way. just a little
????????? please help

 

[Island Hopper]

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Payback, Scotty 905 wasn't refering you to the idle speed screw which you can usually can adjust by turning a knob, he was talking about the pilot screw which is hidden under a tamperproof plug which you must remove in order to adjust. When you pull your choke out partway you are adding richness to the mix and your decel noises stop, so this would suggest your current setting is probably to lean. Also if your guts in your muffler are rotting out this would lesson backpressure and cause the popping on decel, has the bike gotten any louder? If it was running fine before and now seems to be lean, something has changed, like stated above check for exhaust leaks.

 

[Sixgill]

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payback is your bike stock still? as in does it have the stock airbox carb and exhaust?

 

[Ross]

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If it starts without choke that would mean rich, eh ? Too much gas would mean popping in muffler. Too lean popping in carb , right ?

 

[Payback]

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Thanks for the help.....Yes my DR is a fully stock machine.
I'll check for the "real" screw and see if that make a difference. My muffler seems to be in good shape, all connections are tight, no visible cracks....I'll keep you updated. thanks again
payback!

 

[Rawperformance]

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Yup mine did the same after the airbox mod and jet kit. I found the pilot jet too rich. Try going back to 1 1/2 turns. If you start to lean pop bring if out 1/2 a turn at a time untill you are happy. Good luck.