'04 XR650L - Exahust Popping on Deceleration

Howzit,

I have a fully uncorked XRL in a motard config. Everything seems to be running super, but upon high-speed deceleration the exahust pops quite a bit.

Is this because I am too lean or to rich? I thought this was because I was too lean. I richen the fuel mixture, but it does not seem to do much (little though...).

I have a Dynojet kit (main, slow, spring etc...) installed, but later went with a 170 instead of the DJ 165; also, a Unifiter with wide open air access...

Like I said, the bike runs solid.

Any suggestion would be helpful and greatly appreciated...

Thanks!

TZAR

:)

I'm no wrench, but the only time mine pops on decel. is when I hit reserve fuel level so I'd have to guess your lean.

Sorry for liitle detail/help.

Did you put the smog block off kit on? This is the apparatus with the hoses on the left side of the motor. The kit lets you remove this and block off the two holes in the cylinder head. The popping went away when I did this mod. :)

More Info:

I have already installed the smog block off kit, and I've installed a full exhaust (Big Gun header w/ProCircuit T4). Oh yeah, I also made certain that I have no exhaust leaks...

Everything I read says "lean", but I want to get your opinions... Do you think I should go with a larger main (ie: 175)??

Thanks!

TZAR

:)

i have the same problem on my xr650r as soon as i let off

the gas at about 80 mph it backfires

put your finger into the tip of your exhaust , if i remember

correctly if your finger comes out with black soot, your bike is running to rich, the ideal color should be a greyish color, i tried this on my exhaust and my soot was dark black.

I have the same problem with my 95". It got worse when I put on my new exhaust (White Bros header and E-Series). It doesen't do it when I have the choke on, while warming it up(less air) or when I go riding in the high desert(thinner air). I haven't got the bigger jet yet, but its on the list. Let me know what you find out. Thanks :)

Hey TZAR,what pilot jet are you useing ? ON decel you have the throttle chopped so the main is not functioning.You could try turning the mixture screw out to see if it helps.I'm running a 55. :)

Then I would try the 175 main jet. I have a 162 main on mine with a similar setup and it does not pop. Just remember that the Dyno jet numbers are different than the stock jet numbers. :)

Hey TZAR,what pilot jet are you useing ? ON decel you have the throttle chopped so the main is not functioning.You could try turning the mixture screw out to see if it helps.I'm running a 55. :cry:

A larger pilot wuld be my guess as well.

Grave diggin' are we. 1 year old post ???

Getting an edelbrock for mine when they release it mid january. No more worrying about jetting :cry:

Hi Tzar

I agree with MotoChris521, since your carb slide is down during decel the main and needle don't make a big difference. Even if you read your Dynojet papers - they described in mine the popping during deceleration and stated that main jet and needle doesn't do a thing. Either way exhaust leaks, vacuum leaks on the carb or fuel mixture screw / pilot jet.

My XRL has the K&N filter, BigGun race series, DynoJet, and smog stuff removed. The extreme popping started when I removed the smog pump. I blocked off all the vacuum ports on the carb so that can't be the reason as far as vac leak.

I went on mine from a 50 to 55 pilot (sea level) and it solved 50% of the popping especially in the higher RPM range. I thought trying next to open the fuel mix screw a half more turn as dynojet recommends to get rid of the rest. If that doesn't do it I would think an even bigger pilot might help.

Did your 170 main do any difference? Another thing, check your spark plug color in order to tell if your main fits. Otherwise its mostly because its to lean and mainly caused by the idle/low rpm part in your carb as far as I know.

...have fun popping around :cry: (I'm still doing it some...)

Det

Since This Will Ocassionally Ocurrs On A Xr650 , I Would First Ensure That The Valve Lash Is Properly Set Before You Went Into Changing To A New Carb Or Re-jetting It. Since You Said That It Did Not Happen Prior, Check For The Problem Of The Setting Of The Valve Clearance First.......if You Are Not Familiar With Xr650s The Intake Valves Sometimes Suck In A Little Bit....it Is A Quick Fix.....

The pilot jet is to lean, try a 68S pilot and play around with the fuel screw. :cry:

The pilot jet is to lean, try a 68S pilot and play around with the fuel screw. :cry:

a 68 pilot on a 650L, that's pretty steep, it's a 55 stock I believe. I have a 58 with a 155 main (150 stock I believe), IDS2, fully incorked airbox, no smog. Mine doesn't pop a bit.

I'd say take a look at that little diaphram on the right side of your carb wiht the vacum line running from it. Make sure the vacum line is intact to the carb throat. Make sure the diaphram is sound. That is an antibackfire circuit in your carb. It may need rebuilding??

I agree with lrutt, the air cut diaphram is the key.

It appears most smog bypass kits have you pull the vac line to the air cut diaphram.

That is why it usually shows up after smog removal.

The air cut diaphram has to be connected to the vac port on the top front right of the carb to be effective , and it is VERY effective at preventing deceleration popping!!

Bud

I agree with lrutt, the air cut diaphram is the key.

It appears most smog bypass kits have you pull the vac line to the air cut diaphram.

That is why it usually shows up after smog removal.

The air cut diaphram has to be connected to the vac port on the top front right of the carb to be effective , and it is VERY effective at preventing deceleration popping!!

Bud

Thats right, the IMS kit on mine for example plugs every (2) hose you remove on the carb. And on mine it definately started after I plugged everything off on the carb.

My XRL had original a #50 pilot, so I went with a #55 which improved the issue alot but didn't get rid of it completely.

So you say the two hoses I removed on the carb ports need to be interconnected to get rid of that popping? Hmm, I have to look at that - originaly those were connected via a "Y" to the smog pump if I remember that right.

Det

Just be carefull that you don't connect the 2 vacuum ports on the top front of the carb(if you have 2,some have only the one on the right). Mine were connected with a tee and to the air cut diaphram. This not only makes the air cut ineffective, but it also creates a vacuum leak aggravating the popping problem... You should have a single hose(no tee) going from the port near the throttle cables to the air cut diaphram on the right side of the carb.

Bud

Hey Bud,

I just looked at mine, you were right it was a "T" going from the front, right above the engine intake hose on the carb to the diaphragm and (my Ex-) smog pump. I think on the picture you can just see the tip of the front port right above the top philipshead screw of the throttle cable bracket.

diaphragm.jpg

I was just a nice guy and followed the IMS block-off kit instructions, shouldn't they know what to plug and what to reconnect??? I mean I was wondering why to plug two ports when I did it - and they were even mentioning a third hole on some carbs. :cry:

Just common sense if the smog pump needs a vacuum to work then one hose would have been fine, the second connection over the T to the diaphragm left me wondering why that wouldn't need the vacuum anymore. But I trusted their directions on that. That for I believe that you are probably right about that.

On the Honda fiche parts diagram they call it Air-Cut? What exactly does it do? Does it affect the slide position depending on the vacuum when the throttle is released? I really haven't looked at it when I had the carb out to install the new needle.

I'll give it a try as soon as I get a chance. If that really works then I owe you one :cry::cry:

I would have continued to fiddle around with pilot jetting and fuel mixture screw...

Detlef

oops, did I say I owe you one?? Maybe it was Irutt.. Florida is not that faaar :cry:

...but your continued explanations were good too :cry::cry::cry:

Det

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