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major popping/backfiring

McMucker

McMucker

Joined Dec 2005
56 Posts | 0+
Ireland
so just got my 03 650 berg. its amazing but has some serious popping issues on deceleration. I have had the carb off and jets are clean and hoses are ok. I have ran the mixture from between 3.5 to 2 turns out (manual says 1.5-2.5) and it gets a little less the richer I run it but it still happens. even when the bike is soo rich its just gonna crap itself. I was told air getting in at the headers can cause this but I have no experience of this. It is fairly possible that this is the case. Could tight or loose valve adjustment play any part at all in this?
I will examine the pipes this week and have a look at the valves but im a bit scared even if they do say bergs are easy done
If it is leaky pipes how would you guys normally sort this??
I will raise the needle when I have the carb off next and see if this helps. I reckon it wasnt adjusted when akro was put on. I tried getting needle out of the slide last time but couldnt figure it out. any tips?
o heres a little vid of the flames...
vid link
http://www.vanguardoilandgas.com/MOV00016.3gp

its a 3gp video file taken from my phone. you will need quicktime player to watch it. If you dont already have quicktime.. why not?
download qt for xp here
http://www.softwarepatch.com/internet/quicktime.html
 
Your carb jetting numbers please.

A fair bit of exhuast popping during decel is normal.

Exhaust or header leaks can greatly increase this popping issue.

Is the bike otherwise running well?
 
hmm from memory.. 35, 45 and 180 main. I reckon the needle is stock for 03 fse650. unsure of where it is positioned but i would assume it i also stock. I had trouble getting needle out of slide last time.
The bike has an akro end can and it is ran at just above seal level near the sea.
The bike runs ok. Ive only had it going a few days now. It was majorly hard to start. Lay for 3 months then I kicked it for 4 days, on the 5th we bump started it and since then pretty much ok. Never started from e start even when cold but usually will start with a few kicks from cold. altho yesterday it took me 30 mins of kicking and it was warm altho i may have flooded it.
 
Hi McMucker
In my opinion, it is only likely to be air been drawn in on your header pipes, if the poping is only during deceleration. If so, seal all joints with heatproof silicon rubber (any car shop or Halfords will sell it)
It is more likely though, to be your valve timing and that you have set them 180 degrees off TDC. If so, use the pencil in the plug hole method to assist in finding TDC.
All these issues are discussed in great detail in the forums.

Regards
Ady
PS. Check stator hasn't come loose and turned altering ignition.
 
Make sure everything is right mechanically first and foremost.

Valves adjusted, this is one thing that will make starting very difficult if they're tight.

Timing set correctly.

If you've cleaned the carb out real good, and since you mentioned it doesn't pop quite as bad the richer you go on the pilot, I think you're on the right track with raising the needle one notch and then try it.
 
Check to see that valves are set correctly, specifically the intakes aren't tight. Good advice to seal exhaust joints. Lean jetting also causes popping. If adjusting the idle mixture screw a bit richer helps, but then the idle is getting slobbery rich, go up on the pilot and return the idle mixture screw to a setting for proper idling. Pilot not only supplies the idle orifice but also the orifice under the front of the slide which controls the mixture at small throttle openings. Not sure if you are saying that you have a 35 or 45 pilot? 45 is already pretty big, so if that is the case try raising the needle. Hope this helps.
dan
 
Think The 45 Is The Start Jet. The Popping Looks Very Much Like My VOR And Gasgas Which I Found To Be Valve Related.
As For Jetting I'd Look At The Doc And See What It Suggests,They May Be For The 400/501's But They Very Close. Would Have Thought Main Would Be Near The 190-200 Mark And Pilot 38-40 With The Needle In The Middle.
 
oh boy! the jetting info is a worry here isn't it.

so what do you all say when a man has just about the largest main jet in that has ever been recorded ever in the world ever? Bigger still-whay not-200 why stop there, 240-300 nah! let's puyll the MJ out completely!

could you let us know the needle code? it's very important.

try adjusting the PS underneath out about .5 of a turn should do.

35, 45 makes no sense at all. we need figures not bench whinging ( a bit like bench racing but with no positive outcome).

the choke jet should be somewhere between #70 and #80. so that 45PJ is way big enough.

try to do it all on the PS and after you've given us the NEEDLE CODE can check the third suffix if it's too lean.

regards

Taffy
 
I Was Assuming That The Bike Had A Dellorto. The 400 Had A 45 Starter Jet I Believe.
I Know Assumption Is The Mother Of All F£$% Ups,But Those 3 Figures Led Me To Believe That Was The Case.
Wasnt Meaning To Set Up Another Jetting Argument.







PS Taffy,While I Wait For The Christmas/New Year Disruption To End And Get My New Jets,Where Do Yoou Get A PAS From? Do They Do One For The Main Air Jets?
 
you're right it will be a dell orto.

there are some recommended figures on the doc.

regards

Taffy
 
To clear things up a bit, should have a Dellorto PHM 40 unless someone changed it. Stock jetting.... 195 main, DR 270 needle jet, K35 needle, #3 clip position, 33 pilot, 45 start jet, 4.0 slide. Pilot is a bit lean in stock configuration to make the tree huggers happy.
dan
 
Typical Husaberg jet numbers...

Pilot Jet somewhere between 38-45
Main Jet somewhere between 160-180

Your 195 MJ sounds very rich.

If you're still unsure as to what jets are currently in play it would certainly help us help you if you could take the time to confirm which jets you have installed. Guessing should be avoided.
 
Don't have a 650, simply looked it up in Factory parts and service manual for the fellow. Maybe the 195 main is a misprint? I believe the possibility of a misprint is real because Husaberg showed a 195 main being installed in my 501 as well, but upon disassembly it was in fact a 185. Bought the bike new so was factory installed. All other jets in the carb were as stated in the manual. I had cold starting difficulties, flame outs, and some popping. Cured the works with a 42 pilot. When the MX muffler was installed, power was as flat as Kansas on top and I had to up the main to a 190 to get the power back. I'm at sea level.
dan
 
ok well here is what I have..
Took the plug out and it was nealry completely all white... not good
I took the back two sections of the pipes off and slealed the front portion with some pipe gum and rertightened the fittings which will hoopefully stop air getting in as it did seem a bit loose.
I took the carb off for good cleaning. Dell orto phm40 i think it is
Took all the jets out and cleaned with carb cleaner and air.
I have a 45 which i think is starter jet, a 35 which I think is pilot. The main is 180. The needle says k51 and was sat at 2nd notch from the bottom. I moved it right to the bottom to raise it some more. The cylinder jet which the needle goes down into had 268dr inscribed on the side.
I will get a bigger pilot ordered and check the plug after a ride.
I then proceeded to nervously take the valve inspection covers off, not know ing I would find. After some deliberation I reckon I found the right gap to insert feeler guages in. and the .1mm slid right in while still leaving a gap. I then loosened locknut and started to screw the adjuster nut until disaster struck. I dropeed the feckin screwdriver biut into the valve chamber. Tried to fish it out and it is now lodged deeper inside. Hopefully I can fish this out with a magnet tomorrow.
I assume I slot the feeler guage in between the top of the wide round plate that sits on top of spring and under the gold stem which sits above with a slight gap.

Please have a look at this thread to see the pictures of valves and accident!!


risky business this blind DIY
:oops:

these are stock jets??
 
You're up for a rocker cover job, now that you have the bit in there. You need to read my rocker cover help thread, people have been very helpful.

Now don't count on me to help you with the jetting :D

Yes, it is the carb that you say.
 
McM,

I'm not a carburation expert but one thing I have learned from these fellas is to make one adjustment at a time and document them as you go. Get a clear head as to what you have on the bike now and think your strategy through. Make one adjustment and retest.... These carburetor adjustments can be tricky and adjusting too many variables at one time will only have you scratching your skull. Now you wont know what fixed your problem was it the valves, possibly the sealing of the head pipes, maybe the jetting??? First things first, get that screwdriver bit out with a magnet. Should be easy enough without having to take off the head. Just try to make sure it doesn't make its way down the cam chain guides or you will have to remove the whole side cover.... I think it's time to add a big warning to the home page as to not be sticking things into engine orifices that can be easily dislodged and lost somewhere in the internals? Hope you sort this inconvenience out without too much trouble.

Regards,
 
thats good advice by sandskipper.., i would also add that if possible, it would be best to have someone who knows bikes to help you along. i mean trial and error does work but it can end in disaster and cost you mega $$$$
 
A K51 needle is a bit leaner than a K35 (another commonly used needle) and the K51 is usually used in conjunction with a 270-272 needle jet to increase off idle response on MX models. Explanation...the straight shank portion of the needle pulls out of the needle jet when the slide is open approx 10mm. The straight shanks are usually the same diameter among the needle families. A K51/272 combo thus gives you a richer 1/8 to 1/4 range (on the straight shank here) versus a K35/268 combo. 1/2 throttle is similar because the less rapidly tapering K51 is a bit fatter than the K35 at that range countering the larger diameter of the 272 needle jet. During normal driving what you are seeing mostly is the needle function and yours sound a bit lean to me. The feeler gauge goes between the cast looking rocker and the small diameter shaft(valve stem) in the center of the spring retainer.
dan
 

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