650fse Flame outs, Help ?

Get it up to operating temperature and adjust your idle. Then adjust your air screw to obtain maximum idle speed. Start with about 1 1/2 turns from fully seated. Turning the air screw all the way in will richen the idle mixture and backing it out will lean it. Only change one thing at a time. You may want to put the needle back where it was for now because that leaned the midrange and we are trying to richen you up right now.

Read this:
DIALING IN THE PILOT JET

The pilot or idle jet should be the right size to allow you to perform the idle adjustment. If you can’t get it to idle properly, you might have the wrong size jet. Here’s how to tell: let’s say you’re turning the idle air screw in and it should be making the mixture too rich. The engine speed keeps increasing until finally you have the screw turned all the way in, and it’s running best right there. By the time you get the screw turned all the way in, the mixture should have been much too rich. So you can figure that the idle jet is too small, and needs the next size larger.

If you back out the idle air screw and the engine just keeps running faster and faster until finally the screw falls out of the carb, it tells you the idle jet is too big and is letting too much fuel through. Install a smaller (leaner) one.

Some manuals tell you to turn the idle air screw all the way in and then back it out a specified number of turns for a good idle. Usually this is around one or two turns out. If you can’t get a good idle with this setting, or close to it, the idle jet is the wrong size.

Do not touch the throttle when kick starting. A properly set air screw is extremely important to good starting behavior.

Flame outs

Husabutt
Thanks, will experiment with that tomorrow and let you know 1

Not wishing to start a debate, but the mixture screw on 4 strokes is a fuel screw, not an air screw as described by husabutt.

So when you turn the screw in, you will be leaning the idle mixture.
Turning in the screw = less fuel.

Not knowing your elevation, I can't be more specific, but with a 48 pilot, you will probably want to try turning the screw in from the setting that you had with your original jet.

Since the hesitation/stalling is eliminated, at least you know that you are closer to being correct than with the old jet in there.

When you start your bike, do you try the first kick with the choke 'on'?
If not , you may want to try it. It works for my bike.

Splat said:

Not wishing to start a debate, but the mixture screw on 4 strokes is a fuel screw, not an air screw as described by husabutt.

So when you turn the screw in, you will be leaning the idle mixture.
Turning in the screw = less fuel.

Click to expand...

Splat: You are absolutely correct!!! The air screw/fuel screw has the opposite effect on on a four stroke when you turn it.

Thank you for the correction! :spank: :

Flame Outs

What an Epic,

Ok its starting on the button again, 48 pilot, mixture screw three quauters out from stop.
Problem is I left the fuel taps open overnight and had a pool of fuel on the garage floor this morning.
While running the lower short overflow pipe on the left of the carb,one that exits above float bowl, is dripping.
Is this caused by my flooding the carb over night and should it clear, or is it a problem from rebuilding the carb yesterday ?
Wish I had never started this exercise
:?

Flame Outs

Tests Complete,

To conclude

Pilot upped from 40 to 48

Needle lowered by one clip from standard.

Mixture screw turned in from 1.5 turns out to .75 turns out from stop.

The change in performance is so noticable, faster pick up on the throttle and much improved mid range power, lifting front wheel in third of the throttle and wheel going light in fourth on acceleration.

Plug after run, black around thread but ash/brown around central electrode.

Starts of the button cold with no choke and starts aftetr a couple of prods on the button when very hot.

Popping and small yellow flame still present but improved.

The exercise has produced a bike with superior performance which still starts on the button so thanks for the help chaps.

I think I will take the exhaust off at the header pipe and at the can and re assemble using a good sealing compound, and see if this improves the after burn situation.

Still awaiting larger main jet for evaluation. might then play with increasing front sprocket to make the bike more road focused.

Oh, fuel drip has stopped after riding so must be down to flooding over night !

Have you checked your idle speed? With a tach or by ear?

My experience has shown me that most people that set their idle speed by ear, usually set it too low; below spec. Too low of an idle will exasperate the backfire/flame issue.

Try bumping your idle speed up a good 1/2 turn and see if that corrects the backfire.

Alan:

I am glad you are satisfied with the results (read tired of messing with it). The next step would be to richen the midrange by raising the needle (lowering the clip) until the popping completely goes away. Going up one size on the main still may be helpful. As a general rule go as rich as you can till it starts running bad then lean it off. You can't hurt the bike by going too rich. You can fry the motor if you go too lean though. When properly jetted your bike will absolutely rip compared to an ill jetted bike.

Good luck,

Re: Flame Outs

alancar1 said:

What an Epic,

While running the lower short overflow pipe on the left of the carb,one that exits above float bowl, is dripping.
Is this caused by my flooding the carb over night and should it clear, or is it a problem from rebuilding the carb yesterday ?
Wish I had never started this exercise
:?

Click to expand...

The leaking is more than likely caused by the float level being set a tad bit high. Jetting can be a daunting task but the knowledge gained will make you stronger. It won't kill you. If you think this is an epic you should read some jetting threads on other boards. Not many people will touch a jetting thread with a 10 foot pole. Luckily I have an 11 foot pole :wink: .

Flame Outs

Thats what its all about ?
The suns out the roads fairly clear and I have been out for the last hour just riding for the fun of it.
When the bikes on song it beats all the superbikes I've had in the past.
That acceleration combined with huge lumps of mid range torque just put the smile back on your face.
Sat outside the local KTM dealer with a couple of other bikers showing interest in this strange and rare beast, and then it fires up on the button ! Lifes good ?
Thanks again Chaps.