Originally Posted by vormeccano
Since 3 weeks i own a 550fe 07 with 400 km.
Problem : motor bangs and puffs in lower rpm by closing gas.
solvings as so far :
New CDIunit on it.
idle jet is 45 (normal is 38 - 40), standard needle OBDVR, position clip 5 fom above, idling screw is 1,25 windings out. Main jet 180. Inlet rubbers are good ( no leakage).
From idling to gas the bike feels like too rich (sort of threshold in picking up) but closing the gas looks like too lean.
After closing gas the engine keeps running higher revs before normal idling.
Solution? : idling screw tot 1,0 or 0,5 ( aproxx); needle 6 clips from above
Let me see if I have gotten this right. You are the proud owner of a brand new 07 and 400 km's on it. Yes? Or is it a used bike that you have put 400 km's on?
If it is a new bike, have you adjusted the valves yet?
Why did you replace the CDI unit? Did it go bad?
You are saying that the motor exhaust is popping on decel from lower rpm's. Does it not pop on decel in the higher rev's ?? Does it not pop when decelerating from higher revs until the lower revs are reached?
And how does the bike start when cold and hot?
Sorry for the questions, just want to make sure that I understand your situation correctly.
The two things that I know of that make a bike pop on decel are either exhaust leaks, where outside air is getting sucked in. Or the needle is too lean.
And the high idle thing, I have always thought this indicates a lean condition.
There are lot's of threads on jetting in the fuel section, and there is a couple of ways to go to come to the right solution.
However, based on my ASSUMPTIONS of where you live, Holland which is by the ocean and low in altitude or even below sea level, and what the temperature is there, pretty cold this time of year. And, based on your comments here is what "I" think will get you headed towards the right track:
First of all, you can try raising the needle a clip position to #6 or even #7 and see how that affects your problem. I would think at your altitude and temperature that position #6 is where you should be anyway. It will probably help with the popping, but, if you go to #7 my guess is you will be rich from 1/4 to 3/4 throttle. However, if this solves both of your problems, of popping on decel, and the high idle, and you are happy then you are done. It is a given that when you lift the needle, ie go to a lower clip position you will need to drop a main jet size, and visa versa. However, don't do that yet, make just one change at a time until you have solved your problem, and even then just make one change at a time, and keep notes. Good notes.
I think your needle straight is too big, making for a lean condition at closed throttle. I think you are trying to compensate for this by going to a larger pilot jet, and that explains why you think it is too rich when you are just opening the throttle the pilot jet has it's greatest effect from fully closed to 1/4 throttle in concert with the needle jet which also affects air fuel mix at these throttle openings, and up to 3/4 throttle. My suggestion here would be to go to the next smaller needle straight section, or a DVQ needle. Return to the stock settings of position #5 on the needle, and go back to the stock pilot jet, a 40 if I am not mistaken. Adjust as described in 2cnd paragraph below. The needle straight has the greatest effect on starting and idling, about 70 or 80% I'm told.
Always remember to make one change at a time while you are testing or you are lost!!
The fuel screw: Opening it (windings out) releases more fuel, or richens the mixture, and closing it (windings in) leans the mixture. The approximate range of the fuel screw or fms (fuel metering screw) is 1 & 3/8 turns open to 2 & 1/8 turns open. If you are less than 1 & 3/8 turns open you need a smaller pilot, and if you are more than 2 & 1/8 turns out you need a bigger pilot.
Setting the FMS: Get the bike warmed up by riding around for 15 minutes or so. Put the bike on a stand and set the idle around 1500-1600 rpm's, or at a "normal" idle. Turn the fuel screw in until the motor starts to slow down, and the back it out one turn from there. This is just good rule of thumb setting and will get you "in the ball park", however, you may have to fine tune it some later. NOTE: IF THE MOTOR DOES NOT DIE WHEN THE FMS IS LIGHTLY SEATED OR CLOSED THE PJ IS TOO BIG OR THE NEEDLE STRAIGHT IS TOO SMALL. Example: If you find that a 40pj is too small and a 42pj is too big, then you need to change the needle straight size to split the difference. Once you have set the pj size and FMS opening proceed with the following.
Since you have now presumably gone to a thinner needle straight, you will be delivering more fuel during idle and during decel and your popping should cease. If it still has a tendency to pop once and while, raise the needle to position #6 from the top. And like I said before, given your riding conditions I would think that pos #6 is where you should be,but, you will have to test the difference between the two to make that determination.
Lifting the needle is also a way to cure a bogging problem when you open the throttle quickly.
After you have tested the above to your satisfaction, you can start to play around with the main jet. The common thought here is that your main jet is too large, and you would/will be surprised at how small of a main jet most folks are running. You can either go to the threads in the fuel section for other jetting recommendations, or you can just start going down in mj sizes one or two sizes at a time and test it out for yourself. Others are running much smaller main jet sizes, but, are also running different needle tapers than stock which also has an effect.
Hopefully, this advice will get your problem solved that you are experiencing now and you will be happy. Let us know how you are getting on.