Hi PASO´ists
I have mounted my mikunis, and have fired the engine up, and she starts and idles great. But as soon as I give it a bit of throttle, it hesitates and dies. I have checked the membranes, and they look fine. The travel of the needle piston is smooth. But I can see that needles don’t lift when I give it a bit of throttle when the engine is running. Does any body have an idea on what the problem could bee?
Regards
Klaus
Denmark
PASO 750, 1990
Mikuni problems
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paso750
- paso grand pooh-bah
- Posts: 5568
- Joined: Sun Jul 18, 2004 12:00 am
- model: 750 Paso
- year: 1987
- Location: southern Germany
Klaus,
the needles will move by underpressure. So if your engine dies as soon as you open throttle a bit you hardly will see them move.
The sliders move when you open/close throttle ?
Are you trying without airfilters mounted ? The fuel valve at the tank is open ?
Have you tried to let the engine idle for a bit before trying to open throttle ? I`m asking as there may be air in the fuel lines.
Fuel return line, fuel pump are connected ?
(what exhaust are you running ?)
G.
the needles will move by underpressure. So if your engine dies as soon as you open throttle a bit you hardly will see them move.
The sliders move when you open/close throttle ?
Are you trying without airfilters mounted ? The fuel valve at the tank is open ?
Have you tried to let the engine idle for a bit before trying to open throttle ? I`m asking as there may be air in the fuel lines.
Fuel return line, fuel pump are connected ?
(what exhaust are you running ?)
G.
paso750
Hi
The lines should be correctly mounted. From the pump to the “Y” connection. From the “Y” to the carburettors, and the other line with the nozzle, back to the tank. Fuel valve is open. Slides do not open when throttle open close, this is of course when the engine is running, when I am checking this. I have taken of the filters only for checking if this was the issue. Also I have mounted the standard pipes, so I wont make my neighbors go crazy
. I am thinking that there is a problem in getting the under pressure to build up. But why this is, is the question.
Regards
Klaus
The lines should be correctly mounted. From the pump to the “Y” connection. From the “Y” to the carburettors, and the other line with the nozzle, back to the tank. Fuel valve is open. Slides do not open when throttle open close, this is of course when the engine is running, when I am checking this. I have taken of the filters only for checking if this was the issue. Also I have mounted the standard pipes, so I wont make my neighbors go crazy
. I am thinking that there is a problem in getting the under pressure to build up. But why this is, is the question.Regards
Klaus
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paso750
- paso grand pooh-bah
- Posts: 5568
- Joined: Sun Jul 18, 2004 12:00 am
- model: 750 Paso
- year: 1987
- Location: southern Germany
sorry I don`t get this. Slides are operated mechanically so when you open throttle (no matter if engine is running or not) slides will move open. The amount of air being sucked into the carb creates the underpressure that moves the membrane and so the needle.Slides do not open when throttle open close
Which nozzle are you referring to ?
paso750
I think we are confusing each other. The slides are the one's which are attached to the needle and the membrane, so when air passes, it will suck air out of the chamber and there by lifting the slide with the needle, and there for will only lift when engine is running. The shutter is mechanically operated.
Regards
Klaus
Regards
Klaus
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Gwenadu
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paso750
- paso grand pooh-bah
- Posts: 5568
- Joined: Sun Jul 18, 2004 12:00 am
- model: 750 Paso
- year: 1987
- Location: southern Germany
Klaus,
sorry you`re of course right. I`m starting to mix up things of my old Mikuni and the actual Mikuni TDMR. Forget that. I`m in need of vacation.
Does your choke close correctly ? On mine it didn`t so I had to change to another choke cable that was a bit more loose.
Going through the points step by step, what about your airscrews, on which position are they ? Mark the position, turn them clockwise slowely until the stop (do not tighten as that may damage the seats). Note the number of turns and unscrew to the former position. Start the engine, let it run a little, then turn the air screws counterclockwise (opening) in 1/4or 1/2 turn steps. That will reduce fuel flow and if the rest of the jetting is halfway correct the engine should accept throttle at a certain point.
The correct description from the SUDCO Mikuni manual is:
"Selection and setting of the airscrew should be made in the following manner. First warm up the engine adequately and set the idle screw so that the engine revolution at the idling will be 10-20% higher than the number of revolutions you are aiming at. Then turn the airscrew left and right (between 1/4 and 1/2 turn) and select the position where the enigine revolution reaches the maximum. Adjust the idle screw to bring down the engine revolution to your target speed for idling. After this adjustment of the idle screw is made, select once more the position where the engine revolution reaches the maximum, by turning the air screw left and right. At this point, attention should be paid to the following points:
1. if there is a certain range in the opening of the air screw where fast engine revolution can be obtained (for instance the number of revolutions does not change in the range of 1-1/2 to 2.0 turn) for better performance you should select approximately 1-1/2 turns.
2. The maximum number of turns in the opening of the airscrew must be limited to 3. If the airscrew is opened over 3 turns the spring will not work and the airscrew can come off during operation of the vehicle"
You can first try to turn the air screw on one carb to see if there`s any reaction at all, but then you should try to turn the airscrews of both carbs simutaniously. Hope this`ll help.
sorry you`re of course right. I`m starting to mix up things of my old Mikuni and the actual Mikuni TDMR. Forget that. I`m in need of vacation.
Does your choke close correctly ? On mine it didn`t so I had to change to another choke cable that was a bit more loose.
Going through the points step by step, what about your airscrews, on which position are they ? Mark the position, turn them clockwise slowely until the stop (do not tighten as that may damage the seats). Note the number of turns and unscrew to the former position. Start the engine, let it run a little, then turn the air screws counterclockwise (opening) in 1/4or 1/2 turn steps. That will reduce fuel flow and if the rest of the jetting is halfway correct the engine should accept throttle at a certain point.
The correct description from the SUDCO Mikuni manual is:
"Selection and setting of the airscrew should be made in the following manner. First warm up the engine adequately and set the idle screw so that the engine revolution at the idling will be 10-20% higher than the number of revolutions you are aiming at. Then turn the airscrew left and right (between 1/4 and 1/2 turn) and select the position where the enigine revolution reaches the maximum. Adjust the idle screw to bring down the engine revolution to your target speed for idling. After this adjustment of the idle screw is made, select once more the position where the engine revolution reaches the maximum, by turning the air screw left and right. At this point, attention should be paid to the following points:
1. if there is a certain range in the opening of the air screw where fast engine revolution can be obtained (for instance the number of revolutions does not change in the range of 1-1/2 to 2.0 turn) for better performance you should select approximately 1-1/2 turns.
2. The maximum number of turns in the opening of the airscrew must be limited to 3. If the airscrew is opened over 3 turns the spring will not work and the airscrew can come off during operation of the vehicle"
You can first try to turn the air screw on one carb to see if there`s any reaction at all, but then you should try to turn the airscrews of both carbs simutaniously. Hope this`ll help.