Carb puzzle.

[martin]

OK, I give up ! A friend popped over to have his carbs looked at today, and this is what I found.DSCF0144 (600 x 450).jpg

DSCF0145 (600 x 450).jpg

The first pic is the right hand carb, the second is the left. The yellow arrows point to the only adjusting screw on each one, these bear on the idle valve lever, the red arrows point to where the normal idle screws are, these appear to be blocked with a short screw from underneath. Do these, and the sleeved screws mean anything to any one ? Martin.

[stag157.7]

vent3.jpgvent3.jpg655518525169.jpg


standard vent valve

with tamper proof sleeve on idle screw


alan

[martin]

Alan, the adjustable screw has no lock on it where the original does, that set up is surely to deal with the idle valve, and not for slow idle adjustment ? Martin.

[mrwriggs]

Hi martin,

thanks again for today..
just to let you know that she didnt like the journey home to much..struggled to idle. When I went up a slight incline, she missed a beat, then on the flat , I could feel her missing. Kick down and upto 5000rpm cleared it for a little bit. Parked her up in the garage, and the smell of petrol was quite bad..
I m thinking blocked feeds or at least reduced and I have let it get low on fuel so thinking she might have sucked up a load of pooh...Fuel pump?
new coil, new leads and plugs coming next week after payday so will see what happens then..
Sorted my internet so not all bad...:-)

[stag157.7]

Hi martin,

thanks again for today..
just to let you know that she didnt like the journey home to much..struggled to idle. When I went up a slight incline, she missed a beat, then on the flat , I could feel her missing. Kick down and upto 5000rpm cleared it for a little bit. Parked her up in the garage, and the smell of petrol was quite bad..
I m thinking blocked feeds or at least reduced and I have let it get low on fuel so thinking she might have sucked up a load of pooh...Fuel pump?
new coil, new leads and plugs coming next week after payday so will see what happens then..
Sorted my internet so not all bad...:-)

sounds like sticking needle valves or incorrect fuel float level

also check inertia switch,fuel filter

if it misfires electronically then rev counter will dip and fall

fuel problem wont have this effect


alan

[stag157.7]

Alan, the adjustable screw has no lock on it where the original does, that set up is surely to deal with the idle valve, and not for slow idle adjustment ? Martin.

confusion is the early carbs had the adjustment screw in the position you describe
later carbs are different


try this picFLOAT_VENT_VALVE.jpg

[mrwriggs]

Ok, if we go along the electric route, the revs do flutuate somewhat. If I sit at lights and put her into neutral, the revs go up to about 1100. select "D". and the revs drop to anything between 450=900 depends on how long I sit.
I think the coil could be failing

[martin]

Thanks Alan, but your pic shows a spring loaded screw where these have a blanked off hole, and both screws in the problem carbs are in the same plane, sorry to witter on but I really am puzzled. Martin.

[stag157.7]

In neutral your engine is running with no drag on it. When you put it in drive you put some load on it and the rpm's will drop but it should still run smooth.
It is normal and expected for idle speed to drop 200-300 RPM when any driving gear is engaged. Idle speed should be rock steady, not varying up or down. Idle speed should also increase slightly when the transmission is returned to Park or Neutral. With your engine warm in Neutral or Park you should be seeing an idle speed of 700 RPM +-35 RPM.
If your engine drops below 500 RPM in gear at idle, and if it then hunts back and forth between too slow and too fast, then you have a problem that needs fixing.

[stag157.7]

Small Lever & Piston 1 (864 x 648).jpgDSC_7802s.jpg


old and new vent and idle screw set ups

hope it self explanatory

alan