Engine revs high with throttle fully closed ..

[1608]

It can only be the outer cable has come adrift from one or other end and not seating back into the feral or adjuster.

[Taid]

I am taking note of all the points raised but won't be able to follow up for a few days ..

Thank you all for your advice ..

Taid

ps

It can only be the outer cable has come adrift from one or other end and not seating back into the feral or adjuster.

That was my first thought, but the twistgrip/cable still has its 1/16-1/8 free play, with both ends of the cable still in their ferrules and the mid cable adjuster is seated correctly.

pps

Could the main jet have become loose in its positioning and drifted down, enriching the mixture .. (grabbing at straws!)

[Taid]

This is unlikely, but your thoughts please .. just discovered my newly fitted alternator isn't producing any power .. would this make any difference .. I recall way way back on an old car I had , I had the engine running(tick over) without the dynamo connected to the electrics.. then I connected the dynamo and the revs dropped considerably ..

[Steve S]

I had this problem with the concentric on my Lightweight. The cause was overtightening of the carb flange nuts leading to body distortion which made the slide stick. I took off the body and rubbed down the flange face on emery paper on a glass table top and then re-installed it being very careful not to over tighten the two nuts. It was quite surprising how sensitive to the wrong tightness the carb was. Steve S.

[SPRIDDLER]

.. I recall way way back on an old car I had , I had the engine running(tick over) without the dynamo connected to the electrics.. then I connected the dynamo and the revs dropped considerably ..

Whilst the dynamo (or alternator) always absorbs engine power to drive it mechanically the engine power absorbed increases in proportion to the 'work' it's required to do. E.g. recharging a partly or fully discharged battery, running lights etc. Even on my 2yr old car at tickover the revs drop momentarily when I turn on the air conditioning due to the increased power needed by the system but quickly return to normal when the ECU adjusts the tickover.
In short, it's quite normal for the engines on our old bikes without an electronic 'brain' to run faster without the mechanical resistance and the electrical load of a dynamo (or alternator).
As far as your enquiry goes I can't add anything to the comments already expressed.

[alanengineer]

I had the same problem as Steve S. didnt really know what was happening until i started to loosen the carb fixing nut. All of a sudden, click, the slide dropped. Problem found. I have also had the cable snagging causing similar problems

[spookefoote1956]

I had this problem with the concentric on my Lightweight. The cause was overtightening of the carb flange nuts leading to body distortion which made the slide stick. I took off the body and rubbed down the flange face on emery paper on a glass table top and then re-installed it being very careful not to over tighten the two nuts. It was quite surprising how sensitive to the wrong tightness the carb was. Steve S.

Same for me

[Taid]

Re the over-tightening of the flange nuts .. Slackened everything off and nipped up minimum .. no difference ..

Would also say the the O-ring in the flange does stand proud

Also 100% certain throttle body is not sticking

today I have the carb off, and found that I have the brass float but I note that it has a blob of solder on the 'needle platform' (see photo) ..

Capture.JPG

unless this is normal, I guess this indicates it has in, earlier life, been flooding or at least, running rich .. the float needle appears the same as the one in the refresh kit I have just bought.

somewhere I have read about the thickness of the fibre washer under the float needle housing / fuel inlet .. the one I have is quite thick, which may account for a high fuel level??

Incidentally, on observing the 'tickler' I find I have never actually pushed it far enough to touch the float, so the mixture has always been rich enough to start from cold with only the choke .. in fact recently I have been starting from cold without tickling or choke ..

Keeps my mind occupied .. though that isn't the reason I bout the bike ..

[clanger9]

Checking the float level is easy enough: take the cover off the idle jet, fit a length of clear pipe over the jet and hold the other end against the float bowl. The fuel level should settle exactly on the "pip" on the float bowl cover.

[Taid]

Checking the float level is easy enough: take the cover off the idle jet, fit a length of clear pipe over the jet and hold the other end against the float bowl. The fuel level should settle exactly on the "pip" on the float bowl cover.

I've seen that mentioned other places .. my existing end plate doesn't have the amal logo or pip . but they are available ..

once it's all reassembled I'll see about checking it but would like an opinion on the float (above)