Engine revs high with throttle fully closed ..

[Taid]

I think I have found the cause, though why it happened, I have no idea ..

Those who said the throttle slide was sticking were half right ..

This is my current view ....

It was not sticking, you could hear it bottom out when you closed the throttle, but it was not closing fully .

With the main carb body off, I noticed a second drilling next to the one for the needle .. looking at the top, I saw that this second hole was for the end of the nipple on the throttle cable, which seems to extend a long way beyond its position in the the slide ..

I think that somehow this had moved sufficiently for it not to enter the drilling, so preventing the throttle fully closing ..

How did it become disturbed between one run and the next start a few days later? ... I can only think that it moved slightly as I flicked the throttle during during starting ..

I may try to put a taper on the nipple to help it seat properly in future .. or can it be shortened so that it doesn't stand proud .. it is a new cable, fitted a couple of months back ..

Assuming this was the cause .. I'll report later ..(though I am reconning the carb, (new jets, needle, checking fuel level etc) I guess it may remain uncertain as to the cause ..)

thank you all for your interest and advice ..

Taid

[clanger9]

Interesting. I guess if you had too much slack on the throttle cable, it might be possible for the nipple to move out of its slot at idle...

[Taid]

.........................rich or lean, the mixture needs a rather hig amount of air to make the engine running so fast ! 40 MPH in top gear on a M16 = at least 3000 RPM or so.........................................

Have to say that was on no load, just on the stand and in top gear