Fast tickover when hot

[Greybeard]

Hi Beezabods,
My GF runs very nicely through the rev range so I assume the carb is pretty much ok;  however, when the engine is really warmed up the tickover is fast. Why is this?

Neil Ives

[metalflake11]

Could be the carb is getting hot, causing the slide to not being able to settle onto the tickover screw. When it happens wind the screw out to see if the idle speed drops. Do you have an insulator gasket fitted?
                                                                    mf

[Greybeard]

Could be the carb is getting hot, causing the slide to not being able to settle onto the tickover screw. When it happens wind the screw out to see if the idle speed drops. Do you have an insulator gasket fitted?
                                                                    mf

Thanks MF,
I'll get an insulating gasket if you advise it. I'll also try the throttle stop screw when hot.
Graybeard

[metalflake11]

No problem Neil, just check the manifold nuts aren't too tight too. If they are it can distort the carb body, just nip them up, not tighten. On the main page there is a link to the Amal site, the heat insulaters/spacers are on there. Tufnel or Tufnol I think they are called.
                                           mf

[muskrat]

 A common error is to tune the bike before it gets hot (operating temp).
 Make sure the cable has enough slack so the slide will drop to the bottom and use the screw to give the desired tick over. Then adjust the pilot screw to give the best idle then readjust the idle screw. Then adjust the cable so it has about 1/16" slack.
A cold motor should not idle without a bit of choke or a good tickle. If it does it's too rich and will soot plugs when hot.
Do a check for air leaks with WD spray around the flange.
Cheers

[Greybeard]

A common error is to tune the bike before it gets hot (operating temp).
 Make sure the cable has enough slack so the slide will drop to the bottom and use the screw to give the desired tick over. Then adjust the pilot screw to give the best idle then readjust the idle screw. Then adjust the cable so it has about 1/16" slack.
A cold motor should not idle without a bit of choke or a good tickle. If it does it's too rich and will soot plugs when hot.
Do a check for air leaks with WD spray around the flange.
Cheers

Thanks Muskrat,
While working on the bike I stripped and cleaned the carb. The throttle slide was a bit worn so I've fitted a new one. I put the needle clip in the middle position. I was expecting to have to fiddle with the carb to get her running nicely but I've been amazed at how normal everything is! This fast idle when warm is the only problem at the moment.
The bike needs choke when cold in the way you'd expect. The acceleration is progressive. At 40mph, (the fastest I've ridden her yet) the ride is smooth. I have some slack in the throttle cable. I'll check all the things you've mentioned, plus I'll fit a heat insulator washer.

The thing about this bike is that it was only ridden from 1955 to 1975; she's only had twenty years of use.