ATD Springs

[Bill Thomas]

Sounds like Carb' to me !.

 

[Martyn Goodwin]

Sounds like Carb' to me !.

Bill,
I have TWO heat insulators installed, on tween head and manifold and other tween manifold and carb
https://www.feked.com/amal-carburettor-manifold-flange-spacer-5mm-thick.html

So I would be very surprised if it was the carb heating up/fuel vaporisation.

If I park the bike for 1/2 hour or so then upon restart the idle speed is 'normal' but as I mentioned earlier, once the plot warms up the idle speed goes up. No tacho fitted but I estimate cold idle to be around 500 rpm and hot idle to be in excess of 1,000 rpm

 

[Martyn Goodwin]

My guess, the springs are the wrong tree to bark up to. Springs are heat treated to higher temperatures than you´d ever see in an engine. A strobe would tell with hot engine - or alternatively you´d check spring force with some scales when fresh out of oven - no difference I´d think.
An engine will have higher idle speed when hot, just normal, but if too high it may be related to valve clearances - not likely with Vincent engines. What grade of engine oil is used - 50 monograde ?? It takes quite some while to heat up the oil , try minimal oil in tank for shorten time till high idle ?

Vic

Hi Vic,

I am using 10W-30 multigrade non-synthetic with high zinc content

 

[Bill Thomas]

For me the Bike should not tickover nice when cold,
If it does it's too rich ?.
I know as it gets hotter it should go richer, But strange things happen !,
Can't you set the Carb' " Tickover speed " when hot ?,
If it was the ATD I would have thought you would get " Kickback " When starting ?,
I had it with my Twin Special years ago, "D" Distributor, Always started nice, Never Kicked back,
Then it started Kickback,= Broken advance spring !.

I was thinking more of a kind of blockage or fault with the carb',
Can you try another Carb' ?.
Cheers Bill.

 

[BigEd]

It has been a while since I visited this topic and despite much work on ignition timing, magneto setup and ATD tweaking I remain bugged by the phenomenon of having a motor that once hot will not return to a steady idle speed .

To recap I run an original magneto and an original ATD .

Martyn

If you think that the ATD may be the cause could you wire the weights in the closed position? Get it warm by leaving it to tick over or gentle riding at just over tick over speed and then see if you still have the problem.
It might sound a bit radical but isolation or substitution of a component is a good way of troubleshooting. Also, as Bill says, can you try another carb?

 

[Chris Launders]

Alternatively ride it until it's nice and warm, whip the ATD cover off and lockwire it then restart.

Anyway surely it will tickover faster when warm than cold, your oil has thinned out and all your internal clearances have opened up so the engine spins more freely.

 

[Martyn Goodwin]

If you think that the ATD may be the cause could you wire the weights in the closed position? Get it warm by leaving it to tick over or gentle riding at just over tick over speed and then see if you still have the problem.
It might sound a bit radical but isolation or substitution of a component is a good way of troubleshooting. Also, as Bill says, can you try another carb?

Made some small changes today but winter is setting in as has the rain and wind. Plus COVID permitting. given there is a new outbreak here and government imposed movement restrictions are back on.

First chance I get I will be out road testing to see the effect. Then I will reveal all- if it works!

Bugger.

I cannot understand the logic of opening up our borders to foreign travellers from regions ravaged by the virus

 

[delboy]

Made some small changes today but winter is setting in as has the rain and wind. Plus COVID permitting. given there is a new outbreak here and government imposed movement restrictions are back on.

First chance I get I will be out road testing to see the effect. Then I will reveal all- if it works!

Bugger.

I cannot understand the logic of opening up our borders to foreign travellers from regions ravaged by the virus

My only observation is why have you got two insulators?
The rest of us seem to have managed okay with just a gasket for the last 70 years.
Regards,
Delboy.

 

[Bazlerker]

Bill,
I have TWO heat insulators installed, on tween head and manifold and other tween manifold and carb
https://www.feked.com/amal-carburettor-manifold-flange-spacer-5mm-thick.html

So I would be very surprised if it was the carb heating up/fuel vaporisation.

If I park the bike for 1/2 hour or so then upon restart the idle speed is 'normal' but as I mentioned earlier, once the plot warms up the idle speed goes up. No tacho fitted but I estimate cold idle to be around 500 rpm and hot idle to be in excess of 1,000 rpm

2 gaskets increases the number of faces to seal against an air leak by 100%..

 

[Pushrod Twin]

Has anyone made up a Pespex or Lexan clear cover, to fit in place of the ATD access cover, ET136? I suspect there may be fish hooks with this, there will be oil mist in the timing cover, but, with the aid of a strobe as suggested on post #30, it could be a way to confirm whether the weights are actually hanging up, or not.