020t Idling High

[GuyMo]

My 020t is idling high. It’s really bugging me. The saw is in mint condition for its age (2000) having and very little use until I picked it up in November ‘19. I’ve opened her up and theres no scoring etc.
I have tried to sort it, but to no avail. 
 

1. I tuned the carb, and it had no effect.

 

2. I did a pressure/vac test, and it held completely. 

3. Swapped the carb for my 200t (another Zama), still nothing.
 

I was wondering what else I could try?

In advance, I’m very grateful as always for your input!

Thanks.

[Stubby]

7 minutes ago, GuyMo said:

My 020t is idling high. It’s really bugging me. The saw is in mint condition for its age (2000) having and very little use until I picked it up in November ‘19. I’ve opened her up and theres no scoring etc.
I have tried to sort it, but to no avail. 
 

1. I tuned the carb, and it had no effect.

 

2. I did a pressure/vac test, and it held completely. 

3. Swapped the carb for my 200t (another Zama), still nothing.
 

I was wondering what else I could try?

In advance, I’m very grateful as always for your input!

Thanks.

If the known good carb did nothing then maybe there is some air getting in somewhere . Fuel lines , impulse line , crank seals etc etc...

Edited July 7, 2020 by Stubby

[GuyMo]

9 minutes ago, Stubby said:

If the known good carb did nothing then maybe there is some air getting in somewhere . Fuel lines , impulse line , crank seals etc etc...

I’ve not checked the fuel line (silly me).

Surely a pressure and vac test would show a leak in the crank seals and impulse line though? 
 

[Stubby]

1 minute ago, GuyMo said:

I’ve not checked the fuel line (silly me).

Surely a pressure and vac test would show a leak in the crank seals and impulse line though? 
 

Yes it should . Have you done one ? Edit I see you have .

Edited July 7, 2020 by Stubby

[Stubby]

Maybe then it is something mechanical . The throttle linkage perhaps ?  

[spudulike]

If the pressure vacuum check included the manifold and impulse line and a carb swap didn't give an improvement then you really have an issue unless both carbs are shot. The only thing left is the throttle linkage as if the saw isn't leaking air and the throttle valve is completely closed, it is pretty much impossible to get a fast idle speed! 

A split fuel line will give you bogging and is unlikely to give a fast idle. Are you sure you reconnected the impulse line?

 

[Wonky]

Is it the Accelerator pump, but you say both carbs  are the same.. i then maybe a pin hole in the fuel line  or cracks in impulse line which only show up while it’s running...

but it smells of bad air leak syndrome somewhere, I guess  you gotta sniff it out.?

did you rotate the crank while doing the p&v teast.. and wiggle up and down,

you know seals can be fine for  awhile and after a bit of run time the fault shows, the can be seen in tuning a saw then when it’s warm it loses a tune soon after or when cold.

 

i hope it work out ?