One carb misbehaving.

[martin846]

I have a 97 Canadian spec with 20k on the clock.
Until recently it was running nicely. About 130m to reserve.
Recently I noticed the slide of carb 3 was lagging behind very slightly when revved but vacuum readings were identical and it has recently had carbs ultrasonically cleaned and been on a dyno to sync them. Now only going 100m to reserve.
I pulled the plugs and #1 was black but the others were clean.
When I took the carb top (#1) off the top of the diaphragm was wet with fuel.
Any ideas please

 

[sdt354]

I'd check the float level, then verify the needle/seat are doing their jobs.

 

[Parminio]

Check the air cutoff valve.

 

[martin846]

Thhank you.
Think I have sussed it.
The O ring for the Airscrew seems to have disintegrated with the bits blocking the other jet.
All back together and test drive went well. Will pull the plug when it cools down a bit.

 

[Fire-medic]

They're cheap to keep on-hand.

Part #22

Pilot Screw Set
12R-14105-00-00
$6.51

https://www.ronayers.com/oemparts/a/yam/500456a5f8700209bc79313a/carburetor

 

[martin846]

They're cheap to keep on-hand.

Part #22

Pilot Screw Set
12R-14105-00-00
$6.51

https://www.ronayers.com/oemparts/a/yam/500456a5f8700209bc79313a/carburetor
View attachment 72393View attachment 72394View attachment 72395

Sadly £20 here!

 

[Parminio]

Sadly £20 here!

Holy cow!

 

[Fire-medic]

Sadly £20 here!

Yeah, but you've got Prince Harry and Meghan. Gotta pay-for those Royals, somehow.

 

[martin846]

Yeah, but you've got Prince Harry and Meghan. Gotta pay-for those Royals, somehow.

Tip of the iceberg!

 

[martin846]

Done a plug chop and #1 still too rich but no fuel on diaphragm.
To weaken the mix do I turn the airscrew in or out please?

 

[sdt354]

Done a plug chop and #1 still too rich but no fuel on diaphragm.
To weaken the mix do I turn the airscrew in or out please?

In, but I doubt that is the solution. The A/F screw circuit after the beginning of mid-range is not likely the issue. Fuel level check?

 

[martin846]

In, but I doubt that is the solution. The A/F screw circuit after the beginning of mid-range is not likely the issue. Fuel level check?

Hi
I had assumed the problem was airscrew O ring related as the problem cane on suddenly and replacing the O ring has stopped the fuel being on the diaphragm.
When I reassembled the airscrew I did not turn it in enough so when I backed it out the measured turns it was too far out.
I went out this morning and already fuel consumption has improved so I think I am on the right track. I want to lean it off a bit more but wasn't sure which way to turn it.