BS34 pilot circuit cleaning

[XS2-72]

Hello and thank you to the moderators for accepting me into the forum,

My two cents for the carb cleaning line of enquiry-

Recently one of my bs34's began to pop and stall etc and i thought that's easy, just start the compressor and clear the pilot circuit. Yeah, right... Still popped and stalled on idle and roll-off.
Ok, off with it again and this time i stripped it of all jets and rubber parts, boiled it 15 minutes and then sprayed paint thinner AND brake cleaner backwards and forwards through the pilot circuit. The pilot hole and three progression holes now spewed out brake cleaner and all looked good.
Ok, high hopes try again. This time it idled ok for a few minutes but then popped and stalled .
Yet again, off with it, ripped out all seals, the throttle shaft etc for the second time then repeated the boiling, spraying and blowing. It still popped and stalled .
So i decided to remove the brass plug that sits just in front of the mixture screw.
Centre punched it, drilled a small hole with a Dremel, drilled progressively bigger holes until the plug could be poked out. The Dremel is high speed so it does not need to be pushed hard. This minimizes risk of pushing the plug in where it could be stuck.
The pilot bore behind the plug is 3-ish mm so i ran a 3,2mm drill bit all the way, cleared the debris and finally replugged with a stump of aluminum tig rod hammered out to size. Sealed with Loctite.
Now the carb runs as it should.
Removing those brass plugs was easier than expected.

 

[grizld1]

An easier way to remove the plug is to tap it for a 3 mm. screw, install same, grab with locking pliers, and pull. Push the plug back in after the job is done and seal the hole with a dab of silicone to keep water and dirt out of the casting.

 

[XS2-72]

Noted. I'll try that on the other carb if needed.
It is the better choice now that the depth of the plug is known.
Got to be careful with the casting..

 

[650Skull]

From 5Twins info.

Pilot screw Part # Original part # was not used for the US market because of the US EPA mandated restrictions so the part was not available there. A replacement, from another Yamaha cab, is the same as the XS650 BS34 pilot screw. Part # below

 

[5twins]

I have bought several of these 12R-14105-00 mix screws now and they are indeed a perfect match. I don't know why Yamaha never listed them for the XS650. The carbs they are listed for are even newer and have capped mix screws as well.

 

[5twins]

However, he may not be referring to removing the mix screw plug. He might be talking about this plug on the bottom front side of the mix screw tower .....

Thankfully, I've never had to go that far.

 

[XS2-72]

Apologies for my absence. Yes, i was referring to the little brass ball kindly shown above by 5twins.
I never got to know what kind of stubborn crud was in there because of the drilling involved.
Never even got to know if it was a ball or a cylindrical piece. I chose drilling it out before prying or knocking for fear of cracking the case.
And the peened stump of tig rod seemed a good choice because aluminium is soft and malleable.
Regardless, there seem to have been a few others with the same stubborn crud problem so the message is- this is possible so don´t scrap a carb just because of this