VM22SS pilot screws question

[OldPainless]

So, question for the gurus... my 1977 vm22ss carbs have 2x different types of pilot screws. 2 carbs have a very pointy fuel screw and 2 carbs have a less pointed fuel screw. The fuel screws correspond to different sizes of pilot fuel holes in the carb bodies (small for pointy, large for less pointy). Pretty sure it's carbs 2 & 4. Can anyone explain why this is? I had a previous GS550 that had 3 and 1, but it had obviously been modified a lot...

 

[zed1015]

The fuel screws are all the same and should have a sharp point.
The less pointed ones are damaged and the broken tip may still be blocking the pilot outlet.
The holes in the carb bodies do not come in different sizes unless they are corroded or have become enlarged due to a PO's attempt at removing a broken tip.

 

[OldPainless]

I thought as much too but these are obviously manufactured this way and this is the second time I've seen it. The fuel screws appear manufactured this way too - it is not broken off or filed down.

 

[zed1015]

AIR screws on the side are blunt ended but the FUEL screws underneath are always pointed unless they have been broken , messed with or possibly poor aftermarket replacments.
I've been building ,repairing and modifying VM slide carbs for over 40 years and never seen original Mikuni VM fuel screws that are manufactured blunt and neither is there any normal situation that would call for blunting them.
What you often see is the junction of the fracture being rubbed smooth due to surface contact between the main screw shaft and the broken tip.
It's only brass and doesn't take many wasted attempts at adjusting the idle mix to smooth off the break point when the owner doesn't realise the tip of the screw is blocking the pilot outlet.
You should just replace the rounded fuel screws with nice and pointy new ones and make sure the original tips aren't jammed in the outlets before fitting.

 

[Nessism]

https://gsarchive.bwringer.com/cbsaunders/gs/pilot_screw_removal.pdf

Broken tips. Check the carb bodies...

 

[OldPainless]

Well nuts. I have new pilot screws. I assume they'll have to be screwed in further than the others to account for the larger pilot hole now? The sharp tips now poke thru the bodies just a bit.

And all the orifices are clear. Just cleaned the carbs and checked the holes with a flashlight.

 

[zed1015]

From new the tips do protrude into the venturi slightly when fully seated.
Even if the holes appear to be enlarged the screws will still meter the fuel.
Just lightly seat them and adjust as normal.
Any of the outlets that really are actually larger will flow more fuel for the same amount of turns out than the ones that are undamaged so they may need backing off slightly .
Most of the time where a broken tip has been removed the hole may appear to be enlarged from the venturi side but in reality the drilled seat and metering hole diameter on the underside is undamaged and still flows the same.

 

[OldPainless]

Perfect. Thank you.

 

[Ernesto d]

The fuel screws are all the same and should have a sharp point.
The less pointed ones are damaged and the broken tip may still be blocking the pilot outlet.
The holes in the carb bodies do not come in different sizes unless they are corroded or have become enlarged due to a PO's attempt at removing a broken tip.

Greetings, I'm getting ready to fire up some rebuilt carbs on my 77 GS 750. I was reading on the form and saw your hair regetting kits and then the pieces for the choke. I'm interested in doing what I can to start the bike off right. It's not ran for a long time and I've just revealed it and I have yet to fire it up and put gas to it. With the Mikuni vm26, on a 7750, will your items in your signature line help line it out? My dad said before he Parks the bike the last time because it was running rich always, that no matter what he did it always seemed to run rich. I have a K&N filter in it and it has a four-in-one Vance & Hines exhaust on it. Thank you for your time

sorry to piggyback on this thread, I tried to private message you three times and got some sequence sequel error so I'm trying to contact you this way.

 

[zed1015]

Greetings, I'm getting ready to fire up some rebuilt carbs on my 77 GS 750. I was reading on the form and saw your hair regetting kits and then the pieces for the choke. I'm interested in doing what I can to start the bike off right. It's not ran for a long time and I've just revealed it and I have yet to fire it up and put gas to it. With the Mikuni vm26, on a 7750, will your items in your signature line help line it out? My dad said before he Parks the bike the last time because it was running rich always, that no matter what he did it always seemed to run rich. I have a K&N filter in it and it has a four-in-one Vance & Hines exhaust on it. Thank you for your time

sorry to piggyback on this thread, I tried to private message you three times and got some sequence sequel error so I'm trying to contact you this way.

Ernesto.

The choke plunger seals will help but you may not need the air jets..

Email me at zed.1015@yahoo.co.uk and i will advise.

Rob.