Topic: Set screw A installation

[Ace Blackwell]

I have a 77 550F  I’m rebuilding the carbs.  When I put the set screw A and spring in I didn’t get much spring resistance.  Is that common?  At first there was some spring aspect to it, once bottomed out, the spring doesn’t appear to have any purpose.  It acts like a sleeve to the lower section of the hole but it doesn’t give any level of resistance.   Just making sure I haven’t left something out.

[Scott S]

 There's not a ton of resistance. Those are the mixture screws. They control the fuel air mixture, mostly for idle and low speed operation, but they do have an effect on the entire power band.
 If you have the original Keihin brass, use it. Don't use the brass from the kits.

 And make sure you pull and clean the emulsion tubes. They aren't included in the rebuild kits.

[Deltarider]

I wonder... what made you think you would need new parts?

[Ace Blackwell]

My carbs have set idle with gas or open air for 5+ years. Between rust and oxidation the brass was in rough shape. Not sure I needed new set screw or springs. And I did keep the original needles.  I didn’t see the purpose of scrubbing and soaking the old jets when I can swap with new.  However I have kept them all just in case my assumption comes back to haunt me.

[Bodi]

Aftermarket jets, float valves, emulsion tubes, and needles are a gamble. If you can use the original parts or get OEM Keihin replacements, this is considered best. The brass parts wear very very slowly: the needles and emulsion tube needle jets (the top part of them) do wear slightly from rattling together but it takes a ton of miles to show any effect.
Cleaning the brass parts with carb cleaner, ultrasonic bath, or non-abrasive scrubbing all work OK. Clear the emulsion tube cross holes with soft wire (ie copper, not steel).
In my experience - fairly wide - using aftermarket parts from Keyster and others sometimes works great but regularly causes severe running problems that disappear if the original parts were kept and get put back in.

[pjlogue]

What Bodi said and I'll add that I have found the aftermarket springs for the idle needles are bad for the carbs because they, without exception in my experience, all have the spring end wire cut to 90 deg.  This causes a sharp edge the gouges up both the brass needle and the carb body when you screw the needle in leaving chunks of metal that can clog up the passages.  If you have to use the aftermarket springs be sure to file/sand/Dremmel the ends of the springs flat and smooth so the spring end rides on the seat smoothly.  The metal chunks can get jammed in the passages and no amount of air or cleaner will get them out.  Ask me how I know. 

-P.

[Ace Blackwell]

Lol I’ll yield to your experience on that one. I have the original springs and they look good, I’ll swap to them. Just now start to rack the carbs. Still time . Thx for the heads up.

[pjlogue]

Lol I’ll yield to your experience on that one. I have the original springs and they look good, I’ll swap to them. Just now start to rack the carbs. Still time . Thx for the heads up.

When you remove the needles to swap the springs, carefully look down the bore where the needles go and see if you have the metal chips.  If you do you want to be sure you get them all out before putting the carbs into service. 

-P.