Butterfly seals, air jets, mixture screws

[BillyRok]

I ended up removing the carbs on the XJ I'm fixing up to resell. Good thing because things were pretty cruddy, nothing broken or damaged though, and brass plugs still in the towers. There are 3 questions I have before I put them back together (new gaskets as well as needle valves/seats).

1). The carbs are removed from the rack so I can replace the butterfly seals. How hard do the old ones come out? Is it tricky to get the tension springs back like they are now?

2). Putting new o-rings and washers back with the mixture screws. "Lightly seated" is what I've read before backing out 2-3 turns as a starting point for synching. The mixture screw will turn in 12 - 13 turns before it gets tight in the bore and the tip is just protruding into the carb throat. How much before that is considered lightly seated as I can start to feel some resistance after just a couple of turns as the O-ring works its way up the screw and the spring starts to compress?

3). Carbs have the stock 170 air jet in the bell of the carb. I came across the following while searching for answers to my questions...so of course it raised another question. From a thread 2 years ago - -

Those removable jets in the bell are the air pilot circuit jets, the main air jets in the bell are the pressed in ones.

and those pressed-in jets tend to plug-up. I believe they feed air to the sides of the emulsion tubes. Plug it up and your carb is rich in the mid-top end.

What and where are these "pressed in main air jets"? I want to make sure they are clean. Ran each individual carb though an ultra sonic cleaner a number of times until the cleaning solution stayed clean. Don't want to not get something clean!

As always, thank you for the help.

[mack]

carbs

Hi Billy: The seals themselves come out very easily after the shafts are removed. Careful not to mix up the shaft assemblies. Each carb is slightly different. The spring tension is done upon re-assembly by rotating the shaft before slipping in the butterfly. You really can't tighten the shaft nuts until the butterflys are in. This is good because you may need to slide the shaft a bit left or right and rotate the butterfly slightly to get it to seat and seal properly before putting in the screws firmly. Once your sure the plates snap closed and seat properly with no light around the sides or bottom/top of the butterfly you can then snug up the screws after applying blue loctite.
The jets in the bell are for providing air to two circuits. If you can blow compressed air through them they are good to go. The other two holes (top) are for venting and they need to be clean as well Which I'm sure they are if you Ultra sounded the bodies.
The mixture screws will seat just after the tips protrude into the carb throat. Only two fingers turning the screwdriver is all that is needed. Once bottomed out lightly you can back them out the number of turns you want. Remember this is only a rough tuning starting point to get the bike running same as bench syncing. You'll still need to play with the mixture setting und watch your plugs before you get it right. Each carb could be slightly different depending on the valve seats etc . in each cylinder.

[Radioguylogs]

For me, the only hard thing about butterfly shaft seal replacement is getting out the small screws that hold the butterfly plates.

These screw are staked in and are rather soft. Some folks insist you need real JIS screwdriver to remove them. I have done OK with a fresh, sharp #2 Philips screwdriver.

...About getting the shaft springs back in correctly... I usually have to fiddle with them here and there before I stumble on the correct orientation, but it is obvious when you have it right. It's not something to worry about at all.

Biggest worry is breaking off or 'bugering' the head on those little plate screws.

I put a tiny dab of green locktite on the screw threads after they are back in.

PS: Pay attention to which side of the seal goes outward- they are asymmetrical.