CV pistons not actuating

Could be a hole in the diaphragm. Also look into lubing the cylinders as well. I've never had to but I've heard of it, I'm not sure what job of lube to use. Hopefully someone else can chime in.

 

There are pic of bugs stuck, in some of those holes, blow them all out, best of luck. You know the space where the needle rides, is a brass thing,that can be glued to itself, (corn syrup fuel) (main noozle) part 32, listed on carburetor.
Good luck

 

Most likely culprit is the carbs are still dirty. It is not unusual for new XS owners to clean their carbs 2 or 3 times before they are actually clean. They really need to be COMPLETELY stripped apart and cleaned, every piece and every orifice. Also, as MechNewb mentioned, holes in the diaphram is a common problem, as well as other deteriorated rubber bits and pieces in the carbs. Finally, check your ignition timing. IF the timing is off it can also produce similar simptoms.

 

You know, some PO's will but the stuff in backwards. ie the coils could be reversed, and I remember something about timing being off 180. Its been 2 years since I have seen that one. I have been hollered at for doing my technique. I could have lost my CDI.

I also had to resolve the oil case from smelling like fuel? and the fuel running out the air box.
(I re-read your problem)
If you haven't done the boiling thing yet, try it, Use a piano string, or similar soft non-metal, heavy filament fishing string to probe the various passages. make sure you pull out every jet, needle, Coat the rubber stuff with a silicone seal enhancer, It will help remove, and replace, and perhaps add a year or two to the life of the rubber seal. Every thing but the butterfly valves. If you spray carb cleaner, use eye protection, Mikuni made these carbs to spray fluid right into your eyes. With that said, the Idle circuit, when your spraying, We have maps to your carb, One of the passages should produce 3 small skinny streams next to the butterfly valve. Your Idle screw should have a straight long end on it. Sometimes those get broken off. Do a google search for Mikuni BS34 rebuild, you should have a huge hit for the XS400 website, and then the other ones. Mikuni sold carbs to other manufacturers So there is alot of support out there.

 

Although you mentioned you completely stripped the carbs before soaking them in acid, if you did not pull the throttle shaft seals before soaking, I wouldn't be surprised if the seals are shot and leaking large amounts of air where it should not be. Same could go for the enrichment circuit and the idle mixture o-ring (if your model has one).

 

Yeah there should be 2 rubber seals at the bottom.Sometimes they get stuck or worn to the point theres only pieces.Its important you find or replace them or your carbs will suck air and run lean.This will give you idle problems also.I found mine at a local bike shop when I built my carbs.

 

Not working on my end.
As for getting carb spray in the eyes thats actualy a good thing,it helps in removing cataracs

 

I don't see how the butterfly seals leaking air wouldn't cause the cv valves to actuate. It would just run leak which is a second problem.

The hole in your diaphragm will be a tiny pinhole so make you've checked then thoroughly.

 

Okay, Flame coming out of carb, Still with Lou, enriching circuit probably needs alot of work. on the bottom of the idle screws, is 3things, 1 spring, 1 metal washer, and below that is the ity bity rubber washer.

The flame i am inclined to think is the valve clearance.
http://www.mikesxs.net/product/48-5011.html

Do the float check. Get a clear hose, and run it up next to the float bowl. the fuel level should be with in a 1/8 inch from the float bowl seam. Here is what I did. I over killed this one, I picked up extra Tee tube connectors. Just a hose is all you need,

Posted via Mobile

 

Look up "float level, not equal" you will see the difference with good float, bad float

Posted via Mobile

 

I have an 80 with electronic ignition also, and believe me, the ignition timing IS adjustable. After purchasing, the first thing I did clean and rebuild the carbs. After that the bike reasonably OK at idle but had no throttle response at all. I set the timing and it ran smooth and strong throughout the throttle range.

 

When you lift the pistons up by hand and let go, do they drop down immediately or do the slowly fall? They should slowly fall. The exact rate isn't important, but it should take a couple of second for them to come back down.

If the fall immediately, there is an air leak above the diaphragm which is not allowing any vacuum to develop. You may have a timing related problem in some measure, but it look like classic "lean" to me. The needle isn't withdrawing out of the emulsion tube so you aren't drawing near enough fuel through the jet.

It's going to run somewhat lean without air filters, but it should run OK. You need to get those pistons working. As you surmised, something isn't right.

- You don't have idle air screws. These carbs control the idle mixture by varying the fuel, not the air. Yes, the O-rings are important.

Also, with all due respect, you have no idea whether your carbs are clean until you see streams of carb cleaner spraying out every orifice in the carb. How do I know? Mine took 5 cleanings including 2 boils and I would have sworn it was perfectly clean every time. However, having sprayed carb cleaner through every hole in the carb and personally having seen the unrestricted spray of cleaner out the other end of every passage, now I know.....and the fact that my bike has run pretty near perfect for 2 years confirms.

The picture below has the idle mixture on the bottom rather than top, but you get the idea.

 

You can clean out the holes with guitar strings or fishing line if that's what you mean by "confirm the jet stream".