TOPIC:

A sticking valve does not necessarily stick wide open. One can stick open just enough to lose compression, but not far enough to contact the piston or the other valve. A sticking valve, by definition, overcomes the spring.

If the mixture screws do nothing, then there is definitely a problem there. Could be clogged passageways, the tips of the screws could be broken off and maybe lodged in the passageways.

I don't know if 60ml is a lot of fuel for the time you ran the engine, but if the sparkplugs are showing signs of an overly rich mixture, then missing tips of the fuel screws and / or problems with the fuel levels could be causing part of the problems.

The tip of the screws are in perfect shape, i saw those carb missed the small oring at the botton of the mix screws. There are only the springs.
About the sticky valves, during the rebuild i did a valve job, and i saw all valves move smoothly in their guide.
Another thing i m seeing right now is the float needles have the tiny spring loaded pin very weak

Maybe you clanged the valves while assembling the engine, has the cam timing off by one tooth and it tweaked then enough to cause problems. In any case, it sounds like you have so many KNOWN problems, maybe work on fixing the ones you know about first?

I have always think in there carb are Not orings in the mix screw, at the botton, only at the top. Can Simeone tell me what size this tiny rings are? If someone have for sale a spare tk26 set i can Buy it.

DGA wrote: Maybe you clanged the valves while assembling the engine, has the cam timing off by one tooth and it tweaked then enough to cause problems. In any case, it sounds like you have so many KNOWN problems, maybe work on fixing the ones you know about first?

Im absolutely sure the timing is correct.
And this bike had this problem even before i dismantle and rebuild the engine.
The vacuum reading problem is absolutely random, and appear even when the engine running "well". I wonder if an ignition problem, a misfire, or a strange vacuum leak can show this strange thing.
Anyway, i want to know you experience about mix screws during a sync. Are them so sensitive?
I use to :
Warm up the engine.
Use the screw to set 3 and 4 carb in sync
Use the screw to set 1 and 2 carb in sync
Usr the central screw to set #3 and #4 to #1 and2.
Then i try to use the mix screws to definite well any pulsation and/or reach a better idle.
Is this correct?

Most carb banks have a lead caeb. It is not adjustable other than the idle set screw. You bench set the openings, then sync the carbs to the "lead" carb on the bike. Often it's #3. If no "lead" carb you will pick one and adjust the others to it. If not done this way, it's easy to get confused and wind up chasing your tail.
Steve

swest wrote: Most carb banks have a lead caeb. It is not adjustable other than the idle set screw. You bench set the openings, then sync the carbs to the "lead" carb on the bike. Often it's #3. If no "lead" carb you will pick one and adjust the others to it. If not done this way, it's easy to get confused and wind up chasing your tail.
Steve

Yes , the number 3 is the lead. So i think i have to first sync the 4, and then the other two. Is correct?

You'll notice as you get another cylinder close to the lead carb, the others will change some too. Take your time and keep doing it until they are all close to being the same. If one carb is dirty all bets are off.
Steve

Ok. Maybe Im not gathering all the facts here - but it sound like the OP has good compression. If his timing of his cams was off or a sticking valve would show on compression, right? So the other thing I thought about was the coils and making sure they are going to the proper plugs - which he confirmed. But if the wires going to the coils are swapped, wouldn't that reverse what plugs the coils should be on? Maybe worth a shot.

Also he mentions the pilot screws have no effect and are maybe missing o-rings? I would probably figure out what's going on there before vacuum sync. A bench sync should be good enough for now until he gets it able to idle.

As for the loss of vacuum. Is it possible the bike is backfiring some through the carbs? I've had this happen before on mine when I had the coils firing the wrong cylinders and other stuff messed up.

If the O rings are missing on the pilot screws they will be sucking air thus making the adjustments less effective.
Steve

swest wrote: If the O rings are missing on the pilot screws they will be sucking air thus making the adjustments less effective.
Steve

OK i have to find thevorings then.
I THINK I FOUND SOMETHING WRONG ON THE IGNITION!!!!!

just now i put my digital multimeter on the coils terminals. The right wires provide 11.50 volts when i turn the key on.
The left wires provide 0.03 volts when i turn the key on.

During the test i disconnect only the coils from the wires. The rest of the ignition system is still connected. Is this test valid?

I think i have a huge electrical problem then.

The only thing i dont understand is how i can have a (weak, OK) spark in cylinders #2 and #3 with 0.03 volts o_o

How's the battery?
Steve