81 Special Project

[mschor]

I asked a while back about the air filter getting soaked in gas, it's oem, seems like foam. Does it ruin the filter? Also, does the bike need to be tuned with the air box and filter in? Imagining so, but not sure. Oil seems ok, same level and not obviously smelling like gasoline. Pilots are in, ready to put it together tomorrow

[motoman]

I asked a while back about the air filter getting soaked in gas, it's oem, seems like foam. Does it ruin the filter? Also, does the bike need to be tuned with the air box and filter in? Imagining so, but not sure. Oil seems ok, same level and not obviously smelling like gasoline. Pilots are in, ready to put it together tomorrow

Should be no issue using a foam filter. Idle mixtures and carb sync. done with filters and air box on......just the way it would normally be ridden.

[CaptonZap]

If it is an OEM filter, it is a dry element type. The manual says to tap it to dislodge the big pieces, and then use compressd air to blow it out, blowing from the inside. The incoming air goes to the inside of the filter, not the usual way coming from the outside.
If someone has put oil on it, I would wash if out with gas, dry it thoroughly, and re install. Run for a few miles, and check for any deterioration of the element. It is sort of a felt like stuff.
If it is a K&N type foam filter, then it should have a light coating of oil worked in, after being washed clean with gas.

CZ

[mschor]

Cool, well I guess it just got a thorough washing!

[DiverRay]

The manual says to tap it to dislodge the big pieces, and then use compressd air to blow it out, blowing from the inside.

To blow out the dirt, blow TOWARD the inside!! The inside of the filter is dirty air, outside of the filter is the clean side!

[CaptonZap]

To blow out the dirt, blow TOWARD the inside!! The inside of the filter is dirty air, outside of the filter is the clean side!

Sorry Ray, I knew what I meant to say, which was that the air flow was backwards to a normal filter. Thanks for the correction.

CZ

[mschor]

It's a new filter anyway, just overflowed some gas to the airbox, & was checking to make sure the filter would be ok

[mschor]

There's one screw facing the air box in the intake of each carb, what is that screw for? It looks just like a jet, is that the pilot air jet?

[DiverRay]

Yes, that is the pilot air jet.

[mschor]

Cool, so good news is running fuel levels are good. Bad news is it will not take any throttle without stalling. Ran it about 5 minutes, plugs are clean, not black. Boots are tightened down, vacuum hoses attached. I adjusted mixture screws between 2 & 4 turns out and no change.
It has 2 original pilots and 2 new Mikuni from the local dealer just put in.
First time I started this bike after 20 years, it sang. No choke, nothing, instant throttle response. Then I ran it a bit and the plugs fouled, and it's been hit and miss since then. I cleaned up and gapped the original plugs and put them in because they look pretty good.
Possibilities that come to mind are:
Broken off pilot screw.
Something got into the carbs from the tank or when I took them off and scraped off the gasket surfaces and drilled out the pilot screw caps that were on it
What else could this be? A spark issue?
Seems like it's just too lean to me

[motoman]

Cool, so good news is running fuel levels are good. Bad news is it will not take any throttle without stalling. Ran it about 5 minutes, plugs are clean, not black. Boots are tightened down, vacuum hoses attached. I adjusted mixture screws between 2 & 4 turns out and no change.
It has 2 original pilots and 2 new Mikuni from the local dealer just put in.
First time I started this bike after 20 years, it sang. No choke, nothing, instant throttle response. Then I ran it a bit and the plugs fouled, and it's been hit and miss since then. I cleaned up and gapped the original plugs and put them in because they look pretty good.
Possibilities that come to mind are:
Broken off pilot screw.
Something got into the carbs from the tank or when I took them off and scraped off the gasket surfaces and drilled out the pilot screw caps that were on it
What else could this be? A spark issue?
Seems like it's just too lean to me

I suggest when bike is warmed up from running, with bike idleing, plug a se-thru vacuum hose on bottom nub of fuel bowl. Then, with hose held upward beside fuel bowl, unscrew that bowl drain screw a ways that is on side of fuel bowl. Hose will fill with fuel and that hose fuel level will equal fuel level in float bowl. That fuel level should be 3mm down from carb body casting that fuel bowl attaches to. All four HAVE to be the same fuel level.
IMO, at this point, I suspect the actual fuel levels in bowls are too low. Those fuel bowls fuel levels make a huge difference as to its running correctly.
Idle mixture screws next.......done with bike idling. Back screw out(pick one) till no noticed change. Then, slowly start back in with screw until a constant steady drop in running is noticed. Then, back screw out 1/8th turn and absolutely no more than a 1/4 turn. Do other three mixture screws the same.
NOW.....re-sync the four carbs using four vacuum gauges or a mercury manometer.

[mschor]

Does the synchronizer need 4 gauges to be accurate? I have 2 gauge vacuum sync that I was going to use.

[DiverRay]

You can use the two, but it's a PITA. You need to do 3&4, then 1&2, then 2&3. After that, set the mixture for fasted idle one at a time and redo the 3&4, 1&2, 2&3. Three is the carb everyone else sets to.

[mschor]

I double checked the fuel levels again today and they're all exactly the same, but at the bottom of the screw, so that's about 2mm too low all the way across I'm guessing. Consistent, but not perfect. It basically only runs on full choke. I know there are different opinions on the importance of exact fuel levels, but I can probably get them on the money if that'll bring things together, I'm definitely getting better at the carb in and out. I also checked the running voltage at the battery. With the engine off, it measures 11.5v, at quarter throttle it's 13.3v. So it's charging but doesn't reach above 14v. Still no tach movement at all. Do you think these numbers indicate a charging problem, or might it be the tach itself? I'm thinking about buying a diagnostic tach just so I can get it tuned and not have to wait till I get this tach issue solved.

[TopCatGr58]

IF that's the voltage AT the battery, then your battery is WEAK, should be 12.3V or more resting. The charging system actually needs a strong battery to be able to drive the charging system properly....the field coil is powered from the battery, and with the battery weak, then it can't generate as strong of a magnetic field and that can limit how much actual amperage/voltage it can produce.

Would suggest putting your battery on a good charger and see if it will charge up to ~12.5 volts, and then hold that level off the charger overnight. If it drops to below 12 just sitting overnight, then it's time to get a new battery. Load testing it would be nice to know also.

Did you check the 3 large white connectors BEHIND the fuseblock for the ALT to harness for corrosion/melting?? That's where the tach signal wire also comes from.

T.C.