sudden miss

[Nails]

Okay, I got the bike back together after a ton of work including sonic cleaning the carbs, replacing plugs, replacing all filters (including fuel), replacing lots of vacuum and fuel plastic bits, and repairing a smashed header. Synchronized the carbs yesterday, and it purred like a kitten.
But about 8 miles into a wonderful test ride, it suddenly got a bad miss. Starts fine and idles okay, but basically any throttle position produces the miss, most noticeable under load. Each of the headers seems equally hot. Not leaking fluids, like gas from a float bowl. Spark plug wires apparently connected on both ends. My brief ownership hasn't included missing.
I know it could be a zillion things, but I'm guessing some clogged fuel circuit. I'm about to pull the carbs, again.
Any other likely but easier possibilities?

(On the plus side, that brief test run really was splendid. The heinous, gritty wobble was cured with about 5/8 turn of Gene's headset tool. The new bars and cut-down windshield are just right. The cruise control, moved to the fairing, worked as expected. It looks really nice, all simple black and white. I mean, this miss is pretty frustrating -- I wanna ride!)

[Nails]

The plugs were lean, none really different from the rest. It might've been lean enough for a pre-ignition miss.
I don't see any air leaks -- the new air filter still looks fine, without leaks. It has stock jets (35/105 as I recall), but really should be rich up here (7800 ft elevation).
I'll put it back together to see how it runs when not all warmed up. (I reckon I should also fix the temperature gauge, but the fan does come on. The ground trick didn't do the deed.)
The pilot screws are still 2-turns out. I'll try 3. I understand that for these carbs, the pilot screw affects the entire throttle range, more or less (unlike the slow jet on conventional carbs).
It sure did run sweet before this miss came along.

[Jimvoyager01]

I fixed my miss with seafoam good luck

[cushman eagle]

You might try draining the carbs,to see if dirt might have gotten in blocking a jet

[ekap1200]

If you didn't flush out tank, you may need to keep an eye on the fuel and as Loren stated , drain the float bowls. and keep an eye on what gets past the filter. You will be surprised at what gets thru. I had that same condition twice on my bike from picking up bad fuel while going to rallies. Un explainable miss with no signs of fuel leaking and poor fuel mileage. Cleared up with new fuel and blood letting ( draining the bowls )

I have never had issues with altitude compensation. From sea level here in NJ to Estes Park Colorado. Runs the same and does it well. Plugs always look like new, and yesterday I filled up with 200.7 miles taking on 4.1 gal, who can complain with that .

5/8 ths of a turn is quite a bit on that steering , she must have been walking loose for some time. I have seen quite a few, that as I have removed the plastic cover for the bars/key the top nut was hand tight to half off.

Let us know what you find with the miss, hope you get it solved and get some more miles before summer slips by.
Gene Kap

[Nails]

Thanks. I put on a new filter, and a new (longer) fuel line from the pump -- the better to pull the carbs. Which are out again anyway.

I don't see much evidence that any particular cylinder was the miss. Seems a little odd that all the carbs would clog the same at the same time. And this cropped up only 8-10 miles after sonic-cleaning everything. I'll sure dump the float bowls, but I really think it's a jetting issue.

I think the proof will be if there's no miss when it's still warming up.

Do you happen to know how many turns out you've ended up with the pilot screws? I just guessed at 2, and now I'm going to try 3.
When I drilled out the plugs, I touched the screws with the bit. I couldn't tell where they were originally -- one was maybe 2 1/2 turns. And at about 2 3/4 turns, the screws hit some resistance like corroded threads. But one thing's for sure: the plugs where sure white. (I bet they were 2 1/2 turns, to run too lean.)

If this works, I guess I'll just be surprised that the pilot screws are that sensitive.

Regarding your headset tool, I was surprised that so little tightening made such a difference -- I didn't feel any sloppiness with the front tire in the air. I plan to overhaul the forks later, when I'll clean up those threads to adjust it right. (I started out most worried I have to fuss with the forks now, but that at least won't screw up my travel plans.) Thanks again for getting it to me so pronto.

However, I will replace a perfectly good Dunlop 404 -- anyone care to make an offer?

[Nails]

Well, that made things a little better but didn't really fix it.

This bike has run a little funny since I got it in March. I attributed that to filthy carbs that were out of synch. They're clean now, and they weren't really very far out of synch.

But the "choke" cable was mounted funny to the carbs. The enrichment slide didn't turn all the way "off" (slide all the way to the right). It does now.

And it also runs bad now. If I put the "choke" about half on, it runs similar to the way it did in the first place. I'm sure it's running lean (will check a plug again after it cools down).

It has stock jetting, I don't see any air intake leaks, and I'm at a loss what to check next.

Do all of these XIIs run lean -- like pretty much every other bike of that era?

[Mr Jensee]

Neal you might want to inspect your vacuum lines coming off the carbs for tiny cracks. Air getting into these vacuum lines can also lead to an occasional miss. If the tubing is old it pays to just replace them all. Rubber has it's limits. Good luck.

[Nails]

It runs a lot better now that the crankcase vent actually is hooked to the surge airbox right.

It still misses when accelerating, and the choke still makes that go away. But at freeway speed, the choke doesn't seem to help.

Now I can take it into town -- I have an MT66 waiting. I'll ask them to adjust the pilot screws and maybe check the system vacuum. It was a bit low when I synched the carbs, but I'm not sure whether I screwed up that vent connection before or after.

And I need to check the plug color yet again.

Thanks for the help. And apologies for the on-going drama.

[Mr Jensee]

I don't have anything else to do this hot steamy summer. It is raining nearly every day and when it isn't the heat index is in the hundreds. I haven't taken my Voyager out for nearly a month. I just go out there and start it occasionally and have added seafoam to keep the carbs clean. I cant wait for fall and some decent weather. Yes I enjoy reading about the drama.

[Nails]

I don't have any more leaks associated with the surge airbox, and now I'm looking at the regular airbox, especially the funny "air hose" that pushes through a large grommet on the right side of the airbox. This is mentioned in the "Air Cleaner Housing Removal" section of the manual (page 2-15): "air hose connecting the housing to the silencer".

I don't know about the "silencer" part, but understand that all of this Vacuum Switch Valve crap is for the valve-cover reed-valve vacuum system (that Canadian models are spared). If I understand this right, I can plug this airbox hole and the hose that pushes into it, at least long enough to test whether it has a vacuum leak. I suspect that the hose needs to be plugged else it'll leak oil and probably be a vacuum leak (pulling through the crankcase vent). I'm not sure there's any downside to leaving it all plugged kinda forever -- it seems like really unnecessary complexity just sorta tacked on to the rest of the bike.

Also, I see another hose behind (to the left of) the silencer, running up-and-down suspiciously near the battery drain line. It's bracketed to the frame with an S-bend around the frame, and then disappears downward somewhere. The top end has been open a long time. Is the battery drain line supposed to be stuck in this hose -- the hoses look like the right size. (I hate seeing small hoses pushed into larger ones.)

[triton28]

The "muffler" hose on the RH side of the airbox is designed to feed fresh air to the reed valves through a vacuum operated valve.
It can be removed, blanked off and the corresponding hole in the airbox needs to be covered securely.
Yes that hose clipped to the frame is for the battery vent hose.

[Nails]

Yes that hose clipped to the frame is for the battery vent hose.

Thank you.

I put some gorilla tape over that airbox hose, inside the airbox. And then a hose clamp on it. It's temporary of course, but I notice that it's totally invisible and seems plenty durable.

The bike ran a little better yet, but still has a miss when accelerating. No prob until I get to about 1/2 throttle; and the choke definitely helps. It's also wimpy at freeway speeds, but the choke doesn't help that at all.

Next I'll buy some vacuum nipples and plug the other end of that whole reed-valve affair (the two hoses on the outside carbs). I can't find any other vacuum leaks. But the plugs are still a rather light tan color.

The bike is new to me and never has run all that well. I wonder how many more problems it actually has. And I don't know what performance to expect, trying to accelerate up a steep hill in the mountains. But except for the above, it seems strong.

Continued thanks.

[Thadbaker86voyager]

Just a thought and you may have covered this already, but make sure all spark plugs boots are screwed on the spark plug wires completely. Check the ends of spark plug wires. Sometimes trimming them back a little and screwing the boots back on fixes them. Good luck! These bikes really are great when they are working correctly, and are very dependable. Well worth the pain and suffering you are experiencing now.

[Nails]

So I wake up of a morning, despairing that I'll ever figure the damn thing out. My planned trip is already over a month delayed.
And I'm on the freeway (to get that front tire), wondering why I have to wring it's neck to get up this hill.
I hit a little bump, the engine smooths out, and it takes off up the hill. Hallelujah!
Looks like another foray into the float bowls and vicinity. But I want to turn the pilot screws back in again, anyway.

[cranky]

... just maybe, Ya might do some tapping on "stuff" while it's running
and see if anything changes... wiring, do-hickies (technical term...GBG),
etc...... JM2C