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Carb AF setting frustration

1473 Views 13 Replies 3 Participants Last post by  cranstjs
Background 04 1300c Hypercharger, VH Big Shots jets: 200/58 NGK plugs new, Stock needle with one shim

I've messed with fine tuning this bike for more than 8 months with mostly success (recently trying to lean out slightly to get plugs a little more on the brown side).

I've had plenty of success with one shim and around 1.75 turns of AF screw.

Now, my recent puzzler. I decided to remove the one shim since simply leaning AF screw a little bit wasn't achieving the desired plug coloration. I've done that before and noticed it would run kind of crappy for the first few miles and then, once warmed up, it would be ok. This time, after removing shim, I didn't notice any real change in the running, strangely, BUT, I noticed I couldn't adjust the AF properly anymore and "correct" seemed to be fully CW or all the way in (which doesn't seem to make sense).

So I decided the other day to put the shim back in. I did and still, the AF adjustment is "best" at all the way CW.

I removed AF screw all the way to inspect the components and they all seem fine; spring, washer, o-ring. Put it back in with the same experience.

Seems to blip ok at idle with throttle. I took it for a 7 mile ride and checked AF again. Still CW the best.

I have to believe something has changed or 1.75 AF turns would be where I go back to. If I turn the AF screw 1 to 2 turns to 3 turns, it just gets slower RPM and runs worse (stuttering idle). Before, at 1.5 turns, RPMs would rise, as it should. Seems like maybe there is some other path that fuel is taking circumventing the AF path?
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Bypassing the enricher circuit.
Speaking of Enricher, in an effort to ensure that was fully close, I put a bit of a tougher spring in it about 4 months ago. And I haven't used the enricher in more than 8 months. I verified that it is not pulled out as well.

I don't know if that's what your comment means.
That was the meaning.
So if the enricher circuit is closed (seemingly) is there something I'm missing that may have inadvertently changed? One small item; when I first took the shim out and re-assembled I noticed my throttle cable at carburetor (where there is a lock nut on each side of a metal holder) had popped off the holder. The throttle was reacting poorly and I realized the oops and replace it and tightened it up as best I could. That's the only other thing that got messed with other than taking the shim out and putting the shim back in. For many months my AF adjusted fine with my 58 Pilot jet.
Make sure your throttle turns about 1/8 inch it needs some slop to make sure butterfly closes all the way.
Yup, that seems to be fine. I really didn't alter it's adjustment. Put it back the way it was. Still would like to know what has altered the AF setting pushing it toward fully lean. And why the RPMs aren't going up at all as I go 1 to 3 turns CCW.
Thanks. I will re-check. The rubber in slider seems to be in good shape. But I will take it out again and confirm. I didn't take the carb fully off to remove and re-insert shims. Simply lifted gas tank and moved back toward battery so I could get at the 4 screws to remove the piston cover. Then took out needle/rubber assy and changed shim. (out and then in later). And moved gas tank back on again. So the carb/ manifold band was untouched. I appreciate your out of the box thinking though. I've had instances mucking with one thing where another thing is disconnected or moved accidentally. I think I will take off gas tank and re-examine everything between the petcock and the carb, and the needle area.
Air cut off valve could need cleaning if you're mpg has gone down it is a sign.
It is opperated by vacuum forward side of carb.
I haven't noticed a dip in MPG, and I haven't messed with the Air cut off valve, but I will look at it. That would be a kick in the head if suddenly out of nowhere, some other part had an issue.
I finally got a non-rainy day (not complaining with our TX drought) to take tank off an inspect some things. I didn't see anything, at first, that looked loose vacuum wise, and then all of a sudden the vacuum line was pulled out from the air cutoff T. So I thought, hmm, that Charlie was on to something. So I got another piece of tubing and replaced that ACO tube and made sure that T was secure with both lines. Silly that I have 3 T's on the vacuum line and only one of the T's is actually in use. I plugged the hypercharger vacuum T a long time ago as to avoid any leakage at that diaphragm and I don't care if that flap on on the HC wiggles or not. Secondly, the pair valve plugged line on another T. So two plugged T's. Har. I may simplify and ditch those two T's. Anyway, I digress. So I put the tank back on to test if that fixed anything.

Took it for a short ride, a couple of miles and let it run a while to fully warm up. Had AF screw at about 1.5 turns. I messed with turning it all the way in and out as many as 3 turns, slowly, small increments. For most CCW turns, the AF simply made it sound a bit more deep and a slowing of RPMs. So really the change was very subtle. All the way in and RPMs seem to be at max, not unlike before. BUT, on one CCW, turn out, I could swear suddenly the RPMs were getting faster like before I started messing with shim. And I was reacting with, "Hey! Maybe?......" So I repeated from full CW and let it out CCW and, and, ugh; back to doing little if nothing. ???

So I guess I'm going to go back to inspecting the diaphragms, as we discussed earlier.
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I was suspicious of the AF o-ring since it almost worked today with one set of CCW turns but then not again. I still didn't trust he AF o-ring even though it looks ok, no flattening or rough edges. I also bought one of those extended AF knurled screws a few months ago but I never used it. Comes with o-ring and washer and spring. So I went ahead and swapped it out, and it brought a smile to my face when I turned it fully in and the bike stalled. I new I was on a better road. I turned it out and I could hear a smoothing of the idle at about 1.5 turns. It wasn't quite doing the increasing of RPMs 1.5 turns that I was used to but I can hear where it's better and then, if I continue on, it doesn't improve, so I backed it off an 1/8th of a turn and called it good enough. I know the air cut off has never been removed, but I also know that it's a good idea to change it's diaphragm every 25k miles, so it's due. I took it for a couple of mile ride and it feels pretty good through the gears and through the throttle turning. I will ride it for a while and inspect the plugs and see how things look. Thanks so much for the thoughts and direction both of you.
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