Finally ready for a road test!! Woo-hooo!! (Long post)

[QBS]

Check your valve core to make sure it's snugged down.  Easy check: Put air in tire, put spit in the Schrader valve core area and look for bubbles.  If no spit is available use soapy water.  I hope that your Schrader valve core just needs to be snugged down.

[Rikugun]

Fuzzle, I never asked if you ever checked compression on this engine? If so how was it?  Also, did you happen to "bench sync" the carbs before installing them? This would involve ensuring both throttle plates  open simultaneously by visual/tactile means. You would also want to back the idle speed screw all the way out first to negate it's influence. Since firing her up have you checked for air leaks by spraying carb cleaner around the manifolds, ends of the throttle shaft etc. to see if RPM changes occur?

Tuning the carbs is tedious and if they are still dirty, impossible. Having said that, I'd attempt some adjustment before removing them again for cleaning. In theory the sync and mixture adjustments are straightforward but in practice can be difficult if one is unfamiliar with the process and how a particular model responds to adjustments. Difficult as it can be it still must be done. I'd encourage getting your hands on a commercially made sync tool rather than making one. The last thing you need is adding the question of dubious sync tool performance into the mix.

As suggested, the carbs may still be dirty but I'd attempt some adjustments before removing them again. The racing idle sounds suspiciously like one throttle plate is way ahead of the other. To keep it running on essentially one cylinder,  you've probably had to turn the idle speed screw in quite a bit. Try this - start it and as it's warming up back the idle speed screw way out. Keep it running with the choke and throttle until it's warm. Once warm turn the choke off and keep it running at a moderate RPM with the throttle i.e. as slow as it will run without stalling. Now try revving and see if the RPMs comes back down more quickly. If they do I'd go ahead and try some sync and mixture adjustments. Actually, if it were me I'd have the sync tool installed when doing this test to see where it is and adjust accordingly.

[Doc Nielsen]

Can a sync tool be purchased, or easily built? I don't mind paying for quality, as long as the price is reasonable ;)

[Fuzzlewump]

I had the tire re-seated and the guy at the shop said as filthy as the rim was with corrosion, he couldn't guarantee it would hold, but he thought it probably would. So I may have to replace the front rim before long. For today at least, that problem's sorted.  :)

I haven't done a compression test yet, but I intend to as soon as possible. I've sprayed brake cleaner over all my lines and the manifold boots, throttle shaft, no signs of air leaks there. Basically I've just been playing around with the carb adjustments to see what changes I can effect, and to learn how they work.

Here's my understanding so far- could someone please tell me if I'm right?

1. When adjusting the idle mixture screws, IN = LESS FUEL allowed to the circuit, and OUT = MORE FUEL allowed to the circuit.

2. The choke pulled all the way to the left is "OFF" and allows MORE AIR to the circuit...  all the way to the right is "ON" and allows LESS AIR to the circuit.

3. Using the above adjustments, a specific fuel/air mixture is determined for idle. Opening/closing the throttle adds more of that specific mixture, or less of that specific mixture. Throttle does not change the mixture itself, just changes how much of it is applied to the cylinder.

4. Throttle valve adjustments determine how soon or late the mixture is applied to the cylinder when you twist the throttle grip. They need to be synced so that both cylinders are having the mixture applied to them at the same time.

Is this right so far?

I did bench test the throttle valves but I'll keep checking this again. (very pleased to see that my new seals show no air leakage, btw!)

I borrowed my friend's new sync tool and found it simple to use. However, because of the awful misfire on the rear cylinder, I couldn't reach a point anywhere near synchronization.

@Doc Nielsen- The sync tools I've seen in stores are about $100 US. (I'm sorry, I don't know the conversion rate for your country.) Pretty expensive. But they are very nice to use. You can find instructions for making your own for very little money at these links here... http://ridersofvision.net/rovforum/index.php?topic=3488.msg27351#msg27351

[QBS]

Regarding item #2:  The V has no "choke" in the technical sense.  Instead, its' carburetors have an "enrichner" circuit that adds additional fuel to the intake when the left hand actuator is moved left from its, right hand, off position.  More left movement gives it more fuel.  Like a choke, the enrichner circuit feeds the engine the richer mixture that is so helpful when starting from cold.  Far, hard right is off for the enrichner circuit

The enrichner circuit can be used as a work around to keep a V with plugged low speed jets, idling.

[The Prophet of Doom]

Can a sync tool be purchased, or easily built? I don't mind paying for quality, as long as the price is reasonable ;)

I use a Gunston Carbtune (from www.carbtune.com) I'd used round gauges before - sticks are way way easier to read, and these are particularly nice as there is no mercury, just factory balanced weights so they can't get out of calibration.  I thought it was $100 particularly well spent.  There are a few visionaries with these and I haven't heard a bad comment about them.  I use it every time I work on the bike. 

DIY gauge is a huge hassle in comparison, and while it will tell you if your cylinders are unbalanced, it won't tell you if you have low vacuum which is symptomatic of other issues.  If you DIY, someone suggested using vacuum jars between the bike and manometer so if you drop a cylinder while testing it will fill your jar up with ATF not your engine.

Don't forget you have to sync on a warm bike.

[Rick G]

I have a set of 4 vacuum gauges  on a manifold  with 4 balancing valves . I've had it for 12 years and it has proven very satisfactory . Cost  $39.95 in 2001

[Night Vision]

do I understand you haven't sync'd the carbs?  eyeballing will get you running..

don't even mess with the pilot screws until they are sync'd

DIY manometer works fine for 2 cylinders... used it many times...
just be quick on the sync rod in case they are way out.... I've sucked and burned some fork fluid.. its thicker than atf and easier to control... use some 5w20 if you want on your first try

set the pilot screws at three turns out each and sync the carbs.. then you can mess with the idle screws

this is assuming both cylinders are firing correctly

[Fuzzlewump]

do I understand you haven't sync'd the carbs?  eyeballing will get you running..

don't even mess with the pilot screws until they are sync'd

set the pilot screws at three turns out each and sync the carbs.. then you can mess with the idle screws

this is assuming both cylinders are firing correctly

When you say "pilot screws" are you referring to the jets on the top of the carbs? I didn't realize these can be/are supposed to be tweaked.

I tried syncing them with a store-bought manometer but couldn't get very close because of the awful misfire. Took the misfiring carb apart and cleaned it again, investigated it, then tried to sync the valves by sight before starting her up again. Misfire now moved to other cylinder.  ???

I've been taking the genius approach of just adjusting random things until something is fixed, then trying to figure out how that happened.  ::) I'm quickly learning you can't do that with a carburetor, lol.

An experienced wrench friend gave me a hand last night...we didn't get things sorted, but came much closer. I can now move the misfire back and forth between cylinders, almost on command.

The basic puzzle goes something like this (but it has its variations)...

Cylinder 2 sounds great, but Cylinder 1 is misfiring. Adjust idle mix screw on carb 1 until misfire is gone.

Cylinder 2 is now very weak. Using sync rod, open valve on carb 2 until cylinder 2 is as strong as cylinder 1.

Engine revs very high. Bring back down to idle with throttle stop screw.

Cylinder 2 now misfires. Adjust idle mix screw on carb 2 until misfire is gone.

Cylinder 1 is now very weak.....and around and around we go.

This process is a bit complicated by the fact that I have a mysterious gremlin blowing my signal fuse intermittently, so I keep losing my tach reading when I feel I'm getting close to having the carbs sorted. I gotta check this out and fix it first.

I need to go back through the forums and do some more reading up on carbs! Trying to understand them while actually working on them is a completely different gig from just reading about them.

[Rikugun]

When you say "pilot screws" are you referring to the jets on the top of the carbs?

pilot screws just another term for idle mixture screws

...I have a mysterious gremlin blowing my signal fuse intermittently, so I keep losing my tach reading when I feel I'm getting close to having the carbs sorted. I gotta check this out and fix it first.

Good idea. The same brown feeding the signal fuse I think feeds the ignition fuse. Maybe they're related issues - misfire/blown signal fuse?

As far as having to go round and round between sync rod, idle speed, and idle mixture adjustments - that's somewhat normal. I leave my sync tool connected and perform both mixture and sync adjustments concurrently. Having said that, it sounds like you may have another something special going on complicating matters. Any adjustment that causes the idle to rise must be corrected with the idle speed screw to bring it back down before continuing. The sync and mixture adjustments must be done at idle speed. I guess you probably know that but wanted to be sure.  :)

If fixing the signal fuse doesn't help your situation I'd want to learn what is the cause of the traveling misfire - fuel or ignition. There are several different ways to check for spark, some more cumbersome than others and I prefer tets that are performed while running. I have a pen that you touch the spark lead with and a window in the pen body lights with the ignition pulses. Another way is to use a inductive pick-up timing light. Many parts stores like Auto Zone offer free rentals on these and other tools. It's powered by 12VDC with alligator clamps attached to your battery. Then you just move the pick-up clamp to the spark lead on whichever cylinder appears to be misfiring. Squeeze the trigger to see either a steady strobe flash (indicating good ignition signal) or an intermittent flashing like the exhaust note from the suspect cylinder.

I also wanted to comment on engine temps. Obviously the engine has to be at operating temp to properly tune the carbs. What many don't do is warm up the bike sufficiently such that the carbs are also at operating temp. They will not atomize fuel the same cold/warm as when at operating temp. The other side of the coin is too hot. Even if the engine temp gage reads in an acceptable range the carbs may be so hot that vapor lock of the fuel pump and carbs can dramatically affect fueling. Keep a fan pointed at the radiator during tests - maybe even one pointing at the side of the engine. Don't rely on the marginal Vision cooling system alone. If the thing just stops responding to adjustments, turn it off and let it cool for a bit.

[Fuzzlewump]

Thanks again for the advice, guys!

Following your tips, I've managed to finally start getting a grip on this carb tuning thing. I'm running really rich right now but I can get her to a steady low idle with both carbs synced and no misfires...a huge improvement. I feel confident now that the carbs can be tuned tightly to pass emissions in the next month.

My fuse is still blowing on the signal circuit, but by now I'm very familiar with all the wiring on the bike and I'm sure I can locate the root of that problem.

Took the bike out on her first high-speed freeway run and she ran great! I noticed that when filling her up from empty the overflow drain on one of the carbs starts gushing gas for a little bit. Needle valve set is new, no problems from the other carb, so I think it's just a matter of a worn o-ring on the drain screw or float level being set too high.

Going down the road this past weekend, I had a moment of zen where it hit me that I really am past phase one of the rebuild (get her on the road), and now onto phase two (tuning the performance). A very rewarding feeling, very relieving.

[Rikugun]

That's really great news and congrats on the first high speed highway run  ;D Those little zen moments are part of the Vision experience for sure.  :)

Tuning these bikes can be a process and the first step is just learning how! It sounds like you have a better understanding and comfort level with it now.  :) It sounds like you're well on your way to having a nice running Vision.

Regarding the overflowing carb, I doubt it's the drain O-ring but did you replace the one on the needle seat assembly? It could also be the float height adjustment as you mentioned which may also contribute to your rich condition. If it's not just a bit of debris working it's way through and continues to be a problem you'll have to look into it further before optimal tuning results can be had.  Keep at it and let us know what you find. :D

You can check the fuel level in the bowls without removing them. Arguably this is more accurate then just setting float height. The manual may describe how and there are specialty tools available to do this. Depending on your ingenuity you may be able to cobble something together as well with clear tubing and a means to measure the fule level within.