I Have a NEW Bike!!! Well, Almost (Carb Sync)

[Night Vision]

My pilot screws are so far off (5 1/2 turns on both) when I try to move them in to where they should be the bike stalls and floods out.

how do you know where they "should" be. Mine are somewheres around 5 1/2 front and 2 rear. Leave the screws where it runs.... sync the carbs.... adjust the screws if necessary (like Lucky said: Sync - adjust, repeat as necessary)

[VisionaryDan]

Well up until this point most Vision owners are suprised at 5 1/2 turns on the pilot screws are where my carbs are set. I believe the bike is running too lean at an idle. I could be wrong - that is also assuming that more you open up the screws leaner the fuel mixture at idle. 

I have found that when I set the pilots to 5 1/2 the bike runs OK but I get this tap / knocking noise at idle speeds. I have noticed that this seems to quiet down when I adjust in the pilots. I have them at 4 1/2 front and 3 1/2 rear at the momment. The tap / knock has quieted down quite a bit.  I know this may sound like I'm barking up the wrong tree here but that's why I'm posting these questions.

I just ordered a Carbtune manometer tool to sync this up the right way.

Dan

[Lucky]

First, there are no conventions when it comes to pilot settings. wherever it runs best, that's how you set them. if one carb wants 1/2 turn out, & the other want's 8, so be it (but those settings are exagerated)

the settings you mentioned Dan as 'typical' are generally what the factory set them at when new, but that is using O2 readings from the tail pipe to set them.  your bike is 25 years older, loose & worn.

if the bike starts & runs, enough to bring it to operating temp, then go ahead & synq the carbs, set the pilots when your done with that.

set the pilots using the idle drop method. turn one in till the bike just begins to change it's idle (it'll drop slightly, or roughen slightly) then turn the screw out till the same thing happens, counting the turns out as you go.  (it might be a couple of turns where nothing happens) the 'center' point of rough to rough is where you should set them, plus 1/4 turn out.

repeat for the other carb.

THEN test ride the bike. if you have any bog adjust out 1/8 turn, both carbs & test again.

a little clarification: OUT is Richer. note that you are NOT changing the mixture of fuel & air, the jets do that, rather, you are changing the AMOUNT of mixture passing the pilot screw. so when you turn it out, your not really making it 'richer' your just increasing the amount of mix.

--Lucky

[VisionaryDan]

Thanks Lucky that helps a lot. I'll let you know how I make out but I now have something to go by.

Dan

[MotorPlow]

Hey, I got a newer bike. I don't think it's as new as DaveTN's bike, but newer than what I had. I tried syncing the carbs and the bike was running so rough all I could do was get the sync as close as I could. I then decided to play with the mixture screws. The front went well with counting the turns in and then counting the turns out. Setting the screw somewhere in the middle (set at 5 out). Then I moved to the rear carb... WTF, how are you supposed to get a screw driver on that thing. I tried every screw driver I had, including one on a flexible shaft. Nothing worked. Worst part was that I was able to get it screwed in to seat it, but every time I tried to screw it back out the screw driver would come out of the head. It would turn a little and then somewhere in the middle of the turn I would realize that it wasn't turning, but the screw driver was. What I had to do, as I couldn't keep count of the turns, was just listen. I could hear the idle go up and the after a few turns, it would go back down. Then I would turn it in a little again until the idle came back up. Took the bike for a test ride....

Accelerating from 70mph and up really didn't feel all that different, until I realized that I was still in 4th gear! Bump it up to 5th and I was up to 90mph in no time. Now I still think this bike can run a lot better, but right now, it's better than it's been. Now I have to run some errands and then go to work, so we will see how that feels....

[Lucky]

WTF, how are you supposed to get a screw driver on that thing. I tried every screw driver I had, including one on a flexible shaft. Nothing worked.

I have a very long 12" flat blade screwdriver, with a very narrow shaft & it is slightly bent. slide it in behind the engine mount & it's easy as pie...

[h2olawyer]

Using my trusty 40 year old Stanley long shaft, small blade screwdriver (still straight), inserted just in front of the rear engine mount, I made some minor adjustments to my mixture screws.  I was having a very mild, intermittant stumble at the 4~5K range.  It also would tend to bog down when leaving stoplights if I didn't roll the throttle occasionally while idling.  Gave both carbs about 1/4 turn out (richer) & couldn't make it stumble at all on a short ride which uses that RPM range a lot.  Still have some minor post-idle time issues but they are minor.  I'll give this a try on my 300 mile ride tomorrow & see how it does.  Not much noticeable difference in performance but the smoother roll on without fear of a stumble should help the rideability a bunch.

H₂O

[Night Vision]

I have a very long 12" flat blade screwdriver, with a very narrow shaft & it is slightly bent. slide it in behind the engine mount & it's easy as pie...

ditto on the bent driver. it's an oldie too. hex shaft 9" long..
I can send you some plans for one  ;D

[VisionaryDan]

Adjusted the pilot screws per Lucky's instructions - worked like a champ. Bike seems smoother rolling on the throttle. Thanks Lucky - it took me a whole 10 minutes to get it sorted out.

I spent most of the day Saturday working on my two bikes the pilot screw adjustments took the least amount of time. I actually spent most of my free time this week on Vision repair. I think mechanically they are finally ready to go. Maybe I can just ride them for a while now before the weather changes.

Dan

[jasonm.]

once the sync is set. Then you can play with the mixture screws. The mixture screw hardly changes the sync. The mixture screw just optimizes the mixture. Once optimized...you will likely be reducing the idle. BUT it is best to be done with something more sensitive that a human ear. I use a digital tach.  As far as the sync changing with rpms as I stated. Remember valve clearance, carbon on the pistons and other things  can cause this accurance.