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ViragoTechForum.com XV700 Carb Sync (Solved)

#1:  Carb Sync (Solved) Author: Sixties_Strat Post Posted: Sat Jun 19, 2010 6:12 pm

I hooked up my home made sync tool to both carb intakes. The rear carb intake had a plug over it, no vac line. I hooked directly into the nipple with my tool. The front carb has two ports, I tee'd into the smaller one. Put everything back together. Soon as I started the bike the fluid in the manometer all moved towards the front cyl. Had to shut it off before it sucked the oil into the cyl :)This was at idle.
So, what do you think is up here? The bike runs great, syncing the carbs was my last step. I have checked for vac leaks, have none.
Mike

Edit.
Went back and hooked up manometer per Haynes, tank on prime, small hose off the nipple, manometer hooked direct to small nipple front and back. Checked to make sure rear port was not blocked. No difference. Bummer... The front carb slowly sucks the oil towards it, does not level off, just keeps moving towards the front carb.


Last edited by Sixties_Strat on Sun Jun 20, 2010 8:42 pm; edited 1 time in total

#2:  Re: Carb Sync Author: eddiethetech Post Posted: Sun Jun 20, 2010 10:22 am

Unless I'm completely missing something here, it sounds like your manometer is telling you the carbs are out of sync, thus the catchy name. Have you attempted any sort of adjustment of the sync screw? The front is pulling a bit more vacuum, ergo the oil is moving in that direction.

#3:   Author: Sixties_Strat Post Posted: Sun Jun 20, 2010 2:35 pm

Nope, haven't touched the sync screw. I am trying to set the idle sync first. Adjusting either idle screw did not stop the movement.
I was expecting if it was out of sync for the oil in one side of the tube to be higher than the other, not to continuously move towards the stronger carb. Is that a wrong assumption?
Mike

#4:   Author: Sixties_Strat Post Posted: Sun Jun 20, 2010 2:49 pm

I knew I saw this somewhere :) -http://viragotechforum.com/viewtopic.php?t=9745&postdays=0&postorder=asc&&start=20-
Back out to the garage to try again :)
Mike

#5:  Re: Carb Sync Author: eddiethetech Post Posted: Sun Jun 20, 2010 2:53 pm

Drop the left side screw totally off the cam, then set the temp idle with the right side adjuster for testing. Set the idle at about 1000 RPM for starters, then adjust the screw so the tubes balance. Rev it to about 3000 and see how close you are, then dial it in again at the higher revs. There's been much debate about which RPM to use for syncing, so rather than choose sides (against folks way smarter than I) I would go back and forth between idle and 3K until it's perfect. After that set the idle to about 900 and gently raise the left screw against the cam until it just touches. Remember there's a lock nut on that side, so loosen it to back it off and tighten it after you're all done.

#6:   Author: Sixties_Strat Post Posted: Sun Jun 20, 2010 4:11 pm

Thanks Eddie,
I did drop the left screw totally off the cam. Set the idle to 1k with the right screw. Still way to strong on the right side (front) carb. Pulling the oil right up and out of the tube... As I understand it I would need to open the right side more ie tighten the screw thus raising the idle speed even more. Tried that, raised the idle speed to 1500, still pulling to the front carb. Seems to me there is something amiss. I made sure the left carb lever was bottoming out by pushing down on it, it gave a little slowing the rpms but as soon as I let go it came right back. Am I making this harder than it is?
Mike

#7:   Author: slowpoke Post Posted: Sun Jun 20, 2010 4:31 pm

Have you tried adjusting the sync screw located between the carbs?

#8:   Author: Sixties_Strat Post Posted: Sun Jun 20, 2010 4:38 pm

Nope, I was afraid to. What would adjusting the main sync screw do for me?
Mike

#9:  Re: Carb Sync Author: eddiethetech Post Posted: Sun Jun 20, 2010 5:28 pm

That's the screw that syncs the carbs. Its job is to cause the two butterflys to work in unison. Idle speed doesn't help out of sync, so you have to adjust the center screw.

#10:   Author: Sixties_Strat Post Posted: Sun Jun 20, 2010 5:44 pm

Gotcha, Some how I got the idea that the sync screw was only for adjusting at the 3 to 4 k rpm range. And that the idle sync was adjusted by balancing the two idle adjustment screws. Back to the garage to take everything apart again and try it! Thanks man, sorry I am so dense :)
Mike

#11:  Re: Carb Sync Author: eddiethetech Post Posted: Sun Jun 20, 2010 7:49 pm

No worries. It's better to ask than "screw up", so to speak. Laughing That sync screw coordinates the two butterfly shafts. It creates a union that makes the shafts turn as one, and the screw dials in the difference between the two. The left idle is the functional idle adjustment, while the right one sets the absolute low limit, in case you should turn out the left one too far.

#12:   Author: Sixties_Strat Post Posted: Sun Jun 20, 2010 8:41 pm

Sweet, got em synched just fine. Had to re adjust the idle mixture though, was not expecting that. Took her for a run and had some popping on decel. Colortune plug and a few finger burns later and she is dialed in. Thanks again for the help!!
Mike

#13:  Re: Carb Sync (Solved) Author: slowpoke Post Posted: Sun Jun 20, 2010 10:25 pm

Beers
ViragoTechForum.com XV700 Carb Sync (Solved)


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