Strange Carb Sync Problem

[vmaxman99]

Hey guys, been awhile. Have something really weird going on. Inherited a relatively new carb rack from a friend. Put them on my bike and started doing a sync. The first 2 steps work just fine, but when I try to sync the right bank with the left, I have the sync screw completely bottomed out. When I turn the screw out counterclockwise, all it does is increase the idle since it starts to pull on the other side. I pulled the rack off and compared it to my original 54,000 mile rack, and I don't see anything wrong with the assembly. What the hell is going on here?:damn angry:
Mike Costa

 

[Traumahawk]

There are little tabs behind the sync screws that the sync screws push against as you tighten them down. When the bike falls over...etc....has a jarring impact, those tabs can get bent just a bit...even if they dont hit anything...like a tree....etc.

I know this because, carb#4, the sync screw was completely bottomed out to where, i couldnt completely sync all 4 carbs. When I took the carbs off and sent them to dannymax for a rebuild, he was the one that said that the tab was bent just a bit, and asked what I had hit? (Nothing by me....maybe the PO?) He said that he had seen that before...and that the tab has to bent back out just a bit. Now the carbs will sync perfectly.

 

[blaxmax]

Also check to see that the springs are in the right place and completely between the tabs instead of a wrap or two over the tabs.
I have seen a few that were put back together this way and in no way will they sync.

 

[vmaxman99]

Guys, I have my original rack that does sync just fine, and I put the 2 racks side by side and inspected the sync mechanisms. All the springs are in place and I don't see anything bent. The screws on the rack that won't sync look exactly the same as the screws on the rack that will sync and nothing looks bent out of place. weird....

 

[Traumahawk]

Mine didn't look out of place either.....although Danny fixed them.

 

[vmaxman99]

Well, I have to pull the rack again then and really look at it with a magnifier. The rack was shipped, so anything could've happened. I'll let you all know what I discover. Would be fantastic if someone could supply a photo of the bent tab.
Mike

 

[sdt354]

I don't think the tab will be bent enough to notice in a pic. I'd sync them on the bench to better see what's going on, and what is needed to fix it. Use a drill bit for a gauge. Adjust the idle set screw until the drill bit is semi-snug in the first carb's throttle plate (front left). Then work your way around to the one that won't sync. Most likely you can then bend the tab to get adjustment again. Do re-sync again with the motor running, though you'll be close already.

 

[davesax36]

Bench sync saved both of mine last week. It just used a piece of 20ga wire, and everything came together enough to start at least.

 

[dannymax]

I don't think the tab will be bent enough to notice in a pic. I'd sync them on the bench to better see what's going on, and what is needed to fix it. Use a drill bit for a gauge. Adjust the idle set screw until the drill bit is semi-snug in the first carb's throttle plate (front left). Then work your way around to the one that won't sync. Most likely you can then bend the tab to get adjustment again. Do re-sync again with the motor running, though you'll be close already.

Exactly....you would never be able to see the difference between a bent and unbent one.

The real issue is studying the linkage and figuring out what needs bending....and which way to bend it.

 

[thor_eyerdhal]

Beware ,the adjusting range is not wide..
If only ONE of the springs is too compressed (screw over turned), it pushed all the linkage and shift idle speed.. =>No way to find out.

 

[davesax36]

Like Danny and Thor said. Think about how far a half a turn on one of those screws actually moves things. It's such a small amount. I'm sure I'd screwed up at least one of my tabs, but Danny fixed everything, and sent them back running great. If they're too screwy, it would be worth it to send them off to get done.

Did you count the threads showing on the syncable rack and compare that to the messed up one? That might give you an idea. Or, close the butterfly on 2 and see which one won't close by adjusting all the other screws. I thought I had a messed up one once, but I was trying to match stuff up the wrong way.

 

[sdt354]

To further add, before bending, if yoy need to,make sure the adjusting screw isn't bottomed out or at the other extreme of it's adustment. Leave 1/2-3/4 of a turn in each direction for
movement.

 

[vmaxman99]

What size drill bit? Smallest I have is 1/16".

 

[davesax36]

What size drill bit? Smallest I have is 1/16".

I bought a bit just for this at ace. I think it was a number rating for machine work. Very tiny. I think the wire I ended up using came from a phone jack.

 

[vmaxman99]

Ok, thanks. So the sliver of printer paper I've been using as suggested on the V4 Muscle site was a good choice. I did determine under close observation that the tab and lever for the syncing of the 2 banks was bent. What crappy metal! I was shocked at how easy that crap bends. Typical cheesy metal, just like the screws. Anyway, it's all moot now; from screwing with the very fine thread screw too many times, the damn threads in the tab finally gave up. Anybody got those parts laying around?

 

[davesax36]

Talk to Danny, Sean, or Kyle. They'll find you what you need.

 

[sdt354]

Ok, thanks. So the sliver of printer paper I've been using as suggested on the V4 Muscle site was a good choice. I did determine under close observation that the tab and lever for the syncing of the 2 banks was bent. What crappy metal! I was shocked at how easy that crap bends. Typical cheesy metal, just like the screws. Anyway, it's all moot now; from screwing with the very fine thread screw too many times, the damn threads in the tab finally gave up. Anybody got those parts laying around?

Next size up thread and screw will fix it.

 

[dannymax]

What crappy metal! I was shocked at how easy that crap bends.

I believe those tabs are a 'field fix' that were engineered into the system



Anybody got those parts laying around?

I probly have the parts (depending on which carb) but they are part of the throttle plate & rod linkage....you really don't want to get involved in changing those. Take Steve-o's suggestion and go with a size up bolt....it will need to be an extra fine thread to maintain adjustability.

 

[vmaxman99]

I knew there was a reason I bought that Venture rack last year on Ebay! It just became a parts donor to replace the buggered shaft. Wasn't terribly difficult, took it slow and easy and just has to remove one carb from each rack to get what I needed. Hairiest part was getting those tiny, staked in throttle plate screws out very slowly and carefully. Rack is back together and going to do a bench sync.

 

[dannymax]

I knew there was a reason I bought that Venture rack last year on Ebay! It just became a parts donor to replace the buggered shaft. Wasn't terribly difficult, took it slow and easy and just has to remove one carb from each rack to get what I needed. Hairiest part was getting those tiny, staked in throttle plate screws out very slowly and carefully. Rack is back together and going to do a bench sync.

Yup, the screws are the tricky part.....glad you got it, good going! :clapping: