smokinjoe73

Ok so just removed the boost bolt and put on a boost valve, not so easy with tank & body on. My hand really didnt fit but I put a small piece of tubing on the valve to have something to grab to spin it on.

Tomorrow syncing comenses.......

smokinjoe73

Am I wrong to think that putting the T inline to the rear carb would cause a misreading due to the increased air space to the petcock? This is what is making me not want to do this step. Am I way off base with this?

Matt_Hawk

Yes. It will read a little different. The petcock line would have the effect of a longer vacuum line on the rear carb. It's important to have lines of equal length going to each carb. Take it out of the loop and put a 1/8" cap on that nipple. When you are riding, that vacuum diaphram petcock is held open and the vacuum line is shut-no air is coming into the carb. The bike doesn't know there's a line there.

Edit: Imagine sucking in through a garden hose. Now take a 12" long straw the same diameter. Which one is easier? Pressure changes with air volume in the line. As an experiment, I sync'd my carbs both with and without the petcock line just to see how much difference it made. It was slightly noticeable.

What you want to do is pinch the petcock line before you stop the bike and put a capped fitting into it. Then release the line. You've trapped negative pressure in. This tricks the petcock into keeping the fuel on- so you can take all the time you need.

7moore7

This is a total guess on my part, but b/c the vacuum line is always connected to the petcock, would it not be better to take the reading considering this?

In other words, your rear carb is always getting a vacuum signal that takes into account the length of the vacuum line, as well as the small amount of air flexibility that the petcock diaphragm adds. This could totally be shot down, but is how I visualized it when I was doing it.

I guess one way to check would be to hook it up both ways and see if either was out of sync. I may do this next time. Chasing a weird carb backfire in my front cylinder right now though

nath981

I don't remember how the manual describes the procedure, but that would be a good source. The three times I did the sync, i used the the two lines from the carbs only(cut the front carb hose, the added one, the same length as the rear). It probably doesn't matter, but maybe you can get some insights from the manual, or like moore suggested, test both ways to see if there is a difference and let us know the results.

thetophatflash

I would think that knowledge of the minimum vacuum needed to fully open the diaphragm. I doubt a longer line will make a significant difference operationally.

8541Hawk

Well you guys are kind of funny with some of the ideas listed here.

As someone who has worked with vacuum technology for quite a while I guess I'll add my thoughts.

Having equal length lines, not all that important. It is not going to make a noticeable difference. Sure it's nice to have them the same length but not critical. I mean think about it, if one line is 25" long and the other is 30" long how much internal volume difference is there? Maybe a CC or two at the most. Like I said, it is not going to change your reading.

As for leaving the petcock in the circuit when sync'ing. Yes I always do this. Why? Because that is what the bike will see under normal running conditions. Though you can also remove the petcock from the circuit, if you like. Once again, it the big picture, it's not going to change things much, if at all. The one other plus of leaving it (the petcock) in the circuit is it give you a chance to test the diaphragm while sync'ing the carbs.

Now what is important is to check your gauges (whatever kind you use) from time to time.

You do this by hooking up the first line and take a reading. Then hook up the other gauge to the same line and check to see you are getting the same reading. If both gauges read the same on the same cylinder, then you are good to go. If not, you need to figure out why.

All in all it is a very simple procedure.

Tweety

Let me add something to what 8541hawk said... The internal volume difference in the unequal length tubing doesn't matter squat to the carb sync...

Why? Well... Because physics say's so...

The volume in the two tubes remains the same, for both the air and oil... The pressure we are dealing with here is neither enough to distort the tube, or significantly alter the volume of the air or oil to a degree that you can measure with the accuracy we are working with here... For that you need a much higher pressure than what the carbs produce...

So, since the volume remains the same, the ony thing the oil does is move back and forth inside the tube, and what you are measuring with the yardstick on the tube is how far it moves...

On two dial guages, they will be moving in opposite direction in sync with each other (regardless of carb sync), ie the same happens, and you are again just measuring how far the dial is moved...

So, anyone of you, please explain to me how it supposedly is any different to measure the movement if the two tubes are different length? The oil/gauges are still going to move the exact same amount of length/numeric value, regardless of the lenght of tube, or the distribution of that lenght...

As for the petcock... Well, in theory it should remain static once the engine is running, then it should remain fully opened... So if it is operating as expected, it has no measurable effect on the sync... Since the pressure differential is static apart from the first few engine revolutions when it is opened, that means that the carbs should be synced identically with the petcock connected, as they are with it disconnected... This may or may not be entirely true in practice, since at low revs the petcock might fluctuate a bit... But if the sync is performed at high idle, and then re-verified at 3k, you eliminate any fluctuations...

But if any of you prefer equal length tubing, go ahead... It's not going to make the procedure any harder once you have the tubing in place... Nor will it make it easier though...

Grasshopper

Typically syncing the carbs is masking other issues. The carbs should be pretty closesly synced from the factory. If one cylinder has more or less compression than the other you are now compensating with carburation.

Always understand a compression and leakdown test on each cyclinder tells the full story. Don't go too out of your way with a carb sync before you know the facts about the motor first.

8541Hawk

Well I'm not sure how to reply to this. Though I can't agree with the "sync'ing masks other issues" comment.

While I agree that sync'ing the carbs will not fix an underlying problem it is a normal maintenance procedure that should be preformed at least a couple times a year.

On mine I can "feel" when they go out of sync, which is usually spring & fall or when the weather changes.

So if the bike is running fine but maybe a little rough or you haven't checked it for a while, then yes sync the carbs.... if nothing else, it can't hurt.

If the bike has lost power and is running very poorly, well then sync'ing the carbs may help but if you have other mechanical issues going on, then a carb sync will not magically fix them.

smokinjoe73

Ok so is it just me or is it impossible to get the tubes filled with no bubbles? I am using regular motor oil, which I may swap out for stabil, as it would be easier to fill the tubes

7moore7

The first time it took me awhile to get the bubbles out... I just "hung" it by the tubes for a day and the bubbles worked their way out. I kind of planned for this, so if you're in a rush it's not a very helpful solution

nath981

daaammm boy! I told you to put baffles in the tubing to slow the movement of the oil down. Start the bike and put the idling as low as possible, like 800.. Hook up the tubing and start the bike up and the oil will start to move in one direction. If it's moving quickly shut the bike off quickly. Move the screw in one direction. Note that direction(clockwise or counterclock). Start the bike again and if the it's still moving in that direction, shut the bike off and turn the screw again in the same direction(note: we're only talking little bit). If it keeps going in the same direction, shut the bike off and turn the screw in the opp direction as much as you turned and add a little in the opp direction, then start the bike again. You're trying to determine the point at which the direction changes, and then you know you're in the ballpark.

It helps if you have help to shut the engine off quickly, esp the first couple times you do it or when you get the screw completely out of wack.

The baffles and shutting the bike off immediately as soon as you note the oil moving are the keys to minimizing air and too much movement of the oil.

Once you get the oil to stop and change directions, you can assume that you'll have to turn the screw the opp direction when you near the equal oil height. Actually, even if the oil isn't level in the tubing, when it stops moving, you're there. Then if you want to make certain, shut the engine off, let the oil settle to even, then start it up again and you shouldn't have to adjust.

I was trying to save you from all the bubbles and rapid oil movement, waiting to settle, etc., but sometimes we have to learn things the real way.

7moore7

Nath, not to walk over you, but I was totally fine with no baffles. I did have to "quick shut off" a couple of times, but motor oil worked pretty well. I think he was talking about the initial filling of the tubes, which is fairly difficult.

8541Hawk

Never have any problems like these with the old school Hg (mercury) sticks....

I guess I'm from the school of thought that when they made a Hg sync tool, they did have access to dial gauges, water, motor oil and everything else people use.

They still chose to use Hg and there has to be some reason for it.

So I'm not putting down any of the other methods but , for me at least, a set of Hg sticks with a small set of pilot jets ( I think I have 35s in mine) to act as restrictions, just fire the bike up, plug them in, no worries, is the way to go.

Well unless you have a twin-max but that is just me.

Use whatever you have, as doing a sync check is an important maintenance set. Just trying to say that if you do get a chance to pick up a Hg sync tool, you should do it as they do work really well, IMHO.

nath981

oh yeah you're right. Sorry smokin joe. Just ignore my post. I believe I used lightweight fork oil7.5 , so maybe that's why I needed the baffles. That **** took off like a rocket. haha Me and steve29 had lots of fun twirling it trying to get things settled down because he was using his bike for transportation.

thanks for the correction,

smokinjoe73

Yes exactly. I get the procedure but to fill 15ft of tiny tubing with motor oil sucks monkey ***. (to put it in tech terms). I tried gravity first, which no way worked. Then I busted out the mityvac to bleed it through. OK but now cant get the 2 arms empty!. Then sucked hot soapy water through to clean tubes. Nice.

FINALLY, mityvac'd thru some red stabil. Both tubes on yardstick filled 3/4 up and auto leveling (gravity finally helped).

BUT............................. Cant finish the job since I dont have a 7mm socket & cant happily get a phillips in there. Quick trip to store got it but now its dark (I HATE this fake daylight savings crap).

Another try tomorrow.

Hey Nath you sound like cooter on the dukes.

nath981

you mean I'm famous????haha

well sounds like you've been havin a ball. With that thin liquid, you may benefit from baffles, but at least shut off quick. If your adjuster is way out for some reason, you can turn it all the way in one direction and keep adjusting and shuttin off engine till you get it to change directions, then reverse to ballpark it.

sounds like you could benefit from another set of hands and some light. Yeah, I hate these short days too.

8541Hawk

Wouldn't it be easier to use a fluid reservoir and let the pressure differential fill the tubes instead of using a "U" shaped tube? Or does that not work with the lite fluid?

nath981

the next time you have what you perceive to be a thought, be sure to light a match to determine whether the origin of it is your brain or your ***.

nath981

haha.....you mean like 20,000 comedians out of work and your trying to be one. I have the same problem, but it doesn't matter in my case since I work for free.

smokinjoe73

OK guys MY CARBS ARE SYNCED!!!!!!!!!!!

I think my motor swap was quicker and I did that alone. Had my "pit crew" (wife) help.

Turns out the stabil is perfect (color and viscosity) but you have to bend and kink the hoses until you get in the ball park, then unkink them for max sensitivity. I did suck a bit through but since its fuel addative I dont think its an issue. Bike feels better at low throttle inputs and off idle.

All in all a rewarding job but not the cakewalk I was expecting. Its just niggly little things like using a 7mm socket on an extension and universal joint drive. When I tried a screwdriver it skewed the throttle.

Anyway thanks for the help guys.

nath981

bent the tubing huh........ i said baffles boy, ya hear me son.haha

I tried to use a little ratchet and it took me a while to figure out that it was moving the throttle, but too bad it didn't work because that little handle made it easy to adjust.

glad to hear you got em done with a little help from your best friend.

jeremyabbott

I just got the yard stick, 2-stroke oil and 1/8" tubing to make a sych tool. Will 1/8" work ok, and what is the ID of the existing vacuum tubing so I can get a T-Connector that will work correctly? Also, what is the best way to cap the vacuum tubes when not in use?

nath981

should be okay to use 1/8, but i just grabbed aquarium tubing and baffled it with wd40 spray tubing. Just go to auto store and but a set of caps and fittings like y's and t's for vacuum lines.

BeerHunter