Trying to understand carb syncing

[rapidroy5858]

New to the rx1 and trying to understand carb sync..watched the slides today as I opend and closed the throttle on the sled..each one would open a different amount...would this be a sync issue..should they work in unison and all open about the same amount?

 

[smokingcrater]

yes, you are probably out of sync, but don't sync by visually looking at them. A couple bucks worth of tubing and some red transmission fluid is all you need. Once you use that method, you will notice how sensitive it is to syncing, it takes a VERY small turn of the screw to move the fluid column quite a bit!

(btw, syncing only really affects the lower end of the throttle, especially idle. At WOT sync doesn't matter... The needle is pulled all the way out of the jet, and there butterflies will all be open)

 

[grizztracks]

Carb sync is the process of adjusting the carb's throttle plate openings individually so that all cylinders are running approximately the same amount of vacuum. The Yamaha 4 stroke engines have one preset carb that has no adjustment (stator side carb) so you adjust the others to match the preset. I always sync the carbs after cleaning and periodically as general maintenance. I normally run a tank or two of gas through the engine at the beginning of each season then do a sync. This will ensure that the engine has fresh gas in the system. After syncing, reset the idle to 1400-1500 rpm's. I've found that to high of an idle will cause a delay in rpm's returning to an idle when you let off the throttle.

Carb Sync Tool and Procedure

 

[rapidroy5858]

thanks

Thanks for the responses Iwill be doing a cleaning..right now I am just trying a seafoam treatment but I am figuring I'll pull carbs..I did see the set up with tubing and trans fluid..will likely go that route

 

[thobkirk]

Sorry to but in but I am attempting to sync my warrior carbs also. if I am reading this right I connect the tool to the carburetor on the oil tank side and sync the rest to it. do you leave the vacuum line off of that carburetor connected to the tee the whole time?

 

[smokingcrater]

Correct, you keep one side of the sync tool on the non-adjustable carb, and sync every other carb to it. You can do it without a T if you just juggle the lines that go to the fuel pumps.

 

[grizztracks]

I like to keep the fuel pump connected to it's proper location during the sync procedure. If the carb is capped with no vacuum line then use the cap to plug the tee. Replace all vacuum hoses to their proper locations when you move to the next cylinder.

 

[smokingcrater]

I like to keep the fuel pump connected to it's proper location during the sync procedure. If the carb is capped with no vacuum line then use the cap to plug the tee. Replace all vacuum hoses to their proper locations when you move to the next cylinder.

You have me thinking now... Have you tried it both ways? I'm curious of moving the fuel pump hoses makes a difference or not... hmmm

 

[grizztracks]

Not sure if will make that big of a difference but I like to keep it as close to the way it was designed to run when syncing carbs.

 

[rxrider]

I have the Morgan Carb Sync Tool, it will measure all 4 cylinders at one.
Run the engine up to temp and set idle at 1400-1500 rmps. Adjust the center screw first, #2 will adjust to #3, them #3 to #¤4, them #2 to #1

 

[grashoper]

I tried the fluid gauges first and had no luck. I found the sync was so far off, and even starting off with a predetermined position on the adjustments (found in the service manual), the vacuum was so far off i had issues with the fluid coming within a couple inches from getting sucked into the carbs many times... so I elected to build a set of analogue gauges and had fantastic success. I also elected to keep the vacuum/fuel circuit fully intact while making adjustments. The fuel pump may not use much vacuum to operate, but... Given how sensitive these can be, I wanted to have everything the way it would be running without the gauges attached.

EDIT: I should add, that when I built the fluid ones, I never had any adjustable valves in-line (which will eliminate the pulsating, and can be found at pet supply store in the aquarium section) and did have them inline with the analogue set. I would assume if u tried using them with the fluid set, it would make a big difference.

EDIT #2: oh yeah, one more thing, the configuration u see the fluid guages in, is not the origional setup. All lines were originally all tied together, but removed the t's to see if it would help at the time of testing.

If you click on each picture, you will see a fullsize/high res. picture.

http://www.ty4stroke.com/files/20131027_072415_195.jpg


http://www.ty4stroke.com/files/20131027_081927_145.jpg


http://www.ty4stroke.com/files/20131027_075853_151.jpg

 

[rxrider]

Great tool you've built

 

[grashoper]

Great tool you've built

Thank you.. You know, I never really realized just how important, and sensitive these 4 carb. engines are to synchronization and how much of a difference it really makes, especially in idle and throttle responce off the line. It was truly amazing. Maybe because mine was so far out, but regardless.....I think it's important to do the procedure often. Min. one per season. If i remember, I'll do a video once we get closer to winter to demonstrate.

 

[rxrider]

right on grashoper

 

[smokingcrater]

So have you tried hooking the fluid gauge back up after getting it in the neighborhood with the mechanical gauges? The fluid method is MUCH more sensitive, as you found out (almost sucking fluid in), and will also be less prone to a gauge slightly out of calibration with the rest.

(also, on your fluid gauge, you can't take the 4 ends of 2 tubes and connect them to the 4 carb vacuum ports. You need 4 individual pieces of tubing, one end connected to a common 'ground' rail, and the other going to the carbs. 2 pieces of tubing just means you get carb 1 and 2 synced to each other, and 3 and 4, there is no sync outside of the 2 groups. (my apologies if you did that, the pic looks like 2 pieces of tubing though). The alternative is to use 1 loop of tubing, and just keep one end on the reference carb and never move it. Sync all the carbs to that one.)