syncing carbs

[shultz_1978]

http://www.youtube.com/watch?v=mDb7cUWuGts

Don't know if this is where they should be, But they are all running pretty much the same.

If anyone knows where they should be on the gauges? Please let me know. If it is all good the way it is. Thanks a million to everyone that gave me pointers as I started rebuilding my carbs. Joining this forum has been the best help to me for every thing that comes up with these older bikes and saved me money along the way.

Thanks to everyone on this forum. I have always been one of those guys that hates to give my money to some one for doing some thing that with a little time and info . I can do it myself.

Thanks again

[seestheday]

Looks to me like you did a good job bench syncing your carbs.

[shultz_1978]

That is what I am hoping Seetheday. The bike is running really well. Just thought I would get the gauge to see if they were off. What is one more tool in the garage?

[LukeM]

Did your kit come with 4 little plastic restrictor thingies?  What these will do is smooth out the pulses of vacuum coming from your carb bank. They go in the line between the hose and the gauge.

OK, from what I saw on your video, the swing on the needles looks about the same.  They will move the most at idle, and gradually smooth out as you increase the idle.  The goal is to have the same reading across all 4 gauges at idle, part throttle, and half throttle.  You can try it at full throttle, but if you just run it up and get off of it, that should be sufficient. You may find that some RPM ranges will give you a more sync'd reading than others.  Rarely will you get a perfect sync at different RPM settings.  Try and get the "error" the same across the board.  This will give you the best overall performance.

Also, don't forget to point a fan at your engine cylinder head, as it's not healthy to run up the engine without adequate cooling.

And my compliments on your bench sync.  The engine started quickly, and seemed to have a good idle.
Luke M

[shultz_1978]

Thanks Luke it did come with the little restrictor thingies. I just did not use them. I will try in the next few days and see what the gauges do at different RPM's. Thanks for the tip on the fan.

I don't remember who told me to bench sync them, But I just use the shank of a small drill bit.

[shinyribs]

The FSM calls for 20-22 cm/Hg-centimeters of mercury. On one of my vacuum gauges that compares to about 8 in/Hg-inches of mercury





Did your kit come with 4 little valves? If you put them in line to each gauge you can screw them in (closed) and it will lessen the blow of the vacuum pulses giving you a nearly perfectly still needle. Helps a bunch when you're trying to fine tune those puppies. You can also kink the hoses and apply pressure with a cable tie until they smooth out if you don't have the valves.

Regardless,that bike sounds killer dude!!!!

[trapper]

Looks like you're right there. There's no set place they should be. Kinda varies between bikes. But on most inline 4's the number 2 carb will have no adjustment (as I'm sure you noticed) so ya pretty much sync 'em to what the number 2 carb wants to be at.

[chickenstrips]

1. The restrictors will stabilize the vacuum in the gauges and cause the needles to jump around much less. Just don't close the restrictors too much, the needles should vibrate a bit.

2. Don't be concerned about the position of the needle in the gauge. As long as your bike idles at the correct idle speed and each needle is equal in relation to one-another, there's little else to worry about.

3. If you're concerned about low vacuum, check your engine compression. Warm up the engine, unplug all of the spark plugs, connect the tester and compare the PSI to your manual's specs.

4. If your carbs won't sync or you notice some surging/bogging, you may have a vacuum leak or incorrect fuel/air ratio. More on this below.

First, check for vacuum leak:
With the engine idling around recommended idle speed, take a can of carb cleaner or other combustible solvent. Spray it onto one side of one of your boots. Wait approximately 1-minute. If your motor doesn't react differently, spray the other side of that same boot. Then repeat for the other boot on the same carb and continue with each individual carburetor.
IF the engine surges when you spray a boot, that boot is leaking. Don't stop there, be sure you get through the entire procedure and note which ones are an issue. I always recommend replacing all boots at the same interval.

Set air/fuel mix:
Turn the mixture screw on each cylinder all the way in until lightly seated. Then, turn each screw out an equal number of turns, between 2-3 1/2. Check your manual for proper bench setting. Then, with the engine warm, turn the mixture screw on #2 cylinder out or in until you find the highest idle you can achieve with this one adjustment. Once the idle raises, turn the large idle screw out until you return to just BELOW regular idle, the screw that is in the center and adjusts the entire carb set. Repeat for other cylinders, always turning the large idle screw down between adjustments.

Proper sync:
Adjust the large idle adjustment screw (the one that adjusts all carbs) such that your bike maintains close to 1000-1100 RPM (general idle, yours may be different. Check manual). Then, with a manometer, match #1 to #2. Then match #4 to #3 (regardless of where #3 is) and finally match #3 to #2. Set your idle screw one last time.

Not trying to be demeaning or condescending, but you never know who else will find this thread

I'll be posting my compact manometer here once I get the corks for it. Fits in most small tool kits and easy to set-up and store.

Edit: Wow, I made some errors clarifying. Last time I post after spending so many hours exhausting myself on a bike.

[jrodrgz1]

Hey Chickestrips,
thank you for that insight that really helps alot.
I am new to this forum and already found alot of good info.

[chickenstrips]

Sorry, but you should take a look at the edit. I used some terms that could be confusing or ambiguous and went back to clarify. Darn.

[FastCletus]

The accent on the video is funny to me.  Of course I am from the south so I have no room to talk.