Topic: 77 carb sync walk through

[dgilling]

Hey guys,

I've looked around a little and found some for earlier years but does anybody have a 1977 750k carb sync walk through?  i've done it before but don't really remember how i did it.  I don't have a vacuum gauge that has four gauges on it. i have a single gauge and have to go from one carb to the other.  the tool looks like this http://members.aol.com/stepdown53/Unisync.jpg

I'll also take any other carb adjusting tips you want to give me on setting up the carbs after a full rebuild.

thanks

[bryanj]

FIRST do ALL the other tune up bits, Tappets, points gap, timing, cam chain oil etc. Them check the carbs.

Having tried with one gauge in the past I would say dont as as soon as you adjust one the other three alter

[Gordon]

The first step would be to ditch the uni-syn you have there (unless you have an old VW you can use it on), and get a 4-gauge synchronizer. 

Like Bryan said, any adjustment to one carb will affect the other three, and you'll be switching back and forth between all the carbs until you either run out of gas or the engine overheats. 

[dgilling]

where is the best place to get a 4 gauge unit?  What brand? 

And all the other maintenance has been done and now i'm on the carbs after my full carb rebuild.

How about a walk through with the four gauge unit?  How does that go on the 77?

[eldar]

Well a lot of people are going to point you to the morgan carbtune. It is agood but it is also about 100 or so last I knew.

You can do very good though with a set of vacuum gauges though that can be had for around 45 clams or so. Check online and see what you find. You can also get mercury sticks which work good to but having used them, I think I will get the vacuum gauges some time.

[dgilling]

just some regular vacuum gauges that are sold at autozone or something?

[eldar]

yup but get a 4 gauge set.

[75750SS]

Here's some options.

http://www.z1enterprises.com/catalog.aspx?pid=CB750F-1975-CF0

[eldar]

Those z1 are expensive!  I was thinking something more like this. http://www.crc2onlinecatalog.com/Index_Main_Frame.htm

More than adequate for our needs.

[cb750k7]

How about these units?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220200096290&ssPageName=MERC_VI_RSCKCK_Pr12_PcY_BIN_Stores_IT&refitem=220199743296&itemcount=12&refwidgetloc=active_view_item&usedrule1=StoreCatToStoreCat&refwidgettype=cross_promot_widget&_trksid=p284.m184&_trkparms=algo%3DDR%26its%3DS%252BI%252BSS%252BSD%26itu%3DSD%252BISS%252BUCI%252BSI%26otn%3D12

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=330211242187&ssPageName=MERC_VI_RSCKCK_Pr12_PcY_BIN_Stores_IT&refitem=220199743296&itemcount=12&refwidgetloc=active_view_item&usedrule1=StoreCatToStoreCat&refwidgettype=cross_promot_widget&_trksid=p284.m184&_trkparms=algo%3DDR%26its%3DS%252BI%252BSS%252BSD%26itu%3DSD%252BISS%252BUCI%252BSI%26otn%3D12

Will they do the job?

Cheers

Jona

[UnCrash]

Those are D-Lux...

For the cheaper version which I have used with success ---->
http://cgi.ebay.com/ebaymotors/Carburetor-Synchronizer-carb-sync-Gauge-XS-XJ-1100-EMG_W0QQitemZ320216287221QQcmdZViewItem?hash=item320216287221

[cb750k7]

Those are D-Lux...

For the cheaper version which I have used with success ---->
http://cgi.ebay.com/ebaymotors/Carburetor-Synchronizer-carb-sync-Gauge-XS-XJ-1100-EMG_W0QQitemZ320216287221QQcmdZViewItem?hash=item320216287221

What adapters are needed,  5 MM or 6 MM?  (for keihin on K6)?

Tnx

[eldar]

Pretty sure they are 5mm. It is pretty common to use 5mm.

[BobbyR]

I used the $49 set from z1 and it worked great. It comes with the adapters which scrw right into the carb. What I did was install the adapter into carb 4 since it is easy to get to. I plugged each meter onto that adapter and adjusted the needle on the guage so that I was sure they were reading the same.
Then I installed the adapters to the other carbs and began my synch. # 2 is you referenced carb and has no adjustment. Each carb must read the same as #2. As you move from carb to carb you will see each affects the other, so you move back a forth until all 4 read the same. This is why your single gudge method will drive u nuts.

[eldar]

Hell it drives a person nuts anyways as when you tighten the adjustment nut down, it will throw things off.

[05c50]

I've always used the 4 vacuum gauges with very good results. Some people have questioned the calibration of the gauges compared to the mercury sticks. I have found that if I "T" all 4 gauges together and adjust the calibration before I do the sync, I get better results.

.........Paul

[BobbyR]

I don"t T them I just plug each one into the same carb to calibrate. I am really not inyerested in how many inches of mercury they are pulling, i justr need them all even. i put this job off for years, and it made a great deal of difference at idle.

[Johnie]

I love the Morgan carbtune.  But go with what you can afford.  Any quailty 4  gauge system will be better than the 1 reading.  I think you have to at least get something the guys here recommend.  You don't want to sync with a piece of junk or the bike will run like junk. Below is a picture of the Morgan.

[BobbyR]

I don;t like the mercury sticks since if you rev the bike you can suck the mercury into the motor. Not a big deal for the motor, but where are you gonna get more mercury? Sometimes when synching you may want to goose it to see where they settle when the motor come back down to idle. The gauges are cheaper also. 

[dgilling]

this maybe a stupid question but i'm not exactly seeing how you connect the four hoses of each guage to the carburators, how is this done? 

so between the Z1, D-Lux, etc... where can i go pick these up locally? or do i have to order them?

[Johnie]

Remove the vacuum port screw in each carb that I am pointing to in the picture below.  Insert the brass nipple and connect the hose to it.

[eldar]

That would be the page, matty.

[OldSchool_IsCool]

Could always build your own 

[dgilling]

okay i almost have this all figured out i think.  Check me on this please.

I screw the idle air adjustment screws all the way in then back them out one full turn.  This will bench sync the carbs.

Warm the bike up to normal operating temperature.

Then I obtain my handy dandy 4 vacuum gauges (That i probably have to order from the internet???) and i remove the vacuum port screw that is shown by Johnie above (thanks johnie) and place the nipples from the ends of the hoses in accordingly to each carb.  Then I take the gas tank off to get a better shot at the top of the carbs with a longer gas hose still hooked up to the carbs.  I remove the top of the carbs and loosen all the lock nuts on each carb. Question, do i leave the #2 carb where its at and use it as my base or do i set it to have maximum vacuum and then that is my base?  Then with a flat head sync carbs 1, 3, and 4 with number 2, and tighten down the lock nuts when finished.

Next question is what do i do if the bike is still running to rich or lean? how do i tell?

Then i get on the bike and ride off in a blaze of glory with her running better then ever!

[Gordon]

I screw the idle air adjustment screws all the way in then back them out one full turn.  This will bench sync the carbs.

Where did you get that info?
The idle mixture screws have no effect on synching the carbs.

Next question is what do i do if the bike is still running to rich or lean? how do i tell?

Syching the carbs will not solve a rich or lean running condition.  If it's running rich before the synch, it will still be running rich after.

You seem to be confusing air/fuel mixture settings with carb synchronizing.