Keihin CR 29 sync problem

[theoldbluehouse]

Hello guys,
I'm new to the forum so any help is greatly appreciated!
I have a 1972 CB, I've been trying to sync the carbs with the Edelbrook unysync tool and cannot get it right.
The needle goes up almost identical on carb #1 and #4, outter ones, but the others are almost dead. It seems like there is no vacuum on either one. I turn the airscrew in and out and no effect. I have no idea whats going on!
Carb #1 and #4 are half turn out.
Any ideas? thanks

[TOOLS1]

You do not sync the carbs by adjusting the "air" screw. The height of the slides is what needs to be synced between the carbs to produce even vacuum. There should be a means of adjusting the heights of the slides made into the carbs. Most likely under the top caps.  You want to adjust them to the same vacuum at 1000-1200 rpm.
TOOLS

[theoldbluehouse]

TOOLS, thanks for the quick reply.
I've been looking into each carb to see how to adjust the height but no luck. I have the idle-throttle screw that controls idle for all four. I'm gonna dig deeper !
Thanks

[TOOLS1]

There should be one main idle screw that adjusts the idle. That is adjusted after the carbs are synced. However in some cases if the sync adjustments are way off, you might have to make adjustments to the main idle adjuster as you go about syncing the carbs if the idle becomes too high or too low. The "air screws" or in some cases the "fuel screws" are there to adjust the mixture at idle, not the idle it's self. Again, look under the top caps on the carbs. There should be adjustment screws under the caps to adjust the heights of the slides.
TOOLS

[theoldbluehouse]

I think I found the screw that adjusts the valves. Tricky one though, will do the sync tomorrow and see if that helps!
will let you know, thanks!

[theoldbluehouse]

[TOOLS1]

That looks like it. Loosen the locknut, adjust with the screw, and then snug the locknut back up while holding the screw from turning.
TOOLS

[theoldbluehouse]

So after a few hours of trying to align the valves, I think I made it worse than before.
My valves are all off. I tried to carefully adjust fully open and closed but I still don't get good vacuum from the inner carbs! only when I give throttle the slider on the sync tool moves up. I put all back together and now my idle is very high.
I think I don't really get which screw does what, the flat head screw loosens the nut, but it's the lock-nut that actually moves the valve up and down.
I wonder If I have to remove the carbs completely.
Also I don't know how much of an opening the valves need to have at idle.

[TOOLS1]

You adjust the sync with the bike running. However you can get it close with a bench sync using an 1/8 inch drill bit. You stick the drill bit in the rear of the carb until it is under the slide. The you adjust the height of the slide until it just touches the drill bit. The locknut should not make any adjustment to the sync. It should only lock the adjustment screw from moving. Another thought, if you are not getting any vacuum on the middle two carbs, maybe you have bad valves.
TOOLS

[theoldbluehouse]

Tools, you said adjust while the bike is running, does that mean that I can run the bike with the carb tops and pod filters off?
thank you so much for your advice.

[TOOLS1]

Yes! the carb tops are just there to keep crap out of the carbs. You let the engine idle, and adjust each carb to have equal vacuum. If while adjusting the carbs the idle becomes too high or too low, you can compensate with the main idle adjustment knob. When every carb has the same vacuum (7-10 psi) the idle should be 1000-1200 rpm. Also, after each adjustment, you should blip the throttle and then let the engine come back to idle. A lot of times the reading will change after you do this.
TOOLS

[shinyribs]

I'm not trying to nitpick, just wanted to touch on one thing to prevent any possible confusion.

It's not psi you are aiming for, but inches of mercury- in/hg. No offense, Tools. Just trying to avoid any extra confusion for a first time carb synch'er.

BTW, props to you for diving head first in to your carbs. Once you get a handle on it you'll realize it's not a bad job at all. Keep an eye on engine temperature. Turn a box fan on the engine to keep it cool if the synching is taking a long time. If you do this it'll give you a little extra peace of mind while making your adjustments and allow you to work slower and more comfortably.

[theoldbluehouse]

Tools, I'm working on that hopefully I can nail it down this week. shinyribs thanks for your help!

[theoldbluehouse]

Okay, after a few hours of sync and hard work I think I made some progress. I moved the lock-nut and screw carefully and synced one carb at a time! wew! the smallest change made a huge difference and I had to do them a few times. I have the edelbrook unisync and it only has a little plasctic element floating on the meter so I don't know how exact it was. I'll ride the bike tomorrow hopefully everything is good.
Lots of rain around my area!
Thanks guys!

[shinyribs]

Good job!

I tried to find some more in-depth info on the CR Special's, but wow, there is NO info about those carbs anywhere, it seems.

Synching your carbs one at a time ( meaning your tool only measures 1 carb at a time) is haaaaard, repetitive work. If you buy a rack of four gauges , typical to 4 cylinder bikes, you can synch your carbs in about 10-15 minutes, usually. It all depends if yu feel like spending $50-75 on the gauges,though.

[theoldbluehouse]

Actually I did look into buying the four-carb synchronizer but I just didn't know how I would attach it! The Edelbrook goes over the mouth of the carburetor. I don't see a vacuum port to hook up the other sync tool. Well, at least I could not find a way to do it.

[shinyribs]

The little brass tubes pictured with the gauge kit is where you end up hooking the hoses to. There is a port on each carb that is after the slides that they thread in to to give you a vacuum source. Not sure where they are on CR's , but they're on they're somewhere.

[theoldbluehouse]

Actually there isn't a port in the CR's! Unbelievable but true. I have looked all over the net, even the manual and there is no port. I wish I could find a way, because I don't mind spending a little money.
Thanks!

[shinyribs]

You know what? You're exactly right! And yes, I'm sure you knew that, too.

A buddy has a set of CR's on a DOHC Cb and when I asked him about synching he said ''just like stock'', and my brain ceased to think any further about it. Things is, DOHC CB's have vac ports built in to the cylinder head, unlike the SOHC.

Aren't they mounted with some type of aluminum tube adapter to fit them up to the boots? If so, you could drill and tap those for a vac port. Push come to shove, you could probably epoxy threaded pieces of tubing ( maybe even long nuts) in to the rubber boots themselves. Just tossing out ideas, as I don't really know how CR's attach.

[theoldbluehouse]

So far so good, bike idles much better and smoother, but there's a new problem.
It RPM's really high at all gears, it feels rough. I didn't alter anything besides the carbs, once it starts moving I feel that I have to shift earlier than before. I don't know if I'm explaining it correctly, but it's almost like second feels like first, third like second etc.
Could this be a timing issue now? I have the cycle x power arc ignition, that's another beast to deal with.