flow bench for bench syncing

has anyone ever done this? I had the uni-syn from my auto repair days and thought why not give it a try. it worked pretty well with my little shop vac. I think I will give it a try with my large shop vac and see if there is any difference.


flow bench by bmonkey36, on Flickr

it will be interesting to see if they need any adjustment after I get them installed.

FU

 

They will.

The individual cylinders in your motor (any motor for that matter, especially one with any miles on it) will have slight variations in vacuum from one to the next. Especially once fully warmed up.

You'll still need to do a running vac sync when they're on the motor. That being said, I'm sure they're closer now than it would be possible to get them statically (a traditional bench sync.)

 

I would wonder if the Asymmetry of your layout would produce a progressive result. That is, the carb furthest from the vac would require a greater opening at the butterfly to get the same air through the longer/smaller PVC restriction. Idle speculation. HA!

I used to have one of those gadgets forever ago. Worked great on my little old '70 CB175. I miss that bike.

Like Fitz said, I bet it still does better that the conventional method.

I'd sure be curious to hear if your running synch proves it to be good.

 

I gave the asymmetry idea a little thought, but I could not easily come up with an assembly that allowed me to pull the air from the center. I am fairly certain that at idle (with the butterflies closed) the idea is moot. but if I open the throttles, only the first slide will move at all.

I am looking forward to getting the carbs on the bike to see how it all worked out myself.

FU

 

And if it won't fire up, go back and do it the way the legion of engineers that designed it told us to.

You already know that once the butterflies are opened the minute difference between the flows based on location is enough to throw it off.

Also be sure that the bike is 100% warmed up; like 20-mile ride warmed up. Not only does the motor itself change "characteristics" once at op temp, so do the carbs. You're not flow syncing them hot.

I'm very interested to see how this works. Or to what degree it does or doesn't. Good idea, good work; I'm not criticizing at all, I'm playing "devils advocate" which is necessary in any truly scientific experiment. Right now the temperature differences and "offset flow" are looming large as differences to the real world that may or may not help or hinder. Or they may not matter.

I'm staying tuned.

 

thanks fitz. I always appreciate your input. thanks for being there. after my last post earlier, I had a brainstorm (brain fart) about a way to plumb a 4 into 2 into 1 manifold that would be more even in terms of vacuum at each carb. stay tuned...

FU

 

Waste of time, you have to sync' the carbs to the jugs, endof.

 

Wiz, this is all about improving the "bench sync." 'Tis a bit much to go through since they still have to be synced on a warmed up, running motor.

 

edzakery

 

I don't think the assymmetry of the PVC adapter will matter at all.
The opening at the butterfly is a tiny fraction of the shop-vac's capacity.

 

one other side benefit of this apparatus is that it also holds the carbs for float level setting. it can easily be shimmed to make the carbs level.

FU

 

here is the flow bench 2.0...


421 by bmonkey36, on Flickr

it makes a huge difference with an open throttle and the larger shop vac. I can get all 4 slides to rise equally.

FU

 

This just gets more interesting. Definitely curious to see how dialed you are already when you do a running, on-the-bike synch. Where in the NW are you? I'm up in Bellingham.

 

thanks, I am in burien (south seattle). we have some friends in bellingham.

FU

 

did the guy in the plumbing department offer his expert advice ?

 

what guy in the plumbing department? those guys are as rare as hens teeth at the big box stores.

FU

 

I'll bet it would work even better yet if you "tee" #2 and #3 together in the middle there so you have one long manifold fed from both ends.

 

here is a video, because everyone loves watching videos.

http://youtu.be/uNxunboywTs

CN

 

Nice video. What's in the crock-pot; lunch?

 

As Fitz pointed out, it really needs to be sync'ed on the bike when warmed up. I don't seem much more advantage on this as opposed to manual bench sync. The idea of syncing them on the bike, as Fitz said, is to take account the imbalances between each cylinder. One cylinder may have less compression thereby draw air/fuel due to less vacuum then the others. Could be due problem with the rings or the valves (maybe too tight) on that cylinder. So it won't run as efficient as the others. That is why you (first make sure the valves are in tolerance) compensate by syncing the carbs afterwards to allow more air in that cylinder to compensate for the weaker vacuum draw. I'm not an engineer, just what I have learned from others along the way. All you are doing with your shop vac is balancing the carbs to themselves and not your engine.

 

I see another advantage, that you verify that the "sliders" are reacting the same.

But after watching the video and seeing your neat little gadget, no offense, but you're not doing an idle sync. You'll need to install 4 "nipples" just like the intakes have, shut your throttles down to 0.015, and hook-up your choice of sync tool (mine is the 4-tube water Manometer)

Good video BTW.

 

Cyclenoob start with #3 carb the adjustment for it , the idle speed adjuster, effects all the rest off the carbs. You can adjust the tool to get the float exactly on one of the lines by turning the disk in the center of the tool (I think blocking off the other carbs and doing one at a time would work better)

 

you know I didn't even think of that. this seems to work well, so I won't be building another one.

krud kutter (phosphoric acid) I boiled the carbs super clean with it.

yes, I know this. the reason for this apparatus is to get them synced close enough to get the bike to idle and hopefully not require much readjustment if any. as well as hold them for wet setting the floats and it also allows me to test the function of the slides.

ding! ding! ding! yes that is a side benefit. if only I could pull enough air to get the slides to fully open.

I disagree completely. the uni-syn is measuring the air flow according to the idle adjustment. I could install vacuum nipples and use a different type of sync tool, but I would be accomplishing the same thing.

and lastly, thanks.

thanks waldo. I had previously run throught the procedure with flow bench 1.0, so it was already close. in the end they are all the same. and I am fully aware how to adjust the tool. I used it on Volkswagens and Datsun's for 15 years.

FU

 

NOOB I figured if you knew how to use the tool correctly you would have, my bad!!

 

wow! I can't believe it has been a whole year since I synced this set of carbs. I finally installed them and I am happy to say that I did not have to adjust the sync between any of the carbs. the fuel mixture, now that is another thing all together and not one I can build a cheap apparatus to measure. that being said, all I had to do was back off the idle speed screw, (the big finger wheel in the middle of the rack) and enrichen the mixture some (set at 2.5, probably out at 3-4 turns now) just tuned by ear. I will have to break out the color tune and check, but I think I got it pretty close.

edit; I should note that I did not use my yics block off tool when checking the sync. I may have to put it in and run through the sync process, just for fun.



FU

 

cool! thanks for the update

 

Interesting alternative to the bench sync. If you didn't have to fiddle at all with the running sync settings that equals success the way it looks to me. It's good to see that your not stuck thinking that the FSM is like the Bible.
Sorry Bible thumpers....

 

just a complicated way of doing something simple if you happen to have the flow tool sure i like gadgets.

 

a whole bunch of the air flow testers on ebay for 20$

 

I appreciate and respect your opinion.
The above is mine regarding this topic.