Topic: DIY carb sync tool- what to use for fluid?

[kippstakes]

I am putting together a simple carb synchronizing tool out of PVC tubing and would like to know what others have successfully used for fluid in the past. I have heard oil, died h2o, transmission fluid-  quite a few different opinions out there, but which is ideal?  I am leaning toward trans fluid, tho I'm concerned the PVC tubing might not be resistant enough to it.

Ideas?

Thanks

[jerry h]

My honest opinion... don't waste your time.    I did the whole build your own thing, spent a few stubborn weeks trying to get the stupid thing to work correctly, and in the end, put the whole thing in the trash.  I bought a Morgan carb tune ( or any of the other commercial units are fine too) and can sync them up in a few minutes.  Spend your limited available free time riding, rather than trying to get the bubbles to settle down, or futzing with regulators to get a semi intelligent reading on the home made unit.

You will probably get more opinions on this, but I offer what I now wish someone would have told me back when I had the idea to build my own.

[Garage_guy_chris]

I used regular dextron III ATF fluid. I also used small 0.030" Mig welding tips as restrictors/regulators  and they keep things very manageable yet still react plenty fast. This one is only setup for a twin cylinder but i plan on making a 4cylinder sync in the same way before too long

[kippstakes]

Perfect. Looks nice- mine is a bit less refined, but should still serve equally well. I'll go ahead w ATF. Thank you.

[eprovenzano]

I too need to build one...  What are you using as a connector to the carbs?  Can yo supply some pics and or details...

thanks

[ofreen]

but which is ideal? 

Mercury.  Yeah, I know.  Mercury is toxic.  The mercury in my old PCCC tool has killed me several times.

[eigenvector]

I'm of Jerry's mind.  I had a tubing one that I tried a while ago.  All it did was suck, in more ways than one, and finally got in the way stored in the shop, leaked oil on the flooring, and generally made a nuisance of itself.

I bench synced the carbs when I last rebuilt them.  I really don't see the value in syncing them - bike runs fine without it.

[kippstakes]

It's about finished at this point, and didn't set me back much, so it's worth giving a shot.
I'll post pics if I get a chance.

These are the adapters I will be using. They should fit well in the 1/4'' ID pvc tubing I have used. We'll see, have to get the bike back together first.

http://www.ebay.com/itm/NEW-MOTION-PRO-CARBURETOR-CARB-5-MM-ADAPTER-TUNER-SYNCHRONIZER-SYNC-/251917208877?hash=item3aa76f8d2d&vxp=mtr

[Whaleman]

I am sorry but anyone who thinks the carbs on a CB750 do not need to be synced has never heard the smoothness of a professionally synced bike. Yes, it will run bench synced. Dan

[bluefields]

I have to agree, the tubing set up was a total pain. Took up a lot of space and all I accomplished was sucking a bunch of at ffluid into my motor. Admittedly, operator error. All last year I ran the bike on just a bench sync, and it ran fine, but this time I'm going to try something else. Something like this set up:

[ekpent]

The exchange rate is very favorable right now for buying the Carbtune from England. It is cheaper right now than when I bought one around 4 years ago.

[kmb69]

I am sorry but anyone who thinks the carbs on a CB750 do not need to be synced has never heard the smoothness of a professionally synced bike. Yes, it will run bench synced. Dan

DITTO. They run unquestionably smoother and quieter unless you ACCIDENTALLY (what's the odds?) get a bench sync perfect.
This goes right along with Mike's post about using a dwell meter and strobe light to get the timing precise.
I have found that using 4 u-tube glass manometers with mercury is just about as good as it gets.
The difference between using static settings and a precision tuned bike is quite noticeable.
To each his own but you don't know what you are missing.

[70CB750]

Here is one for 50 bucks and shipping:

http://www.ebay.com/itm/PARTS-UNLIMITED-CARBURETOR-SYNCHRONIZER-NEW-/231551263013?hash=item35e987e125&vxp=mtr

[anparkinson]

If you set them up on the bench correctly you don't need to do this. I Adjusted 1, 3 and 4 butterflies to number 2 with a feeler gauge before putting the carbs on the bike. When it was running I used a set of balance gauges and no adjustments at all were necessary. It was spot on.

[Whaleman]

If you were perfect with feeler gauges you just got lucky. The syncing is not about getting the slides or butterflies all the same but getting the vaccume from each cylinder the same. Some cylinders will have small differences in compression ratio, casting flash in the intake, float height and many other differences between the cylinders. A perfectly synced set of carbs will measure a tad different with feeler gauges to make up for these differences in the cylinder health. The bench sync is just so it will start to be able to sync. Dan

[chewbacca5000]

If you set them up on the bench correctly you don't need to do this. I Adjusted 1, 3 and 4 butterflies to number 2 with a feeler gauge before putting the carbs on the bike. When it was running I used a set of balance gauges and no adjustments at all were necessary. It was spot on.

I do the same thing and it is usually very close.  If I buy I set I think I will go with these.

http://www.ebay.com/itm/Vacuum-Carburetor-Synchronizer-carb-sync-Gauge-CB-KZ-GS-XS-550-650-750-850-900-/301178905682?hash=item461fa96452&item=301178905682&vxp=mtr

[Whaleman]

Wow Chew that is a very professional set. I just have my 20 year old cheap set. Dan

[kippstakes]

Yup, after trying the tubes and board setup I think I will opt for the tubes and bottles approach. Cyl 1 had a strong enough vacuum over the others that it almost got a mouth/bore-ful of ATF. The bottle/stopper config. will eliminate that possibility and will an additional cost of four stoppers and gatorade bottles.

[Deltarider]

The bench sync is just so it will start to be able to sync.

My experience is different. After a bench sync (my way) my carbs always proofed to be within 2cm Hg of eachother. That's well within factory specs and the engine runs silksmooth. This has happened at least three times the last fifteen year so I would not call that 'luck'. As a matter of fact, my set of vacuum meters is in a friends workshop now. Then there's also the human ear. Another thing from experience: as long as I don't tinker with the syncscrews or needles the carbs will stay perfectly synced.
BTW, many can hear when carbs are possibly out of sync. Finally I often wonder how Honda synced the carbs on the production line.

[Bailgang]

Finally I often wonder how Honda synced the carbs on the production line.

More than likely the dealership did. I'm not arguing your thoughts on bench syncing but my oldest brother worked for a Kawasaki dealership in the early 70's, he told me that any time a new bike arrived one of the first things they would do before placing the bike in the showroom was do a vac sync on the carbs.

[mitch500]

I built mine in about 2 hours, cost $20. I bought the motion pro 5mm sync adaptors for $12 from my dealer.  I used straight 50w  green oil from my harley, I had no pulsing issues and was easy to sync. I over filled the synchronizer with oil a bit but still worked great.

[Deltarider]

More than likely the dealership did. I'm not arguing your thoughts on bench syncing but my oldest brother worked for a Kawasaki dealership in the early 70's, he told me that any time a new bike arrived one of the first things they would do before placing the bike in the showroom was do a vac sync on the carbs.

Yes, this is well plausible and a practice very likely for all brands.

[Redline it]

I don't want to sound anti establishment, but struggled over 20 times of caps on and caps off, to adjust fuel levels in what finally amounted to "very strange" reactions. The 19 time I blew out the mains backwards and needle jets, again like the first time. And instead of matching fuel inlet needles to jets, and floats to bowls, I mixed them up and randomly selected out of a pile,  I was slightly on the verge of quitting, to the point of "if it didn't work, by overflowing fuel, or none at all, I was gonna ride it anyways like it was." I guessed at the final float bowl height by eyeballing 3 carb changes. The final thing was either bench sync them or put them on. One Carb was from another rack, what I did, is not impressive, but surprising to me. I eyeballed 2 greatly out of range by light coming through the opening carbs to just be close to the same as 2 others. The one carb slide at topped out open is just alittle off, and I was done. Put them on and it started smoother than it has in 35 years, it warmed up, I made 2 carburetor mixture screw adjustments like two 1/4 turns and it responded like I've never seen before. And now there's no gas leaks, no lean cylinders, no vacuum leaks. cb400f has a mind of it's own.