Topic: Carb sync

[Gordon]

While it is possible, to do a good job would be much more difficult than using a four gauge set-up.  The reason I say this is because (in my experience at least) when balancing the carbs, the slightest adjustment to one carbs affect the vacuum reading on each of the other carbs, so there's a lot of back and forth adjusting.  That's a relatively easy task with all the carbs attached to a gauge at the same time, but with only two, you would have to keep moving the gauges back and forth between carbs after each adjustment to see how it affected the other carbs. 

[JonnyHonda]

If you are interested in giving it a try, I found what I was looking for. It's actually for a product called TwinMax, but here are the procedures for more than two cylinders. I agree with the previous post only because of my love/hate relationship with my carbs, doing all four at once was bad enough.

Is that what this product is then, http://cgi.ebay.co.uk/NEW-Motorcycle-Carb-Balancer-Synchroniser-Vacuum-Gauge_W0QQitemZ8045571204QQcategoryZ25623QQrdZ1QQcmdZViewItem

[Jonesy]

It might be OK for initial balancing, as most instructions say to balance the left 2 carbs and the right 2 carbs together, then bring the right and left sides together. But, as Gordon said, you change one carb and it impacts the other 3... Very difficult and probably couldn't get it as close as with 4 gauges.

[JonnyHonda]

Well it seems the best bet is to sync all four together, I'll get a four gauge set and let you all know how I get on. I was trying to save money, I'm up to two CB750's now, and no doubt if another unfinished I'll buy it.

[Bob Wessner]

Is that what this product is then,..

No, the Twinmax is described as "An electronic differential depression gauge." Below is an image. It costs almost $90, way more than you would pay for a four vacuum gauge set-up and almost as much as a Carbtune. I was only referring to the procedures, not the product itself.

[Jay B]

Actually, I think this can be done. I seem to recall having read about someone who did this using gauges that he used primarily for a BMW. Did just what you are suggesting, started with two and always kept one, the same one, as the reference carb. I'll see if I can relocate it.

I'd be the BMW guy Bob's talking about. I use the twinmax and use one carb, usually number 2 as my baseline carb and just set the other three to that. I guess it's worked fine for me.

[Vatch]

I balanced mine with a homemade water manometer, 1 carb at a time against the unadjustable carb.  Yeah, I had to go back and recheck them all a second time after the initial pass, but they all read within 1 cm on the water column, which is pretty close considering the density of water relative to mercury.  The whole process was still only about 30 min, and the manometer cost about $7 US to build.  I plan to build a 4 way manometer for the future.

[DrMark]

Saw this item on EBAY....it looks and sounds so simple. Has anyone here tried it? Here's the EBAY link for more info: http://cgi.ebay.com/NEW-Motorcycle-Carb-Balancer-Synchroniser-Vacuum-Gauge_W0QQitemZ8060066688QQcategoryZ25623QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[Lumbee]

...sounds like it could have merit, but I'd have to see it in action before I plunk down $30 for it.

[Dusthawk]

Tell you what, I just ordered it so when it gets here, I'll give it a shot then let everyone here know.

Peace and Long Rides

Jeff

[Gordon]

Any carb synchronizer that does not allow you to connect (and thus adjust) all four carbs at the same time will end up being a real pain in the ass.  This one only lets you do two at once. 

[Bodi]

This would work, it's just a smaller version of the home-made water manometer that compares 2 carbs at a time.
Doing a sync by comparing 2 carbs at a time is a major pain in the butt but it can be done.
I invested in the Carbtune after trying with the water manometer and getting frustrated, I had a mercury carbstix years ago but misplaced it in a move. Doing the sync when you can see all 4 carbs takes about 10 minutes, with 2 at a time it took forever and still wasn't quite right.

[MRieck]

Seems like it would work. The pain is you can only do 2 carbs at a time which mean you have to do the first set, remove the adaptors and do the second set and remove to do #2 and #3. All on a real hot engine. I'd rather do it in one shot.

[Lumbee]

...I was lucky, a coworker let me use his Carbtune II and it truly is the "shizzle".  Tried to buy it off him, but he says to just nag him when I need to use it..   

[Tim.]

This also doesn't provide a measure of the vacuum for each carb.  While it might work for balancing two carbs, it won't tell you if you have other problems like low-vacuum due to leaks etc.

This won't replace mercury tubes or other sync tools.  Might augment, but I don't see the difference between visually confirming two balls are aligned (insert joke here) or comparing levels of mercury in tubes or comparing position of needles on dials.

[Green550F]

I found these vacume guages pretty cheap. Is it likely they'd work to make a syncronizer guage set?

http://www.plumbersurplus.com/ProductDetail.aspx?Prod=12440&Cat=926

I've made a set of barbs to connect to the intake manifolds.
It was a simple design:
  1) drilled 5/32" holes in some 10-32x.75" screws (use phillips to help center the start point of the drill)
  2) solder nuts in place about 1/3 from the bottom
  3) grind off the screw head
  4) using JB Weld fill in the threads between the nut and where the head was

Fish tank tubing (1/8") fit's over the #10 screw nicely.
Now it's either make a water manometer or try the guages...

[prsman23@hotmail.c]

i've got no clue, but it would be interesting to see if anyone does know if that would do the trick or not!

[brimar6]

I would say NO, not for the precision you would need. I say this because the scale of the guage is to large. A sync job with those guages would put you the ballpark, but it would not be accurate at all. If you could find a vacuum guage with around 50 at the max. end of the scale then you'll be in business. I'll bet if you add up all your time and effort it would'nt be any more expensive to just buy a set. But believe me I understand that "do it yourself" thing. Thats why we all own these little money pits.

[csendker]

I think the picture of the gauge is a generic pressure gauge and not the actual item.  The description is: 2" Dial, 30" Vacuum  while the pic is 200 psi.  Is 30" sufficient?  And what about the accuracy: Accuracy: +/- 3%-2%-3% accuracy (ANSI/ASME Grade B)

I've never synch'd carbs, so I don't know what range or accuracy would do it; for these, at 30", 3% is 0.9".

[WHALEMAN]

I just looked at my gauges and the full scale is 30" vacuume. I do not know if my gauges are 30" vacuume of water or murcury. I know plumbers use water column. My bike seems to want to idle at about 12" on my gauges.

[crazypj]

They not only will work they will work well. I have a set of genuine Honda gauges which are marked in 5cm intervals to -75cm Hg which works out at 29. 21"
The 'normal' setting is around 18~25cm. at idle. The only reservation I would have is geting a matched set, its easy enough to check though, just connect gauges one at a time to a single cylinder, they should all read the same. Honda's have the middle two gauges set slightly lower than he outeres when your actually using them.
 I had to price replacements when I shipped them to US from Britain. Genuine Honda were around $600.00 in 1998 and only available to dealers ( at least in Britain)
Use the correct fittings though, you can get them from K&L Supplies through dealers. They should be 5mm and are not too expensive, I'll find you the part number if you need it
PJ

[brimar6]

Ayah, csendker & crazypj your right, they will work, as long as they are what the description claims.  I just took a quick look at the pic last night. Maybe I should have gone to bed instead.

[Green550F]

Thanks! I'm going to rder them and give it a try!
As for the fittings, I found 10-32 seems to fit perfectly.
I wonder how close that is to 5mm? I also am using rubber washers to ensure a good seal on the fittings.

[Clyde]

Years ago I made up a set from similar gauges and they worked fine for a few years. I mounted them on a stand and set them up to do my 750's
As pointed out they usually read about 200mm/20cm/8inches when you are synching a carb set.
The main problem is to dampen out the engine pulses as the needles will shake to the point of being unreadable. I used some brass tubing and filled it full of soft solder then drilled a small hole up the middle to act as a restrictor. This was placed as close to the engine as possible.
This WAS NOT entirely successful so I then used some clamps as used in fish aquariums for restricting air flow- these worked fine and you can adjust them so that the gauges just pulse slightly. Too much damping will make them useless.
The only other problem was that they can easily go out of calibration, by knocking/bumping or just opening the valves too much due to the extreme fluctuation.
I made up a T-piece and checked each gauge against the No 1 gauge before I started a carb synch. Actual readings are not important, but the aim is to make them the same.
Regds Clyde

[Raul CB750K1]

I've read in other forums about using heating or plumbing gauges for syncing bikes, and all the responses has been afirmative. I'm worried about the calibration and needle bouncing, so I will probably get me a mercury tuner or do my own with coloured water.


Raul