Morgan carbtune vs vac gauges

[edromero]

Arsenic has been telling me over and over that "vacuum gauges are the worst way to synch carbs in the history of forever". I was reluctant to believe him and spend another 100$ for a new synch tool. But, the vac gauges showed me right on...carbtune arrived today and showed me this:

[TRPUT]

The Carbtune probably tells a more accurate story. However, since you're tuning and have camera in hand, try this ...

Balance the carbs using the Carbtune and take a photo of the result.

Then, swap the Carbtune lines 1-2 / 2-1 and 3-4 / 4-3 and take another photo. If all 4 bars still show even, you have a good balancing tool.

[edromero]

I didn't take an after photo, but I can tell you, they were level all the way across, and running beautifully

[arsenic]

I didn't take an after photo, but I can tell you, they were level all the way across, and running beautifully

Will you please trust that I know what I'm talking about now.

[TRPUT]

I didn't take an after photo, but I can tell you, they were level all the way across, and running beautifully

Ah well - next time.

Of course you will get them level. My question is, if you swap the lines over, are they all still level? That will tell you how accurate your Carbtune is. As TMod and I have already discovered, the Carbtune is not necessarily accurate out of the box. If you don't swap the lines to check, you will never know. Or, you can test each tube on a single vacuum to confirm the gauge is calibrated correctly. In short, with a little fiddling, there's a chance you can get her running even more sweetly.

[edromero]

Will you please trust that I know what I'm talking about now.

I never doubted that, I just was reluctant to spend more, but it appears to have been worth it

Ah well - next time.

Of course you will get them level. My question is, if you swap the lines over, are they all still level? That will tell you how accurate your Carbtune is. As TMod and I have already discovered, the Carbtune is not necessarily accurate out of the box. If you don't swap the lines to check, you will never know. Or, you can test each tube on a single vacuum to confirm the gauge is calibrated correctly. In short, with a little fiddling, there's a chance you can get her running even more sweetly.

Ok I'll try that. I'll get to ride it tomorrow and get an initial asessment

The Carbtune probably tells a more accurate story. However, since you're tuning and have camera in hand, try this ...

Balance the carbs using the Carbtune and take a photo of the result.

Then, swap the Carbtune lines 1-2 / 2-1 and 3-4 / 4-3 and take another photo. If all 4 bars still show even, you have a good balancing tool.

And if they aren't balanced, how do you compensate for the variation?

[TRPUT]

And if they aren't balanced, how do you compensate for the variation?

You might be lucky and have an accurate gauge, but it's worth checking. Pull the back off and check it out. See this (thanks again to TMod):

http://katriders.com/vb/showthread.php?t=85245

I've said it before and I'll say it again ... there are so many variables involved in how this thing works it is physically impossible for it to be naturally calibrated at all vacuum levels. 4 springs ... 4 tubes ... 4 rods ... washers ... enough size, weight, tension and friction variations to render the thing useless if it isn't calibrated correctly for its specific use. (For this reason, the Motion Pro is a better tool because it is inherently accurate - but it is a little more fiddly too. As with everything else, there are no free lunches with balancing tools.) The trick is to set it correctly at the levels you will use for the Kat. So, use one vacuum port on the Kat - preferably through a 4-way splitter - and adjust the nuts on those slide bars until they are all even.

Option 2. Use the reverse method I mentioned previously. If there is a variation, set the carbs so the variations in readings are the same - but reversed, when you swap lines over in 3 stages - 1 - 2 / 3 - 4 / 2 - 3.

[mammut89]

grats on the adjustment and new tool/toy , money well spent

[steves]

also make sure you have the restrictors installed.

[curseboy]

In the past I've used the vacuum gauges. I even set them all "equal" with a separate vacuum source (a hand vacuum pump) at about the range used when sync'ing. I made a homemade manometer, and the "best case" of sync was about .5" of Hg off, with the worst being about 1.5 off.
And it turns out, my bike runs and idles even smoother now!

I knew the gauges weren't the best choice but I had no idea that they would be so off.

[edromero]

You might be lucky and have an accurate gauge, but it's worth checking. Pull the back off and check it out. See this (thanks again to TMod):

http://katriders.com/vb/showthread.php?t=85245

I've said it before and I'll say it again ... there are so many variables involved in how this thing works it is physically impossible for it to be naturally calibrated at all vacuum levels. 4 springs ... 4 tubes ... 4 rods ... washers ... enough size, weight, tension and friction variations to render the thing useless if it isn't calibrated correctly for its specific use. (For this reason, the Motion Pro is a better tool because it is inherently accurate - but it is a little more fiddly too. As with everything else, there are no free lunches with balancing tools.) The trick is to set it correctly at the levels you will use for the Kat. So, use one vacuum port on the Kat - preferably through a 4-way splitter - and adjust the nuts on those slide bars until they are all even.

Option 2. Use the reverse method I mentioned previously. If there is a variation, set the carbs so the variations in readings are the same - but reversed, when you swap lines over in 3 stages - 1 - 2 / 3 - 4 / 2 - 3.

Where do you think I could find a 4 way splitter?

[Wild-Bill]

Pick up 3 vacuum Ts and about a foot of hose from Autozone.

Let's see if this turns out right...

\  / \  /
 T    T
  \   /
    T
    | 

Well, not quite. Spaces don't work right on here.

[edromero]

Thanks I got em from pep boys. I'll do it tonight

[edromero]

Calibration result

This is all four rods connected to the same carb. This is how It came from the factory

[TRPUT]

That's not bad. 1 and 4 equal and 2 and 3 equal ... and all within 1/2cmHg. I would probably fiddle with them to get them even, or just remember when you adjust your carbs that "balanced" looks like that picture.