Carb synch woes

[sdinino]

I spent an afternoon with a vacuum gauge and an 8mm wrench trying to get the dang carbs synched. The rear cyl consistently seemed to suck more than the front - 15 vs. 8. No amount of fiddling with the sync rod seemed to get them any closer together. Do I just have a leak somewhere, or is there a trick to this?

[Dave T.]

With 7" of vacuum difference, I would check your setup and vacuum tools. What kind of tool are you using? I bought a Motion Pro mercury type vacuum tool from Dennis Kirk. It has small restrictors at the top of the gauge so the readings are more stable. Does your tool check each individually or are both done side by side?

Why are you syncing your carbs in the first place? High, irregular idle? How well does it run with this 7" difference? I would loosen the sync rod, back off the idle speed screw completely, close both throttle plates and go from there.

Also triple check for vacuum leaks everywhere for inaccuracies. I assume you have the petcock valve on prime and are using the vacuum port for the front cylinder and the capped one for the rear (or vice versa). The proper tools make all the difference and can make life easier. I would check compression also. If you have a lot less compression up front (more than 10% less) I would say you may need top end work. Be prepared to face the consequenses ?:P . Fun huh?