Engine vacuum.

Bike is a 1981 KZ1000-K1 LTD? What kind of vacuum would I see in either cm Hg or inches of water if I connect a vacuum gauge to one of the nipples on my carbs? Trying to compare a factory number to where I am now with the 3X cams and overlapping valves.

The gauge will just bounce so bad you won't be able to read it.

I'm with Baldy on this one. I have a Uni-Sync tool which goes over the Airhorn on a carb, but it is a pretty simple sync tool. There are the purpose built carb sticks, and several home made versions. I have found the Vacuum balance tool which cost like $5 to make works real good. Its in "File Base" and uses a yard stick, some clear tube and ATF. If the fluid flows in one direction,when hooked to two carbs, then it is a stronger pull on vacuum.
As far as actual #'s to look at. I would think you would need to have the 4 gauges, with the restrictions to see each individual cylinders vacuum. But to compare you would have had to do a before and after on the same bike, with the same Vacuum set up.
Cams will lower the Idle vacuum, increase the port runner reversion. Common with higher duration cams, late closing Intake. Gives much more top end though, a trade most HP junkies will make.

Vacuum gauges will work fine but only if they have dampers on the vacuum lines. Otherwise they will bounce with each intake pulse. Here's what I use. Ed

I have had a VDO vacuum gauge on 2 of my bikes. I was always suprised to see how low the running vacuum was at road speeds. My cars will pull 10 + in. Hg, but the bikes only 4 to 5. To get the highest readings you will need to have good leakdown % and set valves to the wide end of the spec.

kimsmith4807 wrote: Bike is a 1981 KZ1000-K1 LTD? What kind of vacuum would I see in either cm Hg or inches of water if I connect a vacuum gauge to one of the nipples on my carbs? Trying to compare a factory number to where I am now with the 3X cams and overlapping valves.

Kim,

To answer your specific question.....With the relatively long duration of your cams it's likely your vacuum readings at idle will be around 5-6" Hg. That does depend on how they are timed though.

LarryC wrote:

kimsmith4807 wrote: Bike is a 1981 KZ1000-K1 LTD? What kind of vacuum would I see in either cm Hg or inches of water if I connect a vacuum gauge to one of the nipples on my carbs? Trying to compare a factory number to where I am now with the 3X cams and overlapping valves.

Kim,

To answer your specific question.....With the relatively long duration of your cams it's likely your vacuum readings at idle will be around 5-6" Hg. That does depend on how they are timed though.

And what would it have been stock, roughly?