Vacuum Test Questions

[Druncle Kev]

Hi from Texas,

I recently purchased my first bike. She is a 96 500ltd with 900 miles on it.

I'm trying to do a few things to get her in tip top running condition.

She has plenty of get up and go, but I'm getting around 37mpg.

My thought was to test for vacuum leaks and carburetor synchronization.

I'll be purchasing this vacuum tester, but I have no idea how much of a vacuum it should be pulling.
http://www.amazon.com/Actron-CP7802-Vac ... cuum+gauge

Thanks guys and gals.

P.S.
This forum has already been a huge help for me.

[Triangles]

If 37mpg is the best you can do something is very wrong! DON'T waste your money on that vacuum gauge! It is of no use synching the carbs. you need a differential pressure manometer. More or less you balance the vacuum between the two intakes by turning the adjustment screw. I did this years ago simply using some vinyl tubing zip tied to a piece of wood in a giant "U" shape. It was a pain in the ass and I inadvertently sucked the colored water into the engine a couple times. I don't recommend going this route. I had planned to make my own improved model but adding up all the hardware costs and time it just makes more sense to buy a real manometer to do the job.

From my practical experience if you have the carbs removed you can visually adjust it so that the butterfly valves close simultaneously. This will get you very close to being balanced. Likely close enough that you wouldn't be able to tell the difference had you used a manometer.

If the bike is that old but only has 900 miles, I would think it is very likely you have plugged passages in the carbs that will require disassembly and soaking the carbs in some strong solvents to dissolve the blockages. Resist the urge to poke wires thru any passages. It's too easy to inadvertently enlarge passages which will muck things up just as much as plugged passages. I've also noticed that after my bike sits for a month or more it can take as many as 5 tanks of gas to dissolve any gunk in my carbs.