Carb bench test.

[chewy999]

I've heard mentioned in recent threads I've read, about a bench test for carbs where you have an external fuel supply.
Is there a thread to explain how to do this and why?
Or, can someone explain (simply) what the procedure is, with maybe some pictures.

[RB]

put carbs on bench level them, take caps off so yoiu can see down the throats. hook gas source to #3 carb inlet pipe. In the pic the source is really not high enough to get correct pressure but it still works..6' is optimum

carbs testing 1.JPG (125.77 KiB) Viewed 290 times

[chewy999]

Thanks for that.
What are you actually looking for, in other words, what's the point of doing this?

[robin1731]

Thanks for that.
What are you actually looking for, in other words, what's the point of doing this?

It will show you if there are going to be any leaks. Will show if the float valve needles are sealing. If the plenum seal is sealing. If you have 1100 carbs you can test the accelerator pump. If you open the drain screws you can see that each bowl is getting fuel.

Turn the gas on and watch for a minute or so. If no leaks leave it on for several minutes. I've had it take 2-3 minutes for a float valve to start leaking. It is close to sealing but not completely.

Much easier to fix any issues on the bench than to have to remove the carbs from the bike.

.

[RB]

Yep, all that..and you can see what is leaking..up the jets.. float or seat issues, at the carb to plenum..o ring issues, in the plenum... plenum gasket.

[chewy999]

Thanks guys, got new (genuine) float valves on the way so when I fit them I'll do the test.

[pidjones]

I use 91% isopropyl alcohol for testing. Much less smell and damage if spilled, plus it evaporates and if some is left behind it mixes and burns.

[Sugs]

This^^^^^

[robin1731]

But then when done you have to drain the carbs. Maybe dry out the bowls. With gasoline you install the carbs on the bike and they are already primed.

.

[Sugs]

Sorry, I hate the smell of gas stinking up my garage, hands, rags and everything else. And if there is a leak they aren't going back on the bike right away anyway. No biggie to drain IMO, and you can still prime them when ready. Just a preference.

[chewy999]

Sorry, I hate the smell of gas stinking up my garage, hands, rags and everything else.

Nicer than diesel though!

Thanks for all the replies and advice.