What's the safest way to check for vacuum leaks?

[confab]

Propane?

[confab]

It does seem like if it ignited, it would flash off quickly and be less of a problem than covering your scooter with a flammable liquid. Which would not.

What do you do?

[DoomBuggy]

I've always used starter fluid judiciously applied to the mounting areas.

[confab]

That is what I am doing currently..

But in the back of my mind, there's always a mild freak out going. Hoping it doesn't ignite.

[confab]

I've used carb cleaner also.. But I'm not sure how good it works?

[NickP]

I use starting fluid or carb cleaner myself. However, the safest way would be to use a smoke machine.

[JBinNC]

BEST, and safest way is to pressurize the intake manifold (10 psi or so) and use soapy water. Of course that requires removing the carb and making a block-off plate with air fitting.

Jim

[DoomBuggy]

And if the carb to manifold gasket ( o-ring ) is the issue, it will drive you bat shit crazy, lol.

But I agree pressure test with soap is the hot ticket

[docmel]

Using carb cleaner, ether, etc works. WD 40 works. All mentioned will work to detect an intake leak Just listen for any change in idle quality.
Some products will make it go up, some will make it stumble. All you are lookimg for is a change in idle quality to tell you you have a leak. Pick your choice on which is safer to use

[farmall]

Pressure testing is more reliable (the reason HVAC leak tests are done with nitrogen by the pros and vacuum by those with only a pump).

A simple plate bolted to the carb flange or a rubber stopper shoved into the hole are two common pressure testing methods. It only takes a few psi. Dish detergent and water will to for leak testing (also handy mounting tires for those who lack tire mounting compound which is glorious).

A Schrader valve and some scrap metal are easy to come by and an intake gasket makes a fine pattern.

https://www.lowbrowcustoms.com/products/pangor-products-2-bolt-manifold-pressure-tester-1966-2006-harley-davidson-big-twin-and-sportsters

[drivermark]

I've used my weed burner to check for vacuum leaks, I unscrew the bell end and remove it and just barely crack the valve open and use the wand right around the manifold and carb connections.

[confab]

Thanks all for your help..

[Guest]

with the heat of the motor & all the electrics on a bike I never use a flamable spray, bloody stupid thing to use,
soapy water & the proper test plate with valve or bung made for the job for me.
one thing I do when instaling the 'O' rings is to lightly coat them in Blue Hyloma,
it is fuel proof & non setting, so will always help with any leaks, & when the manifold is fitted I run a real small amount around the joint each side from the inside, it can just about be done if ya got long fingers & a short Shovelhead/sportster type manifold,
so far touch wood I have never had a manifold leak despite on a few occasions, not using a carb support.

[frisco1rigid]

I have always used Carb Cleaner.
The EVO seals, Shovel O-rings or Rubber bands are there to prevent Vacuum leak Not to block inner pressure from pushing past the seals/o-rings etc. the former sucks them together the latter pushes them apart.
BUT --I confess I never went to the trouble to pressurize, waay more hassle than I needed to learn.

I also lightly coat my shovel O-rings and EVO seals.