New or old way to test Diaphragms?

I was just sitting here thinkin, and i think i may have thought of a good way to test the pistons and diaphragm movement while the carbs are off the bike.

Would it not make sence that if you took a compressed air nozzle and shot the air into the carb (about an inch back, like it would normally flow) and NOT full out pressure either, that the slides should move up.

Thought it might be a good way to test the movement and test for diaphragm holes after cleaning, before cleaning etc.

Thoughts?

Kev

Edit: The butterflies would have to be full open of course.

 

I do not believe that trick will work. The diaphragms work off of vacuum, not air pressure. You may try sticking the hose from your vacuum cleaner on the engine side of the carb. I have never tried it so I dont know if it pulls enough vac. to work.

 

From what I understand, these carbs work on pressure difference, not strictly vacuum. Lower pressure at the head side of the carbs and high pressure on the airbox side...
If you blow compressed air into the crescent passage just above the main bore, the slide should shoot up. You kinda have to be careful -- it doesn't take much air to make it move, and you can potentially damage it.

This still won't tell you if you have leaks in the diaphragm; only whether it moves freely or not.

Chacal made a very informative write-up about it here.

 

Hold them up to the light & stretch the rubber a bit.

 

VACUUM CLEANER=BAD You can seriously damage or tear them. Remember, you can still buy brand new ones... for well over $100 EACH.

Wiz is right, and that is the best method. Hold them in front of a light and gently flex the rubber. The most common failure is pinholes, and they aren't easy to see.

 

Unless the diaphragms are already damaged, using a household vacuum couldnt possible pull hard enough to damage them. If you dont believe me; remove one of your airbox boots, rev the engine, and hold your hand over the carb throat. Theres no comparison between a vacuum cleaner and the vacuum of a running engine.....the engine pulls a hell of a lot more vac. than the vac. cleaner.

 

You missed the point, using a vacuum won't tell you if there is damage to the diaphragm, only if the slide is moving.

 

I wasn't thinkin of trying to replace the look at the light way to check was just thinkin of a quicker way to "quick test" if you will, before ripping them apart.

I'm pretty sure it would work, cause the only reason they rise, is because of the depression created by the venturi as the air rushes through the smaller space right where the piston is (venturi). Just haven't tried it in practice yet

Thanks for yer input and thoughts guys! Keep em comin!

 

Right. However, as Wiz pointed out, you're only testing the "rising." You could have pinholes and the diaphragms still rise; how soon, how far and at what rate would be affected. You have no way of "seeing" a deficiency in that motion.