Topic: '78 CB750 PD carbs, "clear tube test" before installing question

[denward17]

If I wanted to pre-check bowl level before installing carbs, I connect a clear tube to each bowl drain and just loosen the drain screw?

[newday777]

If I wanted to pre-check bowl level before installing carbs, I connect a clear tube to each bowl drain and just loosen the drain screw?

Nope.
You need to have bowl drain plugs with a bung on each.

[newday777]

http://forums.sohc4.net/index.php?topic=188718.0

[Geoff Hastings]

I did exactly that, just connected clear tubes to the carb drains, turned the tubes up right and then opened the drain screws. Clearly showed the difference in fuel level. The bike idles so much better.

[BenelliSEI]

I did exactly that, just connected clear tubes to the carb drains, turned the tubes up right and then opened the drain screws. Clearly showed the difference in fuel level. The bike idles so much better.

That’s not correct. The float bowls overflow is the tube in the middle. It is too high in the floatbowl.

[denward17]

^But on this carb type, doesn't the drain let fuel out of the bottom of the bowl when the drain screw is loosened?

[BenelliSEI]

^But on this carb type, doesn't the drain let fuel out of the bottom of the bowl when the drain screw is loosened?

You are absolutely correct! I’m confused again!

[madmtnmotors]

^But on this carb type, doesn't the drain let fuel out of the bottom of the bowl when the drain screw is loosened?

You are absolutely correct! I’m confused again!

Yep. The PD "abominations" (I haven't had any issues with them) do indeed drain out the bottom and the clear tube can be connected there, then loosen the drain screw.

EZPZ

[Don R]

 I'm also a fan of the bench test. I suspend the carbs over a paint roller pan and give them a day to soak.

[MauiK3]

Clear tube is great, it gave me more confidence that I had them right.