Vacuum Leak (video)

[Pio412]

As you all know ive been choochin' away at getting this machine running perfect, and you all helped me do that! But me being a perfectionist, I STILL felt it was running a bit off even after all the trail and error with syncing, carb cleaning yada yada YADA. Anybody else it would have probably been good enough... but not me.

https://youtube.com/shorts/97p0eOF04PY?feature=share

Anyways

So after a ride I figured I'll spray the damn intake boots with carb cleaner thinking... I DOUBT THIS WILL DO ANYTHING. Because I sprayed both boots before with no result. So why would this even do anything now? Well I decided to spray ALOT more carb cleaner instead of just a teeny tiny bit. And this is what I got (check out the video)

So this Rpm drop is obviously an induction of a vacuum leak right? I'm not crazy right? This damn boot is leaking...

Clamp is tight just incase anybody was wondering

[navigator]

The intake manifolds can become brittle and can crack over time.
Inspect them. Replace if necessary or smear a coating of RTV on them.

[Designer]

I'd start with what Mighty Navigator said.

Small lineal Cracks that are virtually unseeable can be the source of your anguish

[Herb]

If the boots had ever been off of the cylinders the seal between the boots and the cylinder might be bad or a small crack right at after the carb clamp, that is a pretty comoon place for those cracks.

It is hard to say what the issue is until you pull the boot and check it out.

[Pio412]

Okay so I removed the manifold, checked for cracks, they look great! checked the seal, looks good added some grease for a better seal and installed them. still running the same.....

hmmmmmm

[Lechy]

2 things further to check.
1. The small manifold from carb to head has an o-ring on the head side, check its condition.
2. Check the vacuum port screw has a copper or fiber sealing washer.