Vibrating Thottle Body

[RTNewbie]

I recently did my first valve adjust and subsequent idle adjust and TB sync with my shiny new Twinmax. The valves were in need of a very slight adjustment but the TB's were way out. It runs really nice now.

In the process, I noticed the rt side TB cam wheel vibrating/turning while the bike was at idle. I also noticed that the vacuum cap on the bottom of the left TB was missing.

Although i have little experience with the boxer, i should say the bike was running pretty well when i last rode it in the fall. I am sure all conditions were similar the whole time.

My question is: What is the deal with the TB cam wheel vibration/turning and how poorly was the bike running without the vacuum plug?

[PGlaves]

I recently did my first valve adjust and subsequent idle adjust and TB sync with my shiny new Twinmax. The valves were in need of a very slight adjustment but the TB's were way out. It runs really nice now.

In the process, I noticed the rt side TB cam wheel vibrating/turning while the bike was at idle. I also noticed that the vacuum cap on the bottom of the left TB was missing.

Although i have little experience with the boxer, i should say the bike was running pretty well when i last rode it in the fall. I am sure all conditions were similar the whole time.

My question is: What is the deal with the TB cam wheel vibration/turning and how poorly was the bike running without the vacuum plug?


The vibrating TB pulley is usually a sign of a worn throttle plate shaft. See if it is actually rotating off the idle stop or not. If it is not rotating off the idle stop what you see is the shaft wobbling with the intake pulses.

The cap off the take off stub allows an air leak. It could cause a lean mixture so get a cap back on there.