2 Mystery Plugs On The Front Of My 2016 Bonneville T-100 Engine

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Magic

 

Hey, no worries about reposting—it happens! Let's see if we can figure this out together.

It sounds like you’ve got some mystery plugs on your hands, and I totally get how that can be frustrating, especially when the service manual doesn’t mention them.

1. Vertical Plug (Torx T-50)
The vertical plug on the bottom is most likely a drain plug or an access point for checking/adjusting something, like the gearbox or engine internals. Some bikes have plugs like this to drain fluids or access internal parts without needing to disassemble larger components.

• Before you remove it, check around the area for any signs of fluid buildup or leaks. If it's a drain plug, removing it might result in some fluid coming out, so have a catch pan ready just in case.
• If you're unsure, you might want to ask around on forums specific to your bike model or reach out to someone who’s worked on it before.

2. Horizontal Plug (10mm Hex)
The horizontal one sounds like it could be another access plug, possibly for something related to timing or a balancing shaft. The fact that it’s hard to access due to the exhaust pipes suggests it’s not something you'd need to remove regularly, which makes it feel more like a service access plug.

• If you’re curious about removing it, I’d recommend first seeing if anyone else on bike-specific forums has done it, or if there’s any additional info from others with the same model.
• If you do decide to remove it, make sure you’re ready for what’s behind it—whether that’s fluid, a spring, or something else.

Additional Tips:

• Ask around on forums dedicated to your bike model if you haven't already. You’ll likely find someone who’s encountered the same plugs and can offer firsthand advice.
• Check parts diagrams: Sometimes you can find a detailed parts breakdown online that shows what each plug or part is for. It might give you a better clue about what these plugs are doing.
• Take it slow: If you're unsure about removing either plug and you don’t find clear info, it might be worth holding off until you have a better idea of their purpose.

 

@MoreCowbell They are nothing to worry about. Stop worrying and enjoy the bike.

 

They could be "drillings" to allow internal manufacture like for example oilways, from the outside. Certain machining processes may have to be done from the outside but, as in my example above of an oilway, you don't want the oil externally so it is capped.

Why do you want to mess with them as it could turn into a can of worms?

I'd leave well alone until such time as a full engine strip is required, THEN remove them to allow full casting cleaning

 

Can I ask why do you want to know?

Are they causing a problem.

From your picture...they are so close in I cant id the area they are.