Modern Vespa

Hello all,

I did a search but couldn't find anything. I was doing my oil and gear oil change on my 2022 Vespa Sprint 150 Racing Sixties today. I finished everything, and had one last screw to put in, the one where you fill the gear oil. I started screwing it in, and it just kept spinning, not tightening. I look down, and there's a piece of the threaded section on the shop towel I placed underneath! I've attached some images. Has anyone ever experienced this, and or, does anyone have any suggestions on moving forward. Am I replacing the whole crankcase, and where the heck do I even get one? I've been looking online and can't find anything. Thank you in advance!

The upside is that this is not under pressure. A skilled welder can weld that piece back in place. Then drill out the old threads, tap, and install a TimeSert (not a HeliCoil) to bring the hole back to standard size. You'll need to clean it up really well before welding.

I agree welding + Time Sert is the A+ fix. But that's going to be pretty expensive and probably a hassle. Why not Helicoil here? Low pressure, low torque, and rarely opened - seems like a good application for it.

Personally, I'd look at installing a Helicoil here. It's inexpensive, durable, and can be done with basic tools in a home garage.

On the Heli Coil you need a nice cylindrical hole, it won't be able to be installed, there is a missing straight edge, in your case there is a piece missing. If it is threaded deeper in the block I would use a longer screw with sealant (as a temporary solution), which will not weld the missing piece to the block.

A HeliCoil would never hold here. Half the hole is broken off. Nothing for the HeliCoil to grab a hold of. As soon as you put a bolt in and start to tighten it, the HeliCoil would deform and pull loose. Compared to the cost of a new case, repairing this one properly is cheap. I'd bet it can be done for <$200.

Can you drill and tap a new hole on the flat surface above? Use a slightly longer bolt and JB-Weld to seal the original.....?

I had a fellow Vespista with mechanical experience and aluminum experience come look at it. He is having me JB Weld it back in, and filling the hole with JBWeld, and then he will tap in new threads. Fingers crossed! 🤞🏻 thank you all for the additional advice!

That's a perfectly reasonable solution, as it's not under pressure at all. It's certainly what I'd try first off!

A little late to the thread, but I have used JB Weld SteelStick epoxy.

It's a much more dense, durable solution than regular JB Weld. A friend cracked his case on his XR 250 on its first ride (long time ago). Laid the bike on its side to keep the oil in, cut off a piece of the SteelStick, mushed it in his fingers, until it became like clay. It also heats up, then he filled the crack. It lasted for decades.

It takes to being drilled and tapped much better than regular JB. I used JB to locate and hold a sealed bearing in a hub and it failed on one ride (bicycle wheel). I didn't plan on reusing and installing another bearing, so I used the SteelStick. Never a problem!

Thank you for sharing! I will definitely keep this in mind if my current fix fails!

Here is the final outcome. The person who was helping came this morning to check my work with the JB Weld and to drill and tap the new threads. So far so good! This photo was taken before I put it in for good with the washer.


Thanks again for all the help!

Now I can go on my trip next week!