Modern Vespa

So I am doing some thorough maintenance on the scooter fleet starting with the planned SCBR scooter.

I changed the coolant and the bleed screw would not stop leaking thru the top hole. The other end of that hole is below the oring and on the seat above the needle. It is as tight as I dare go but still leaks.

Unless I am missing something this would indicate either an issue with the bleed screw or the matching seat on the thermostat cover.

Anyone else run into this issue?

The bleeder screw does not like excessive pressure. Use the search function and check the thread archives. It's been discussed a lot over the years. You will find a number of solid solutions with pictures.

This is leaking with out the engine running, just the static head pressure from tank being slightly higher than the bleed screw so there is no pressure to speak of.

You didn't read the manual to get the correct torque for that, did you... Yup, just 3Nm - no more!. Hardly even finger-tight. Any more and you strip the thread, as has been mentioned here on MV multiple times.

However, an easy get-out is available! Drill, tap and fit an M3x0.5 screw. Then order a new thermostat (~$45 shipped) and replace when you next change the coolant.

Not sure why you think it is stuck in there or the thread is stripped. Neither is the case here. It was tightened but not overtighten so it broke or got stuck. It is leaking thru the bleed hole at top even with engine not running. This would indicate that the screw taper where the hole is above the needle is not seating to prevent coolant from leaking. If it was leaking via the threads, then that would indicate an oring failure.

So once more time, has anyone not had the bleed screw seat on the seat in the thermostat case? This is a metal to metal seat.

OK, 'thread stripped' is the wrong terminology - but the excessive torque has damaged the sealing surfaces so much that they leak.

Just put that screw in, and fork out for a new thermostat.

When I picked up my replacement thermostat housing from Scooterpartsco Jorge said it was a common replacement part, they get screwed up all the time, they are just a plastic part prone to all sorts of damage.

Ok, guess I will be ordering a thermostat cover. When you buy a used scoot, you never know the complete history!

If it wasn't leaking before, then the previous history is irrelevant. I've buggered one of these myself, and not that long ago.

well apparently it was small enough that the rubber cap contained it. It was when I took the rubber cap off that the drip was apparent.

Will plumbers teflon tape work?

No, as the configuration is the hole that leads to the top opening is below the oring and thread portion. This hole is on the chamfer of the bleed screw and seats on a mirror image of that to seal.

I literally just do them finger tight, and then a bit of a heavier turn pressure still with fingers. But be careful. It's possible to break them even with finger pressure. The point being, they seal real easy!

Just in time! I'll be there shortly. Problem is I've got a bit of a grip, so I sometimes have to tell myself to back off... but maybe I'll just leave the wrench alone.

well, ordered up a new tstat housing assembly along with other various scooter parts.

In the meantime, I am continuing with other maintenance items on this scooter. I did remove the exhaust and clean off all rust on it in prep of VHT paint job. Need to make a little paint booth first. On a good note, I casually mentioned to the wife that after painting I need to cure it in her oven. She didn't blink and just said ok! I have to see if the Viking oven can get to 600 deg for the final cure.

Depending on where I order from, I might wind up with an extra two T-shirts a mug and a couple of keychains.

Smell-wise, the initial spraying is pretty bad. I thought I could get away with it in my basement shop not connected to our forced air heating system....you could still smell it. Probably best to spray and go in the house for coffee before the next coat. Baking wasn't bad, though Mrs. f didn't exactly agree. I was thinking our pizza might taste interesting that night, but it seemed just fine.

Are you doing a primer? I didn't get down to bare metal, and of course didn't buy any, so went ahead and painted. Let's see....

It's much better to cure it on the bike. The fumes that come off it as it cures in an oven are horrible, and probably toxic. They linger for a while, even when it is warm enough to open all the windows and drive the fumes out with a fan.

Probably true. Though I'd say by far the worst is the initial spray. I mostly went for it due to the cold weather and uncertainty of when I'd actually be running it....

Old thread but asking a question about a fix. Is the consensus an M3 bolt to fix the leak? I'll have to see what my local hardware has for a tap.