Modern Vespa

Agreed. I'd use teflon tape to seal it. If you use a 2 flute end mill to spot face. It won't provide a flat surface(unless you have one(special). In this case N.P.T. works better.

Be vewy vewy careful on that tap depth, huh huh huh.

A experienced machinist never crosses their fingers and hopes for the best. If he fails, he just has an extra oil pan with a hole in it. Prototype machining is so much fun.

I have not measured the oil temp on a Vespa, but I would not use anything that wasn't rated for at least 250 degrees. Oil temperatures of 175 - 200 degrees are not at all uncommon in modern engines, depending on operating conditions.

Teflon tape just lets you tighten the connection tighter, which on tapered threads can form a better seal depending on the materials & how clean the threads are it will make a seal, I would glue it in with epoxy, JB weld

I would use a smaller size sight glass, finer threads make a better seal
https://www.amazon.com/uxcell-Threaded-Stainless-Compressor-Fittings/dp/B08LCXJL4K?th=1

If the site glass were to break or go bad for some reason, would I be able to unscrew it if it's secured with JB Weld? Heat gun or propane torch?

JB weld is pretty strong when used correctly. Maybe with a good impact Gun it would break up. It's fairly brittle when fully cured. I don't think a heat gun would help. It's rated for over 500 degrees. I don't know what happens to it when using a torch.

I would really like to have the ability to replace the sight glass if disaster strikes. What do you think of this stuff? It's good up to 300ﾟ but removable with more heat.

I would treat it like a drain plug.

I'm a bit confused. You've talked about different thread types, Teflon tape vs o-rings, etc. Personally I tend to avoid high strength thread lockers unless specifically called for due to the removal hassles. The ultimate goal is to make sure the sight glass threads are sealed. I doubt it is going to vibrate loose. To that end, an O-ring provides some friction and dampening from vibration. So does Teflon tape. If you do not wind up using Teflon tape, you could use either a low strength thread locker or a smear of hi temp RTV, which would probably be my choice. Hi temp RTV is both oil resistant and when cured retains some flexibility to absorb vibration. It will also facilitate much easier removal should the need arise.

Thanks Bueller. I appreciate your input. I don't know which thread type or sealant is best. That's why I'm throwing it out there, because there are a lot of people here with vastly more knowledge than I have about motors, oil, and such. I listen to all the suggestions and then look at the preponderance of the evidence and weigh that against what I can do in my shop with my tools. Thanks to Steelbyte's post about the thread on the German forum, I discovered that the company uses tapered threads and high strength thread lock. So I have now ordered the stainless steel 1/2" NPT sight glass that breaknwind recommended. As adri suggested, it is becoming somewhat of a community project. I hope I can machine the pan successfully, and I will pass along anything I learn in the process. Thanks to everyone who has contributed. I have learned so much and am excited (as well as nervous) about doing it.

If that's the way they put it together I'm guessing they don't really intend for it to ever be taken apart. That's not to say it can't be taken apart, but they probably build them for one time assembly and will tell you to buy a replacement oil pan if the sight glass ever leaks or gets broken.

The question you asked earlier if 300 degree high strength is sufficient, yes, I'd suspect it would be. Motor oil should never get that hot.

If you need to remove the sightglass something else has already gone very wrong
It'll come out
Of course heating up epoxy softens it some
Permanent gasket glue would be another good choice

If the glass component ended up breaking, I'd imagine there's trouble afoot elsewhere.

I've replaced cloudy glasses on two bikes. They can get cruddy even on well-treated machines.

Were those actual glass, or something else? I'd be surprised at glass getting so cruddy that it can't be cleaned effectively.

Bmw plastic removed by melting a hole with soldering iron and prying out the plastic lens.Removed the glass lens from Ducati by plucking out the rubber seal. How do you clean the inside of a sight glass without removal?

In the case of this Vespa one, by direct washing with 'whatever' as it's easy to get to. I have no idea how your BMW or Ducati ones were accessible or otherwise.

Point taken. Over and out,

I'm waiting on some mail order items to be delivered today but went ahead and drained the oil and started taking things apart. I have only changed the oil one time on this bike (and no other maintenance on any scooter), so taking it apart is definitely outside my comfort zone. I'm watching Robot's video and moving along one bolt at a time. So far, so good.

I always thought I would make a metal clutch tool, but I was in a hurry and didn't want to take the time. This one out of scrap plywood worked fine removing the clutch nut. I don't know yet about torquing it back on. For the limited use it gets, it should hold up. If not, I'll make a metal one later.

I got the initial roughing out of the oil pan done yesterday. Basically all I did was cut off the fins leaving a little bit to be cleaned up after drilling the hole. The setup took a long time because the top surface to be machined is not parallel to the bottom surface. I made an angled wooden fixture by propping up one side of a board and running it through the drum sander. The fixture is bolted to the rotary table, and the pan is screwed to that. The spindle was centered over the rotary table for the initial plunge cut. Then I offset the X axis .120" and rotated the table to create clearance around the sight glass.

Here is a video showing the very slow cutting process. I was worried that there might be some chatter because of the wooden fixture not being as rigid as a metal one, but everything remained rock solid and it cut smooth as butter.

Glad you could improvise. If you tilted the spindle. you'd have to plunge cut. This way you get a flat surface to work with and truing a spindle( I always called it "tramming the head") is a PITA. But you do lose extra cooling fins surface. No big deal.

Yes, at first I did tilt the spindle in the Y axis but I still had it locked in my brain that I wanted to make a circular cut with the rotary table. That won't work with the head tilted since the bottom of the end mill has to stay parallel to the rotational axis of the table as the work rotates. Tilting and plunging would sure work, but overall it might not give as clean a result as the circular milling. It was an interesting setup.

Yesterday I got the hole drilled and tapped. Even though the pan is pretty thin, the sight glass feels really secure when threaded in.

I decided to seal the sight glass with high temp. RTV Silicone (Thanks Bueller). I used a nylon washer under the nut, and the thread depth is just right so that the washer is slightly compressed when the threads are torqued down. With the silicone gasket under the washer and filling the threads, I feeling a lot more confident about the seal. The new oil pan gasket is supposed to be delivered today. I will wait 24 hours before filling with oil, but so far it looks and feels good to me. Fingers are still crossed!

Looks pretty good. Looking forward to seeing how it all works installed!

I'm ready for the unveiling ceremony.

... and the ensuing road test!

Don't we all just want to see a trail of oil down the street


Just kidding, looks like a fine job

Maybe I should try to aim my rear view mirrors down at the road behind me for the first ride?😉

I got everything put back together and since I just changed the oil two months ago, I put the same oil back in. After running it for a minute or two, I needed to top it off. I got a little too rambunctious and over filled it.
I didn't feel like trying to drain some oil out of the drain plug, so I devised a tube on a syringe to suck some of it back out of the dipstick hole. I pulled 3 syringes full back out. Once I got the level stabilized, I rode 25 miles, stopping to feel under the sight glass occasionally. It was bone dry every time and remains that way tonight. The 2nd picture shows the level when the dipstick shows full. I thought the little red ball would float on top of the oil level, but actually the top of the ball is at the level of the oil. It seems pretty easy to see, but I might store a little flashlight nearby too. So far it seems like a complete success. I know I will keep wiping underneath that sight glass every day for a long time just to be sure.

Nice going!

Thanks so much. Here is how it looked after riding for a few miles.

Nice project!

I'm a bit late into the party, but for the next one: as motorcycles have had sight glasses for a really long time, many brands sell the glasses as spares too.

For example, Suzuki tends to have good price/quality ratio in spares as it is not a 'premium' brand, yet have (mostly) very solid quality and is globally wide spread.

You need to add this to the Wiki.

I'm glad it was a success. I like the plastic ball touch, it makes the oil level even more visible. I'll be posting you my oil pan tomorrow

Wow! Looking good! Thinking to do this mod on my 125LX since there aren't any oil pans with a sight glass.

Any chance you could send me the link from the tapp and oil sight glass you used?

I didn't know I could. I thought that was something the moderators compiled.

Thanks...so far I'm 1 for 1; I don't want to make it 1 for 2.

Thanks. I had the tap on hand already. You can pick up a 1/2" NPT tap at most hardware stores. Just be sure you match it to the sight glass you buy. Here's the one I bought:

Compressor Oil Sight Glass 1/2 NPT Male Hex Head Stainless Steel Oil Sight Glass Liquid Level Gauge Oil Indicator Window For Air Compressor Gearbox Hydraulic Tank Sight Glass (1/2'' NPT Male) https://www.amazon.com/dp/B09FPQ1X4T/ref=cm_sw_r_apan_i_N3PMMF1PPM25QDZAJ6E6?_encoding=UTF8&psc=1

I chose it because it has a high temperature rating. A lot of them on Amazon don't even mention temperature.

If you read How To Use This Wiki you'll note that as long as you've made 100 posts (so you are a known contributor to MV) then you can create and edit articles. All instructions are there...

The front page is usually locked, but a moderator can unlock it for you if you ask nicely, so that a link can be placed there to your new article.

Moderators have enough to do without doing all the Wiki contributions!