Modern Vespa

I’m working on my GL front suspension, this is the old style suspension. It’s a pain in the a**. There’s something called a trunnion in the exploded views that goes on one of the pivots, it’s basically a grease fitting with needle bearings inside and it supports the bottom of the front spring. The parts book calls for a washer and “packing” on both sides of the trunnion. Is “packing” rubber o-rings?


The trunnion is on the end of the spring

i just tore down the front fork of my GL on Sunday and didn't notice any o-rings, but after doing battle with the SIP site, it would appear that there are a couple of o-rings on there after all.

Packing traditionally refers to this waxy string stuff (love my description there?) that is wrapped around a shaft and then compressed to prevent leakage. I've dealt with it on both propeller shafts of boats, where it's impossible to fit an o-ring without major disassembly and faucets, but not on a scooter.

Yep, the part you’re referring to (#57) is an o-ring. There’s one on either side of the trunion to keep grease in & dirt out. I just rebuilt the front end of my GL a few months ago and happen to have a pic.

Those tiny needle bearings take patience for sure. And pay attention to the washers that go on the outside of the o-rings - they have different inner diameters.

This trunnion also came on the GS150. The other models at this time came with a needless trunnion.

There are two washers on either side of the trunnion; they have specific measurements. You do not want to loose this as nothing from the hardware shops fits abs these are not being reproduced.

I have the O-rings in Viton if any interest. The O-rings keep road grime from getting into the trunnion.

I had the same question and used this video as reference:
https://youtu.be/6-8iHISFrDs
They replaced the needle bearing for a brass style bearing.
I used the needle bearing and it took me a lot of time to get it correct. The hardest part was to place the spring (in my case a stiff Stoffi spring).
Take your time and good luck.

The only reason to replace the needles for needleless is damage or missing parts. The trunnion with needles is a better design.

I agree. Try not to lose any needles. They’re an oddball size.

Preserving here for posterity (& Google), the trunnion needle bearings on a Vespa GL are 2.0x11.6mm, 18 per side for a total of 36.

That'd be the same size as the input shaft needle bearings, which makes sense from a manufacturing efficiency perspective.

I had to count and make sure I hadn't lost any since some fell on the floor when I tore my fork down on Sunday, so I figured I'd measure as well.

I don’t have 36 needles!
I really struggled trying to install the trunion. (SIP calls a spring attachment). I had ordered a new spring a few weeks ago and chose a 190 mm sport. The old one is 180 mm. The problem with the new spring is it’s too long making it a real struggle to install the trunion. I went back to the older spring and got that installed.
But after reading the previous post about trunion needles, I decided to take the old spring off and start over.
I lost some of the needles in the trunion (2) and replaced them with with needles I had laying around from the input shaft on the motor. They were close in size but had tapered ends. They might have worked, but I’ve got time, and I want to order a new spring anyway. So I’ll order the needles. They have them in stock, 64 cents each.
I can also order the correct rubber o-rings while I’m at it.
Looking at available springs on the website, I see sizes ranging from 155 mm up to 190 mm. Not sure which size to get?

I think 180 mm is stock size.

here is a quick trick to get the spring mounted. Screw in the upper spring plate all the way into he spring, the threaded stud will now be below the spring end. now the spring should go into the fork very easy, no upper plate threaded rod to get hung up on the fork. once in place, use a screwdriver to move the upper plate into position.

[quote="GickSpeed" here is a quick trick to get the spring mounted. Screw in the upper spring plate all the way into he spring, the threaded stud will now be below the spring end. now the spring should go into the fork very easy, no upper plate threaded rod to get hung up on the fork. once in place, use a screwdriver to move the upper plate into position.[/quote]

I was able to finish the front suspension finally this morning, I ended up installing a new “trunnion” I got from scooter Mercato. I think it will do the job. I did save the old trunnion and I have 31 needle bearings. Thank you GickSpeed for the tip on installing the oversized spring, it worked. Also wanted to thank Pilaf for the reference video, that helped me a lot too.
I’m hoping to install the upper and lower bearing sets and install the fork tomorrow.

Hey Tom,

Here are some pictures showing the hole locations on the fender so you can drill the re-pop. Sorry it took so long. Work has been a bee-yotch this week.

Lemme know if those get you what you need. If not, I'll get back out and try capturing a rubbing and measure that or something.

Work's not getting less crazy, I'm just getting more over it.


no measures

the attachment holes are 1/2" from their bottom to the embossing. The trim attachment is centered vertically on those holes.

edge of the tape was aligned to the beginning of the embossing.

forward hole is 5 1/2" from the other mounting hole. The lower fork attachment is 3 3/4" and just enough up for a bolt & washer to clear the edge of the fender embossing.

Thanks for posting this video. I already see 2 things I need to redo on the fork cause I did it wrong!

It’s a good video but he left one of the washers off the trunnion.

Thanks Chandler! I got the holes drilled and your measurements really helped. I’m going to wait for the trim to get here, before I install the front suspension on the scooter. Also had to order the “shark bolts”.
I’m not sure what that hole near the bottom of the mudguard is for, there nothing to connect it to on the suspension so I didn’t do that one.

Weird.

That's one of the reason why I watched it. Trying to figure out what washers go where! Brilliant me took it apart and forgot to keep track of what went where. Most of them are pretty self explanatory as the washers only fit in one spot. But I had a few where they could go anywhere. Luckily the washer he forgot, was never removed on mine. I keep that part installed. It moves freely so I think it doesn't need to be tinkered with.