Modern Vespa

My mechanic replaced my lambda sensor (I keep getting P0130) and when I got the bike back it sounded slightly different and I noticed while stopped at the lights that my right angle seemed to notice heat.

so stuck my header under and noticed that the exhaust midpipe (Arrow) was not slipped on quite as far on as I normally do myself, a few millimetres less. ie not fully butted against the flange on the header. started removing it (was harder than usual - doubt he used any anti-seize) and saw that it was cracked.

aarrgghh.

I've ordered the sip stainless one instead hoping it would be less likely to ever crack in the future. https://www.sip-scootershop.com/en/product/exhaust-manifold-sip_842683VA

"Gee, I wonder what that snap was when I was tightening the lambda sensor the wrong way."
Those flange nuts don't look disturbed, so I'm thinking the sensor was installed with the muffler on the bike.
My new saying. "You can't make big bucks if you have pride in a job well done"

Since I'm going to replace this myself (and argue with my mechanic afterwards), does anyone have and tips or dos and don'ts? Like is there anything special when screwing the lambda in? Thinking I'll hold the header in a vice while doing this ...

Perhaps the old lambda sensor was cranked on so hard during removal that it both bent the flange and broke the pipe?

Use PB Blaster or something similar on the studs the day before you loosen the nuts. Robot just did a video on replacing a broke exhaust stud. Best to avoid that and also avoid rounding off a nut. If a nut is still not loosening after applying a reasonable amount of torque, stop and heat it up with a torch before proceeding. Don't burn anything important if you end up using a torch in a confined space.

highly recommend replacing the exhaust studs and nuts with new after removing .

Bummer man. Wish I could offer some words of wisdom, but all my vehicles are 10-20 years old. Never had to worry about sensors. My exhaust pipe rusted clean off of my truck on the highway during the summer. I just hung it up with some straps and kept going another 50 km until I could deal with it

You have an MP3 250 with the fuel injected Piaggio Quasar engine which doesn't use an oxygen sensor (lambda sensor)?

My Beo 500ie (460cc actually) with the MASTER engine has fuel injection but no lambda sensor. It runs an automated table based on engine temperature and incoming air temperature from a sensor in the throttle body. Pretty crude compared to how a real feedback system would work. I think the later MASTER models (engine size increased to 492cc) did come with a lambda sensor.

didn't think of the studs. I did order new nuts and a new gasket (the copper one between the header and the head)

That pipe is obviously too small for the number of lambdas passing through it.

and being a kiwi you'd know all about lambs wouldn't you 🇳🇿=🐑

I'd warm it up slightly and hit the nuts with some type of penetrating oil. if they come off clean, then I wouldn't sweat the studs and run on fresh ones. give the old ones to your friend Justin Case to hold for safe keeping. He's probably got a drawer somewhere in the garage.

don't clamp the pipe in a vise the sensor should thread in easily and doesn't torque up massively tight. you should be able to achieve sufficient results just by holding it in your hands.

I'd order a new exhaust gasket in case you need one as well.

thnks.

didn't order an exhaust gasket as am using an Arrow exhaust (never understood why all the aftermarkets don't use some type of gasket/busing between the midpipe and header)

Justin Case has a very full drawer

No, sold it some time in 2020. Wasn't snowing enough to justify keeping it as my winter beater over something smaller and simpler.

You'll note that the profile on the left side of your post says you still have it. You may want to bring your profile up to date.

When I replaced mine last year I found a combination of a wobble extension and a universal joint socket made it easier to get to the stud nuts.

The SIP stainless pipe is a nice upgrade. I also went with this one when making the swap.

Good luck!

Correct. It's said that for many years. My post is more recent, so you can trust it to be more recent lol

a 1/4" 6" extension with a wobble and short socket make this a breeze. it's the sweet spot where you can get at both nuts easily and don't wind up skinning your knuckles on the swing arm or getting jammed up against the ground.

Presumably it's said that for many years because you haven't updated your profile for many years. Instead of someone having to ask which bikes you actually currently own, or some other basic fact that would normally appear in your profile - why not just do the update?

''it's the sweet spot where you can get at both nuts easily and don't wind up skinning your knuckles on the swing arm or getting jammed up''

I think you're asking the wrong question... I don't see it as Why not just do the update, I see it as why?

Anywhere where what I ride is relevant, I mention it in the post. This is much more helpful for people reading old threads.

And honestly, I currently have about 5 bikes (okay, 6, but one is retired). By the end of the year one will sell because it's a finished project, one will sell because I just want to try something different, and two new ones will take their place...

I really don't see any need to update my profile 4x a year on every motorcycle forum I'm on (a handful).

I'm also not really sure why what is on my profile is so important to you

You may have a good point. I am beginning to wonder why YOUR profile would be important to anyone.

In any case, this discussion has certainly gone on longer than it is worth.

Agreed. It shouldn't be. The content of the post might. Ride safe.

it can be important to everybody because it adds credibility to what advice you may give.

ex: if I'm asking questions about hopping up a 4T 50 and I see in your profile that you have a hopped up 4T 50 then I can assume that your comment carries some relevance behind it.

Exactly. And you, sir, are both weird and cool.
Oh, and insane.

is that a clinical diagnosis?



asking for my insurance carrier

Sure. Sure. Absolutely clinical. Scientific studies were performed to come to this, um, conclusion. No, no, wait, it's a diagnosis. Yes, many studies resulted in this diagnosis. It's all documented right here on MV, after all....

old (OEM) and new (SIP) pic just for the heck of it

PS that's not rust on the old, that's baked on mud

At some point on this site I had come across someone's post regarding using a non-graphite gasket at that joint which resulted in the pipe cracking. It was explained (prolly by Jimc, maybe Greasy) that the joint needs to slip, if ever so slightly, due to contract/expand cool/heat forces. I'm not saying that's what happened in your case, just throwing it out there as food for thought.

Often referred to as an open loop system.

this is correct. It needs to move ever so slightly.

Oof, I've owned 5 of the same Suzuki and know my way around it blindfolded, but I don't currently own one... so I guess if I don't currently own one I lack credibility on it... bummer lol

But if you were on a Suzuki forum that would be important, no?

I just think that you can't quite grasp the bigger picture. But it's all good man. You do you.

I get it, but in the post being commented on, I explicitly mentioned that I didn't have any motorcycles with a lambda sensor.

The part I don't get is why a profile sidebar from god knows when would take precedence over someone telling you what their current, right now, situation is.

I don't like chocolate.
"It says here you like chocolate"
But I stopped liking chocolate.
"BUT IT SAYS HERE THAT YOU USED TO!"

Ok, so what? lol

You know, this is getting tiresome. Why don't you just give it a rest.

The best socket I have found for the nuts on the exhaust is the 10mm that comes in the cheapest socket set you can possibly find. Harbor freight has one for about five dollars, and the sockets are tiny, iwith very little metal around them. That's why they are so cheap, and why they are perfect for installing these nuts.

I've not had a lot of luck with Arrow exhaust manifolds. I've probably got three laying around that look similar. The pipes are great, but the manifolds, not so much.

Arrow manifolds? Didn't know Arrow made manifolds, or did you mean for some other bike other than a Vespa. (or did you mean what I call the midpipe)

And what problems?

The extra bonus is that the odd say the socket will fail if you try over-torquing the nuts.

which is exactly why I've never understood why all the after market exahusts don't use a bushing or similar.

I have been following Robots guide for installing an Akra on a 2020. ie use antiseeze, loosen all when lining up and the torques that he says. One day i hope i'll have all the torques on my bike memorised