Modern Vespa

Seems like I'm coming on here every other week with a problem. *wince* Sorry!

Out for a ride today, my engine suddenly went from a relatively quiet purr to a loud roar. I was afraid my muffler had fallen off but it's still there - something has come detached underneath. (head-desk) The engine light popped on and off as I rode it home.

Hubby thinks he can fix it. Guess my riding season is over. There are no dealers where I live - I'll have to ride it over an hour away to the Detroit area to find someone to work on it.

Some muffler probs are easier to fix than others. It's probably the graphite gasket between the exhaust pipe and the muffler slipped or deteriorated. It's really easy to replace. But stick your head down there and listen to where it's leaking- it should be obvious- or better yet have your husband do it

its probably the graphite gasket between the muffle and the pipe that is gone. cheap enough to fix and see your self, remove the muffler is all.

I agree. Simple system should be very easy to look and tell where the noise is coming from.

Two bolts hold the front pipe to the bottom of the motor. The oxygen sensor is threaded in to the pipe halfway to the muffler. If that has come out it will definitely make the injection system unhappy. The muffler joint graphite could be leaking. Easy enough to slide the muffler off and replace the bushing.

From COLD, start it up and put your hand around the joint with the graphite gasket (don't touch the exhaust pipe itself). Just feel for puffs of exhaust escaping around the gasket. You'll have a few seconds to safely do it, before things heat up. Otherwise use a dollar bill or similar to see if there's wind in the region....

Thank you all again for your help. Where would be purchase a replacement gasket?

Piaggio #874946 (They're not cheap)

AF1, ScooterWest, and ScooterPartsCo all have them.

Supposedly there is a Yamaha substitute that may work for less money. YMMV

Look through here -> Exhaust Bushing

The slippery graphite is meant to give the muffler joint a little flexibility so the front pipe doesn't crack due to expansion and contraction. The bushing wears out and crushes down over time.

Thanks again.

My husband just took the pipe off and to both of us, it looks like the pipe sheered off. The edge of the pipe is rough, unlike the other end, which is smooth. I'll post a picture of it when I get a decent one. Happily, the sensor is intact.

Pictures...

Is the graphite gasket that small piece in the schematic shown connecting the pipe to the muffler?

My husband wants to know if there's a way to swing the triangular bracket out of the way in order to get to the bolts?

Does anyone know where I can order a part? I'm coming up empty with Google.

Looks like you need a new exhaust header. The flange part sheared off. AF1 will have one, but I'd try EBay too. Do you have an aftermarket exhaust or stock? Sometimes aftermarket mufflers put a lot of stress on the header.

Anyway, the only way to get those two nuts off the head is to use a ratcheting box-end wrench from the side. 13mm is the size. It barely fits. You can drop the bracket that the pipe goes through, but that's a much bigger job because there are a couple of needle bearings that will come loose and need to be reassembled and the preload will need to be set on them.

Make sure to get a new exhaust gasket as well as a new graphite gasket. You'll probably need new nuts and may need new studs for the head.

In the diagram below- #29, #26, #11, and 2ea #25. The studs are on the cylinder head assembly, but if their threads are bunged up, I'd get a pair of those, too.

Bummer that the pipe is broken. Not knowing what resources are available in your area, there might be a skilled welder that could put it back together. Or buy a new part. You'll have to decide which path is more cost effective.

www.parts-piaggio.com has the nicest online parts diagrams where you can get the factory part numbers. --> https://www.parts-piaggio.com/piaggio-scooters/400-PIAGGIO-SCOOTER/MP3/2009/MP3-ie-MIC/Engine/Silencer/836/44/43019052/1672

#11 is the graphite bushing
#29 is the header pipe

Then go to whichever online supply house you prefer and put the part number in the search box.

AF1 is in Texas --> https://www.af1racing.com/store/Scripts/prodView.asp?idproduct=54689&sku=B014382&description=EXHAUST+MANIFOLD+WITH+I%2EP%2E+%2D+B014382

ScooterPartsCo is in Charleston -> https://scooterpartsco.com/ (I didn't find the header pipe there, but a phone call might yield success.)

Scooterwest is in San Diego --> https://www.scooterwest.com/exhaust-muffler-manifold-header-mp3-500-873323.html

These three do booming business and have a steady flow of shipments coming across the pond so if they don't have what you need in stock they can get it in short order. There are other suppliers available and sometimes even Ebay is worth a try.

Which triangle bracket? I'll look at mine as soon as it cools down.

yup you need a new head pipe. I just had one and sent it to someone in Louisiana a couple weeks ago.

to get the exhaust flange nuts off you need a flex head wrench and or a swivel for socket . I suggest using 1/4" drive for sockets.

First get some VERY good spray rust prentrant like KROIL
https://www.google.com/search?client=safari&rls=en&q=kroil&ie=UTF-8&oe=UTF-8

spray the nuts and let set off an hour and then spray again, do this 3-4 times before trying to remove the nuts.

once you get the nuts off the flange could possibly be welded back on by a skilled stainless welder.

if you order a new pipe be sure to also get new exhaust studs and nuts as well.

when installing the new part be sure not to tighten down the nuts until all is fitted with the pipe and muffler.

Ugh. That's a really awkward spot to get to. If you remove the plastic cover from the bottom you might be ale to see a little better but you still won't get your hands in there. Rocker panels have to come off at least.

Maintenance manuals says (in very cavalier fashion)

Exhaust assy. Removal
- Remove the side fairings.
- Remove the central frame cover.
- Remove the exhaust end.
- Disconnect the lambda probe connector.
- Unscrew the probe.
- Working from both sides, release the two clamps (bolts)
securing the exhaust manifold to the head.
- Detach the exhaust manifold making it pass
through the swinging arm.

Rocker panels have to come off at least. That means "peeling the banana". You have to start at the license plate light and work your way forward. Tail piece, tail lights, rear skirts, back rest, grab bars, rear fenders, seat, center tunnel, floor boards, rocker panels.

Then you should be ale to get a wrench on the nuts. Mine look very rusted which is not encouraging. Probably strip them trying to get them off. If that happens I'd be removing the motor from the frame. That's a whole other headache.

it can be done with out removing the rocker panels. I have done it a couple times for friends. But I also have a lift which makes getting to the underside a lot easier. You can also support the rear end in the air and remove the shocks to change the angle of the engine mount to help with access as well.

Yeah and revit up while he`s down there. Just kidding or maybe not!

Looks like poor assembly, or possibly a knock from a fall, has put permanent stress on the pipe. Assemble the new parts with plenty of coppaslip grease on the joints including the graphite sleeve. Tighten each fixing and clamp progressively and waggle the system about as you go to find the most relaxed state. When this is done the manifold nuts can be fully tightened but I would always tighten the centre clamp last.

OAD: I'd like to see it done without removing everything. I'll bring the popcorn. Heck I'll bring the beer!

I considered the possibility of jacking the motor up and down. Not sure how much it would help or how much travel is available as the pipe still has to pass through the lower bracket.

come on down. I like REALLY good bourbon.

I've done it at least four times to fit and then remove an aftermarket full system on the MP3 400. The right hand nut/stud is unscrewed from beneath and the left hand one via the spark plug access cover. A wide selection of tools is needed as well as plenty of patience because sometimes you can only find room to turn the nut by one or two flats at a time. The biggest time saver was a ratchet ring spanner which only worked after I had cut about 1 inch from the handle so that I could get it in on the spark plug side with room to turn it.

exactly right

searched ebay for you but come up empty.

welding is not an option. these glow red hot when running. the metal absorbs carbon and would contaminate the weld process. weld would be very brittle and not last.

hmm. how do they put the flanges on then?

they are welded on when new.

used stainless manifolds cannot be tig welded.

why not?

Stainless steel can be welded just fine.

I agree with Madison Sully. I work with Stainless steel and I can assure all of you that it can be welded! It doesn't matter if it's old or new!

Even after all the heat cycles it's had? It'd have to be welded while set up in an accurate jig as well, otherwise it'll snap someplace else PDQ.

Just buy new.

You can still weld it but it is 50/50. I do agree with that!

Fowlers of Bristol UK have these in stock brand new at £88.42p INCLUDING 20% tax but as your not in the EU you would get it tax free. Postage might be a bummer though but it might be worth a ask. Piaggio pt number was B014382 now 1A007654. Theres also a complete 400 exhaust system on UK ebay for £35 but the cost of posting to the USA would be out of this world due to the weight of the silencer or should i say anchor for the latest USA aircraft carrier.

Metallurgically speaking, yes. Accurate jig, absolutely, and skilled welder to boot.

If it was me, I'd buy new. But to say you cannot weld "used" stainless steel is inaccurate.

I am not saying you cannot weld used stainless. the knowledge I am trying to share comes from fabrication shop that specialize in fabrication of exhaust systems. large part of their business is making custom header to mount turbo on car. I take them a cracked header for them to weld. they explained the carbon impregnates into the stainless. they say you cant get a clean weld puddle. results are a very brittle weld.

typical of you guys. you dont want to learn. you just want to be right.

give em a call. see if they will weld it for you. let us know what they say.

https://www.autoyas.com/US/Tampa/110159237670/DB-Fab%3A-Fabthis

I'm a metallurgical engineer.
Have a great day.

that makes it even worse for you.

so what your saying is they don't have the proper welding techniques then and its easier for them to just sell you a new system.

Cleaning and properly prepping the exhaust is key to good welds first, the they need to ensure the correct temp for the thickness of the material and finally they must ensure the exact makeup of the material they are welding.

How to get the side fairings off? The shop manual is less than helpful.