Vespa PX200 - Malossi - Blown engine

[paul d]

Heartbreaking. I wonder has the volume of gearoil changed or does it smell strongly of petrol? I'd be curious too about any leak from the head, barrel base or manifold. wellseal or any quality sealant is essential on a modified vespa in my experience. A spotless petrol tank is another essential. A retorque of the cylinder after 100ish miles has to be done too. From how the damage looks, your very close to a perfect set up. When it's right you'll be able to ride flat out without drama. Good luck with it!

[paulnobodyimportant]

Are modified Vespa's good only for sprinting? Even if I had the jetting and ignition right, should I refrain from long top speed runs in the future? I'm not planning on it, just curious...

Just to put in my bit. I have a 210 Malossi, probably 5 years old now, so not the new kits, running on a S1/24/24 carb and upjetted at the time according to the Malossi recommendations, ie 18 degrees BTDC and a 130 main jet.

I've done several long, long motorway runs, at WOT alongside two T5's with Malossi kits, only stopping to fill with fuel every 90 minutes or so. In all cases no problems with engine failures that you experienced. Admittedly, probably only hitting 70mph or so. Late last year I had my barrel tweaked by Michael Abbey and from doing plug chops, I definitely need to up my main jet

For what its worth, my opinion is that your main jet is far too low for a 30PHBH carb, timing a bit too high and as others have said, you need a cooler plug like 8 for buzzing around locally and a 9 plug for WOT on long runs.

But get it set up correctly and you will have no problems in doing long speed runs

[225worb]

Good shout Paul
I run a watercooled head on my 225, up geared and B9 es and fuel pumped 30mm, i do abuse it though really properly abuse it ( thats maybe why it breaks cases regulary lol), sprinting, and fast road use especially when going to rallies..
28bhp.......
Best advice ..replace the damage parts and take it for a Dyno.....Readspeed/diablo ...

[arrow]

Hi everyone,

I bought the replacement cylinder, piston and piston ring. I am also looking at my options for the variable ignition. When everything is installed, I will also perform a leakdown test. I am also looking into installing a Malossi X360 reed valve kit since what I read so far about reed valves are so positive. I'd love to hear the pros and cons of such a modification.

[paulnobodyimportant]

options for the variable ignition

I've got the Kytronik box on most of my scooters, including the Malossi, although there are other boxes that vary your ignition. Version 3 has just come out. You can get direct from Ky-tronik, but MB will have some soon. https://www.kytronik.com/collections/al ... 0253167047

Have a read on the Ky-Tronik site or the MB site

[Spanish Fly]

Arrow.
How full was your fuel tank when disaster stuck? A PHBH will sit higher than an Si.
Are you running a fuel pump?

SF

[arrow]

It was close to full tank actually. I don't have a fuel pump, only a fast flow fuel tap.

[arrow]

Hi everyone,

This certainly took an interesting twist. The new cylinder kit arrived today so the mechanics decided to check the electrical system when they noticed that the crank pin was a bit wallowy. Then they took the engine apart and saw the carnage:

https://flic.kr/p/RHNeLn

https://flic.kr/p/RwYDCc

The mechanic is now thinking that a particle was swallowed through the intake and got wedged between the crank and the port, which then damaged the crank, made it go out of balance and in turn made the piston hit the cylinder.

What do you think of this?

[mick1]

I'd suspect a piece of the Nicasil "de-laminated" and caused the damage. The Nicasil is very hard and can cause the damage seen in the pictures. I saw a lambretta cylinder that lost a piece the size of a finger nail, this got jammed in the crank causing a seizure. There was damage to the crank, cylinder, cylinder head and barrel.

[Jack221]

A very sad sight indeed. Obviously you can go reed if you so wish but possible to patch it up with some chemical metal and a new crank. Won't make much, if any difference to the performance. The rotary pad sealing is not so important as often thought.

The cause is still the jetting. It was running way too weak and the colour of it and the marks prove that. A full on proper overheat does make the crank web swell and on a previously tight rotary pad clearance, they will touch. Once the ally builds up on the crank web it makes a proper mess.

Don't worry though. It will be ok again. Chemical metal for the quick way or a reed block if that makes you happy.