Modern Vespa

Hi

I recently replaced both the starter motor and the bendix on my GT125L, thinking that one or other was the fault that led to the starter whirring but not turning over the engine.

After reassembling the drive pulley (variator) , I noticed that it could turn freely clockwise and anti-clockwise - no grating or grinding, just smooth turning with my hand. There was no resistance and no compression etc.

Is there a simple reason why the Variator could turn like this or does it imply a broken con rod or something? Can the Drive pulley assembly somehow 'disconnect' from the crankshaft?

It's weird, because this started with the scooter cutting out in traffic on the move (no drama but seemed odd) and then when I tried to restart, the starter whirred as if the bendix was stuck.

I don't know if the motor is complete toast and beyond economic repair - or whether there is something simple going on that I'm missing.

Any thoughts would be much appreciated. Thanks

This sounds suspicious. It could be a major engine issue. Did you check the engine oil level before or after the engine stopping incident? If too low it could potentially be a seized motor but I doubt it.

It could also be a problem with the starter gear ring no longer being located properly on the crankshaft so it's just spinning round without engaging the motor. Of course, if the first thing is true then the second thing could be true too.

This is definitely strange.
There is a fixed mechanical connection between the piston, the connecting rod, the drive shaft and the drive pulley.

On what side of the engine is your starter? I expect it is on the the right side.

The usual explanation of this is when the driving pulley splines have sheared off. Not that uncommon for the Leader engines if the variator nut has come loose or the belt's been changed and the driving pulley isn't fully home.

Could be.
How to check?

Open it up and take a look! The driving pulley is aluminium, so its splines shear way before any damage is done to the crankshaft splines. It actually doesn't take that much torque to shear them - often it's when the one-time use nut with its integral Belleville washer has been reused, especially if the belt isn't positioned just right. That said, most times the nut is reused it's AOK, but it only takes a mistake in the torquing up or the placement of the belt between the pulleys to create the problem.

I'm not saying this problem *is* that, but it's the most likely scenario given the symptoms so far.

It's one of those obvious things, but did you forget to put the spark plug back in?
If there's a spark plug, open the little black cap in front of the variator cover, and try to start the bike. If you can see into the variator cover and everything spins very fast, it does sound like a top end problem. Otherwise, JimC is likely right and the outer plate is splineless.

^^^^ A good quick way to test.

Thanks to everyone for all the great suggestions. Today, I went in again and removed the entire Variator, sliders etc. The output shaft can be turned easily with my hand - no hint of friction or compression or anything - no noise either. So I suspect a broken conrod towards the crankshaft end with the piston high in the cylinder and thereby not contacting the other half of the con-rod as it rotates.
Anyone seeking a good non-runner, let me know!
Thanks again one and all for the replies!

Bum and bugger. Sorry to hear that.

That just sucks. Maybe you can part it out to recoup some investment or find a replacement engine to drop in.

It could be and sounds very probable you have a broken connecting rod.

In your first post you said "the scooter cutting out in traffic on the move". A broken connecting rod normally does not happen just like that without any warning, warning then as unusual mechanical noises from the engine. Or it goes with a big bang.
But apparantly you did not notice anything beforehand?

Yep -I'll sell the scoot complete as a project or sell it in pieces on Ebay! I've just bought a PX125 with 3k miles on that arrives from Scotland on Sunday so it's mot all bad. Out with the old, in with th enew! It was kinda time for an upgrade anyway!

That's the spirit!

It's worth pulling the head off to see what you're dealing with.

^^

I'd be intrigued to know as well.

it almost sounds like the crank web separated from the pin. if it was a con rod it would have made a tremendous amount of noise. and you'd either hear it clanking around while turning it or you wouldn't be able to turn it at all.

We've not had confirmation that the spark plug is in... (though I assume it is).

I also would expect if it were the connecting rod you would have had a lot of noise.

That is why I asked if the starter motor is on the left or on the right side of the engine.
In my BV the transmission is on the left side but the starter engine is on the right side. I do not know how it is on the GT 125.

On the other hand hcurran already made the choice to go for a PX 125.

On the GT the starter motor drives the variator driving pulley via a bendix gear.

Not a PX, it's a white 2013 GTS 125 Super !

Correction, it's a 125 GTS Super🙃
Actually I will tear it down in the new year and report back.

Definitely in. Even if it was out youd feel the resistance of the piston in the cylinder and it wouldn't be as free as it is. Feels just like a newly fitted crank before anything is attached to it

That's a pretty common engine. Should be cheap and easy to find a replacement, if you did decide to keep it. A motor out of any of these will fit.

APRILIA APRILIA ATLANTIC - Arrecife 125 4T LC
APRILIA APRILIA SR MAX 125 ie 4T LC euro 3 2011->2014 (M357M)
GILERA GILERA DNA 125 4T LC
GILERA GILERA NEXUS 125 4T LC euro 3 2007->2008 (M355M)
GILERA GILERA NEXUS 125 ie 4T LC euro 3 2008->2010 (M357M)
GILERA GILERA RUNNER ST 125 4T LC euro 3
GILERA GILERA RUNNER VX 125 4T LC <2005>
MALAGUTI MALAGUTI MADISON 3 125 4T LC (PIAGGIO)
PIAGGIO PIAGGIO MP3 125 4T LC euro 3 (LEADER)
PIAGGIO PIAGGIO SUPER HEXAGON GTX 125 4T LC
PIAGGIO PIAGGIO X7 125 4T LC euro 3 (LEADER)
PIAGGIO PIAGGIO X7 EVO 125 ie 4T LC euro 3 2009->2010 (QUASAR M623M)
PIAGGIO PIAGGIO X8 125 4T LC euro 2-3 (LEADER)
PIAGGIO PIAGGIO X9 4V 125 4T LC
PIAGGIO PIAGGIO X9 4V Evolution 125 4T LC euro 2-3
PIAGGIO PIAGGIO XEvo 125 4T LC euro 3 (LEADER)
VESPA VESPA Granturismo L - GT 125 4T LC (LEADER)
VESPA VESPA GTS 125 4T LC euro 3 <-2013 (M315M)
VESPA VESPA GTS Super 125 ie 4T LC euro 3 <2013>2016 (M455M)
VESPA VESPA GTV 125 4T LC (LEADER)

Please do. Very interested in this case.

Reading that the starter engine is on the same (left) side of the engine as is the transmission I think greasy125's explanation stands a good chance.

my thoughts exactly. I'd find one from a breaker or a wrecked bike, possibly eBay and just take an afternoon and snap it in.

Happy New Year and thanks for that list. Just in case I caused confusion, can I check that your list above refers to replacement motors for the the blown motor in my '04 GT125L Granturismo (Carb).
I have since bought a great 2013 GTS125 Super which is running fine! I'll update my profile now!

While I'm deeply sorry for your loss… We love gory post-mortem pics.

Well, I finally got into the engine and the answer was remarkably simple. One link in the cam chain had broken neatly and by coincidence, the exhaust valves were in the open position, ergo - no compression! That is why it turned over so easily. No damage seems to be done

Now a couple of questions: I need to remove the large plate (called the oil guard I think) in order to fit a new chain around the crank. Is that oil guard a disposable item? Is there a way to remove it - other than a £50 special tool Refitting it - same question.

And finally, is it likely that anything on the tensioner front should be replaced while I'm in there?

Many thanks as always