Modern Vespa

My 09 GTS250 stopped running in November. I was on the freeway near top speen when I lost all power and costed to the sholder. After failing to start and seeing nothing obviously wrong I sent for a tow truck.

I just looked at it and discovered that the engine destroyed itself. An exhaust value made contact with the piston, broke off, rattled around the cylender, ruining the head, punching 2 holes in the piston, and finally logging itself in a 3rd hole and welded itself to the piston. I included autopsy photos for your enjoyment.

I've several questions I haven't found anything in the forum about. Any and all ideas are welcome.

1- Has anyone heard of this happening before? Did I experience a known problem or an unheard-of failure. The cam shaft, sprocket, and timing chain looked great. So, I'm suspecting a valve spring failure due to fatigue.

2- Assuming that there is nothing to replace in the bottom end, what's the best route for parts to fix this? I haven't prices out oem parts yet. I've sceen Molissi performance kits with the head, piston cylinder, and everything needed to put them together for $575 to $875. Is this a good idea? The cylender lining is pitted and scored. It cannot be used as is. Can it be bored out or resleved? Are there OEM or aftermarket overbore pistons?

3. I cannot get the cases apart to inspect in there until I remove the oil seal between the transmission and the engine case. This requires a special tool. Anyone know how to make a tool or open this with standard tools.so I don't have to reinvent the wheel?

Any other questions I haven't thought to ask?

Thanks for any and all help!

well, that's just terrible. What was the mileage and service history like?

Anyway, given that the piston is blowed thru I'd suspect contamination in the bottom end.

Personally, I'd just replace the entire unit out right. Ultimately that will be the most economical route time, labor and dollar wise.

If you're aching to tear down the rest and don't want to buy the tool for the "timing seal" you can use a slide hammer to pop one side or a gear puller with two really long m6 bolts to pop it out.

Good luck with it!

-g

That should buff right out.

Seriously, I have a 2009 GTS 250 and also and my engine gave up under almost identical circumstances (top speed on highway, etc.). Of course, it was a high mileage engine with more than 130,000 km on the clock.

I was lucky enough to have recently bought a donor scooter with a low mileage engine (same year) from an insurance company that had been declared a total loss... so within a week I was out on the road with the newish engine installed and the blown engine sitting on the shelf at my mechanics place awiating my plans for a rebuild.

I never bothered to open up the engine I pulled since I didn't have the bucks for a rebuild. But now that I've seen your picks I'll make sure to open it up before I invest in the kit for the rebuild.

Good luck with your next move.

Don't feel so bad, this same thing happened on my wife's Toyota Rav4. $3200 later all was right again after installing a donor engine with 62,000 miles on it. So, these things happen and usually at the worst time (mine was right before Christmas). I agree with Greasy, find a donor engine as there are more totaled GT250s out there than you think, and replacing the engine outright will be a lot less hassle that rebuilding. If you do want to rebuild, there is a Malossi top end kit on the for sale section right now. but if the bottom big end is loosy, goosy, it's game over. Either way good luck, sorry about your troubles, but it rains on everyone, some just get more than others.

The heads were known to break off exhaust valves on the air cooled BMW twins (800 and 1000cc) with the same result you experienced. Folks would replace them as a precaution at about 50k miles.

How many miles do you have on the GT250?

I agree the best, cheapest, quickest way out here is a donor engine. Good luck.

This is the head on a brand new Sym 150 I rode in Egypt. Less then 2,000km on the machine.

My GTS only had about 15000 miles. I bought it new in 2011. It was serviced as scheduled in the manual.

Disappointing that it should fail so early, then.

What fuel did you use? Especially, regular vs premium.

I have a theory. Knowing lower octane rating causes detonation. Running a lot of WOT can cause the detonation that can harm the valves.

But if you ran premium, my theory is crap.

There were two engines with the exact issue, broken valve destroying the top end, in the old scooter warehouse in Jacksonville a few years ago. One was a scooter I sold to a friend, so not an unusual issue with these.

I used premium. 91-93 octane (R+M/2) depending on what the station has

Can you offer any additional context . . wide-open-throttle abuse . . type of oil used? Sym typically has an excellent reputation . . and the 150 engine even has roller rocker arms. Have to wonder if monitoring cylinder head temperature would have made any difference.

Then it is a design flaw.

One of my GT's now has 76,000 miles on the engine, but I am changing the engine out as it has some issues, notably blown out spark plug (stripped threads in the head) and a propensity to losoen the variator nut (neither of my other two GT's do this when installed exactly the same).

I think the dropped valve is not too far off so I am heading it off early.

I went and checked my notes. It had less the 500 Km and had been ridden wot for those. It was most likely a valve that was not set right from the beginning. The other 25 scooter did 3000 km with wot and no problem. This was just one of those things.

Does anyone know if Vespa uses sodium filled exhaust valves?

If the bearing feels okay, get all the crap out, then stick a new top end on it and be good to go. The heavy crap settles in the bottom. A cold oil change will get a lot of it out. That's where you don't heat up the motor before you do the oil change. Cold oil will carry more crap out. Flush it once with diesel or kerosene, and then remove the oil pan and get what you see out. Heavy chunks settle, and don't come back to haunt you on a four stroke like they did on a two stroke.
If you were happy with the lackluster performance before it blew up, get a donor motor. If you weren't, it's time for a Malossi cylinder and head.

[quote="greasy
If you're aching to tear down the rest and don't want to buy the tool for the "timing seal" you can use a slide hammer to pop one side or a gear puller with two really long m6 bolts to pop it out.
-g[/quote]

Thanks for this! The puller did the trick, and I needed it to remove the fly wheel too.

check the spring in the broken valve, I wonder if it was the spring. Otherwise I would thing the valve was too tight.

John

For what should I look when checking the spring? All the manual says is, "Inspecting the springs and half-cones - Check that the upper spring caps and the cotter halves show no signs of abnormal wear." What's abnormal wear? Is there anyway to assess metal fatigue in the spring?

Thanks

Besides valve spring failure, if you were having a shop check your valves, are you sure they did it? Check your old invoices to see if you were charged for valve adjustment. I've learned from this forum and from some shop mechanics that some of them do NOT check valves according to the Vespa maintenance schedule.

For example: Vespa Motorsport in San Diego checks valves according to the schedule, and the techs say they're almost always slightly tight. OTOH, my local Vespa dealer does not check valves until 10,000 miles +, on the theory they never need adjustment before then.

I checked my Sprint at first service and both intake valves were slightly tight from natural wear and seating. My wife's Primavera valves were perfectly in spec, no adjustment needed. Maybe service departments think it's only 1 in 10 bikes that need adjustment, so don't bother checking, which seems crazy to me, since it's legitimate labor for which they can bill and we would pay. Your pics look, to me, like a too tight valve the motor decided to eat.

I'm really sorry you're going through this. If it were me, I'd follow Motovista's advice to clean detritus out of the bottom end, then install a Malossi top end. There's a how-to video here:

Thanks for the Video. The valves were never checked. The maintenance schedule from doesn't call for any attention to the valves until 20,000km, and my GTS never made it to that. I didn't think much of it, as it doesn't rev particularly high and my last 2 modern bikes have called for no attention to the valves for 16,000 to 20,000 miles. Lesson learned.

I'm pretty sure the gts250 engine calls for the for it at 12k with belt service. I remember doing the research on my 07 gts.

The springs will break into two pieces, then the valve dangles down and gets smashed.

Sorry for your trouble



John

Thanks for the condolences. The shop and user manuals on the wiki here show 20,000 KM. If you meant 12,000mi, will it just got there. The spring wasn't broken. As the cam, chain, and sprockets are perfect, I'm guessing (assuming the valve wasn't too tight from for while) the spring lost some of its "springyness" and could not close the valve fast enough, causing the piston to hit it before it was out of the way.

Really unfortunate this has happened. Tight valves won't normally cause this sort of damage, but as tv is saying, broken valve springs will. However, if it's not a broken valve spring that's caused it then it's most likely down to a faulty valve (a casting weakness) or the engine was running with the mixture too weak causing it to run much too hot and destroying the valve. Or, the wrong fuel causing overheating. Although detonation won't normally cause an exhaust valve to break as they are closed when combustion takes place. It's normally only the piston that suffers. I wonder too, is the camchain tensioner ok. If it allowed the camchain to jump a tooth it may have caused a valve to contact the piston. I don't see any damage to the other exhaust valve though. Intriguing issue.

Super bummer about the Scooter.
Maybe this helps...
I have my original GTS 300 cylinder and top end bits that you can have for little more than the price of shipping.
There were maybe 2k miles on it when I installed the Malossi stuff, and unlike your engine, mine was fine.
I have been sitting on this since then.
Nobody wanted it, but you seem like a candidate.
Let me know.

[/quote]

Thanks for the offer! Unfortunately, I just bought the Malossi head and cylinder kit myself. It was offered in the for sale forum for well below the cost of new and I snatched it up- Thanks anyways!

[/quote]Thanks for the offer! Unfortunately, I just bought the Malossi head and cylinder kit myself. It was offered in the for sale forum for well below the cost of new and I snatched it up- Thanks anyways![/quote]

Fantastic! Was is my tip off to you in my post or were you already looking? Either way, I'm stoked for you. I've never heard anything but good about this kit and Malossi in general.

You made the right decision. Have fun.

That reminds me, as soon as weather warms up a bit, I think I'll check my valve clearances.

A tight exhaust valve (not closing properly due to tight tolerances) can overheat, causing it to seize in the valve guide, staying open instead of following the cam lobe. If it's bad enough, you can get piston contact. If you are not replacing the crankshaft and connecting rod, I'd take a real close look at both. Obviously they are not designed to handle the stress of trying to compress a valve head. Wouldn't be surprised to see a bent rod, and perhaps a bent crankshaft.
If I was you, I'd be looking for a complete replacement engine...

Do you know this happened or are you just making it up? I have seen a lot of scooters and what you are describing just doesn't happen anymore for at least 30 years.

It's rare indeed, but it can still happen and actually does. Mostly to engines that are not maintained correctly, but sometimes a glitch in the manufacturing process can cause it, but that's very rare. Engines that are WOT'd alot are also more at risk. The GTS engines of whatever size are very robust and are not known for this type of problem. It's a trouble free engine usually if maintained correctly.

Late to the thread but FWIW I had a similar experience. I had a valve head break off and ding the head and piston. Mine was not as dramatic as yours or others that I have seen because when it happened I was decelerating in light traffic at about 15 mph and the engine was running at idle speed. If I remember correctly it had about 25,000 miles on it at the time and all maintenance had been done including valve adjustments. As you can see the valve spring was not broken. I can't seem to find the pictures of the top of the piston or the bottom of the head but the piston was not blown through like yours and I transplanted the head piston and cylinder from a donor motor with a bad bottom end and was back on the road and it is still running well at now over 40,000 miles.

Good luck.

It's not common - but does happen very occasionally. We spotted this in Italy while one of our scoots was having a top-end and stator sorted:

My GTS 250 and GTS 300 ABS manuals both call for belt service at 15K km or about 9K miles. Both call for a valve clearance adjustment at 20K km or about 12K miles.

Literally just had the same happen to me on my 2500km trip..luckily it happened on the last day

On Chinese scooters the valve heads are spun welded onto the shaft. It's the reason why exhaust valves stretch so much in the first thousand miles. Heat on that side requires religious valve adjustment before the first thousand miles. Does Piaggio do the same technique?

Interesting question on spin welding. One answer might come from a simple metallurgical failure analysis on the broken valve stem left in the guide. At the fracture site: Is there evidence of bending? Fatigue /beachmarks? Heat affected zone at a weld joint? Ductile or brittle failure?

Is it usually the exhaust valve next to the cam chain that fails?

So many questions...

Bill

I think most automotive companies use that technology. Certainly the valve heads are welded to the stems, the valve isn't turned from a single piece of metal.

Sorry guys I did mean miles 12k miles.

I sold the GTS at 9k so I never checked the lash.


KZ the QC on the Chinese is not the same on the Italian engines. Yes on my chinese engines I had to do the lash adjustment about 4 or 5 times till it stabilized and would hold.




John

I don't doubt it John. My experience has been that stability comes after about three clearance checks. That's the worst CCS blowup I ever saw.