Modern Vespa

So today i took a trip out to meet V oodoo since we live in the same town. It was a good visit, he has a LOT of parts squirreled away and a lot of interesting rides.

On the way back home I was just enjoying the ride, cruising along at about 45. The engine made a little hiccup but I thought my hand had just slipped on the throttle. It happened again and I thought, gee I wonder if that's a soft seize? About that moment a crazy screech happens, which I realize is the rear wheel fully locked up. A couple more milliseconds and the I pull the clutch and coast to the side of the road.

So what happened? I know the engine is seized, the bike will not kick over. I think the question is whether its the crank or the piston. This is a 2008 Stella that V oodoo rolled over to 2000 miles while he was riding it and I was riding his scoot. SR Race exhaust, P200 air cleaner and Bald John jetting (55-160 idle, 160 air corrector and a 100 main jet).

Earlier in this morning I had switched the mixer tube from an E3 to a BE3. The plug had been black and sooty and I'd decided the BE3 might provide just enough leaning out to get where I needed. The attached plug photo is the plug that I pulled once my heart-rate had returned to normal; about 10 minutes later.

Tomorrow I'll pull the head and try to pull the jug. That should at least tell me whether the seize was the crank or the piston. Looking at some spark plug photos, it seems like the plug is lean, which could mean less overall work if I can get the top end off.

Are there any tricks to getting a seized cylinder off the piston?

Hal

If it is seized real good, I guessing it is down lower than the piston. But before all the assuming on my part, just start by pulling the head off for a look. Unless the piston is at TDC, you should be able to check out the cylinder walls for scoring. If that looks good, take off the cylinder and take a better look at the piston, rings and lower cylinder. You should be able to peek down at the lower end of the rod as well. Look for any metallic dust and give the rod a wiggle. There should be a wee bit of side to side play, but nothing up and down. You'll find the answer, take some pics and report back. And good luck.

As far is "unlocking" the piston from the cylinder I have seen it a few ways from using the kick start and have the cylinder and piston lift up1-2" then sticking a piece of wood between the cylinder and the engine case and continue to use the kick start. you could also just try a hard plastic mallet and don't try hard and see if the piston is not lock too hard. I also seen people making a small metal plate using the cylinder studs and putting a small wooden block on top of the piston. Either way, just use to WD-40 to see if that can lossen up.


My last hard seize was on a POS Pinasco 215cc also at 45 mph. This cylinder kit always gave me many problems from day one, it soft seized on me 3-4 times before finally crumbling like blue cheese. The "mighty" nickasil cylinder liner proven to be the destructive piece of weak metalurgic.


What oil are you using? . Changing the subject, if your engine tuner up to be a total catastrophic failure let me know, I have a LML non injected engine with 300 miles.

I have a Stella 150 with a DR177 and Sito plus exhaust and drilled airfilter. With the research I have been doing as a starting point, people using a 55/160 slow or idle jet, with 160/BE3 / xx seems to be in the xx= 106/108/110 + range. I've been looking for a place to start since I'm cleaning up my carburetor and putting in a set of Boyesen reeds. I don't like the factory jetting with a richer 102 main.

You can try heating the cylinder up, penetrating oil and a mallet on a fat wood peg - that's off the cuff and maybe the pros know better. Where you find the piston is in the cylinder will make some difference. If it's near the top, you have more work and a longer way to get it out, but easier to get it broken loose. If it's lower you have a shorter way out but may need to block the cylinder up w/ small hardwood blocks to get the travel you need on the piston as noted above.

BTW, small world, I have a new unused LML top end that should be the same as yours and also a CHT you may BORROW until you get your own?

Well I'm happy to report that I'm now a member of the Stella Siezed Crank club. When I first pulled the head I thought it was definitely the piston that seized, but when the cylinder just slid up the piston, i knew it was worse. So there is a cracked ring, thats what was bouncing around in the head I think. I can't get the wrist pin out without pulling the flywheel, so I need to get the engine out, and take it apart. Something in the bottom end is also seized. The connecting rod will move up and down but the crank does not rotate and I am not able to turn over the engine with the kickstarter or by turning the flywheel over.

I've attached some photos of the carnage. Also here is a link to the engine running about 3 hours before it blew up. I'd thought it sounded a little rattly, maybe the ring had already broken off?

Hal

Maybe your clutch "blew up"...

I’m currently working on a randoms Stella down by me. Engine sounded rattly and then died. His problem was the piston skirt broke and then sabotaged everything else. Since early Stellas are known for bad crank bearings and lower quality, were replacing things with and doing a bolt on kit. See the attached photo to see what we’re planning/ how much things will cost.

Not trying to be a smart ass, I'm really curious. If I had to replace a crank and had my cases split, why would I not put in a 60mm stroke crank?

https://www.sip-scootershop.com/en/products/long+stroke+crankshaft+mazzu_46000000

Smart Ass away! This guy that I’m working for knows nothing about scooters. I’m trying to give him some performance gains but as much reliability as possible. Money is also a factor in this decision too. So, simple setup, lower costs, less tuning and quicker turnaround time were all factored into his setup.

Ok, sounds like good reasons. I haven't researched it much, as the previous owner of my scooter put in the same crank your using, figured I'm going to keep using it. Need to read up on 60mm crankshafts, one of these days. Figured when I learned more and got brave or had to split my cases I would look I to it more.

Whoa, hey man, I'm really sorry this happened to you. I think Rob Hodge came up with that about 20% of these engines fail? Bottom end goes out and takes the top with it, sometimes it's the top and takes the bottom. It looks like a lot of bad things were happening at the same time. Either way, this sucks. The Stella wonky crank club is not one I want to be a member of.

longer piston travel increases the capacity slightly and alters the timing which affects the RPM/torque. for example, what I am currently working on. Malossi 166 kit is 166cc with stock 57mm crank. but with 60mm crank I have installed it is closer to 177cc. using that long stroke crank has also adjusted the default timing of the cylinder ports higher closer to higher RPM performance.

57mm crank stock 166 timing on mine:
113/166
installing a 60mm crank changed the stock timing to:
126/175.

raising the timings equates to peakier performace...more RPM and less torque.

Speed is very expensive! If we went long stroke we’d need to port cases $$, need a stronger clutch $$$, go with a different primary $$, bigger carb $$$, replace anything left from LML $$$$ and then he’d have to pay me for my time to get everything correct and tuned $$. If he wanted all that I might do it, but would probably tell him to just find a P200.

I set out looking for a "project" to move up from my Honda Passport. I stumbled into this Stella and it was cheap enough, clean enough, and low mileage enough that I was swayed to go down this path. I don't regret it and I'm just looking at this like I now have the "project" that I wanted -- mechanical work with a solid rust free body. After I bought it I always knew it might become a project Until it exploded I was quite happy with the performance. I'm thinking the "budget" crank from Mercado, maybe bump up to the Malossi 166.

I'm excited to really clean everything, and get it to a point that is clean and where you can work on it without getting grubby.

I'm sure i'll have more questions, so I'll post them as I go. My main worry at this point is that the case got damaged in some way so as to render it un-useable. Fingers crossed that isn't the case.

Hal

I found the same project and am in the process of cleaning mine up. I bought it because it already had a new crank and DR177 kit. I would have to look at the receipts, but mine had a crank end case bearing seize. The previous owner had the crank replaced and a new half case that the bearing spun in. I want to pull the DR177 kit and learn about porting and timing. Want to take the squish down to about 1mm from 2+ mm, can't remember the exact number.

A 60 crank in a stock cylinder can be quicker than a 57 crank in a 166 kit.

Can someone list what are the tools I need to get the engine to the point of having the case split and re-assembling?

It seems like at minimum I need:

Flywheel lock
Flywheel extractor
clutch lock
clutch nut wrench

Its not clear whether I also need the tool to split the case or to extract the crank.

I'm going to start building a list of parts and tools I need for the overhaul.

Hal

Case splitting tool and the crank install tool are not necessary but definitely make the job easy. Feeler gauge for crank bearings. Various punches for bearings and seals but you can use steel pipes or sockets that fit for punches. Timing wheel and gun for setting ignition timing. Torque wrench also helps.

I should mention that I've rebuilt Saab V4 engines and transmissions, Citroen DS engines, and Honda Passports and have a significantly deep set of tools and tool-making tools. So I'm fairly familiar with rebuilding things and being creative about tool use. Its mostly just what are the things you want to have.

Edit: I just learned I have access to all the scooter specific tools I need.


Hal

Wow this really sucks snail snot, I feal bad for the Op. I had Gick Speed do me up a motor and upped the carb a bit but nothing else as it suits my intentions of simply putting and enjoying the vintage feel.

I think I'm going to go fairly stock with the rebuild. It was plenty quick for my needs as it was and I don't really need more performance in exchange for fuel mileage and longevity and a broad power band.

I do have a couple questions for the group:

The LML is a 5 port cylinder that functions as a 3 port given that the case lacks 5 true ports, correct? In my obsessive reading over the last 48 hours a lot of people suggest that the LML 5 port motor is a little faster/torqueier than a comparable PX150 with the 3 port engine. Assuming I am going to stay at 150cc, am I better using the LML 5 port cylinder kit over a new 3 port Piaggio kit?

My old cylinder should hone out just fine but my piston is pretty rough, do I have to use an LML 5 port piston or will a Piaggio 3 port piston work?

Lastly, just to throw a wrench in the works, is there any advantage to moving up to the ASC/Mercado 166cc kit?

Sorry if this is too many questions, just trying to plan out the best course of action.

Hal

Just gonna bump this once, as I still don't have this question answered.

Does anyone know if a Piaggio 3 Port 150cc piston will work in the LML 5 port cylinder? Yes I know its not actually a 5 port like a T5. I'm just wondering if the ports in the piston will match? My head and cylinder are salvageable but I'd prefer to use a Piaggio piston with more readily available rings than the LML piston.

Hal

So I went and dug through Voodoo's part stash over the weekend and answered my own question at last. Overall the LML and the PX piston are identical in height, dome radius, and wrist pin location.

The big differences are the ports and the rings. The porting on the PX 3 Port piston is smaller than the LML. The overall location are the same and it would be possible to mill the ports to match an LML piston.

The rings are quite different however. LML rings are 1.5mm, Piaggio are 2mm in the groove, but the outer profile is wider. In reading about rings, I think thinner rings run more efficiently and allow higher RPM.

Like I said, you probably CAN make a PX piston work but it would take some porting to the piston.

Hal