Modern Vespa

So, I took the plunge and bought a non running scooter that the PO said needed a clutch. its much worse than that and he knew it...
It is a 1974 50 special with polini 130 kit. i didn't take a great look at it (which is unlike me) and its got a really jacked up motor... so im gonna rebuild it.

I thought id share my experience with anyone that cares to read along.
Im looking for advice as I go, I'm a decent mechanic but have never opened a vespa motor up myself. It doesn't look too hard.

I've gotten alot of pretty good advice so far from this community with this scooter so far as well as with my p200 ive been riding for 2 years or so. (blew that motor up but sent it out to get repaired.

anyways...

So far the crank is bad on the flywheel side and Im just getting into opening it up. The old flywheel was put on wrong so he thought it would be a good idea to JB weld the woodruff key in and run it until it failed.

I got the motor out and on the bench.
starting to disassemble and clean all the parts as I go...



the head was not tight and leaking like a sieve (hope its not warped.) ill know soon...

I found threads from the oil drain plug in the bolt threads... its only one full turn, should be OK, hope i dont need to repair it...

You can helicoil the plug hole, lap the head, and there is a crank for $80 at scooter mercato. If you run the bill over $100,(easily done) you can take off 10% of the bill. And Dave is good people. Keep the faith. Good luck.

Not too bad, I have seen worse!

The DR130 kit is only $130 and well worth it if anything on the stock needs replacing/repair.

Get ready for a new crank and bearings, it will add up but it needs to be done looking at that crank...

You'll want to change the primary gearing, the 50 should have come with a 4 speed that if the cross is good is usually good enough as 50's don't put much stress on the gears.

Good luck!

got head and cylinder off. pic of ports.
the studs were loose...
there's some scoring on one side of piston/cylinder. its not bad but you can feel it with your finger. not deep.
can i clean up the piston and re-install or is it all a loss?

polini head/ says PM on cylinder

it was a 3 speed but it was changed to 4 gears.
ill get in there and see which are in there.
(can i measure or count teeth or something??)

the head sits flat on a piece of glass, looks OK. i have a helicoil set too. pretty easy. dont wanna if i dont have to though.

gonna have to quit for tonight without splitting the case.
i got about 4 pounds of oil, grease and road debris out of every little nook and cranny. the head leaking really made it dirty...

probably wont be able to get back to it until tuesday...

thanks for the comments so far fellas!

the base gasket was the thinnest little metal gasket ive ever seen. it was ripped too...

swingarm bushings.
i dont know how this stayed on the road...
the list is getting bigger.
clauss make smallframe bushings... good stuff

You know there are methods of cleaning that taper up.

I don't know if yours is too far gone but you can try cleaning up the high spots and get a nice clean surface out of it.

After that you get this paste that etches the two surfaces of the crank and flywheel. Tuners do this to ensure no slipping. I read it in a lambretta book. I have never done this though.

Its the taper that keeps the flywheel secure....the keyway is just for alignment. Although you would also have to address that keyway none the less.

Just a thought.

jsunstar, you are not alone. I am also pulling apart a VBC engine and like you are experiencing, the list keeps getting longer. Good news on mine is that the rotary pad is in excellent shape. Bad news is that I can't mill in a third port like I wanted to because there is a hollow web in that area below the surface. Keep posting, that scooter is definitely worth the time you'll be putting in it. I wish I was back in Florida now like you. Winter sucks. Make sure you give Dave @ Scooter Mercato a call when you are ready to order. Good Luck

Why did I get a negative for quoting out of a tuners book?

jimmy, it wasnt me.(at least i didnt do it knowingly) ...... you've been a great help.
ive heard the same from the local yamaha/genuine shop that the taper can be repaired. this guy used to be a vespa dealer here and is the only local source of info i have. (albeit, hes kinda hard to talk to). i find better advice here on this board though.

Yea, as I said, i don't know about your particular crank cause all im looking at are pictures.
Often people will diagnose from a photo.........kinda silly really.

The paste is called 'grinding paste'. Motocross has been using it for eons. I heard about it first from mini bike and go-kart times.

The key way is to align the crank, the taper/boss connection is what keeps the crank from slipping.

So tuners like to use the paste to insure the marriage.

Its all in books and online. I read mine from the Stickys book in the crank check section.

it's not new as Jimmy says.. I use it.. valve grinding paste. but it's not going to work on that fubar crank you have.. that crank is toast.

I don't think i said it was new you silly boy.

I first heard about it back in my mini bike days and motcross guys have been using it for eons.

[quote="jimmyb865"] I MEANT!!!! ... it's not new... as Jimmy says!!! (AS IN.. Jimmy already said it's not new!)

GET IT? too damn hard

[quote="Vader19"] Lost in translation.

That's what happens when you take a California raisin and mix it with a Chicago hot dog.

Cylinder needs honed and new upsize piston IMO. Crank is shot too, some break at that spot and the ones I've seen break have been much nicer looking than that one.

When you buy a vintage Vespa, you're basically buying a never-ending project. Large frames are a little better in that regards, but a kitted small frame... it's change this, then change that, then this again, then that again. Just go with it. It's part of the fun. It can turn into an obsession, and if that happens.. all I can say is... welcome to the club

Well said Groover.

By the time you sent off the crankshaft to get machined, the money spent would probably be close to purchasing a new one. I would just bin your old crank personally. Get your calipers out and measure the crank, smallframes have 3 different tapers. My guess yours is the stock small taper 19/20. Older PK models retained the small taper and soon went to the 20/20. The tuners pick is the beefy ETS at 24/25, (first number is flywheel seal diameter and second is the bearing diameter). You'll find out soon enough when you open the engine up on condition of the rotary pad. You could also do a leak down test. Reed valve vs rotary induction will also influence the choice of your crankshaft.

I would definitely lap the flywheel to the new crankshaft because of the JB weld remnants smearing on the inside of the flywheel. And yup Jimmy's correct that this will provide a proper fit between the mating surfaces.

On the cylinder you might get by a cylinder hone and picking up new piston rings. Measure the bore of cylinder, the polini kit it is 57mm. It looks like the PO didn't chamfer the ports, you need to do this or risk snagging a ring. Don't forget to check the clearance gap on the rings with your rebuild.

Budget plays a big factor in what you choose. Keep the Polini cylinder or you could pick up a DR kit or even a stock ET3 setup for less. I'm with Groover, go for the 1st size overbore at 57.4mm and fit Grand Sport Road Piston. Way better rings over the stock polini which have known to be brittle and snag.

Good luck in bringing this saga to an end.

im obsessive by nature. its already taken over.
i had the feeling it would be a project when i bought it.
its OK though, i haven't rebuilt a bike in a couple years. plus I'm learning a shit load about a vespas. always wanted one.

I have turned my work office into my after-work shop. plenty of ice cold AC, cable, a fridge and plenty of light and room. and the boss doesnt mind.



thanks for the input,

the crank is getting replaced for sure, they are too cheap not too.
i wasn't sure of the piston though. i kinda figured as much to replace and hone the cylinder. ill look into which one as per the suggestions.

ive been dismantling and cleaning. i cant take something off without cleaning it, checking it and bagging/labeling/boxing it/taking a picture of it.

ive had to stop at the clutch basket removal as i dont have the clutch puller.
the clutch parts were easy to take out as the retaining ring was off and the clutch blew apart. when i was loosening the bolts on the clutch cover, i knew what happened, the spring was pushing the cover off.
most of it is fine but one cork plate, the metal collar, and the retaining ring is buggered. it was a brand new clutch too... add that to the list (which is getting pretty formative.)

the inside of the clutch cover is pretty scraped up too. it all works fine, the brass (plunger?) and the ( clutch actuator?) are all fine and smooth. just ugly.

ive also found some bits.

these were around the bottom of the threads where the clutch nut goes... cant figure where they came from... they look like threads from something but i cant find where they came from yet...

also, these nibs fell out...
they look like teeth. but so far, I haven't found any broken teeth yet.

im still cleaning and dismantling...

gotta order parts and tools soon. i need a clutch puller. i was waiting to make an order until after i figured which crank i needed but i need the puller before i can remove the crank...

and heres a lesson learned. dont try to hold the basket with bare hands while trying to loosen the clutch bolt.
that shit is sharp. thumb and pointer finger. deep too.
note the band-aid under the glove.

buggered.

Hammer time? Or a new part?

That basket is garbage. A penney wedged in the primary gears works for loosening the crank gear nut. you can get that off and the small gear too by turning the primary basket so the large cutout is over the crank gear. Then you can split the cases.
Are those treads the ones the clutch puller threads onto? Bummer. Not that the part was any good, but you may have a trick getting the small basket off the xmas tree gear without threads for the puller.

Good thing you had no choice but go through this engine carefully. Those broken teeth in there could have caused some major damage and to the engine and yourself (by locking up the gears when you least expect it). They could be from a previous breakdown. In my experience, the only time I've seen broken gears on a Vespa (very unlikely to happen with factory stuff) is when back in the day before these parts were available, the "short 4th" was done the old fashioned way; and that was to mill the final 3rd gear off a three speed gear tree with a lathe, then mill off the final fourth gear off the four speed and braze that final 3rd gear onto the 4 speed tree, then replace the 4th gear with the 3rd gear, and voila'... short 4th. The problem with that was that that short 4th would lose its tempering and the gear would eventually break a tooth after a couple thousand miles, and when it would break, the rear wheel would lock-up 100%. It happened to me twice. I raced small-frames in the early 80's in Italy, and a lot of things were homemade like that.

The clutch can be removed by tapping the threaded shaft with a pointed drift (nut on but loose to the level of the shaft) while the cases are allowed to separate...

really TR?
have you tried this?
ive been dragging my feet and looking locally for the clutch tool cause id have to make 2 orders. one for the tool and another for the parts i need after i get the engine split...

yes, don't tell the purists! I have rebuilt countless smallies and I do not own the puller. Obviously, a typical rebuild doesn't require the clutch basket to be pulled, but I have done this many a time. I am curious if others do as well?

It only takes a very light tap or three to remove. The basket is supported well on the bearing so it comes apart easily with little stress on the bearing. If you are replacing the bearing, it is a no brainer. If the bearing is still good and it takes more than the usual encouragement, you will want the puller or to replace the bearing.

Hopefully the rest of your motor is in working condition. Have you split the cases and inspected the gears, yet?

thanks,
ill give it a cautious try.
i was waiting to get the clutch off before opening it... this may solve both issues.
or as my luck has been going, ill break something. haha
thanks

couldnt get the basket off although i didnt wanna hit it too hard... wussed out. my luck hasn't been too good with this thing and i don't wanna do any more damage than already has been done.

oh, I found where the teeth came from... i peeked inside.
it looks like a grenade went off in there... ill be surprised if this motor isnt toast.
i cant waitto get it all the way apart and see what else i find...


and the saga continues ........................................................

what a bummer!

You can get the fly case off with the tree in place, just have to wiggle a bit to get past the tree...

i tried, couldnt get it to go....if the stud wasn't there it would pop off
im gonna take it to the yamaha place monday. they have a puller.

so far i need a crank, piston, cylinder hone, gearbox kit, clutch, gaskets, bearings, seals, the top hardware to attach the front shock (its missing...), cables and ????


im not discouraged though. im learning alot.

after i got one of the studs out, i was able to open it up.
i still need to get the clutch puller to get the rest apart to clean/rebuild but i have what i need out to make an order.

the input shaft gear is ruined so ill be replacing that assembly. ive been looking around and don't see much else wrong. just metal all over the place from the blown gear.
the corresponding output gear is OK. its nicked up here and there but its not bad.

the crank looks great other than the ruined shaft...
it is a Mazzucchelli i think as it has MMC on the con rod.
26mm fly side bearing
78mm duration
13.5/19mm taper
the conrod is 97mm
i have to pick a crank, any more suggestions?

although there is a little wear on the flywheel side of the crank where it looks like it was rubbing on the bearing. the bearing isn't flush with the case. it sticks up a bit (and apparently rubs on the crank. there was a little space between the bearing and seal... not sure if its supposed to be flush. if so, it wasnt pushed in enough.

the rotary pad looks good. no scratches.

have these cases been matched to the jug?? that intake looks pretty std you may want to get into it with the dremel..... let this baby breath

it doesnt look like they have... im sorta shy to do it though.
if so, do i need to fill in behind the area i grind w weld? ive seen some discussions that people have to fill in around the other side...
gotta clean up that little ding though...

If you go with a DR kit the ports will match up well enough. If you rebore the polini kit you could match the cases up. There is enough meat there to match things up. Just don't get all crazy.

exactly as has been said.... clean it up enuf so theres a smooth transition unless your building a beast or trying to squeeze every last bit out of it there is no reason to go crazy.

on my smallie I did everything with a file and sandpaper.