Modern Vespa

Picked up this 1976 Primavera 125 ET3 recently and am in the process of tearing into the motor to rebuild and hopefully get the bike in running condition -- it had not run for about 5 years, to judge by the registration. Somebody loved this bike at some time. It has Bitubo gas shocks and (as I discovered today) a Polini top end. But I am getting ahead of myself. Here is the bike on the day I received it:



Here is the motor out of the frame. The motors are much easier to remove from these small frames than the motor from my P200E -- they are much lighter too!



And onto the bench. Note that somebody noted on a piece of masking tape that the tire was installed backwards!





Head off and the first surprise -- a Polini head!



Cylinder has some seizure marks -- will a hone take care of this?



Removing the flywheel. Note that this motor is FILTHY and covered in oil. Judging from the mess and the condition of the piston, it has been a while since anybody was inside of this:



The CDI was in the glove box, not on the back of the motor, and the condition of the wires on the stator is not that great. I will run new wires.



End of the line for today. No small frame clutch puller! Will pick this up when mine arrives.



In the meantime, I am curious what people think can be done with the cylinder. There are some seizure marks, but no scoring. Can I just do a hone and install a new piston?

And what is that large bolt in the middle of the front motor mount arm? I did not see it connected to anything. Thanks!!

That's for your pipe. It looks like you have a modified top end. More oompf.

I like to clean a motor before I work on it. It looks like you also may have had a bad head gasket. That's probably a 130. If the piston measures 57mm than you have a polini 130. What carb is with it?

Also if you look at the pic of your piston you will see where that lines up with the leak on your head. You were probably introducing some air there and it got hot.

Clean the piston and post some pics. All may be okay and a light hand hone could be all that's needed.

The stator doesn't look horrible from here and the cdi is in the correct place.

To add to what jimmy said, if your bike has a stock pipe, (which it may not since you've got a Polini top end on there), there is a plate that holds the exhaust and allows it to pivot when needed. That bolt holds the plate. http://www.scootersoriginali.com/osc/product_info.php?products_id=2390

Mine was missing when I got my ET3, along with the header nuts. The header pipe was actually just sitting on top if the tire and the owner was ring it this way. The engine was cruddy as hell.

Looking forward to following your progress. I just started a thread myself in the project forum.

The banana pipe is on sale right now at Motorsport.

There's also one on scoonet.

My suggestion is, unless you're going with a $300+ plus pipe, is to get the sito banana. It is a torquey pipe, sounds great, made well. I had a sport pipe on my smally and swaped to the banana.


What carb is with the motor?

Finally got the clutch puller and removed the clutch stack:



However, I am completely unable to get these cases apart. I have wrestled, tapped, and even drove a wooden drift in between the two halves to try and work them apart. Nothing works.



The two cases wiggle a little, especially around the gearbox area, but the crankcase area does not budge at all. Any ideas? Do I need to remove the clutch basket? That does not really want to come off of the countershaft either.

Removed flywheel seal and applied heat. Still nothing.

The Xmas tree def needs to be free of the clutch basket to separate. Also, a penny pinched between the primary gears will hold them so you can loosen and remove the crank gear

How do I remove the Xmas tree gear? Just yank on it? Not getting any real movement. Or do I remove the small primary first?

Your clutch is out already, it sits on the end of the xmas tree. So, that's not the issue.

It is better to remove the primary gear before splitting the cases as the crank is supported on both sides.

Given the polini kit and the up gear on the primary, this engine may have a ball bearing installed on the flywheel side (instead of the split roller as stock. If so you will need to heat around the bearing on the fly side case for it to release. You may be able to look between the crank and case and see what type bearing it has.

^^^^^^^^^^^^^^^^^^
And that is why I'm glad I learned to read. Awesome advice.

Progress! I looked at the flyside bearing as Oops helpfully suggested, and it does indeed have a single bearing rather than the stock two part. So after removing the small primary gear, I had at it with the torch:



Three minutes later the cases finally pulled apart!



A little more heat and a rubber mallet finally released the crank from the flyside, though the bearing is still attached. Any ideas what sort of crank this is?



Gears out - need to figure out how to remove the selector so that I can remove the axle:



Enough work for tonight.



A couple of questions:

(1) How do I remove the Xmas tree from the flyside case, or the single piece bearing from the crank?

(2) Which way on the selector is fourth gear? And do I just pound out the rear axle when the selector is in fourth gear? Won't that harm the selector arm?

if you move the selector all the way down to first (toward the clutch side) and give the axle a little love tap with a mallet it should free it self up from the bearing and be loose on the selector stirrup; then you can wiggle it out of the case.

can't tell on the crank, it's small taper and stock appearing. are there any markings on the conrod? a piaggio crest is of course stock, a small trident looking thing could be mecur or mazz. without comparing it to another crank or a degree wheel it's hard to say.

also, can't tell if it's the glare from the flash and oil on the gears or if they are chipped on the cross lands, a closer/clearer picture would be awesome.

you'll need a bearing separator to safely remove the bearing from the crank, or at least that's my preferred method.

to remove the tree, you can try heating the case from behind the bearing and it may fall out-- or the tree may come away clean. if not, two tiny prybars 180* apart with a little heat and gentle persuasion should lift it out.

best,
-greasy

Nice work Nomad.. and thanks to Marc, Patrick and Greasy for their valuable input.. I don't even have a small frame (yet!), but this is a great primer / lesson!
Again, nice job.. this is fun to watch unfold!

Cheers..

Lots of progress on the engine teardown tonight. First I removed the kickstarter and the kickstarter pawl/spring assembly:



That freed the clutch basket, which popped right out with a few taps from the mallet:



Next I removed the bolt supporting the gear selector and pounded the rear axle out of its bearing (more on the selector later):





Time to go to work on the bearings, starting with the main crank bearing:



The main crank bearing popped right out with a few whacks from the mallet, and the clutch bearing fell out along with it!



Last one -- rear wheel bearing:







A little heat to the outside of the case, and the Xmas tree popped out. The bearing turns easily, and I will probably reinstall as is:



Removing the studs with the tried & true method:



Time for cleanup!



Cleaned up nicely!





Today's questions:

(1) Regarding the gear selector, do I need to remove this? Is there any seal underneath it that can leak? I took a few whacks at the pin, but it would not budge. Any tips?

(2) The conrod has "MMC" or "WWC" stamped on it. Any ideas what this is?

(3) Is this a stock Prima pipe? (see below)







That's it for tonight! Thanks!

The bearing on the xmas tree is only like $1.00 (is that a 608, can't remember). Anyhow, it takes a good bit of load so replace it while you are in there.

The pipe is the older polini type (several copied polini). They are better than stock but not that great. I feel you should either spend $100 or $400 on a pipe. Nothing in the middle is worth the extra money. That pipe falls into the $100 side.

Unless it was leaking from the selector I wouldn't bother removing it. There is an 0-ring in there but removing and reassembling it is a pain.

How common is a leak from the selector and is this an O-ring that normally would be supplied with an O-ring set (I ordered a set from Scooters O)?

The engine had so much crap everywhere that it was impossible to tell where any leaks started, though there was definitely a leak from the head, as the photos indicate.

I think I will take some heat to the batwing and see if I cannot "persuade" the tapered pin to come out. Would hate to put this back together and THEN discover that I have a leak out of the selector.

nice work!
i see you've got an aftermarket primary. count the teeth and figure out what the ratio is, you may want to switch it out for something more city oriented...

there is an o-ring on the selector shaft that can leak. and, chances are that it will given the unknown provenance of the motor. while, as mr. owens states, the operation is a PITA royale i'd recommend replacing it for peace of mind.

mmc is a mazz crank. looking at the photos there appears to have been some work on it-- factory or otherwise-- and given the other components involved i'd say that the chances of it being a cut crank are fairly decent.

the pipe looks like a polini, but there were several other companies making similar pipes at the time-- proma, malossi, FAR, etx. but either way i'd just clean that mess up and shoot it with some hi-temp and run it.

i'm in the same camp as patrick, either spend under 150 or spend 400 anything in the middle just really isn't worth the time.

best,
-greasy

Will definitely replace the O-ring on the selector. Interesting on the Mazz crank. Did I buy a former screamer?

Nice job of picture taking & describing your steps. I've opened large frame motors, but not any smallies so far so I'm gonna bookmark this for when I do.



I have a couple of these ho hum pipes and noticed some small differences. On the header pipe, the cheaper, newer one had the same smaller diameter all the way to the connection(bottom of pic) while the other one was tapered, getting bigger towards the muff. I think yours is the second type.

Mostly, yes. The up gear looks a bit too tall for the rest of the setup, tooth count would confirm this. Maybe I missed it, what carb did it have?

With a proper pipe and a 24mm carb or larger this bike would pull that gearing and output 12hp or so. As built it was probably 8-10 and would have screamed in 1-3 but would have had a hard time pulling 4th.

Brought the bike over to Greasy this weekend to have a look. It has a small (29 tooth) primary and a small 4th gear as well. Looks like whoever built it before had some idea what he was doing.

In other news, the batwing pin is a $$@@! to remove. I have heated, whacked, and still cannot get the pin to budge. It is particularly hard to remove by oneself, as the batwing keeps rotating. Can anybody tell me for certain (or post a photo) of which side of the batwing takes the narrow part of the pin? This sucker absolutely will not budge. Hopefully I have not deformed the hole in the bottom of the case that it passes through. We will see.

I can't say which way the pin is tapered, but at this point you've surely mushroomed the thing anyhow. time to get out the dremel and take it down flush. After heating the shaft use a nail set tool tap it thru.

Mushroomed, and broken off a bit inside the pin. I have made a royal mess of this.

Great thread. I will be referring back here in the eventual task if engine rebuild.

Update!! Still struggling with the pin in the damn batwing -- I have drilled, heated, pounded, and destroyed a number of drill bits to zero success. It is still stuck. Will seek some help this weekend when I pick up my barrel/piston.

Was riding my P200 tonight and got hit by a car!! She was making an illegal U-turn from the righthand lane (I was in the left) and in my hard stop (on a wet road) I skidded the rear around to avoid T-boning her. Ended up hitting exactly parallel without going down. Busted my turn signal, dented the right cowl and put another dent into the legshield. She was panicked and I had to calm her down. Motor seemed to run fine -- will take a few pictures and post. Banged my right hand but does not seem serious.

Careful out there!!

Damn. Sorry to hear it. Glad you're ok.

I Wish I had some advice on that pin. I had the exact opposite problem with the shifter arm pin on my P200 shifter box. I replaced it and it wouldn't stay in. Luckily someone on here donated a whole shifter box and got me back on the road.

Good luck.

Between shipping delays imposed by the Philadelphia USPS sorting facility and my collision with the inattentive driver, my progress on the rebuild stalled out. However, the selector is being cut out and will be replaced (with a new O-ring) this week. Should have all of my parts on Friday, and will resume the thread with photos then.

While waiting for parts, I attacked the Polini exhaust with the bench grinder, sandpaper and Naval Jelly:



And then the bearings arrived from Scooters O! Popped in the rear bearing first. Prefer a dead blow to the mallet shown in this picture.



Don't forget your circlips!



Main, clutch bell, and rear wheel bearing installed, with the clutch basket:



View from the reverse, with the clutch seal also installed, along with a new kickstarter O-ring:



Waiting on my crank, so I attacked the rat's nest of wiring in this bike. It looks like somebody just bodged wires onto a harness with no real thought to where anything goes. There are countless blue wires without terminators and lots of blue/yellow electrical tape. Since I am doing the cables anyway, I thought I would rip out the old harness(es) and replace with a fresh one:



There is this odd box bolted to the interior of the frame, with the yellow wire hardwired into the harness. Looks like an A/C rectifier -- anybody know how the yellow wire is supposed to connect to the harness? The yellow wire was spliced to a white wire in this case:



Twice the number of wires, and most are blue! Azzuri!





Transmission and clutch cable housings replaced. Will do throttle once I have the new harness installed:



And here is the headset with the speedo fitted. Where does the screw at the bottom of the speedo attach, and how do you get it in?



Questions for today:

(1) What is the yellow wire connected to the (rectifier) and how does it connect to the harness?

(2) My clutch and transmission cable housings are too long (compared to the old ones, which appear to be stock). Is there a way to shorten the housings?

(3) How does the speedo unit screw into the headset? Look at that photo -- am I missing a bracket?

I believe the yellow wire is tied to the A/C out wire from the stator and the A/C in to the harness which should go up the switch and is distributed from there out to the headlight H/L, brake switch, tail lamp and horn. Assuming this is a non battery arrangement.

You just cut the cable housings. then cut the outer wrap to the depth of the barrel ends and put the old barrel ends on the cut end of the housings(unless you've ordered extra barrel ends).

There should be a hole on the bottom of the head set, just rearward of the headlight fastening slot. A long screw comes up from there into the speedo.

Thanks! Any idea why the rectifier would not show up on a diagram like this?

http://www.scooterhelp.com/electrics/wiring/VMB1T.pdf

Do you have a photo of said rectifier and its location.

I think we have the same bike, and mine has no rectifier.

The posted wiring diagram is correct to what I have.

Maybe someone installed the rectifier as a "fix".

Also looks like somebody installed half of an old wiring harness as a "fix" too. Here is the rectifier box, which is installed under the seat on the glovebox side of the frame:

I don't remember seeing anything like that. Ill double check my parts box when I get home and let you know what I find.

Thanks for checking! I suspect it may be an add-on, given that the hard-wired yellow wire is spliced into a white wire -- you can see this in the photo.

It is a regulator, not a rectifier. Indeed it is an add on. Keeps bulbs from blowing.

Thanks! How should I wire it to the new harness?

Since you are putting in a new harness I'd suggest leaving it out. Just make sure you have all the bulbs shown, and they are the correct wattage.

The yellow regulator wire would tie into the yellow stator wire as it goes up to the handlebar switch, and the blue stator wire as it goes to the rear brake switch.

Great thread and great work Nomad.. thanks for taking the time to take Quality pics and posting good descriptions!
Cheers