Modern Vespa

Wooohooo - Parts are on their way! Thanks ScooterMercato!

They should be here by Tuesday, so I need to clean some case surfaces and get ready to put the engine back together (again) and get it rolling!

I hope the spare tire doesn't bug me where it is - I'm 6'3", but I like to ride slid way back. We'll see. Thanks for the heads up FM....

I'm 6'1 and have long legs and the behind-the-legshield spare holder on my Super (8" wheel) allows plenty of knee room. Oddly, the same holder on the GL with a 10" wheel feels cramped. Neither interferes with the brake though.

Looks like the 8" bracket was designed so the wheel tilts up against the leg shield bend. The 10" versions I've seen are vertical (?)

Yeah the 10" one is pretty much vertical

Looks ace!

The new Mazz crank came in! I went ahead and replaced the seals and bearings while I was at it.

I've got the case halves together, and hopefully will finish it up today.

I need some help from "the Collective".

To recap - had pinging noise, like piston slap happening.
Thought it was crank big bearing - still slaps with new crank and new piston.
Realized I'd honed the cylinder with a three legged stone hooked to a drill - three times. Maybe I bored the cylinder so much that now it was enlarged to not fit the piston properly.
Pulled the engine yesterday and measured the cylinder and piston.

Difference between the two is .78mm. I'm thinking this is too much. Is this too much clearance?

Piston size 62.30
Cylinder wall: 63.08

I measured for an hour, so this is pretty accurate (within .02mm) at the top, bottom, and through the exhaust port, or in the middle.

I *may* be corrected on this, but as I understand it the TOP of the cylinder is the narrowest part, so likely it is more sloppy as you go down. Not sure about the tolerance part.

I read .005 somewhere for 2 strokes, so yours seems a *bit* out of spec and maybe slappy. Especially since you are measuring at the top.

Based on the P's factory manual (I know it's not a P but close enough) 150 clearance is .225 and the 200 clearance is .215. I would guess your piston to cylinder clearance should be somewhere between .215 to .225. Need to measure below the piston rings on piston and further down the cylinder like in the manual.

http://www.scooterhelp.com/manuals/VNX1T.VSX1T.service.manual/VNX1T.VSX1T.serv.man.r.pdf Page 48.

Hope that helps.

Put the piston in the bore about halfway down, then measure the gap with a pair of feeler gauges. That'll give you better results. At least I hope it does, because that's how I do it.

I bought a bore gauge. Seemed prudent.

If these indeed are your measurements, it's like you've gone to 3rd oversize (usually 0.2mm - 0.25mm per step). Maybe you should have the cylinder and piston checked by a shop just to be sure...

Thanks for the input guys!

SaFIS - you're probably right. I called Matt at ScooterMercato and he doesn't think using a honing stone would take that much off to cause it to slap that much. I'm currently checking ring gap to see if they are too tight, which could cause too much pressure, and the slap.

Frankly, I'm pissed off, bummed, and cannot quite believe I could f*$k it up that much with how little I rode it. The new piston, crank, small end bearing should've took care of it.

I'm gonna check around locally to see if there is anybody that can hone this cylinder.

In the meantime, I might just buy a new kit....

So I checked the new ring gap (which I didn't do when I got the new piston, totally spaced it), and it's HUGE, like I'm surprised it'd start huge.

So I called Matt - again - and we came up with a game plan. I'm going to put the old rings in and give it a go.

If it still slaps I'll buy a new kit. Or if I can find someone local, have the cylinder honed and get a new piston for it.

Hey, at least I'm not splitting the cases this time, so that's good....

Meh. That's nothing. Call me back once you've
- Blown up a motor on the stand while test running it and deciding to see how high it'll rev
- Blown up a motor dialing in the main jet by mis-reading the jet and installing one 10 sizes smaller than you intended
- Blown up a motor when a wrist pin circlip comes loose a week after rebuild
- Blown up a motor because the washer you found on the floor wasn't the one that you weren't sure fell in the intake
- Blown up a motor because you're an underskilled idiot
- Blown up a motor because a cylinder stud came loose on the highway
- Blown up so many motors you have literally lost count...

Just look at all those things you have to look forward to!

Ha! Thanks for making me smile and lighten up on myself

Glad I could help!

And I even forgot some of my most exotic explosions
- Blown up your motor because you cracked the cases with monster tuning and a bad gear change
- Blown up your motor by shattering the cruciform getting on the highway
- Blown up your motor by shearing the axle in two
- Blown up your motor by shearing the clutch woodruff key

Those are more Boss Level motor explosions, though.

Could you have it NiChrome plated and rebored? I had a Suzuki cylinder done a couple years ago by usnicom.com. I don't remember what it cost though. I'm not sure how these come stock, but it could make the cylinder tougher than stock.

Hmmm, I'll check it out - thanks for the tip!

you can measure a cylinder with a set of dial calipers for a rough estimate, but that is really not the way you want to do it. you should be using what is called a "bore gauge." This will give you accurate readings though the length of the cylinder. . . and that is important. The diameter can change if there is a problem with the original boring of the cylinder and now with your honing.

When i bore a cylinder for 1st and 2nd over pistons, i am in the .003 ballpark.

Hope that helps.

Just catching up.
Good grief!


Don't quite understand how the rings could be so crazy wrong sized.
Working on these things is patience personified.

As for CM - eh hem. Fire in the garage...
Just sayin.

Thanks Gick for your knowledge. It helped. Big time nuts. It's like a set of 150 rings were stuck in the 177 box. They're even a different color, verses the ones that came with the original kit.

It was ordered directly from SIP through "The Market". If I'd of known that I probably would've ordered a Grand Sport. Live and learn...

Spraking of live and learn, I've learned a few really good things that I'll always do from this point forward:

1) Verify ring gap
2) Don't assume the factory gave me the proper stuff
3) It could always be worse - just look at CM1s "list"
4) I learned a few things, which is good. Better than knowing everything.

I alteady got the piston and cylinder reinstalled and pressure tested. Tomorrow i'll put it back in, and see what happens. It's always exciting cause you never know what can happen!

Which one?

At some point - I am going to just come to your area of the world to enjoy a cup of that coffee.
Always impressed with how tidy you keep the work area.
And - as you know - B62 is one of my favorites.

That ring gap is crazy.
Good reminder for me as I enter that phase.

You are welcome ANYTIME! I just got word that May 4 - 6th is the Oregon 100 Rally put on by the Top Dead Center SC out of Eugene, inland from here about an hour. It's a fabulous event and a good excuse to head on up!

Charlieman's calendar
(hopefully I will be done by then with my build...)

Most Excellent!

I bought a bore gauge, dial indicator and a set of cheap micrometers after finding a bent crank in my VW bus that the machinist said was good to go. Always a good idea to measure yourself. Stuff gets put in the wrong box and parts are sometimes out of spec straight from the factory.

So I put the old, original piston rings on the new piston.

Chris came over today on this rainy day and we put the engine back in, and a fast flow fuel tap and no kink hose.

Slight tinging but nowhere where it makes me think "Shut it off, shut it off before it implodes!"

I'm gonna ride it until I deem it not right. At that point it'll be a new kit or machine shop home and a new piston.

Thanks everyone for your help! It's greatly appreciated!

I haven't updated in a while because other machines and priorities have taken... priority.

To recap: the piston was slapping, probably because of my exuberance with the honing stones. It got worse with the new piston.

So I was going to drive it until it imploded, but instead I left it parked.. .

Then a new Pinasco 177 kit showed up on my door! A gift from my good buddy Chris! I think he was tired of me moping about and not wanting to ride B62. Super kind of him - thanks man!

I took some time yesterday and today to pull the engine, inspect the top end closely, install the new kit, and go for a spin up the street!

I'm pleased to say the rattle seems gone. I'm gonna go nice and easy on this new cylinder and piston, but not too easy

I took my time during disassembly to see if I could find the "smoking gun" to the rattle but no such luck. I'm gonna go with I oblonged the cylinder or something whacked like that.

During reassembly, I also took my time, using new greased up gaskets, and of course doing a leak down test.

Tomorrow I'll take it around the neighborhood. I'm pretty excited to have it back on the road.

Oh, I almost forgot, I bought a side stand like SoCalGuys. I flippin love it!

I put the engine back in today. I also took a vid of the leak tester apparatus I put together.

https://youtube.com/shorts/W8eV83Ct14g

I'm gonna run it with a 130/E3/125 & 48/140

The E3 is between a BE4 & BE5 and I don't have a BE5 and the BE4 feels too rich, so until I get the BE5...

That side-stand makes the SIP version look like it stepped out of an ice cold shower.

Nice progress! Looking forward to seeing this run.

I like your leak-tester setup thru the spark plug. What did you use for the spark plug thread connection?

Thanks GL. I used a hose from a non working pressure gauge. I drilled out the end just to ensure it flows freely.

This setup only works on the non-200cc scoots though because the exhaust flange on the 200cc has a notch cut into it, which makes the rubber plug useless. I suppose I could rig up something to block the exhaust for 200cc, but haven't done it yet. I just use an inner tube connected to the exhaust and plug the spark plug hole...

It's not roadworthy until the master tuner comes over and gives it his official Okay Dokey 😀

Now I need to keep an eye out for a spare qauge while thrifting. I ordered some bits from McMastercarr which arrive tmrw; included within are rubber caps to fit 200cc exhaust stubs. If they fit proper, I'll hook you up.

Sweet! Thanks man!

I really like using the plug because the reading is more accurate. With an inner tube, it starts to expand, lowering the pressure. It took me a few to realize I didn't have a leak, just the inner tube expanding.

I hate using the inner tube, just my personal taste; I like to have a proper tool. On a smallie I use a plate to block the exhaust port; and an old intake manifold + a thick rubber cap for the carb side-the rubber cap has a bras bung threaded & rtv'd into it for the pressure gauge.

I'm glad I saw your leak tester here, because I ordered the parts from MC earlier in the week, with the caps and other supplies for my LF tester. Good timing

I love it when things line up like that! I thought about drilling.out a spark plug and sticking a hose on it, then realized I had a flaky pressure gauge to sacrifice. Much easier...

What a good read for a Sunday nt.
B62 looking fab.
Noted stamp on piston.

My pressure test method is bout the same.
Motor looks tight.
Very nice!