Modern Vespa

Yesterday, I spent a lot of time at the kitchen counter with my vernier calipers and the Lambretta Images Port Timing Calculator, followed by some time in the garage and finished up the porting. All is looking good and I'm right at 124TD / 172 ED. Adjusted the bottom of the exhaust to match the piston at TDC, life was good.

Naturally, with everything going so well, it was the perfect time to realize I made a significant mistake in this whole process. I ordered the wrong crank for this motor, not paying proper attention to the fact that some Sprints' cranks had the later PX flywheel cone. Some did not. Mine is the Did Not kind.

Lucky for me, I can spend my way out of the problem, but it's going to cost me $200 (with shipping), a week of time and a lot of self-flagellation.

So assuming no one tells me not to, I'm going to order the Mazzi long stroke crank shaft that has a P series cone for the SIP Ignition, but fits the old seal.

It was a dumb mistake on my part to forget to verify rather than blithely trusting SIP's fit list for the part rather than using my eyes & brain. I don't know that I'll ever build up a P series motor with a rotary on it, or if I do, it'll be a P200, so I'd be willing to let it go relatively cheap to someone so I don't have to look at my mistake on the parts shelf every time I'm in the garage.

In the meantime, assembly of other components continues. Cruciform swapped, axle and drive shaft bearings installed. Crank seals, xmas tree and gear stack will go back in today.

Assuming no more parts ordering failures on my part, short of crank installation and any adjustments that the new crank requires (I'll have to measure stroke again, but I'm not going to bother until I get the new crank), this thing should be ready to seal up.

Maybe check out the DRT seal adapters. I used them with the PX taper conversion crank in my VBC motor. Better seals (Viton) and in theory can be changed much more easily. I used a stock PX stator, flywheel and CDI. All lovely and stronger than with the original narrow taper crank.

Unfortunately, I don't think that's an option.

The adapters are for using old cranks with modern seals. I'm not dead yet, but I think I'm still looking at a new crank.

I MIGHT be able to make it work on the clutch side, but it would require installing the clutch side bearing on the gear box side of the seal, then closing up the lubrication channel in the case. That scares me a little, because I don't feel like I can know if that bearing will get enough lubrication or not in that configuration.

On the fly side, I'd need a 24x32x6 seal to fit the adapter. A little googling led me to a 24x32x7, but that's the closest I could get.

To me, that feels like a lot of engineering for not a lot of cost savings versus just ordering the new crank.

Sorry I wasn't clear. You need to buy a different crank any how, the adapters are for the narrow taper or hybrid (PX taper) cranks. The seals come with the adapters and are easy to source if/when they fail. My thinking was that while I was in there, I would improve what I could.

Remember to install both bearings on the crank before assembly.

I was over-thinking to make up for my previous under-thinking

Chandlerman, you may find my project thread interesting and helpful in places. It was my first attempt at a pre-P motor. Your Sprint V and my Super had similar motors from the factory, but the Sprint V was given a 3 port cylinder, 10" wheel, gearing to suit, a better SI carb (20/20?) and exhaust. Both will end up as 190cc three porters on 10s.

VBC1M (190 Super) engine build

That thread was a great read, Swa. It was

I'm going back and forth on whether or not to throw the seal adapters in my SIP cart. Eventually, I'm going to need to rebuild my VBB's motor, too, and I could also use them on it, but since it's just sitting on the shelf right now, I haven't been in too much of a hurry since it's only a two port, and the first time I rebuilt it, there was a lot of blood and cursing involved.

Plus, I have a multitude of other projects in front of it, including my boat restoration (which I have committed to have in the water in under four months from now), the GL, and a bunch of work on my house that my wife is getting fairly impatient about...

I second that! Great read swa. And I'm digging this thread also. I seem to learn something from every post I read so thank you for posting!

The clutch side bearing would get plenty of lubrication - this is of course how the P motors are set up. But what you would need to do is create a new circlip groove in the case to retain the bearing. Not impossible, but maybe trickier than you wanted. Also that seal you found would be fine... if it stuck out towards the stator another 1mm then it should be no big deal. Plus it's a double lip seal. Bonus.
There was a thread on the old ScooterCentral / even older StellaSpeed forum "So you wanna install a P crank in a Sprint" that went through this... from memory he used a Rally 180 seal on the flyside. He just used bearing retainer on the clutch side, and said it worked fine, but I couldn't live with that.[/url]

The clutch side bearing would get plenty of lubrication - this is of course how the P motors are set up. But what you would need to do is create a new circlip groove in the case to retain the bearing. Not impossible, but maybe trickier than you wanted. Also that seal you found would be fine... if it stuck out towards the stator another 1mm then it should be no big deal. Plus it's a double lip seal. Bonus.
There was a thread on the old ScooterCentral / even older StellaSpeed forum "So you wanna install a P crank in a Sprint" that went through this... from memory he used a Rally 180 seal on the flyside. He just used bearing retainer on the clutch side, and said it worked fine, but I couldn't live with that.

Aha! Found it!!!
https://web.archive.org/web/20160310065830/http://www.scootercentral.net/forums/viewtopic.php?t=16229

I say cut your old crank.

New crank is already on its way from Deutschland, so that decision is made.

The issue of needing a circlip groove cut on the clutch side of the cases seems to be the biggest obstacle to doing the swap out, but that's more work than I'm going to track down or take on. At this point, I want to get this sucker back on the road so I can focus on other projects for a little bit.

There's also the issue of how much engineering and expense is required versus just going with the correct part for the job. It's kind've an interesting problem, but if I'm going to do a bunch of extra work on something like this, it's going to be to make it faster and/or more reliable. One thing I think we all know is that nothing ever seems to get done to make things cheaper

Sounds like the operation was a success. Any pictures of the cylinder? And final dimensions?

Unfortunate to have a last minute crank fiasco but seems like all under control. I'm sure the PX Mazz one will sell. Someone here could buy it and stick it in a stock 125 to make an interesting thread.

I'll post some this evening, Jack.

Short version is that everything matched up to what I was aiming for with no mistakes.

I was going to just wait until the new crank arrived, then re-measure everything to make sure it's all still good.

Sounds interesting! I'm not familiar with the concept though...

It could be quite useful! Hey Chandler, got a link?

Made some progress today.

Also today, discovered that I lost the old kick start gear spring and forgot to order a new one.

Scooter Mercato, here I come...

... Well that sucks!

PM me your addy & I'll send you this.
Big snowstorms here, but there's a window tomorrow morning & I plan on getting out to the post office if I can.
Wish me luck.

That spring I had. It was the one that presses the kickstart gear out of the way.

For some reason, I really struggled to get the quadrant return spring installed today.

I finally made a shim out of a scrap of aluminum sheeting which I put inside the spring and used as both a guide to keep in in line and also drive it around the shaft. Solved the problem about as easy as could be.

Hmmm....I think its not lost. In those older engines, do they not have that spring?

Yep, you have the riveted on leaf spring. No need for the coil spring.

So it sounds like the only thing I've lost is my mind, and it's been gone for years at this point.

Actual stroke on it was 60.1mm.

I just buttoned up the motor and just took final port timing measurements with the new crank.

176 ED / 124 TD / 26 BD

with a 1.5mm base gasket.

I'll take that

Top of crown to top of cylinder was only .6mm, though, so the head will need to get milled down for proper squish, but that's relatively secondary and I'll get to that once I confirm that everything else is solid.

Next up, leakdown testing!

Looking good Chandlerman. Could you do me a favor and post a pic of your leakdown mechanism. I'm getting ready to fab something up and I'm particularly curious how you interface with the carb intake.

Thanks man!

For the carb, I do it with the airbox installed, so I use a piece of innertube that I've cut more-or-less like a gasket, then bolt an old carb body over that.

Ahh, got it. Then just blow up the.....exhaust. That just sounds wrong! Thanks, I'll probably do the same...

Blank off the inlet (I use a piece of neoprene from an old wet suit under the carb box), put an expansion plug in the exhaust stub, and pump air in through the spark plug hole.

A little over target. With the 1.5mm packer at least it can be lowered if 4th doesn't pull.

Be prerpared for rpm. Not to strong on the ignition timing. 16 degrees is a good place to start. Make sure that WOT splutters bad, before down jetting. If you only follow one rule, then this is the one.

It's on!

First kick on the stand
Once I confirmed it was all looking solid, other than that weird little rubbing sounds right after I started it (anyone know what that is? Nothing seems awry other than that), I put it in the bike. What a pain in the butt that always is, even when it goes well.

I completely spaced on checking compression and squish until just now, but it'll be there when I get to it.

Initial jetting is starting from what came in the DRT modified carb, plus the main jet from the Venturi, so 190/BE4/140.

I still need to sort out a better airbox, too, so the venturi isn't just choking from lack of headroom. Maybe I can get one of my 3D printing friends to kick out a spacer for me, or just order one.

It's been snowing all day, so no action shots just yet and the clutch still needs a little bit more adjustment, but as of right now I'm feeling like this is going to be another solid build.

Now, it's time to start looking at the rest of the bike. First thing I noticed was that the throttle tube is extremely stiff. I don't know if it's just frozen up, or actually bent. Either way, it's going to need some love.

I'll replace most of the cables while I have the headset open, too.

I'll have to do some franken-wiring on the electrical system as I swap it over to DC and install LED lights.

The turn signals, while original, are in varying levels of disrepair. Some have duct tape on the stems, some have zip ties holding them on. Some have both. It's going to take some work to sort that out.

I need to get some more of those adjustable mirrors since I put the first one I bought on the Stella.

And last, but by no means least, I'm running the stock clutch. It looks like I could install a modern clutch in it, but I'll need to cut back a flange inside the case which I'm guessing is intended to help guide oil onto the clutch.

Damn dude, you are THE MAN! Great job!

Sounds nice n crisp... is the flywheel cover rubbing?

I don't think it's that. The sound is constant even when I blip the motor, so it pretty much has to be something in the drive shaft. Maybe the rear wheel seal or something, even though I greased it for assembly.

I'll keep an ear out for it next time I fire it up.

WOW that sounds sweet, Im going back and re-read everything you did from the top of the post again. Very nice.

Thanks, everyone!

Even though I seem to be getting pretty good at this tuning stuff , I always have a tremendous sense of Imposter Syndrome whenever I come down to the end of a project and have to see if it actually works or not.

A couple more notes which slipped my mind last night, included as much for posterity as anything...

I got lucky eyeballing the initial timing with no marks on the case. I went back and checked it and it was 15 deg BTDC at 7,000 RPM's with the variable timing, 23 at idle, so I'm not going to worry about that for now.

Despite the snow being up to about 4" (6" this morning, for those following along in the home game) and lack of any electrical system, I tried to take it around the block last night, but didn't get any further than immediately outside the garage. The clutch was dragging, but producing enough torque at idle that it was just spinning the rear wheel in the snow of I didn't put too much weight on it.

I also replaced the fuel tap with a SIP faster flow tap and installed a Clauss Studios rear shock buffer and new Carbone Sport rear shock. Unless the front suspension is completely awful, I may leave it alone until I put a disc brake on it. I didn't order one earlier because they were backorderd. But that's not to say that a new front shock might not leap into my cart the next time I'm ordering parts...

I didn't key in on it at first, but there's no flywheel cover on it in that video...

Ha! I didn't notice either. Ok so maybe it's the sound of no fly wheel cover ... y'know, like one hand clapping ... a tree in the forest ...

Maybe I just don't spend enough time in California (which I would love to rectify if the housing wasn't so flippin' expensive), but I generally prefer a little less Zen in my motorcycle maintenance...

Tonight's adventure started with getting the clutch adjusted so I was finally able to take it for a quick spin around the neighborhood, despite no lights and a very stiff throttle tube.

Nevertheless, I did it, fearing black ice the whole way, and it was pretty glorious, even if I was afraid of the throttle sticking and laying it down the whole time.

After that, I returned to the well-lit sanity of the garage, where I pulled the throttle tube and was pleased to discover it was just frozen in place by old grease, replaced the front brake cable inner & outer, and had the fine adjuster for the brake cable shear off when I tried to remove it.

Luckily, I was able to cut a slot in the end of it with a cutoff wheel in the ol' Dremel, so removal was just unscrewing it with a screwdriver.

Now, I'm back onto the electrical system. The headlight was a sealed beam H4, 4.75", so I ordered one of these and will try to get the turn signals and the dual-contact brake/tail light sourced in the morning.

I'm also now looking at the wiring diagram to figure out how I want to tie the two systems together, along with how to do it in an aesthetically pleasing manner.

Speaking of the turn signals, I know they're basically made of 100% pure, refined Unobtainium, so I'm now looking at how best to repair them. Some of them have stress cracks in the housing and some just have the "chrome" peeling. I'm wondering if I can super-glue the cracks, then possibly repaint with chrome spray paint.

Finally, I swapped the seat from the GL onto the Sprint, so no more tractor seat. Looks better already to me

So, basically, another successful night in the garage.

Test ride on frozen streets. Gnarly. You're haulin on getting it together! As far as the unobtanium, your plan sounds good. I like using JB Weld for pretty much everything.

And thanks for the writeup. Nice to see it rolling. Now about that boat.....

I was thinking more "dumb" than "gnarly," but I'll take it

New tail/brake and turn signal bulbs are ordered. This morning, I'm going to finally go do the title paperwork and get plates, insurance, wheel tax (municipal parking fee) sorted.

It also occurred to me that I need to put rebuilding the front hub on the to-do list because the grease in it is probably just as hard and counterproductive as it was in the shift tube.

And I still need to deal with the (lack of) air filter, whether with a spacer for the air box or some other method.

That, plus everything above, should at least get me back on the road.