Modern Vespa

So I'm finally getting around to completing the rebuild of my Stella motor and started thinking about porting.

When I looked at the ports on the DR cylinder compared to the ports in the LML cases, I realized that there's more than a bit of a mismatch. The ports on the DR are MUCH smaller than the LML's.

Thus, I've decided to open up the two side ports on the DR.

While most of what I've found on the topic seems to be about expanding the porting in cases to match cylinders, I assume the opposite is true.

Thus, I'm thinking that my cuts will look more or less like:


or, from the other side:



(The cuts would not extend past the current lower edge of the cutout, I just extended the lines down there. Also, I now realize green was a really poor color choice for marking the pictures up.)

So I now have a number of questions:

1) Does my basic approach look correct of what I'm cutting?

2) How important is it that I round the corners of my cuts? Can they be pretty much square if I chamfer them?

3) What all should I polish through there?

4) What else should I consider cutting as long as I'm doing all this?

5) (extra credit) I also have to replace the crank. Would a cut crank make sense here?

Thanks, everyone!

Your plan looks good. And a cut crankshaft is always a good idea.

agree the plan looks good. Also consider putting the piston in the cylinder to see how the window in the piston lines up with your cuts.

rounded corners are actually easier to make most times than square and tend to be stronger.

You want to match both the angle and location where the cylinder and cases meet, so take it slow and check the fit often.

It's a DR kit, which I've had good luck with in the past, other than the part where I blew it up due to bad timing.

I put the piston in to the extent that I could without the crank and it's nearly the same size as the ports in the cases, so I'm not planning on messing with them. Of course, to my mind, that makes the tiny ports in the barrel all the more nonsensical:


and


For aligning the piston to the barrel, in the absence of a crank I'm using the third port since it's the same size on both the piston and the barrel.

I've got the previous cylinder, which got trashed when I broke a ring so I'm thinking I'll use it as a practice run before I do the Real Deal on the new one.

For making the actual cuts, and this is the background on why I asked about square versus round corners, I was going to drill the corners, then use a cutting wheel to take off the straight cuts to remove the bulk of the metal, then file/dremel my way to the finish so I'm not grinding a bunch of metal that I don't have to:
(blue == existing port; orange == drill/cut. Phear my mad MS Paint skillz!)

I'd rough out the the green cuts with the cut off and then finish the rest with a nice carbide bit in the dremel. for the finish I like to bolt the cylinder to the case half with the studs to make sure everything lines up and the angles match.

some tape on the inner wall as a guide can help as well. It also saves your ass some times when you slip.

Had to do the same thing to a Malossi recently. Wear glasses! took me two days to get a bit of cast iron out of my eye! Your plan looks spot on. Remember to chamfer the ports. If you fancy it clean up the castings in the transfers and knife edge the splits. then polish the exhaust port.
see below.




Left, widened, cleaned and knife edged. Right, work to be done


Exhaust port

I'm going thru sort of the same thing except in reverse. I need to weld and open up the ports on these old GL cases to match this lightly used, but sporty 166? top end. I'll replace the JB Weld on the cylinder mounting pad with real welding too & lightly machine the pad flat. I have use of a Foredom to enlarge & finish the ports.

The base gasket is laying on the motor


seems to be a problem

The cases will be bolted together & preheated prior to welding, except for the pad areas.

Any tips or warnings I should be aware of ?

Should be something like this if things go well:
I'm intrigued. Made or bought? The best info I could find on this is here:http://www.scooterhelp.com/tuning/vespa.cranks.html. Can you tell us more, Just remove the small chunk shown, blend it in smoothly & that's it or is this something best purchased already done? Thanks for any additional insights.

Buy one. You can cut yours and malossi have dimensions on how. You can download them off their site. Unless your Piaggio one is very new get a new one as the kit will test it.

I'll be buying the cut crankshaft. My current crank is the stock LML and it's both thrashed by the parts of the engine that rattled around with it when it blew up as well as having several thousand miles on it.

Nice, the LML one is made of old carling cans as well. Do you have the reed valve LML?

LOL! Yeah, I'm probably going to make a few cuts through it with the angle grinder to see if what I've heard about how some of their cranks have visibly inferior metal in their core.

I've got the LML reed block, but put some GGR hot reeds on it shortly before I blew the whole thing up.

I was going to stick with the LML block and a 24/24si carb for a while because the cost of parts for this project is already pushing past what I can hide from my wife...

I finally got around to tackling porting the cases and new head for my LML.

After a little over an hour with a carbide cutting blade in my dremel, things were looking good, even if my ears were ringing a little bit. I should have worn ear plugs, but if that was the biggest mistake I made today, I'm happy.

I was pleasantly surprised how easy this was. Lots of test fitting & measuring. Tons of WD-40 to keep the cutter lubricated.

My strategy was to match the smaller opening to the larger, but increase the openings beyond that. Even that resulted in removing a LOT of metal, though. The LML has some pretty big ports, even stock.

Head:

and third port:



And the casings. I opened up the main ports just a tiny bit on the casings. Seem to have not gotten a picture of that, though.

And the third port:


Here's the half-way point. That's looking at the un-ported side through the new ports:


and here's one comparing the ported top end to the un-ported, blown DR top end that was on the bike previously:

Good work mate.

Research and simple tools. Mostly that's all it takes.

Yeah, I'm getting pretty excited to get this rebuild finished up. I'm starting to order parts now, thinking about going with a P200 gear stack since I've got to replace the spring drive anyway, but I'm still trying to figure out how much replacing that will ultimately lead to.

I'm pretty sure the stella/LML has the late 150EFL gear stack. 99.9% sure.

This stack is identical to P200 with the exception of the Cush gear and the clutch gear.

I'm not sure your DR would push the 200 gears well enough in top. I'd go with a clutch upgear that should see you flying.

Goto scooterhelps gear calculator and use p150efl (late)

If your replacing the Cush spring's put in the p200 ones (pair)

Now, it's time for some work on the airbox & reed block.

Based on what blake7even had to say in his sleeper thread, my plan is to port the reed block and cut out the center bar like so:

the airbox like:


And I'm guessing, just blend the cases here:


One thing I saw which is a bit worrisome is the lip of the reed rubber (Oh noes!) from when I ate a bit of piston ring and killed the motor:


So this may all be a bit of a practice run anyway, but it's easy enough to replace (i.e. no case splitting) that I'm not concerned.

Don't worry about the damage. You will need to cut yourself a new reed from Carbon anyway so just cut it a touch longer.
Bend the pate to allow it to open a touch more but dry build first so you can be sure it doesn't touch the crank.

I think i had better type 'touch' again to make sure.

Before you do this....



do this, then blend.

14674198384_0f42939bfb_k by Blake7even, on Flickr

to get to this...

IMAGE_50 by Blake7even, on Flickr

Good marked up images, should help others. I can see many a build with these cases. The quality is excellent and they are a plenty. SIP's glorious bastard uses one with a Quaty Kit. I bet it screams.

I replaced the reed a while back with a GGR Hot Reed


but did not bend the stopper down. You can see the line from the oil of where the lip of the reed was. I'll stick with that to start.

I'm sure my wife will be thrilled to hear the sound of the Dremel again, but not half as thrilled as when a bunch of boxes from Hodgespeed show up...

Last edited by chandlerman on Mon Aug 04, 2014 6:19 pm; edited 1 time in total

That will be fine. I have the same material only mine is 0.33mm. Yours is 0.45. I'll bet theres nothing in it.

You can buy a sheet of that Polini or Malossi carbon fairly cheap and make a bunch of reeds if you needed a new one at some point.

Hey Blake,

I've got a question about what you did in the area I've marked in green:


Did you just round off the edge,or did you open in up more seriously, i.e. something like this?


Thanks for the annotations and pictures. It's helping me a ton and I hope it will help others out as well.

In other news, I've pretty much finished up the reed block and airbox.

Its opening is now about 800mm^2. This may be more work than the DR will benefit from, but I've enjoyed the practice

Hi mate,

The reed block looks really good. Nice work.

On this lip


It's hard to explain but if you slide your barrel on and lay on your crank you will see that there is very little space between the crank and the case for fuel to flow. It will flow round there but the majority wil come from between the crank webs. 'Up the middle as it were. Quite a lot of the side flow on the flywheel side is for the bearings.

When you get this you'll see that you rounded the conrners on both halfs of the case like below in RED not really for that area (although it helps) but more so that shape was there where the cases join (centre of crank web).

At the GREEN circle I rounded the lip a touch but it's not important. There is a massive pressure change there anyway so think of it as a waterfall and break the edge.



Now this is why the Malossi piston has massive cutouts down the side and extra holes above the con rod to let the fuel surging up the centre of the case, up and inside the piston to escape sideways into the transfers.



So it might be worth looking at your piston to see if there is somthing you can do to help this flow. Looking at this image of a DR piston I found on google it looks like the upper port is catered for quite well but you may be able to tickle the side port transfers.


Good luck.

Thanks for the clarification on what you did with the Green Circle. I figured it was just rounded off, but wanted to be sure I understood. You're right about fitting the crank in there. While all I have right now is the old LML crank, once I stuck it in place, things made a lot more sense.

For the piston, I only opened up the sides a little (maybe 2mm per edge ), but it matches the openings in the jug and the cases, so it will be enough.


(That's the new one on the bottom along with "Shiva, Destroyer of Engines" on the top with stock openings)

For the top port, I hadn't done anything with it yet. Fitting it along with the crank for alignment, there's some room for improvement there

so I've got it marked where I'll open it out:


(The mark along the base is just for alignment)

I probably won't take any metal out of the top of the main opening, though, because I didn't open up the ports themselves, so there's a limit for how much good it would do. The opening in the jug is already matched to the cases, so it will stay as-is.

This whole process has given me a new appreciation for the difference in design decisions between different top ends. I've always run either stock or just bolted-on kits in the past--I just wasn't at the necessary level to appreciate the engineering differences between them.

Thanks again, Blake, for your help with my project and also for blazing the trail with your well-documented Sleeper build.

Good man. Cut that piston out and bolt that thing bac together!

At this point, other than the piston some last little bits of polishing, it's all about waiting for the parts to arrive!

Always the toughest part of any project.

So how important is a smooth surface? Lets say I have an intake manifold on a 4 stroke, what would be the acceptable level of surface roughness? I see you guys here getting pretty smooth surfaces wherever there is air/fuel/oil flow.

It's much more important on the exhaust than intake... apparently a surface that has dimples like a golf ball (but smaller) sets up a boundary layer to help resist fuel sticking to the sides. But probably harder to achieve than a smooth finish.

^Yeah this.^

Polishing to a mirror is for the exhaust port. It doesn't creat ANY extra performance. It just stops carbon buildup sticking to the port and closing it up over time.

A rough flap wheel on a dremel is about right. The dimples/imperfections increase surface area and so surface tension. A shot blasted finish would be awsome but I leave it at this.

I'm finishing things on the intake with a flat file where where I want a straight edge, then a quick rubdown with rough grit emery paper lubed with WD-40.

I've gone through a ton of WD-40 on this thing. Keeps the cutting bit and file from gunking up, plus it keeps the shavings from flying around as much as dry cutting.

This may be better, 99 euro

http://www.mrp-racing.de/index.php?a=92&lang=eng


+ the reed case at 49 euro



Or even 'atomic performance' have a reed block and reeds for 39 dollars! Should fit.

Thanks, Blake!

I almost did that exact same cut n' paste myself so I'd have it in this thread

I think Vader has tried them all - except the Atomic - so would have something useful to add.

and some cast offs to sell to hopefully!

He said on the other thread that he had the LML MMW2 lower on scoot.net at the moment. Had a look but I couldn't find it.

That's because I already bought it off him in preparation for Round Two where I go whole-hog on the reed block and add a side draft carb.

That won't happen until the spring, though, because this project is already over budget. For now, I'll make do with a 24/24si and my widened stock reed block.

From the other thread Which casing will work ? That prompted me to have look. Check this pic - $35. http://www.partsforscooters.com/169-124_Minarelli_FG_Intake
And this kit for a Minarelli 50 with everything including 28mm carb, $150!! Probably not of the most exacting quality, but still. Looks like that reed setup might fit nicely on an LML with a bit of additional work.
http://www.ebay.com.au/itm/Performance-intake-28mm-PWK-Carburetor-for-minarelli-JOG-1E40QMB-50cc-90cc-/331075572112?_trksid=p2054897.l4275[/quote]

howzabout the 30mm version? It's the same price.

What's the opinion of the crowd as to how much pain this will be to get running?

I'm mostly concerned with the likelihood that it won't fit on the damn motor, but also a little concerned with getting it tuned properly since all my prior experience is with si carbs.

Whoa! Now you're talking!

So first thing is it needs a connection from the bottom of the reed block to the case... making that would give you the opportunity to angle the whole thing so the reeds "point" at the opening in the case. This is something I've been wondering about with the RD350 reeds too - one is angled nicely into the opening/crank web and the other towards the 'ramp' bit over the clutch. I imagine you'd make the connection piece from a lump of solid aluminum.
Then you have the direction that the inlet opening (with the rubber connector) is pointing... does that leave enough room to position the carb ideally? Not sure about that, you'd probably need to be holding it to know for sure.

Whatever reed arrangement you end up with, the carb is basically going to be the same so your tuning issues will be the same. There are plenty of people here with this style of carb to help set it up.

It'd be nice to see an image comparison of a bunch of reed blocks like this to find one that's just right for the LML.

Well, I figured WTF and just dropped the $150, including shipping. I figure it'll be easier to figure out the basics of fitting it with the motor out of the bike.

I know that I'm solidly into "Too much is never enough" mode, but sometimes I just can't help myself.