Sprocatti Reed Valve Kickstart Update

Sprocatti MHR Big Bore

The long promised update. It's been a long day's work! But it has finally been finished; at least the main course was: fitting the crankshaft into the crankcase. The cylinder is a direct fit, just needs some base gaskets-adjustment to properly fit on to the engine.

The crankcases were a right bitch.... Honestly. This is exactly what I expected, but I hoped it were not to be the case. The cases fitted on to each other perfectly, but when they did, they were too tight. The crankshaft simply didn't turn freely. It needed too much force to pull through.

It was clear; a case gasket was needed. Obviously these don't come stock, so time to break out the cutting board gear and custom fit two gaskets.

You might say: Isn't that obvious? Well no, it isn't. Usually the aftermarket crankcases should take into account the extra clearance needed for the crankshaft, but let's face it, it's not a Polini or Malossi case where everthing is fucking prefect. Custom crankcases need custom work. So stop bitching. This is one of the best engines out for Piaggio / Vespa. No faith? Then go fuck yourself...

I custom cut some case gaskets to fit the crankcases and the job was done. It took an hour or two; better safe than sorry. The engine fit together like a charm after fitting the gaskets. The crankshaft moved freely and all was well.

Kickstart Parts

As we have mentioned before, this engine will be started via a kickstart system. We have pearl blasted a kickstart pinion and totally rebuilt it (with a new HK 1514 bearing). It now moves smoothly.

It still does not fit on the engine proplerly. The Sprocatti engine's crankshaft still sticks out about 3 to 4mm too much. We will soon be milling a new adaptor piece for the kickstart adjustment. We can simply place rings to make up for the space, but let's be honest, how lame is that? We wouldn't be MOPARTS RACING if we weren't the best, right?

Now drool at some pics:

Look how close that crankshaft runs through the casket/inlet housing. It's a millimeter of clearance, tops.. (roughly 3/64 inch for my American friends)...

Sprocatti Reed Valve - New Project!

Here's the latest addition to the family: Sprocatti Reed Valve engine.

Full specs:

• Sprocatti Reed Valve Kickstart engine
• Malossi MHR Big Bore Cylinder Kit (XSH tuned) Liquid Cooled
• Custom kickstart crankshaft (46mm stroke)
• HPI Internal Rotor
• 21mm Dell'orto Carb
• Exhaust: Not yet chosen / To be determined

This engine is the "little brother" of the Sprocatti Rotary Valve (Disco Rotante) engine. It's got a nice reed valve port at the rear bottom end of the engine. This is the 4-stud version. It is also available in a 3-stud form so that you can mount normal Vespa / Piaggio cylinders to it (with a push start system).

The reed valve system is actually a manifold and petal system in one. The Malossi cases for Vespa / Piaggio have a seperate V-force 4-petal reed valve system and a seperate manifold. This Sprocatti Reed Valve system is two-in-one. It also has a more direct flow through the chamber to the cylinder (if modified properly). This engine has a lot of potential, but it needs a bit of fine-tuning and finishing before usage, but that's normal if your building a complete engine from scratch.

Kickstart Modification

This engine has the option for a kickstart system. It's not stock. The engine is delivered from Sprocatti with the small case milled falt down but still closed. You need to mill open the small half youself to have the crankshaft fit through. We've already completed this step.

The crankshaft has also already been modified. The bearing pen which sits on the right half of a kickstart crankshaft was pressed out of the crankshaft half. We then milled the a hole into a all-round racing Vespa / Piaggio crankshaft and press fitted the kickstart bearing pen into it.

The normal crankshaft for this scooter cylinder is a 44-stroke. This engine requires a 91mm long connecting rod. We used a Top Racing 91mm connecting rod (originally meant for Zundapp / Kreidler) and fitted this into the crankshaft.

As you can see, all this is needed to properly adjust the crankshaft for this engine, otherwise starting it will be a bitch (just as is the case with our other Sprocatti Rotary Valve engine). The crankshaft adjustment is a precise and expensive modification if you have it done by a third party. Why? Think about it:

1. You need to buy a kickstart set (crankshaft, pedals, spring, axle, etc.; difficult to find!). You will need to sacrifice the crankshaft as you only need the kickstart part off it.
2. You then need to press it or have it pressed out.
3. A new crankshaft is needed, preferably a 46mm stroke crankshaft for a Liquid Cooled cylinder kit.
4. To be on the safe side you may want to place a thicker connecting rod into the crankshaft. The stock Vespa / Piaggio ones are rather thin and weak. I'm sure they would hold, but a Top Racing connecting rod from a Zundapp / Kreidler is only about 30 euros (45 dollars) and is far thicker and sturdier.
5. The crankshaft then needs to be refitted and aligned properly.

Fine tuning

The finishing on the engine is acceptable, but it's definitely advisable to break out the pro-tuning tools to finish the engine off properly. The cylinder has already been tuned by a Dutch tuning company, XSH. The inlet of this Sprocatti Reed Valve engine can still be raised and widened if desired. Also, the transfers from the engine to cylinder need to be matched - this is not only the case for our Malossi MHR Big Bore cylinder kit, but would be the case for pretty much any other kit too.

We have still to decide what build we are going to do, which moped that is. Tempted to put it under a Ciao, possibly a Bravo. Tell us what you think!

Enough talk. Here are some pics.

See how the stock connecting rod (top rod) is a lot thinner than the 91mm long Top Racing rod right below it? The Top Racing rod is actually even thicker than the Simonini's connecting rod (crankshaft to the left).

This is how the engine will eventually fit together when finished. Inside view with right half of the crankshaft off.

The crankshaft's connecting rod does come awfully close to the crankshaft housing. This will be milled away for more clearance just to be safe.

The piston also reaches deep into the crankcase housing. The part where it nearly touches will also be milled away.

A rear view to the Reed Valve Manifold.

Gasket cut and finished.

The Malossi MHR Big Bore Cylinder!!!

Smooth exhaust port.

In this last picture you can see how the kickstart pinion fits on to the engine

That's all for now. More pics and updates to follow soon!

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Fred

Back ONLINE! Keep up with us...

People! We are back.

I've been getting a lot of mails from old customers and people asking me what happened to MoParts Webshop. No worries! We were offline for a short period but will soon be back with some new developments.

We will be launching a new webshop withing the next few weeks. It is basically the same webshop as before (www.moparts-webshop.com) but then newer. Our new webshop platform will be more userfriendly and professional. You can expect the same level of service from us as before! ;)

Furthermore, we are still busy as ever with all our projects. We haven't been idling, we've been going at it at full speed!

Look out for a new update soon regarding a few new crazy projects!

Fred