Lambretta Auspuff Test Big Box Reso Rennauspuff

Lambretta expansion chamber and big box Clubman prototype test

Lambretta exhaust test, while the new and upcoming Lambretta Big Box is currently in production. Unfortunately, a delivery date is still unknown. Auspuff Test auf dem Scooter Center Leisungsprüfstand

Lambretta exhausts onthe dyno

Before we have send the final sample to Spain, we put the new box through its paces. Additionally we have another prototype box from our friend Chalky from Replay Scooters and JPP on the dyno:

  • bgm PRO BigBox Proto
  • JPP Box Proto

The following expansion chambers competed against the boxes:

  • the TSR Evo,
  • the JL3 and
  • in MB3

And all three reso systems did better against the boxes than we would have expected! Die Lambretta Auspuffanlagen

The Lambretta engine

The test engine was constructed as follows:

Results & conclusion of the test

Nice and clear to see how well the box scores right from the start not only with power but also with plenty of torque compared to the ‘racing exhausts’.


That’s what makes the bgm PRO boxes so nice to drive. There is always enough power available without having to struggle with gear connection problems or having to twist the throttle like crazy to get things moving. The moderate consumption values of the engine concepts with the bgm boxes are another advantage, apart from the original appearance and pleasant sound level. Another outstanding feature is the registered-design of the mounting system with adjustment options in both horizontal and vertical directions. This allows tolerances and, above all, spacers used for different strokes and connecting rod lengths to be compensated for.

Lambretta exhaust test performance diagrams

Here you can find the performance diagrams as PDF:

Vespa Wideframe Tuning

Vespa Wideframe models are more popular than ever.

There are not only refined new spare parts on the market, but also development in performance increase.
Existing cast iron cylinders have been refined to wring a little more performance out of them with a rather high input of work.

New Pinasco cylinder

Pinasco will soon offer a new aluminium cylinder with 160cc for the old Vespa engines with 3 studs.

Our loyal customer Andreas Nagy has always been a good friend of this slightly particular Vespa model. He puts a lot of effort in increasing performance of the Wideframes and closely cooperates with Pinasco.

He visited us on our dynamometer with a prototype of the 160cc V2 cylinder. Caliper Bracket 007

Secret prototype of the new Vespa cylinder

Caliper Bracket 009

We would have liked to take an even closer look on the 160 Pinasco.
Sadly the prototype of this cylinder remained hidden under the cylinder covering.Caliper Bracket 006

Vespa Wideframe racing cylinder

Andreas and we have tested some exhausts on our Scooter Center P4 dynamometer. For example a BGM PRO BigBox Touring exhaust for PX models, whose suspension we have modified to make it fit a Wideframe.

Leistungsdiagramm Prüfstand Pinasco BBT Vespa Wideframe

Performance characteristic dynamometer Pinasco Vespa Wideframe cylinder prototype

10HP and 100 km/h

Sure: a Malossi MHR reaches more than 35HP almost easily on a PX. Compared to this, the 10 horses of a Pinasco racing cylinder won’t take anyone’s breath away. But, please, don’t forget the original “performance” of Wideframes! Original 5HP would have a top speed of about 70km/h on a plain track.

With now 10HP on the 8 inch small rear wheel and a corresponding primary reduction, you may expect more than 100km/h. Just like for an original PX200 for instance.

We are looking forward to the potential of the Pinasco cylinder.

You will of course be kept up to date: here in the Scooter Center Blog!


Bon voyage – Dean comes with the BSG Corse bike to visit Scooter Center

Dean Orton, the main man behind Rimini Lambretta Centre, came to visit us for a couple of days. On his way from Italy to Venlo Scooter Run and afterwards to the Harz ring for the ESC race, he came to visit his old friends here. The reason for Dean’s days off from work was to give the BSG corse engine a proper test ride and thrash it as hard as possible.

BSG Corse Lambretta test riding


The testing of the engine is done in the proper way, just the way it will be used by a common rider. First of all the scooter is packed with Dean’s mod tat and additionally with:

  • a second expansion chamber to be tested
  • a bag full of spares and
  • camping gear for Venlo.

Then the bike is thrashed about the motorways and country roads across Europe (Rimini, Italy – Austria – Germany – Venlo, Netherlands). His test ride also took him to Scooter Center Cologne and to the Harz ring for the ESC race.

80mph – restricted to 50hp

This is real testing over a long distance with sitting happily at 80 mph all day and plenty of throttle left to easily hit 95 mph and all this with a very short gear ratio of 4.9.

The 305 cc barrel on the CNC machined casings is restricted by the programmable ignition to 50 hp. Unrestricted it gave a 63 hp at the Rimini Lambretta Centre dyno.

Scooter Racing at the Harz ring

At the Harz ring this weekend there will be held the next ESC race. Dean met the Casa Lambretta racing team last night. Today the first testing of the Casa race bikes will take place and the last preparation before the races will be done. The Casa Lambretta race bikes feature the Casa Performance range as well as some BGM parts that are used on these bikes. We were happy to supply the front and rear shockers, the Silentblocks as well as our BGM Superstrong Lambretta clutches for the bikes.

Our first time!

Even if we know each other for decades and the shops were founded roughly at the same time, we haven’t managed to visit each other’s shops until the year 2015. dean-orton-lambretta-dean-orton-lambretta

On the 25th of April we were invited to the Open Day and shop opening of the new Rimini Lambretta Centre premises. This weekend was one of the best ever, with a stunning shop, loads of food and drinks and the test riding of scooters that made history –like both Innocenti twin cylinder prototypes- and bikes that probably will make history – like the BSG 305 cc one

Here is the video of Philipp riding the BSG Corse Lambretta

On Monday we finally had the pleasure to welcome Dean at our place! It was a pleasure every single second and a lot of piss taking has taken place. After a first tour through the shop on Monday and even some business talk we had dinner together and the stories never ended. While Dean quotes our Generation XI Smallframe Vespa as the most beautiful object in the universe, he can’t be stopped to let us know that the look of the BGM Lambretta Test Bike is the most shittiest Lambretta he ever came across. A theory we are confronted with from the first day Dean saw the Test Bike at the 2nd edition of the Riva del Garda Customshow in 2013. To stop this, we will send the Test Bike over to them to have the optics matched to the perfectly working engineering of it.


On Tuesday Dean tested the bike in the rain on the beautiful routes around Cologne/Bergheim and came in for the traditional afternoon tea and some more stories and ideas about how to improve Lambretta parts.

On Wednesday the plans were to do another tour and take some pictures of how we proceed orders to show them at home. This has been missed though, because we wanted to see how the BSG engine performed on the dyno with the different pipes Dean had with him. Sadly we ran out of time and hadn’t the chance to put the Big Box on the 305, to modify an U-bend for the exhaust stub took too long and lunch was waiting and afterwards Dean had to leave.

We send our best regards to all the staff at Rimini Lambretta Centre and to Vittorio and his race team and keep our fingers crossed!

New Vespa touring exhaust

We received the first production pattern of the BigBox Touring for 200cc Vespa PX engines today.

Assessing looks and fit are part of a normal sample exam. And so are test runs on our Scooter Center P4 dynamometer.

We already mentioned in previous entries relating to this Vespa exhaust, that the BigBox Touring has a drastically smaller U-bend than the BigBox Sport, its larger sister.

BigBox P200_2

The missing black, heat-resistant cover layer makes the BigBox Touring look somewhat naked. We also attach significance to closely assessing all the joints without the cover layer, though.

BigBox P200_3

Test assembly on a Vespa Sprint with a 200cc engine

One of the first parts of the exam was the assembly in a Vespa VLB (Sprint). Usually space issues arise, when fitted in combination with a 200cc PX-engine. Especially around the centre stand, in particular in the “U’s” and the laps for the stand springs. Depending on the assembly of the exhaust, stand feed rubbers might collide with the U-bend.

We especially focused on these narrow spaces to see whether everything fits. The BigBox fits even to vehicles with a two-spring-system at the centre stand, which has only be introduced to the German market. The stand feed rubbers have a save distance to the hot U-bend.

BigBox P200_4

Just as its larger sister the BigBox Touring comes with a solid clamping and additional holders for exhaust springs.

You want to play it safe? Our retaining plate incl. exhaust springs perfectly matches your BigBox.


Performance measurement Vespa exhaust

Once we agree with the looks, processing and fitting we continue with performance measurements.

First “testing victim” is a cast iron Polini with 207cc, SI24 carburetor in a standard Vespa PX200 engine.

bigbox touring 200

Early torque for day to day use and touring

When developing the BigBox Touring we focused on having the possible torque available early and that there is a high amount of pressure in the exhaust with low revs.

The earlier and more homogeneous torque is provided by the engine, the nicer is a day to day drive. Our cast iron test engine by Polini with a BigBox touring reaches more than 18Nm at 3900rpm. Translated to the 4th gear this means smooth cruising at 50km/h with a very good potential to accelerate up to the final revs.

Increased transmission possible

Depending on the engine you fit the BigBox Touring on, an increased primary transmission can be used reasonably to go easy on revs while retaining the same cruising speed. Increasing transmission is easiest when using a clutch sprocket. The BGM clutch sprocket for Cosa clutches or a sustainable solution like our BGM Superstrong clutch are very fitting examples. An increased transmission may increase the top speed by 5km/h at same revs.


Let’s test – BigBox Touring is waiting for you!

You want to know what the Vespa Touring exhaust BGM PRO BigBox Touring can do to your personal engine? Just send us a date inquiry to

Our test pattern is waiting for you on our dynamometer.

35PS und 34NM at the start

Vespa 235cc

More than 235ccm and a CNC motor housing on a Vespa PX are the exception on our Scooter dnyo jet.

Only a few enthusiasts venture out to such financial and screw generic challenge on a Scooter.

Look at this outwardly unassuming, silver Vespa PX:


27.06.2014 007

38er Keihin Airstriker

27.06.2014 002

Gearing is designed to more than 50hp

Aeroengine Simonini clyinder with 70mm bore and 235cc!


At the moment “only” 35PS and 34nm – BUT: the owner will be further optimizing this engine. We will meet again on the dyno :-).

We are very excited!




We had a closer look at the new Malossi Sport and MHR cylinder kits earlier. Now we check the new Polini 221 cc cylinder kit that is supossed to be used with 60 mm stroke crankshafts.

The cylinder head ist the one that is used on the Polini 210 cc as well. So let us have a look at the compression ratio of the head that is used with both kits.

Once the long threaded spark is fitted the head is tight enough for it’s closer inspection. To have our Plexiglas high tech measurement equioment sealed properly too with put a little bit grease on the head’s gasket surface.

Zylinderkopf Polini221

With Plexiglas plate attached we fill up the combustion chamber with oil to get the volume of the combustion chamber.

Zylinderkopf Polini221_2

With 25 ml putted into it, we have a 25 cc combustion chamber volume.

To get the complete combustion chamber volume (Vc) we need the volume of the curved piston dome. With a freely selected recess of the piston we can calculate the volume above the piston. We have the piston recessed by 6 mm here.

kolbenboden polini221

6.85 x 6.85 x 0.785 x 0.6 = 22.1 cc is the Volume of this area.

Sealed with grease and filled up with a light oil we see 14.6 ml (= 14.6 cc). So we have 22.1-14.6=7.5 cc for the volume of the piston dome.

To get the show complete we know need to have a look at the squis area volume. This needs to be measured at the engine with the parts like crank, barrel, piston and head mounted. We measure a 2.2 mm squish clearance. This gives a volume of 8.1 cc.

So we have a combustion chamber volume of:

Cylinder head 25 cc

+Squish clearance 8,1cc

-piston dome 7,5cc


This gives a compression ratio ? of

Cylinder 221 cc + combustion chamber area 25,6 cc / combustion chamber volume 25,6 cc

= 246,6ccm /25,6ccm


So slightly higher compression ratio then the Malossi with ?=9,3 (on a 57 mm stroke engine!)

This is the Polini 221 engine of a customer.

Polini 221cc, Kurbelwelle Polini 60mm stroke, Dellorto PHBH 28, Polini inlet manifold for rotary valve and with our bgm BigBox. With a standard base gasket there are port timings of 120°/170°. All details are written in the diagramm.


This is a Plug & Play engine with no further porting. And one has to admit that 26 Nm of torque are lots. Especially if they are so low down in the power band.

At 4.000 rpm we have 20 Nm this is double the torque a standard P2 engine has at peak.

Depending on the preferred riding style and for what the scooter should be used too, a taller gear ratio makes sense to not over-rev the engine all the time. The very well balanced and smooth running Polini crankshaft is a perfect companion for travelling as well as street racing…

This engine setup and a longer gear ratio should give an engine that should sit for long distance travells easily at 120 km/h. Here **as an example with an original gearbox, compared to our bgm bgm Superstrong clutch with DRT sprocket with one tooth more and the original primary drive of the P2 with 65 teeth.

PX200 24_65

With 20 hp at 7.000 rpm it should be easy to do the often quoted 120 km/h mark.

** The”GearCalc” calculator was given to use from GSF member Motorhead. Cheers!

Vespa Auspuff Exhaust bgm PRO MB Big Box Prototype

Vespa exhaust bgm PRO

Our exhaust manufacturer has delivered the first samples made after the sample developed by Mark Broadhurst. We received samples for the P2 as well as for the 125 and 150 P-range engines.

First sight: Well done! Optics and machining as desired. Thick, massive made, shape of the U-bend spot on and the measurements of the exhaust bushing is right too.

If it proofs itself at the dyno, the manufacturer could start. An a delivery date within this year could easily been done.

For testing we had this engines:

All dyno runs were done on proper warmed up engines. The comparsion is against the exhausts already fitted to each scooter and against SIP Road exhaust.

Nearly all scooters were used on the road afterwards to see the changes done to the power characteristics in the real world too. And all the riders were happy how the engines transformed and were much faster and easier to ride.

Upshot: Production can be started!

To do the first dyno runs, we just had to fit the cables. You might remember?

The engine came at least the idel and main jet, while the needle were missing.

The needle is very important for a smooth engine run and picking the right one can be tricky. In our online shop, you can find our pre-selction of needles. All these are good working ones on scooter engines. Here you see our dyno colletion of the D needles only.

Kleine Auswahl an Keihin Nadeln

Kleine Auswahl an Keihin Nadeln

From our experiences and findings the DGL needle works very well on rotary valve engines. The DEK needle with which the Keihin 35 is delivered, is a little bit on the rich side low down.

Next step is to check the timing of the ignition system. Vespatronic. Sadly the welded engine casing makes it necessary to modify the stator plate. And even more sad, it is where the ignition marks are and after the mods are done were.

gsf wsm2012 018

We need to do new markings using a piston stopper. Using a piston stopper we fimitteln wir wie immer durch eine Umschlagsmessung.

We know turn the flywheel clockwise and anti clockwise untill it is blocked b ythe stopper.

Kolbenstopper zur Umschlagsmessung

Kolbenstopper zur Umschlagsmessung

We know mark the stops at the casing with the arrow on the flywheel as reference. This need to natch exactly, sadly the camera doesn’t justice to this at the picture.

OT Markierung 1

OT Markierung 1

We know need to find the middle between the two marks. This is our top dead centre.

gsf wsm2012 009

After finding the top dead centre, we know need to figure out where our 18° pre-ignition settimng is.

We measure the circumfarance of the flywheel.

This is 529 mm. If you divide this by 360, you know the mm of the circumfarance that equals 1°. We take this and multiplie it with the wanted 18°.

Here it is like this: 529/360*18= 26.45 mm.

We know measure this 26.45 mm on the flywheel starting from the arrow on the flywheel.

gsf wsm2012 010

Know it is time to strobe the setting to be sure that everything is spot on.

We found the ignition timing is 16° instead of the 18°. We leave it as it is for the moment and idle the engine up for the first runs.

gsf wsm2012 013

While warming the engine up and switching thru the gears, we find the 3rd gear jumps out. Damn! Okay, the solution for the moment is to measure it in fourth. Because of the higher gearing the power output is not as high as it would be in the 3rd gear. Which is normally used for dyno work.

First try…

1 GSF- Weihnachtsspendenmotor 2012

The carb setting is too rich. The power before the exhaust starts to work is very bad.

We change the idle jet to a 45 and see…

2 GSF- Weihnachtsspendenmotor 2012

Because we are not 100% happyyet, we try the 145 main next::

3 GSF- Weihnachtsspendenmotor 2012

We haven’t found more peak power. But the graph is much smoother and the engine responds much better to the throttle action. Something you simply can’t picture with a graph only.

Now we change the ignition timing to 18°…

4 GSF- Weihnachtsspendenmotor 2012

That was it, more power before the pipe starts to work, more peak and more torque.

Now we finish with a run thru all four gears.

GSF- Weihnachtsspendenmotor 2012 kmh

20 hp in third gear. Mission completed.

This is the final report about our pre-Xmas dyno shootout!

The 29.9 hp at the rear wheel of a Cast Polini 133 cylinder kit with 54mm bgm crankshaft, Keihin PWK35AS carb and Feuerzauber exhaust had to be bettered.

With 29.3 hp Jonas did very well, but missed the goal. Followed by Mathias with 29.2 hp on a Polini 133 rotary inlet engine.

Together -Jonas and Scooter Center- decided to donate the 100€ shopping voucher for “scooterist-chairty / GSF-Spendenaktion.

Scooter Center likes the idea and is addiotionally offering free dyno time to set up the Charity engine.

The gallery shows the atmosphere of the dyno shootout. Something that will hopefully continued very soon. What do you think?fin.

Because virtual reality can hardly ever beat proper live action, we recommend to have a look at the small but mean Smallframe engines the next time.

Thanks to all the people that dropped in during the day. It was pure fun and we hope to see you soon!

[nggallery id=19] [nggallery id=18]


Scooter Center xmas final. On the last two Fridays before Christmas, 14th and 21st December 2012, we invite all of you to our shop in Glessen between 10am and 5pm. Program for you:

· Dyno competition in different categories

· Irish coffee

· Warm pretzels

· Hardcore engines

· 20 % discount in our shop (codeword: Xmas)

· Who beats Alex on our dyno?*

* With a Smallframe up to 140cc (one exhaust and regular intake)!

The price for the winner will be a Scooter Center voucher worth 100€!!!

Our test engine is running, we let it warm up properly. The jetting seems to be right with idle jet 48/160, air correcter jet of 160, atomizer BE3 and main of 140. So now we will see how powerful this engine is.

First of all the gear ratio needs to be measured. We measure this at least twice to be 100% sure. The gear ratio is 3.21. This can even be typed manually into the dyno software at a later date.

When you are operarting a dyno a scientific operation is a good gesture to make sure that the results can be compared. After the first three runs we see that the power output is always nearly the same. A good sign, here is the best result:

Nice to see that the engine starts to lift the power low down in the rev range. As expected from the Polini kit. A quick road test shows that is a treat to use on the street. At slightly higher idle revs of 3.500 rpm the engine pushes -thanks to 17 Nm- heavily.

The inlet induction sound is nice too. The Polini solution works not just power wise, it reduces induction sound as well. The adaptor has a small collar built in that breaks up the acoustic wave what gives a very discret induction sound.

Back from the road testing to the dyno, we take a closer look to the head design. Next we are going to test the MMW head. The previous fitted Worb head gave a squish clearance of 1.7mm. To achieve this with the MMW head we are going to fit a 0.7mm head gasket. One quick note: Never combine normal head gasket with O-rings on heads. This doesn’t work on the road. For short testing on the dyno it can be done though. And we needed to do this to make the heads test comparable with the same squish clearance.

After some more runs we have a direct comparsion of the heads:


BLUE: Worb5

The higher power output of the MMW head is caused by the slightly higher (but still road safe) compression ratio and the difference in the combustion chamber design.

The highest torque reading is still at 4700 rpm, but rises to very good 22 Nm. At 7k rpm we still have 17 hp and 17 Nm. God figures for high speed motorway use.

The 60mm MMW head we are not going to test anymore. Not because we are lazy, it is more because there is no sense in it all. We already saw that the higher compression works. the 60mm version would reduce this, so we are not to keen to loose power.

A wider power band with a little more peak power at high revs would be nice though. This really seperates good road engines from the very fast ones that are hard to catch on open roads.

Well… what could be done. Something like a luxury problem here. A good working engine with nice power output in a useable rev range and we are still thinking of how it could improved.

There it is our MBgm Vespa BIG BOX. Sounds like fun to get this on the Polini. Doesn’t it?

This should be done tomorrow!

Stay tuned!

Only a few stepd left untill we can dyno test our new engine.

The engine will go into the Silver Fern and be tested for Rally going and daily commuting then.
While fitting the flywheel care must been taken that the slot in the flywheel cone aligns with the woodruf key.

Afterwards the flywheel nut can be tightened down to 65Nm. The washer needs to be fitted, otherwise the nut will come loose.

The rear brake drum goes on the shaft next. We only put it on loose and fix it with the nut.

As sson as the rear brake is adjusted we will tighten it down to 110Nm. Securing cage and splint must be there.

For adjusting the clutch you need a little bit play at the clutch lever. This should be around 1.5mm and 2mm.

Oil and fuel hose are connected. folgen. The air bubble at the oil hose is a very good indication to see if there is oil pumped into the carb.

But the air bubble shouldn’t be much bigger than that. Otherwise there is the risk that the oil pump runs dry. And so will do the lubrication then.

For the first firing we fill the fuel tank up with 1 litre of oil petrol mixture of 4%. This should be done to have a proper lubricated engine from the start and to compensate the oil pumps delay.

The engine starts and we let it idle for a while. Then we see that all cables are connected properly. We rund down to fourth and everything is okay. The clutch works perfect.And the oil pump operates as well.

So we are ready for the first dyno sessions. Watch this space.

Ludwig & Scherer are THE two-stroke exhaust specialists! Especially for the Smallframe engines, their products seem to turn into instant classics. Their official first release, the “Hammerzombie”, is our evergreen when it comes to powering Smallframes. The “Big Bertha“ was developed for Parmakit’s SP09 cylinder. Power unfolds continuously on a wide power band, easily surpassing the 20 hp mark. The “Franz“ is state of the art at the moment for really powerful engines with a broad power band. With exhaust port timings of 190°-185° it works best. With a ported Polini 133cc cast barrel, 54mm bgm crankshaft, Vespatronic ignition and 30mm Mikuni carb (main 290, needle 5EN68, pilot jet 20) our Alex has achieved 27 hp at the rear wheel. Workmanship, mountings, muffler and fit leave nothing to be desired. The exhaust are available for scoots with the small luggage box on the left hand side as well as for those without it.

And as if there is no stopping them: their latest exhaust – the “Feuerzauber” reached Alex at the last minute! In direct comparison to “Franz” the exhaust starts slightly later but has a visibly higher peak and achieves a 1,000 rpm wider band. 29 hp with the cast iron Polini is worth mentioning! We recommend 128° for the port transfer and 192° at the exhaust port. Workmanship, mountings, muffler and fit leave nothing to be desired!

After the Lambretta bgm & MB Developments BIG BOX exhaust project was as far that we can’t do anything more than waiting for the manufacturer and sending reminders every then and now, we thought to move on.

During the early 90ties we sold quite a few T5 and P 200 conversions that Mark did for us. Along the loads of Lambretta conversions. but back to the plot we thought a BIG BOX for the Vespa would be nice and have send some sets of shells to Doncaster. After the Eurolambretta Maks started to weld his ideas into the new BIG BOX. Monday morning it arrived and we started dyno’ing.

We tested on these engines so far:

Here is a selection of some dyno sheets. Uwe did a lot more and we will post some in the next days!

Hope you like it!


Today we had a real beauty on our Dyno. A Vespa Rally 200.

The aim of this project was to get a tractor torque engine for daily driving.

Base was a Vespa PX200 Motor, the rotary valve in the housing has been expanded for more discreet inlet angle before TDC. Crankshaft is a genuine PX200 crank with 57mm stroke.

The new 210 Polini is filled by a SI26 carb with Polini induction funnel.

Because of the Polini induction funnel the available torque in the lower rev range stands out very clearly. The same engine with a Malossi cylinder without the Polini funnel is “missing” almost 4Nm in the same rpm range!

The alloy Polini is supported by a SIP Road exhaust.

From idle speed the engine has proper torque and power.

15hp and 23Nm from 4500 U/min speak for themselves.

With a taller Primary gear the torque can be stretched and relatively high speeds can be achieved at low rpm.

Nice set-up!

The European Scooter Challenge (ESC) is just about to start. New engines and new scooters will be seen across the race tracks in Germany, France, Austria and Hungary.

We just had a typical K1 engine on our test rig recently which we tested for its performance and functioning.

According to the ESC rules, the stroke is limited to 51mm. Therefore, a bgm crankshaft with 51mm stroke and 105mm rod is used.

The engine is running on a Polini Evo cylinder with 2 flaps 0.35mm carbon material converted Polini membrane and a Strohspeed intake socket. A 33 Keihin carburetor is injecting the 2stroke petrol. In order to keep the crankcase clean, the air is sucked through a Marchald air filter. The outstanding air flow rate of Marchald filters and the resulting low power dissipation make this road-proven filter very interesting for racing engines.

A Vespatronic ignition set at 24°-16° BTDC makes it smooth.

The K1 engine is fitted with a Franz exhaust. Good torque values and moderate revs make this exhaust interesting for the round circuits.

The gerated power is currently supported by a XL2 clutch in combination with a DRT auxiliary shaft. More on this later. Now let’s discuss the test rig curve:

All in all it is a typical Franz engine. Frequency range starts between 5500 and 6000 rev/min, peak at 9000 rev/min.

11hp at 6000rev/min uphill makes this setup really nice to drive.

With more than 20hp from 7300 to 9700 rev/min it is possible to drive within the power band due to the DRT auxiliary shaft.

Now come the crucial point, the clutch is not the best choice for this power range. Nearly 20NM are showing us the limits of a XL2 clutch. So we have to reopen the casings and insert a Hartz4 clutch.

Maybe this will change something regarding power and torque.

Even if a non-slip clutch does not increase any further, then at least the wear out is halted. A slipping clutch won’t last many laps on the racing track. Even on the road this circumstance can lead to consequential damages.

Maybe we will find enough time to make a Portmap of the cylinder. Let’s see.