Yesterday our friend Ercole was here again in order to get his Lambretta D Racer ready for the Cologne run on the Nurburgring. His first visit can be found here.
This time he changed the carburator from 25mm to a VHS 30mm carburator.
The blue line shows the test rig from yesterday and the red one his first visit. 1hp more power and a better acceleration was the resut. The Scooter Center Team wishes him all the best for his upcoming run.
The assembly of the Vespatronic needs a lot of TLC and improved interpretation.
A further complication is the fact that the attached wiring diagram is not correct.
According to the wiring diagram, the mass and excitation voltage would be simply put together and distributed again to the ports 1 and 2 of the CDI.
It is of course only right to wire red/black from the stator plate to -1 – (the wider slot) which is connected with green on the wiring loom and blue to -2 – to connect (the narrow slot), which is connected with black on the wiring loom.
Likelihood of confusion exists with the cable box; here different colours need to be combined. All cables with dissolved connectors and which are energised during running engine have been provided with plug-in sleeves. The earth connection is not as potentially dangerous and can be equipped with a plug.
In order not to confuse the exciting voltage and the on-board vehicle electrical system which are both connected with a plug-in sleeve, you can use the following memory hook: “blue sea under the yellow sun” – in practice this works really well…
For test purposes we will adjust the stator plate to the later mark of the 2 marks available.
Once we have placed all the glory in the cable box and the flywheel is mounted again, we can start the engine to control the ignition timing.
The marks for the TDC of 25 ° have been previously determined and marked by reversal measurement.
A quick check with the strobe light…
The ignition is set to 25 ° at 2000rpm. This is a satisfactory starting point for a run on the test rig.
The goal was a 25 hp engine but have a look at the diagram yourself.
Without air filter was the 148 main jet was still OK but with filter we had to use a 145 main jet and in addition to that we had to move the NAPE needle a clip on the 2nd Position from the top.
19hp and 25Nm at 6.000rpm speaks for itself. Even at 8.600rpm there are 25hp and 20Nm on the rear wheel. In this power range there will be no power loss when changing gears. It is incredibly awesome…
To get an idea of how fast this baby can get in the end, we will make another test run – HP vs. Km/h
At a speed of 140 km/h there are still 24hp left…
What do you think? Mission accomplished?
Only thing left now is to place the remaining parts again and then we are ready for a practical test on the road…
Last week our friend Harald from Aachen came to play around on our dyno.He was not 100% happy with the carb setting and wanted to test the slow running and improve throttle response.
These are the parts that are fitted to his engine:
Cylinder: Monza 70mm bore
Crankshaft:BGM 60/110mm
Carb: Mikuni TMX 30
Exhaust: JL-KRP3
Port timings : 186°/126°
Squish: 1,7mm
Easy to spot that there was room to improve the jetting. The blue curve shows the difference.
Thanks to a different slide (richer) and to a altered needle position power and torque low down have been increased further. And the over rev potential is much better too.
Our good customer Sven came ob saturday to show his new Vespa Spezial.
A real stunner. And the clours work together pretty well, especially with the nice bgm PRO SC shockers!
At the dyno we checked the engine and its power output! There is no porting work done to the barrel. It went to the casings completeley Plug & Play!
The port timings are transfers 128° and exhaust 190°. This gives a blow down timing of 31°. With slightly more blow down timing the exhaust Big Bertha would work even better. Maybe we will see Sven reworking the port timings in the future!?
These are the selected engine parts:
Cylinder kit: Parmakit SP09
Crankshaft: BGM 51/105
Carb:Keihin PWK 33
Intake system: Polin reeds with Strohspeed manifold
Ignition: Vespatronic
Exhaust: Big Bertha
Friday Dennis one of the guys from our Raceteam came to test his high speed circuit racing engine.
The engine is finished with these parts and the results on our P4 dyno were very impressing.
Cylinder: Parmakit 144cc, 60mm bore
Crankshaft: BGM 51/105
Carb: Keihin PWM 38
Exhaust:Big Bertha
This was the first dyno run and the jetting was: idle jet 52, main jet 160, needle DEG. For a first dyno run with probably some room for improvements smiles were all over. With 2.46er primary drive by DRT thisshould be a nice ride on fast tracks like the Nürburgring or Bilster Berg race track.
As mentioned earlierPolini is going to release the alloy barrelfor the 200cc casings for long stroked engines later next year. The Polini 210cc alloy kit can be used with a 60mm stroke crankshaft, but you are limited in doing so because of different reasons. The kit contains a oiston with the top ring in L-shape. This type of piston rings runs to the top of the piston.
If you are going to use a longer stroked crankshaft e.g. 60mm instead of 57mm the 3mm longer stroke needs to be equaled in one way or another…
With the piston running 1.5mm in each direction (top and bottom dead centre) the barrel needs to be 1.5mm longer. Normally this is equaled by a base or head gasket.
With a two stroke engines power determined by the port timings, this can cause headaches or been seen as the perfect way to get the tune on barrels sorted to one’s needs. With the port timings as a trigonometric function the transfer timings are altered above average. The timings of the transfers and exhaust should always be in a certain level to work properly.
With the Polini as it comes you can use a base gasket only to equal the stroke. With a head gasket the L-type piston ring could cause trouble by running at least partially out of the bore. Is a base gasket used the port timings are raised about average and the blow down timing is affected heavily. Limiting the power up the rev range.
To achieve the good and torquey power output that the new Polini kit has out of the box, a head gasket is recommended to for te right timings. But there is the L-ring prob…
Facts…
Out of the box the new Polini has port timings of 123° transfers to 171°exhaust timing with the 57mm crankshaft. One of the best kits out of the box for touring and good power low down.
If you are going to fit the kit with a 60mm crankshaft and simply use a 1.5mm base gasket the port timings are changed to around 135°/179°.
If you are looking at the bow down timing only it is changed from 24° to 22° only. If you look at the 22° this would be still okay for a broad power curve. But if you have a look at the changes of te port timings the 135° transfer timings is far away for a road going engine. This crap design can be used with an exhaust based on the original design to make it work. So a Sito Plus or SIP Road would be the ones to go for.
230cc???
One of our customers (Thomas aka schoeni230) had a full go on the Polini alloy barrel subject. He is using it with a custom made 62.5mm crankshaft.
With a special piston instead of the standard Polini L-ring item the problem with the L-ring running out of the bore is cured.
This piston makes it possible to have the piston running out of the bore to a cretain degree:
This way a 0.4mm base gasket was sufficient to get everything right. Even with the longer stroke of 5.5mm the port timings were nearly in a reasonable area.
With ~133°/179° and a special cylinder head to cover the longer stroke the engines runs pretty well with a exhaust based on the PEP Big Bore design. The high torque and a really broad power band makes it a really good Rally going engine with hight top speed under every circumstance. And the top power output is -with the design of the exhaust in mind- stunning as well.
The carb used is a 35mm Keihin PWK with a Scooter & Service Reed Manifold (with V-Force Reeds). The ignition is one of the Vespatronic ones.
The barrel is nearly untouched. The exhaust port was altered only. The width and height were slightly enlarged.
UPSHOT:
Even with the port timings on the strange side, the engine should be best of all worlds and really catches one’s demands for a strong road going engine. With more than 20hp beyond the 9k rev mark.
One weak point for sure is the piston running out of the bore. Giving alignment issues of head to bore and the thermal thing at the sides of the piston are an issue as well.
The upcoming Polini for the 60mm crankshaft should be a massive step to built one of these dream engines without the need to cut so much corners.
If you are fancy this NOW, contact us. We are happy to give you advice how to built a similar engine with the 60mm crankshaft.
Once again you are welcome to our OPEN DAY. On Saturday the 18th of September 2010 we will be opened from 10:00 – 16:00 h. Anevent mainly organized for our friends with geared scooters like Lambretta and Vespa.
Highlights:
No matter for the weather
If it rains, no worries. We are prepared to keep you dry. At least while you are here at Scooter Center. We are looking forward for a relaxed meet & greet. And we are searching for the highest power output at the dyno. So don’t miss it!
You can find SCK Classic Day #3 at bei Facebook
