Clutch & Gears

Clutch

The diaphragm clutch looks quite conventional, right down to the use of 10 “fingers” (also known as clutch release arms).

Mecatecno's assembly video below shows the installation of an S3 clutch pack.  The plates are the same as those used by GasGas, so their various thickness steel plates would be available for tuning lever effort and travel needed to engage or disengage (and also to compensate for friction plate wear). 

GasGas steel plates are available in the following thicknesses: 1.3, 1.4, 1.5, and 1.6mm.

One notable departure from a standard clutch design is the lack of a large center nut.  Instead, there is a small screw.

I was a bit concerned about the paper gaskets I saw in Mecatecno's assembly video.  They appeared very thin.  But not to worry,  the clutch cover gasket measures 0.75mm and seems adequately robust.  No adhesives are used on the gasket. 

I disassembled the clutch to make measurements for future reference.  The ten M4 screws that hold the spring retainer required a 2.5mm hex key.  I was disappointed to see that one the ten screw's “drive socket” had been buggered at the factory.  This made removing the screw difficult. 

These screws seem like something that requires proper torquing.  Although I have a variety of 2.5mm hex keys, none could be turned with a torque wrench.  I have ordered Wiha Tools item number 71316 which is described as a 2.5mm hex bit with 3/8" drive.

Overall Gearing

Based on observation (counting teeth) I have determined the following.

Secondary: 10T front sprocket (GasGas spline pattern) drives 44T rear sprocket for a 4.4:1 ratio.  The Iris chain is a 520 with an easily removable master link.  This latter fact is a big deal if you ever need to push or tow the bike a long distance.  Because there is no neutral, removing the chain is the only way to make the bike roll easily.

Primary: 25T motor gear drives a 75T clutch basket gear for a 3.0:1 ratio.

The transmission ratio is 1.78:1.  (This is 3rd gear for a 5-speed Sherco gearbox.)

Thus, the overall ratio is: 4.4 x 3.0 x 1.78 = 23.46

A top speed of 28 mph has been measured via GPS.  This corresponds to a maximum motor speed of about 8500 rpm using a standard trials tire.

It could also explain the US importer's 46 mph top speed statement as a misprint of units.  28 mph is fairly close to 46 km/h.

For comparison, the EM Race (before 2024) had an overall motor speed reduction ratio of 14.39:1 and a measured motor maximum of 8,160 rpm.  This yields a top speed of about 70 km/h (44 mph) with the same tire dimension used for the Dragonfly calculation.

Front Sprocket Issues

I pulled the front sprocket to verify what appeared to be a GasGas spline pattern.  It is.  But what a struggle to remove/reinstall that sprocket!  The swingarm protector/chain guide is hard plastic and part of it extends from the swingarm pivot to the sprocket.  I needed to bend this piece significantly to remove/install the sprocket.  (Later I determined it's easy to just remove the swingarm protector entirely if you want to change the sprocket.)

Then I found it impossible to re-install the sprocket circlip due to the sprocket being too far outboard.  There was a 25 x 30 x 2.5 white plastic spacer inboard of the sprocket.  See adjacent photo.  This spacer is not shown on the gearbox parts diagram. 

So I replaced the 2.5mm thick plastic spacer with a metal one that's 1mm thick.  This allows clearance between the circlip and the sprocket.  With the original spacer in place, the countershaft would need to be pulled outboard forcefully to refit the retaining circlip.

To understand why I substituted a 1-mm spacer, refer to Mecatecno's parts diagram above for the relevant item numbers.  

Upon removal of the cover plate (item 1) I discovered there were three O-rings (item 4) installed rather than the two shown.  Apparently, this was done to move the bushing (item 5) far enough outboard that its end would clear the seal (item 3).  But when attempting to reinstall the sprocket, considerable force was needed to compress the O-rings.  It is interesting to note that the cross section of each O-ring is 1.5mm (the difference between the original plastic spacer and my steel spacer).