Hi all, I just found this site - at last,
I have the EC50 which is pretty much identical to the SM, purchased it at 6 mths old in 2003 for the wife, sold my own bike & started riding hers, at first i hated it (lack of power)but then learned how to ride it (ring its ass every where you go),It would now go down as one of the best bikes ive ever ridden/owned, I have no hesitation riding A & B grade sections on trail rides.
As for the engine first mods to do are cut the expansion chamber in the middle as close to the weld as possible, rip out all the power deadning mesh thats there & weld it up. Next drill the air box & let the thing breath,you might have to check your carb settings to make sure your mixtures are good. Buy the time you have done this you should be good for approx 45 mph depending on your gearing and totally transform the power delivery into something enjoyable.
The motor on these is also used on the Gilera GSM and old Derbi Senda (pre 2000 models).
You will find very little information on them if you go looking for Gas GAS.
I have just put the big bore kit on it & what a difference. Power is very similar to the KTM sx 85 but has smoother more usable delivery.
The one that was recomended to me was the Italian made Malossi or the Gilardoni (Gilardoni cylinders are used as standard) rather than the cheaper Taiwan or China made units.
I went for the Malossi MHR (full race), 21mm pwk carb & bigger inlet manifold.
total cost was around $650.00 nz$ .
Engine number is EBE050
Hope this helps & I haven't waffled on too much , theres some part nos and info below.
Alex
Cylinder Metra Kit Pro race Derbi 70cc
(# 65199)
race set-up. 18-20 Horse Power is reachable! Fits the EBE050 engine untill
2005
Size : 47,60mm
Brench : Pro Race
Type : Metra kit
Color : Aluminium/ gold
Material : Aluminium
PinSize : Pen 12
Cooling : LC
Volume : 70cc
Fits : Derbi GPR, GPR Nude, GPR Racing, Senda DRD R, Senda DRD SM,
Senda Extreme, Senda Extreme SM, Senda R
Gilera RCR, SMT
Cylinder Hebo Manston Replica Derbi 70cc
(Artnr. HR4000145N)
The Manston Replica cylinders are developed by Hebo and produced by
Athena.
Wide butterfly ports and an aluminium insidehead are the
charasteristics of
Derbi GPR, GPR Nude, GPR Racing, Senda DRD R, Senda DRD SM, Senda
Extreme,
Senda Extreme SM, Senda R
Gilera RCR, SM
MALOSSI
MHR Replica (mid race) 79cc # 31-11693
MHR (full race) 79cc #311985
MHR Team (full worked) 79cc
WWW.malossi.com