Hi everyone, I need some help diagnosing a problem with my Aprilia SR.
Engine setup
Cylinder: Malossi MHR Racing 70cc
Carburetor: Polini PWK 26mm/ tried keihin 24 too
Exhaust: DDL exhaust
Crankshaft: Doppler Endurance
Reed valve: Stage6-style VForce 3
Intake manifold: Straight intake
Air filter: Malossi E13 (
Fuel: Motul 800 premix, 1:25
Main jet: 125
Transmission: Polini variator and a custom/special crankshaft setup
IMPORTANT: I have a special Polini engine/crankshaft setup with a variator designed for 9 rollers instead of the standard 6. The variator has a smooth bore with no splines. It uses nine small rollers, and the correct special variator setup is required. This is not a standard 6-roller variator setup.
Symptoms
The scooter has very poor low- and mid-range acceleration and struggles to engage the powerband properly. Depending on the transmission setup, it either barely moves unless I give it full throttle or revs very high without pulling properly.
At high RPM, it sometimes behaves as if it is hitting a rev limiter: it stutters/bogs and refuses to rev cleanly through the powerband.

I was offered this engine for 40 euros. The owner said it needs to have it's piston rings replaced. Does anyone know what could it come from? Also it's reliability and speed.

I have a Riga delta rmr 24 frame and I'm thinking of putting this onto it

Recently rebuilt this broken minarelli V1. Replaced the crank, bearings, seals, clutch and got the DOS 70 cc cylinder - it was water logged and rusted. It now start sright up but it’s got this weird rattle which seems like it’s coming from the cylinder head, is this normal? I’ve tried different gaskets different thicknesses not getting much luck, also checker there is little to no movement of piston at TDC when head is off no dont think its piston slap. Anyone got any ideas or is this just what’s to expect?

Absolutely legendary exhaust for Czech tuning, true to see if they have new exhausts or if they’re in business. Didn’t find much, does anyone know about themt.