How do you de restrict using Minarelli 50cc 2T engines?
De restrict using Minarelli 50cc 2T engines step 1
There are two restrictions used on scooters fitted with the Minarelli 50cc engine. One is located on the exhaust system and the other in the variator.
Let’s start with the exhaust system. You have the choice to either de restrict the original system, or simply swap it for an aftermarket exhaust that doesn’t have a run off catch pipe. If you choose to de restrict the original then you will need to start by removing the exhaust from the bike, you will see a fairly large run off pipe that leads to a dead end similar to the one shown in the picture below.
You will need to cut this pipe off near the base and crimp it together, once done weld the crimped edge making sure it’s sealed; you have now de restricted the original exhaust system.
De restrict using Minarelli 50cc 2T engines step 2
The restriction located in the variator is very easy to remove however you will need a lock tool or impact gun in order to remove the nut that holds it all in place. Start by removing the crankcase cover, this is on the left hand side of your engine where the kickstart is usually found. You can do this by removing all of the bolts around the perimeter then ease it off.
De restrict using Minarelli 50cc 2T engines step 3
Now you can see the drive belt and the front fan pulley which is held in place by one nut on the end of crankshaft.
De restrict using Minarelli 50cc 2T engines step 4
Using your lock tool or impact gun remove this nut and slide the castle washer and fan pulley off the end of the crankshaft. Be sure to keep things in order as you take them off so you know which way they need to go back on.
De restrict using Minarelli 50cc 2T engines step 5
If you pull the belt to one side you will now see that the restriction is visible, you are looking for a spacer-washer that sits on top of a large silver bush “bush pin” which the variator slides backwards and forwards on. The restriction spacer stops the variator moving the full length of the bush pin which in turn prevents the belt from being pushed to the outer point of the variators circumference, because of this speeds above 30mph cannot be reached.
De restrict using Minarelli 50cc 2T engines step 6
All you need to do is remove this washer then re install the fan pulley etc as you removed it. Make sure the washer you remove is the one that is over the top of the large cannon bush, any other washers other than this one need to remain in place, just as you found it. Tighten the crank nut back up and re install the crankcase cover.
Once you have de restricted your scooter in the two places we have mentioned you may need to increase the main jet size in your carburettor. On early scooter models using Minarelli engines the Dellorto carburettor was mainly used, you won’t need to increase the fuel flow if this is the case providing the standard exhaust system is still being used. For later models around 2004 > onwards using the Gurtner carburettor you will need to increase the main jet to either a 68 or 70.
De restrict using Minarelli 50cc 2T engines step 7
To do this you may need to remove any panels that stop you gaining access to the carburettor.
Alternatively you could lie down under the bike and release the two screws on the bottom of the carb that hold the float bowl in place.
De restrict using Minarelli 50cc 2T engines step 8
Once undone remove the float bowl, you should now see a small jet in the centre of the carburettor that looks like a grub screw.
De restrict using Minarelli 50cc 2T engines step 9
Unscrew the main jet and replace with the new one. Then reverse the process to re install the float bowl and refit the carburettor to the scooter. Once everything is plumbed back in the fuel flow will reinstate as soon as you try to start the scooter.