SYM Owners Forum

Scooter Models => DD 50 => Topic started by: skebegigi on May 29, 2012, 04:07:50 PM

Title: DIY mods
Post by: skebegigi on May 29, 2012, 04:07:50 PM
I'm going to get a 2012 SYM DD50 in a few days but I wanted to do slight mods myself, since I always enjoyed tinkering with all my vehicles.
Is there any mod manuals out there, other than the regular repair manual?
Any help on this would be appreciated.

I guess no one is around . . . .
: (
Title: Re: DIY mods
Post by: sidthesloth on June 30, 2012, 05:14:31 AM
Is the DD50 the same as the Honda Dio and Kymco ZX50?
Title: Re: DIY mods
Post by: skebegigi on July 09, 2012, 07:30:54 PM
Yes, the SYM uses the same motor as the DIO.
Title: Re: DIY mods
Post by: sidthesloth on July 10, 2012, 02:32:48 AM
If you go over to there are some people there that are quite knowledgable in the ZX50. If thebatman and zombie can't help, then noone can. :)
Title: Re: DIY mods
Post by: skebegigi on July 10, 2012, 11:43:28 PM
Hey thanks for the info!  Gonna check it out as soon as I can.
Title: Re: DIY mods
Post by: campurvis on July 25, 2012, 04:35:58 AM
Small 2T motors generally respond to the same basic hop-up procedures.  I always keep them pretty mild. For example, get a machine shop to mill about .015-.020” off of the head to increase compression a tiny bit.  Next you need to get exhaust gases out faster through the exhaust port and a fuel charge in faster (transfer ports). You can use a port grinding tool to do this or you can shave 1.5-2.0 mm off of the top of the cylinder and add the same thickness back on by adding an aluminium spacer under the cylinder that you fabricate yourself, or—leave the cylinder alone completely and work on the piston.

To modify the piston, place it in the cylinder and mark the top of it at both side edges of the  transfer ports and both side edges of the exhaust port.  Set the marked piston on a bench.  Draw lines from the center of the piston to the edge marks for the ports.  You will now have triangles marked on the top of your piston.

Put a mark on each triangle about ˝” back from the outer edge of the piston. Now each triangle has a clearly marked outer section.  This is where you will be removing material from the top of the piston.  Return to the edge of the piston top and measure down the side of the piston 1.5-2.0 mm. Make sure this mark is at least 1.5-2.0 mm above the groove where your top piston ring resides.  Take small hand files and gently taper the outer section of triangles down to this mark.  When done you’ll have three gently sloping indentations in your piston that start about ˝” in from the outer diameter of the piston and direct flow to your ports.  This is a lot of work and it is easy to make expensive mistakes but it will give your engine a little more pep.  If you are in doubt about any of these instructions get a book on 2 stroke performance mods.

Without a properly designed expansion chamber and appropriate carburetion and ignition timing changes you are not going to get much extra power out of a tiny 50cc motor.  
The simplest effective modification I can think of for any small scooter  like this is to install  rollers that are 1 gram lighter than the stock rollers and call it a day.

In some countries, various power restrictors are built into 50cc bikes.  If you live in a country like that you will have to remove the restrictors.  You can ask a local shop how best to do that. (