Motobecane TM4 – 2018 update

My trusty Motobecane TM4 had some issues that i’ve pushed off for some time now. The original cylinder was a bit weak and the engine needed some new bearings. The moped has sat many years, only had 1200 km on the odometer when i got it. That has led to condensation in the engine, everything above the oil level was a bit rusty, and especially the ignition side mainbearing.

The engine is easy to work with, took me 5 hours including cleaning and making my own gaskets. New bearings and seals.

My german model had a Gilardoni R2051 cylinder mounted, i’ve never been truly happy with it. I got myself a N2052 model with a bit longer port duration. I like the way it rides now, more power over all. Maybe i’ll upgrade the carb at some time, at the moment it’s a Dellorto SHA 14.12 that i’ve drilled to 13,5 mm venturi.

Check the gallery for all the details:

Moped Speed Calculator

Another spreadsheet i’ve made, to calculate the speed of your moped at a given RPM. You need to know the details of your engine, gearbox, sprockets and rear wheel. You can find most of it in a spare parts catalogue, or simply count the teeth on all sprockets.

Moped Speed Calculator

Only type in the blue fields!

If you want to calculate the velocity for a single speed engine like a Puch Maxi, just type the same value in “1 Gear” in the primary and secondary fields. I’ve made the file up to a 6 speed gearbox.

You can use MS Excel, OpenOffice, LibreOffice or a similar program.

Moped Engine Timing Calculator

I’ve made a spreadsheet that you can use to calculate the ingition timing, to convert mm before top dead center to degrees, and reverse. I think the file is self explanatory, click the link below and try it out.

Ignition Timing Calculator

You can use MS Excel, OpenOffice, LibreOffice or a similar program.