Henrik Y

I remember seeing a twin cylinder motorcycle getting Vespa cylinders some years ago and was searching but couldn't find it again, maybe it was that one. I have an old Suzuki GT125 twin cylinder engine in bad shape that I was thinking about putting two VMC 100 cylinders on as they have the same stroke at 43mm, then you have 200cc instead of 125cc and some large reed valves on top of that. This is with a 125cc vespa gasket, the VMC 100 is a little narrower over the transfer channels so it looks like it could work. Fitment to the block is no problem, the problem is the short stroke at only 50mm. The Suzuki GP125 has an odd size conrod with 14mm and 19mm pins so with a 15mm piston pin I had to try and get a thinner bearing. I suspected that the cage would fail so I made washers on the outside to hold it in place, it did fail after a while and a small piece of the cage came out and made some dent's in the piston. I only noticed when lifting the cylinder head. I then used only needles with no cage and it also worked for a while, but then the side washer failed and destroyed the cylinder, I suspect it was because of the small oil groves I made, the pins probably managed to snag in there and eventually break it apart so without those groves it probably would've worked. The first fail, all the needles stayed in place and I could ride home without noticing. The one left after the second catastrophic fail and you can see the marks of the needles digging into the groves. The left washer is gone. The rebuild after that I changed to a go-kart conrod which where longer and with 15mm and 20mm pins. I didn't have the tools to bore a crank with enough precision so instead I ground down the ends of the 20mm pin to 19mm and also made them eccentric so now I have about 51,5mm stroke which is the most I can get without the conrod hitting the case. I have a second engine as a spare, might do a VMC Crono build with that one. I think those durations will work with 50mm stroke as well if you up the revs a bit to around 10krpm unlike the low revving scooters.

Hello! I don't have a scooter but I do have an ET7 cylinder on my Suzuki GP125. The GP125 has a rotary valve so the scooter cylinders are pretty much the only modern made option when it comes to air cooled cylinders without reed intakes on them. It runs pretty good, can lift the front wheel a bit at 100kmh and has a top speed of 165kmh at the moment which probably could be improved a little. I'm also partially paraplegic and confined to a wheelchair and can't walk, have just enough function in my legs to be able to sit on small bikes which was the reason I got this small 125 in the first place. I can just about get my feet up on the pegs so had to figure out a solution for the shifting and then I got some inspiration from the Vespa Scooters so made this hand shifter which works great.