vespa t5

going through the parts i have lying around i could put together a t5 engine with unmatching casings - ive heard different things what are the thoughts here? also ive seen large frame engines in small frame scooters - is that a difficult thing to do?

Hi there Domsmudge, Its not a good idea to build what you would consider to be a rally / distanxce engine from unmatched casings, BUT, if building a sprinter for a weekend, or for blasting around locally,(push home distances) then why not. Also, with very carefull build and long carefull run in then a reliable engine is a possibility. As you are probably aware, the matched halves are machined together so cranks/ gears/ bearings/ shafts all line up. I have a similar concern when welding casings either for repair or tuning, Distortion, and Ive yet to have one that wont run. As for large frame engines in small-frames, its fairly easy, a bit of cutting, both engine and frame, out with a big hammer and a few beers and its sorted,

domsmudge,
RE large frame engine in small frame: I have one on the road at the moment (I say on the road in the loosest of senses). as BEERACE says, just abit of chopping and hammering; it’s best if you have a small frame engine to hand as well, for measuring. I mounted a rim on both engines then put a straight edge from two points on one side of the rim up to the middle (ish) of the engine mount, then marked this point. did the same on the other engine. this gives you a bench mark related to the line of the rear wheel, you can use this to measure out to the edges of the steel inner bits of the mount, then work out how much to chop of each side… you have to do it this way because you have to chop more of one side than the other, it’s about 13mm of one and 8mm of the other of something, can’t really remember??? next thing to do is drill mount bolt holes in the frame out to take the large frame bolt, you have to get the hole central or you’ll either crab down the road, have a rear wheel leaning over one way or both. next get you hammer out and beat an area in the frame so the cylinder/head can fit and move freely.
my frame is a PK and i just used the PK shock from the standard mount with no problems at all, but apparantly with primmy’s 50’s ect you have to weld a little plate on and mount the top of the shock an inch or so back because it binds due to the angle… not sure about that one? the shock mount on the engine is only about an inch further back on the L/F engine, can’t see it making a huge difference, hasn’t on my PK…

good luck, few beers on a sunny afternoon… proper job… few more beers and you’ll end up with a monstrosity death trap like mine [:)]

thanks beerace - i’ll give it a go - and good luck with the back - hope you are able to enjoy some of the summer