Carb advice - what size

[Snails]

Ok so I've nearly finished building my 175 engine. Its a SR 175 barrel with some slight tuning/tidying done to it.

It was my intention to fit a 25mm carb to it but I ideally I'd now like to fit that to my 125 Vespa (really I'd prefer a 24mm but I dont want to go and buy another - anyone want to swap?). Anyways a friend has offered my a 26mm that I can fit to my 175. Would that be too big? I'm pretty sure it wouldn't as I remember when I was specing the engine up about 10 years ago the motivation for 25mm was that it allowed me to still use the original air filter. I'm led to believe there are good alternatives available now that mean I could fit the 26 and still keep the panels intact and have an air filter? Cheap ones, not the modified air intake...

Also would I need to change the inlet manifold if I was changing from 25mm to 26? Again I kind of assume not? In the picture below the 25 is the bottom one. Would I need a different one of the rubber attachments to fit to the manifold?

[Monty]

I have a 26mm on my muggy and was wanting to use the air box. The first manifold I got was short so gave me panel clearance and the carb sat low so the distance between the carb and the air filter were similar to a jetex so the rubber fitted. The problem was that the carb sat on the cowling and kept falling off. The next manifold from Mike Pheonix was a lot higher. It was a bloody good fit with an MB rubber so has never fallen off but no way to fit the rubber to the filter. Far to close. So had to go for a remote filter. It took some time to get used to the induction noise but it runs sweet enough. I didn't want to go the 28 mm route that seems to be the standard carb for these muggy so. If you are happy with your manifold the rubber should pull up the extra. Bit of a mine field if you go looking for another one.

[Snails]

Thanks Monty, not got the engine in the scoot yet, want to get at least one of my others back in one piece before I take this off the road so i guess I will have to wait a bit to check those clearances

[Monty]

How's the Lou going

[Snails]

Not good. Had to strip it down again as the frame struts snapped again. All sorted now but the prospect of putting it back together is not something I am looking forward to.