Probably gonna go stupid with the bore

[Roytheroach]

There are 63mm cylinders for 54mm bolt spacing. Also found a 4v head that even uses possibly the same cam (y shaped rocker) so if I'm lucky I'll run my a9. The head fits on a 63mm bore with 54mm spacing. I do love an over-square motor, gimme all them rpms. It looks like it uses the same size gy6 valves just twice as many.

The bore is like 50 bucks for the jug, pison, rings, gaskets. The head is over 400 for the complete head and valve cover. So bore first, running the big valve head that came with my current 72cc setup

I am fully aware the crank is eventually gonna pop. Offerings to the gods of speed. Gotta look into something that can handle stupid rpms, like aiming for 12k. The kymco crank is high quality but I'm really pushing it with that giant piston. If I do upgrade I'd like to keep it at the same stroke, maybe go up to 200cc but idk.

Has anyone done this? Aside from boring/rotary grinding the case, what should I expect to deal with?

There will be a steel pan under the seat to protect myself from catastrophic engine failure shrapnel

Gonna make a new engine cover/cooling duct for the cylinder and probably get a fan with curved blades instead of the cheesy factory ones. Maybe a leaf blower impeller lol

I'll step up the carb too, running 22mm now, gotta figure out what size I want n get the jet kit

[Stig / Major Tom]

A nice lightly used 125 Agility out of the budget😊?
I do understand if some prefer modding, to riding.
Stig

[JJJoseph]

Has anyone done this? Aside from boring/rotary grinding the case, what should I expect to deal with?

I've done plenty of big bore kits, and they always end up breaking the crankshaft.  It's not a huge BANG, it just comes to a slow, grinding halt, usually in the middle of a bridge in rush hour.  When the crank breaks, it usually messes up the stator because the end of the broken crank starts wobbling off-center.  Sometimes the other end breaks and cuts a big hole in the end of the crankcase.  If I think of anything else I'll let you know!

[Kansas kymco]

Would it be cheaper to find a used 125 engine on ebay you could bolt in?  Or is it the quest to find out what the limits?

[Roytheroach]

A nice lightly used 125 Agility out of the budget😊?
I do understand if some prefer modding, to riding.
Stig

That actually makes sense, I enjoy messing with it more than anything. It's fun to get results. It's fun to have the wildest one around. It's fun to shoot flames and see faster 1/4 mile times than before you installed that whatever lol

I basically only ride it to see how I affected it.

Also... like the whole bike is perfectly good, I think it looks cool. I think it's the coolest moped I ever saw. I love the fairing. And how I stretched it 11" in the rear and took off the rear fairing and flipped the seat onto where the back seat was and now it has a fancy teardrop single seat. And how I've put 5 years into building it into this monstrosity that EVERYONE asks me about when they see it... it costs 50 dollars to make it BIGGER than a whole agility 125 scooter. AND THEN I GET TO TUNE IT MORE MUAHAHAHAHAHA

You go buy a bigger bike I'm having a grand time over here bud. Cheers!

[Roytheroach]

Would it be cheaper to find a used 125 engine on ebay you could bolt in?  Or is it the quest to find out what the limits?

The only ones I can find use a different engine mount location. I'd love to throw in a $250 150cc turnkey gy6 but then I gotta get back to welding. I already had to redo the extended engine mount I have now twice to get it right how I want it. The only big difference will be case shape and cylinder bolt spacing really


Once I blow it up, because I will never stop making it faster, when that case or crank is no longer usable, might as well do a proper swap so I can get even bigger cc's with the 57mm spacing block

[JJJoseph]

Would it be cheaper to find a used 125 engine on ebay you could bolt in?

The 50cc (qmb39 models) are designed to foil that approach.  You can't put a 125cc gy6 engine into a qmb39 frame.  It's totally impossible without cutting the frame in two, and splicing in a complete ass-end from  the 125.  I know that Honda Ruckus owners do things like this, but they're paying thou$ands for adapters, frame extenders, and machine-shop work. Far cheaper to sell it and buy a 125cc.

[Kansas kymco]

The 50cc (qmb39 models) are designed to foil that approach.  You can't put a 125cc gy6 engine into a qmb39 frame.  It's totally impossible without cutting the frame in two, and splicing in a complete ass-end from  the 125.  I know that Honda Ruckus owners do things like this, but they're paying thou$ands for adapters, frame extenders, and machine-shop work. Far cheaper to sell it and buy a 125cc.

Did not know that.  Glad you spoke up.

[Roytheroach]

The 50cc (qmb39 models) are designed to foil that approach.  You can't put a 125cc gy6 engine into a qmb39 frame.  It's totally impossible without cutting the frame in two, and splicing in a complete ass-end from  the 125.  I know that Honda Ruckus owners do things like this, but they're paying thou$ands for adapters, frame extenders, and machine-shop work. Far cheaper to sell it and buy a 125cc.

I restore antique cars for work, and fabricate a lot. No challenge for me, but you're right, average Joe likely needs to have a shop do the work.

If I can keep the bottom end and case from being terminated, 130cc sounds great to me. And with that 4 valve head it's gonna be an absolute screamer