Kymco SC10AS 100cc and beyond:

[ryan_ott]

Something out of balance for awhile..

[oldgeek]

Mar 23, 2020 22:38:19 GMT -5 ryan_ott said:

Something out of balance for awhile..

I never really noticed any bad vibes. The stock Kymco flywheels are pretty good, much better than the stock minas IMO. But I feel like the balance factor could have been off. The 50mm kit was designed for a stock stroke of 41.4mm But somehow the 52.6mm stroker crank set up very well. So it could be the 50 x 52.6 had something to do with it.

[Kenho21]

That was a pretty gnarly failure to say the least. Like Brent said, glad you walked away from it. Catastrophic failure and traffic on a scooter are a bad combo.

[Jwhood]

Yeah luckily you didn't have a complete lock up,I had a cylinder seize coming down a hill ripping I think it was the scariest thing that ever happened to me on 2 wheels and can't believe I controlled it without really hurting myself,glad u made it out unscathed

[pitobread]

I wouldn't say balance. I would say John is on point with crack propagated from the bottom of the key way sharp corner.

Corner radius are good!

[oldgeek]

I am going to resurrect this thread as I am currently working on some more motor combinations that are 120cc+ I have a few assorted cranks in various strokes and 2 Tadia cast cylinders one LC and one AC version, both are 54mm.
I recently finished making a template for cutting the cylinder throat on the Kymco cases allowing me to fit the larger cylinders. Last week I purchased a small trim router to use with the template, it works like a charm! I chose a set of junk Kymco cases for the trial run and I also used my other cutting setup to enlarge the crank area for the bigger crank.
I started fitting the various cylinders and cranks using slip bearings, it was no surprise nothing set up very well. The Tadia cylinders leave a lot to be desired as far as fitup and finish. I set the LC cylinder up with each crank and the piston ended up below the transfers at BDC and below the deck at TDC, no easy way to fix that. I looked over at the mini lathe and said why not. I then spent a couple hours or so trying to get the cylinder mounted and running true on the lathe, then another hour or so trying to figure out tooling. I managed to get almost 1mm cut from the base area, it came out pretty good, it may even seal if I ever end up using the cylinder. It was a long and tedious process to get that cut done.

[oldgeek]

I wanted to post a couple pictures that support what was done. Durations before cutting the base of the cylinder were around 197 exhaust 135 transfers After removing around 1mm from the cylinder base the durations are now around 192 exhaust 130 transfers. All measurements were made without base gaskets or torqueing. So I guess this cylinder would match up to an expansion pipe as is.

Before cutting the base of the cylinder on the lathe:



After cutting the base of the cylinder on the lathe:



Interesting is the metal head gasket provided. Pretty thick and poorly matched to the cooling passages. Seems it would be pretty restrictive to water flow.

[Lucass2T]

Aug 15, 2023 20:40:24 GMT -5 oldgeek said:

I wanted to post a couple pictures that support what was done. Durations before cutting the base of the cylinder were around 197 exhaust 135 transfers After removing around 1mm from the cylinder base the durations are now around 192 exhaust 130 transfers. All measurements were made without base gaskets or torqueing. So I guess this cylinder would match up to an expansion pipe as is.

Before cutting the base of the cylinder on the lathe:



After cutting the base of the cylinder on the lathe:



Interesting is the metal head gasket provided. Pretty thick and poorly matched to the cooling passages. Seems it would be pretty restrictive to water flow.

Nice work!
Those are some pretty high timings. Probably good for around 11-12k rpm peak power. With
a beefy pipe and big carb you'll make some nice power I believe!

[aeroxbud]

Nice work. It's going to be a ripper. 👍

[pinkscoot]

Good to see you back at it.

[190mech]

Those smaller transfer channels in the headgasket are there ot slow down flow and increase cooling transfer..
The transfer port ducts look very rough cast (much like the Tiada AC jug I have), a bit of time smoothing them out will help..What is the bore and stroke of that build?

[oldgeek]

Aug 16, 2023 16:25:02 GMT -5 190mech said:

Those smaller transfer channels in the headgasket are there ot slow down flow and increase cooling transfer..
The transfer port ducts look very rough cast (much like the Tiada AC jug I have), a bit of time smoothing them out will help..What is the bore and stroke of that build?

Do you think a regular gasket would be ok? I think squish will be wide if I use that steel gasket. Bore 54mm Stroke 52.6mm
I may not even build this one up, I have limited case sets to work with and I dont know if I want to dedicate a set of cases to this cylinder. I dont even really have a LC scooter yet because there is still a lot to be done on the custom scoot before it is ready.

I am working on repairing a set of cases that I purchased a couple years ago. The PO used a hammer and chisel to get the cylinder off Lol! I fired up the TIG welder today, my first attempt at welding cast aluminum. So far so good, struggling with trying to mill the cylinder mounting surface flat. These castings are pretty dirty to weld, lots of stuff in the pores.
I thought I had pictures before I started working on them but cant seem to find them. This one is halfway through the prep.


Setup on the mill, kind of Lol!

[190mech]

Your welds look fine, preheating them with a propane torch usually helps.. A fly cutter in the mill makes very smooth cuts and an angle plate helps to mount the cases to the mill table, even a piece of 6" angle iron works well. Set up time is always time consuming when doing a milling operation like that..It's all looking good!

[oldgeek]

I finished up a light pass or two on the mill. then used my flat diamond credit card files to polish and flatten even more. The pictures are misleading as it looks rough but it is actually very nice and flat.


I started trying gaskets and found a problem. It appears I need to build it up further out than I did.





Funny thing is, the 50mm TriPort cylinder fits perfectly.


Looks like I will be welding some more and milling again to make the 54mm cylinder fit. Lol! Its ok, I am kind of liking learning to TIG the cast aluminum. I have been watching Justin on The Fabrication Series Youtube channel ever since I got the TIG machine. He is a pretty good teacher and has great techniques for TIG welding cast aluminum.

[190mech]

Lookin good, pad some more beads on while you can to make room for the future!