Kymco SC10AS 100cc and beyond:

[Timmer]

I have limited experience with tpu, i’ve only used Eryone’s so far, which was ‘95A’ in hardness. It flexes a bit, is relatively easy to print (somewhat comparable to pla , yet slower). There are also softer/more flexible TPU 85A, but that seems to be a bit more difficult to print, and is recommended for direct drive extruders, not for bowden setups.
As for brands for tpu, the usual suspects i’d say, any decent brand will probably do.

[190mech]

A flycutter gives a nice finish and are cheaper than most indexable cutters. Whichever you use, I'd lap it with some 280 grit paper on a piece of glass for final finish..

[oldgeek]

Sept 29, 2024 3:37:00 GMT -5 Timmer said:

I have limited experience with tpu, i’ve only used Eryone’s so far, which was ‘95A’ in hardness. It flexes a bit, is relatively easy to print (somewhat comparable to pla , yet slower). There are also softer/more flexible TPU 85A, but that seems to be a bit more difficult to print, and is recommended for direct drive extruders, not for bowden setups.
As for brands for tpu, the usual suspects i’d say, any decent brand will probably do.

Thanks for the info. I am very new to 3D printing, I wonder what hardness would work best in this application?

I am also starting to think a properly annealed copper gasket would work well.

[Timmer]

I'd just use the normal 95A that i have, and print with that. TPU is chemical resistant, has a high temp resistance (compared to normal filaments) of around 90°C before deforming.

I went to look for the YT channel i watched a year or two ago, that did some gasket testing with TPU;
The Eddies
I found it informative, and i assume it's beginner friendly, as he explains everything quite well too

[oldgeek]

Sept 29, 2024 13:37:08 GMT -5 Timmer said:

I'd just use the normal 95A that i have, and print with that. TPU is chemical resistant, has a high temp resistance (compared to normal filaments) of around 90°C before deforming.

I went to look for the YT channel i watched a year or two ago, that did some gasket testing with TPU;
The Eddies
I found it informative, and i assume it's beginner friendly, as he explains everything quite well too

Thanks again. I got the gasket layout into cad and made a couple test prints in PLA.

[oldgeek]

The silicone sheet arrived yesterday, I cut a gasket from it and torqued the head down. As suspected it extruded the silicone everywhere. I think the TPU would do the same as the silicone, maybe not as bad. I am working on a copper gasket now.
I ordered the fly cutter, but it will be end of week Oct 14 before it arrives. I plan to mill the chamfer off of the head to give it a better chance to seal the water jacket. What could go wrong? LOL


I completely rebuilt the center stand pivot points on the Naked Kymco today, figured it would be a whole lot easier without a motor in the scoot.

I also started on the new case spacer for the TPR86 build, I lucked out and found some aluminum sheet that was the correct thickness in my scrap pile 3/32 or 2.4mm for the rest of the world. I am not sure what grade it is but it is very hard stuff to cut on the scroll saw.

[oldgeek]

TPR 86 motor:
I finished the case spacer and the cylinder base spacer. In the picture it looks like the holes for the cylinder studs are off center, because they are. I had to move them a little due to the case spacer and it helps to make this minarelli cylinder fit the vertical Kymco cases (AF16 type cases)



Next up notice the cylinder overhang at the transfers. I may or may not try to fill that area with epoxy. I just dont think it will be that much of an issue. It is just under 2mm on one side and 2.4mm on the intake side, which is not a big deal on that side.




Squish ends up a little tight at .8mm with the cylinder torqued to spec, It is supposed to be .9-.10 I may have to do something about that, maybe cut a base gasket from shim stock?

[oldgeek]

TPR 86 motor:
I have a question about intake area and flow. I will be using the 25mm PHBL carb. The area of the 25mm circle is about 491 mm sq. The Kymco intake windows area is approximately 840mm sq. Assuming my calculmations are correct, is there really any need to open the windows up? Possibly just remove the hard edges of both windows?
This is not the actual cases I am using, just a photo I already have.

[Lucass2T]

Oct 3, 2024 18:06:42 GMT -5 oldgeek said:

TPR 86 motor:
I have a question about intake area and flow. I will be using the 25mm PHBL carb. The area of the 25mm circle is about 491 mm sq. The Kymco intake windows area is approximately 840mm sq. Assuming my calculmations are correct, is there really any need to open the windows up? Possibly just remove the hard edges of both windows?
This is not the actual cases I am using, just a photo I already have.

Ideally, you want to keep transitions (which cause eddies) low, flow path straight (high flow) and the windows as small as possible. In piston ported engines you aim for an intake port area thats 10% bigger than the carburetor throat area. So the windows should be around 10% larger than the carb I assume. That would mean making them smaller. I would make sure the flow path from the reed cage to the windows is as smooth as possible with the smallest possible transition. Get creative with JB weld or 3d print some inserts.
You can smooth out the windows at the crank side to promote flow and make the transition the least abrupt as possible.
btw, eddies and reduced flow occur when the mixture encounters a path that is stepped up, not stepped down.

[oldgeek]

Oct 4, 2024 3:03:26 GMT -5 Lucass2T said:

Oct 3, 2024 18:06:42 GMT -5 oldgeek said:

TPR 86 motor:
I have a question about intake area and flow. I will be using the 25mm PHBL carb. The area of the 25mm circle is about 491 mm sq. The Kymco intake windows area is approximately 840mm sq. Assuming my calculmations are correct, is there really any need to open the windows up? Possibly just remove the hard edges of both windows?
This is not the actual cases I am using, just a photo I already have.

Ideally, you want to keep transitions (which cause eddies) low, flow path straight (high flow) and the windows as small as possible. In piston ported engines you aim for an intake port area thats 10% bigger than the carburetor throat area. So the windows should be around 10% larger than the carb I assume. That would mean making them smaller. I would make sure the flow path from the reed cage to the windows is as smooth as possible with the smallest possible transition. Get creative with JB weld or 3d print some inserts.
You can smooth out the windows at the crank side to promote flow and make the transition the least abrupt as possible.
btw, eddies and reduced flow occur when the mixture encounters a path that is stepped up, not stepped down.

So if I am understanding correctly, the overhang at the transfers is not so much of a problem.
I was planning to use the typical CT style intake that allows you to use the much larger reed block. But I think I will try a stock style reed setup, coupled with an intake that is specifically for the vertical style motors and the PHBL carb. This will keep the intake tract constant until it exits the windows.

[Lucass2T]

Oct 4, 2024 6:45:34 GMT -5 oldgeek said:

Oct 4, 2024 3:03:26 GMT -5 Lucass2T said:

Ideally, you want to keep transitions (which cause eddies) low, flow path straight (high flow) and the windows as small as possible. In piston ported engines you aim for an intake port area thats 10% bigger than the carburetor throat area. So the windows should be around 10% larger than the carb I assume. That would mean making them smaller. I would make sure the flow path from the reed cage to the windows is as smooth as possible with the smallest possible transition. Get creative with JB weld or 3d print some inserts.
You can smooth out the windows at the crank side to promote flow and make the transition the least abrupt as possible.
btw, eddies and reduced flow occur when the mixture encounters a path that is stepped up, not stepped down.

So if I am understanding correctly, the overhang at the transfers is not so much of a problem.
I was planning to use the typical CT style intake that allows you to use the much larger reed block. But I think I will try a stock style reed setup, coupled with an intake that is specifically for the vertical style motors and the PHBL carb. This will keep the intake tract constant until it exits the windows.

Correct, thats not as bad as the other way around. Best is to have no steps at all amd have one constant path. Smooth transitions are okay but none is better. But that is physically impossible in a two stroke.
Bell wrote about it in his book somewhere if I remember right.

[oldgeek]

Cut a base spacer from .005 shim stock, that was fun! Rechecked squish and it was .91mm after adding this shim.


I ordered a 25mm PHBL from ScooterPartsCo a while back, they refunded my money today, said it was out of stock from their supplier. I have been searching high and low for one that is not over $200 but I cannot find one. I am thinking about a clone from Amazon for $75 I have had decent luck with the clone PHBG's from ebay so....

[Lucass2T]

No no no no clones please!😭 How about looking for a 2nd hand one or maybe go with a 21mm PHBG? Or find something from the older 80cc MX scene? Cr80, yz80, kx80, rm80 etc etc. Or maybe re-jet a 4t road bike carb?

[90GTVert]

Not sure how it works out with shipping, but says in stock and $125.
www.sip-scootershop.com/en/product/carburettor-dell-orto-phbl-25-bs-02731-round-slider_41000000?usrc=phbl%2025
EDIT : For me shipping is between $38-$145 so you could surely get it under $200 based on that. Look at their tuning supplies too if you're gonna order. I think that's where I got my PHBL long ago.

A lot of people like clones. First one I bought was the 34mm "Keihin" PWK. I'm scared now after the needle bushing just falls out. If they can't make that fit right consistently, I have to wonder how close anything in the carb is. I'm sure clone quality varies quite a bit though.

[Timmer]

www.scootfast.net/fr/dellorto-carburettor-25-mm-phbl.html

This is in France, so i don’t know how much shipping will be, if it’s too much i might buy it and ship it to you, but i’d have to check how much that’ll be (and i have no idea where you’re located )