Any idea how much to make a 50cc piston?

timmo1, Mar 19, 1:09am
On a whim I bought a 1974 Daihatsu Hallo, a 3 wheel tilting scooter. It needs replacement rings and possibly a replacement piston. Due to its rarity, these are proving difficult (impossible!!) to find.
One option/last resort is to look into getting one CNC machined or similar- It's only a wee 50cc piston and I know that the cost will likely be prohibitively expensive, but would like to know if anyone has any ideas about how much it might cost as a ball park figure.
Piston is 41mm dia, 50mm high, 2 rings, 12mm wrist pin diameter and the intake/exhaust port windows.

floscey, Mar 19, 1:12am
contact JP engineering in OZ they make custom pistons .Also Denco engineering in CHCH.

timmo1, Mar 19, 1:37am
Ok- sent JP Engineering an email. I'll have to give Denco a call later.
Anyone want to hazard a guess/ball park figure! At this stage I just want to see if its a feasible option or not!

noswalg, Mar 19, 2:21am
Have you contacted scootling in auckland to see if they have anything lying around!

skin1235, Mar 19, 2:26am
try the local chainsaw shop too, those measurements could match their books somewhere
another measure you will need is pin size and crown above pin center

tatts2, Mar 19, 2:40am
Check this out mite be useful

pauldw, Mar 19, 2:53am
If you are googling Daihatsu 'Hallo' timmo1 is already in many of the threads you'll find :)

timmo1, Mar 19, 2:57am
That is certainly useful- I've got a couple of 'maybes' from that list although it omits the Japanese brands.

timmo1, Mar 19, 2:58am
Not yet, will do :) Cheers

timmo1, Mar 19, 3:10am
yeah I've already talked to the local motorbike shop who couldn't suggest anything. The local Sthil shop couldn't suggest anything either as, according to the guy I talked to they only have compatibility information (i.e. this piston will fit this chainsaw) rather than full lists of dimensions.

(I do also have the other measurements such as the compression height btw :))

mrfxit, Mar 19, 3:22am
LOL yea . modern parts ppl are really good "on the books" & pretty hopeless at matching anything physical.
Best bet would be to take the piston & barrel around a few "small motor" wreckers & SEE what piston fits what bore

timmo1, Mar 19, 3:26am
Thanks Kaz
From looking at the JR50, the pin to crown height distance looks to large I think but I did have that one on my list.
I've begun a list of 'possible' pistons that may work but its hard finding out all the various dimensions from the web.

Pw50 seems like another possibility, thanks- Ill see what I can find

timmo1, Mar 19, 3:29am
For the record here are the dimensions of mine:

Bore: 41mm
Stroke: 37.8 mm
Piston Height: 50mm
Pin Dia: 12mm
Pin centre to crown: 22mm
Window Dimensions: 25mm H X 15W

skin1235, Mar 19, 3:31am
don't discount the close sizes either
typical - honda 350 quad engines use 2 different bores, one accepts an aftermarket new piston at $145, the other requires a genuine honda part @ $245, the good part to know is that the aftermarket piston is 1mm larger than the genuine honda one - and it only cost $45 to bore the smaller barrell to the larger size slug
you may find that by boring the barrel to 41.5 or 42 you can get a suitable match, ie also look at the next sizes up

timmo1, Mar 19, 3:33am
True- There is quite a large one here in Tauranga, I'll see what they say.
There are just so many variables.some can be overcome (i.e. piston height, wrist pin diameter, window dimensions), some can't (pin center to crown, window placement, ring locator placement)

skin1235, Mar 19, 3:34am
stroke is not essential as long as the skirt does not exceed the 50 below crown

timmo1, Mar 19, 3:34am
Yep that's on the cards too :) It's a cast iron head so there is scope to go maybe +1.5mm OS without taking too much off.

timmo1, Mar 19, 3:36am
While I've got everyone here, I may as well ask- On another thread I've made, I've asked if the portion of the piston skirt missing makes it unusable!!action=display&board=50ac&thread=288&page=1

There is a picture about halfway down that thread which shows the damage. I should be able to source rings from another piston, but I'm not sure if the piston itself is trashed due to that bit missing!

mrfxit, Mar 19, 3:44am
At low rev's/ no load it would be fine, anything else & it would be off balance & probably vibrate/ tilt &. .BANG

Sure as shooting a mob of Turkeys with a machine gun , You going to crank/load it up a few times to many