Im impressed!

[crassius]

only grubee site I find has gasket set with standard green gasket in the pic, and they want $10 for one set - is there a diff site for the canada supplier?

 

[Frankenstein]

I'm really curious as to the difference between the bronze bushing over the bearings. Is the bushing actually better or what?

Since the bearing doesn't actually rotate and really just turns back and forth for the most part I could see the bushing having an advantage.

Are the bearings actually cheaper than bushings or something leading to the switch? From what I read I thought most of the older motors came with a bushing...

 

[zippinaround]

i recently whipped the small end bearing from a 49cc mini moto engine that was pushing 12k rpm it was the exact same as the one in my 48cc china girl , the main difference being the space between the bearing and the piston in the mini moto engine there was minimal space and it seemed good as new and the e-clips appeared fine too whereas in the china girl theres a good gap between the bearing and piston, seemed slightly worn but it was the e-clips that had noticeable wear probably from the bearing shifting the pin from side to side while spinning another 500 miles would have surely seen an e-clip failure.

 

[Street Ryderz]

just ordered 10 full gasket sets from china for $11 and not sure what will show up - I'll see if I can locate that grubee site in case I still need the thick ones

got the high torque pk80 motors now with 40mm stroke and 38mm rods, so need two thick base gaskets to make piston/head room

These came from motorizedbicyle.ca They are $4.99 can for the whole set and are of good quality imo!

 

[Street Ryderz]

Turns out I was wrong! the bearing didn't let go at all it was one like the top set in pic,But I was right about something bouncing around in there and turns out the top ring broke kinda oddly and scored the cylinder!look at the pics the piston top and chamber of head are all dented up, the cylinder walls just below the top of the stroke where the highest ring pressure is has exposed aluminium and one between the right side transfer and intake and some how the top ring shifted its gap just to the left of the lower one.

 

[Frankenstein]

I have a piston somewhere where the little brass pin just jumped out, it ended up on the other side of the piston as part of the piston edge above the ring, it's a bright little brass shine in the aluminum. The ring spun in the groove and only managed to wear my cylinder right down to the bare aluminum. Died a block from home..

Lucky the ring didn't break into bits and tear up the cylinder, it was one of my best running cylinders and piston combos, I'm looking at possibly either redoing the ports and piston cuts exactly the same, or getting the cylinder plated with nikasil, and making an exact duplicate of that piston and getting that coated and upping the rings and pins if possible.

Seriously it had a real heavy torque pick up in the lower mid range that went all the way to about 80% max rpm! Even loaded down with a large steel vintage 2 gallon tank it still felt very strong. Really felt nice up hills, just rolled right up with no worries at all. Cut grass nicely too after rain. I think the big tank caused some over heating issues, understandable in the middle of summer, where it was even too hot riding in shorts and t shirt at good speeds. I might reserve that tank if I ever repair it to winter only and then it could be more appropriate for the temps, even benefit maybe by keeping the carb and engine warmer.

 

[crassius]

These came from motorizedbicyle.ca They are $4.99 can for the whole set and are of good quality imo!View attachment 75333

thanx, I bookmarked it - when my sets come in I'll see if I get the type I want, if not I'll contact the grubee guys

can't pass up trying the full set for a buck tho at "http://stores.ebay.com/motorcycleandchainsawaccessories/"

 

[Frankenstein]

Here's that piston, that bright spot is the pin burnished into the piston skirt. I was wrong about the placement but here, it's under the bottom piston ring.

 

[Street Ryderz]

Idk about that I have never seen a brass pin in there!every piston I have had or seen has steel pins that do serious damage!Anyway managed to get the rings out of piston and there is a good amount missing!
It looks like the pin for top ring is gone and there is a piece of ring wedged in its place,The indents in piston top are very cylindrical and maybe was the pin that did that,very similar in shape to the ones made when a roller from bearing bounces around in there!

 

[crassius]

yeah, seen pins loose and pins pushed in so far they don't grab the ring - luckily, I see those very rarely