My son's chain was constantly needing to be tightened after every ride. I finally found a huge crack in his tubular swingarm. He is a small - medium sized 8 yo and I have him ride the quad as agressively as he can. The tubular swing arm is indeed the weakest link in these chinese quads. I almost pulled it out before he cracked it to have a new one custom made ( I knew it'd be a matter of time). It cracked the tubing along a crappy weld. We were able to re-weld and add reinforcing to the swing arm. He shouldn't break it now.

Just wanted to give a heads up. A kid could get hurt if it broke completely after a big landing.

 

.

Thanks for the "heads up" on the weak Swing Arm on the brand of your mini. Many of the minis are made for "around the house" and mild trail riding. When extreme riding and/or extreme bumpy racing, their swing arms do tend to break. The Polaris brand is known for broken Swing arms under extreme riding conditions.

To reduce swing arms breaking, some install better shocks. For example: Works, Elkas, PEPs, etc. Better then factory shocks provide smooth and more depth suspension movement.

Others also install a better Swing Arm. KFAB makes a near bullet proof Swing Arm design. For a picture, surf: http://www.kfabproducts.com/prodpics/swing_arm.jpg


Thanks for sharing the dangers of driving a mini past is engineering expectations.


.

 

i notice on your post it says sunl/kazuma 90, the sunl 90 doesn't use a tubular swing arm it has a box swing arm, the sunl 50 and 70 uses the tubular swing arm,

 

i think there are many variations of the same quad. mine had 122 stickers on it and it said it was a 90 on the invoice. i have no idea who actually made it. it looks like the kazuma and sunl 90's i've seen.

the point is the tubular swing arm.
A) it was welded off set and not aligned with the quad's frame.
B) it was cold bent tubing with creases at the bends and welds that were pencil thin.

if the chinese build tanks like this, i think we can take them in the big showdown.