Believe I've just learnt the answer to this question the hard way but can anyone tell me wether the arrow on the piston is supposed to face down to the wheel or up to the seat? Mallosi 70cc kit on speedfight 2
arrow points to exhaust port. on a two stroke it always denotes the exhuast port so the piston is installed with that arrow pointing to the exhaust port only
Hmmm that's what I did but just literally lasted ten minutes and now piston is scored like hell. I thought I had read that the arrow had to face down
did you run some two stroke oil round the cylinder before seating home the piston ? did you make sure the rings were inserted into the piston in the right direction . they usually have a letter or mark denoting the top of the ring faces top up on piston. drag off that cylinder and piston as it sits now and get some good clear photos and post up here so we can work out whats happened to that jug and piston.
Ran 2stroke all round but didn't check the rings. Looks like that's where I've gone wrong. And ill get some photos up of it tomorrow night. The jug looks fine but the piston and rings have basically worn togetger and won't even come apart
I didn't check for any markings on the rings when I installed my Malossi 70 kit as there was no mention of any in the instruction book, so I was either very lucky or they are reversible ?? Sent from my SM-G930F using Tapatalk
I'm just gunna order another one now and be more care ful next time. Just a few questions, I got a 17.5mm phva carb which came with a 95 jet in it. The standard jet was 55, would I need to down jet the new jet to 10-15% more than the 55 or?
The piston rings on a speedfight can only go one way as the pegs on the pistons are offset and the rings have a chamfer to fit. Something else is causing the problem. Is it a liquid cooled or air cooled? If it's LC is the thermostat opening??
Get a pic up of the piston, sounds like something went wrong sonewhere. Why did you change it? Just upgrading or was the old one dead?
Did you check the piston ring gap? Maybe when it got hot the rings expanded and ends lifted? The reason for the arrow pointing to the exhaust port is that it ensures the piston is set so the ring gaps don't run past the exhaust port opening and catch the edges. You'll notice that the joins are offset and run against smooth walls. Were your ring gaps lined with their pins?