Who knows 2-strokes?
I’m slowly realizing I know jack shit about 2-stroke motors.
I took my top end off.
From what I can tell… Some dip shit before me put in a reed-valve piston into a piston-port engine.
Let me back up a step if you know jack like me.
Apparently in these old shitty jap 2-strokes, there are piston-port heads and reed-valve heads. Reed-valve is the newer style of the two.
Basically it means what style of air / fuel intake is it. Piston-port uses the piston as the intake valve and the exhaust valve. Reed-valve uses flaps and piston as the intake valve and the piston as the exhaust valve. I’m sure my explanation is ultra generalized but from a beginner understanding it’s probably fine.
Anyway, my engine is the older piston-port but when I took the head off the piston in it was a reed-valve piston since it has the holes on the intake side.
The holes on the intake side of the piston lets the intake flow draw more air in which is something reed-valve heads want / need.
No idea why someone put a reed-valve piston in a port-piston head. The holes would draw too much air from my understanding. I’m assuming it was a dip shit and this is one of the reasons the bike ran like total garbage. Anyway, I’m putting in a wiseco piston and doing the crank seals. Plus I’m going to try shaving down the bottom of the intake skirt a tiny bit as the dude in one of the bottom images suggests since I have a pod filter and jetted carb.
Overall I’m cleaning this thing up a bit because it’s a piece of junk right now.
Anyone know 2-strokes and have input / suggestions for me?
Oh… and this thing is a joke to work on. Took like 5 mins to rip off the little shit it had on it. And another 5 mins to take the top end of the engine off.
Piston on the right is the wiseco piston and the correct type of piston for a piston-port head.
5 responses to “Who knows 2-strokes?”
Published - Jan 15, 2011
Did the carbs on my 1987 cbr250r today. Way more headache than anything Honda from the 70’s. 1) Get all the plastic shit off 2) Get the carbs out. Man that shit looks different, Never seen carbs under the tank before. 3) New OEM air filter. That old one was seriously black as shit. 4) […]