Piston problems

[gary55]

I hate to make universal statements about these motors, as one never knows do one, but it would seem that most A80s are 40mm stroke & 40mm rods while most PK80s are 40mm stroke & 38mm rod.

As rule of thumb from outside of motor, I note that a bit of extra vibration at low speed and a bit more low end torque seems to indicate the motor is the short rod type.

Only opening it up and measuring center to center on rod bearings would tell for sure.

I couldn't agree with you more. I'm trying to wrap my brain around all the variations of components used in these engines, but I'm not there yet.

 

[MotorBicycleRacing]

you would think that they are different but both pistons are the same .both are low ???

Post a pic of both pistons side by side.
How much is the piston sticking out of the cylinder?

When you build a motor always turn the piston over to check the deck height
and squish clearance before putting the head on!

I use the nut on the end of the magnet to do that with the motor lying on the
clutch side.

 

[Xboxbum]

About quarter inch its the piston i order a new one but i hsv another problem i csn use help with .i keep striping the thread off my right pedal this id my third one cant figure out why this is happening any clue?

 

[Xboxbum]

Magnet?? You lost me!

 

[MotorBicycleRacing]

About quarter inch its the piston i order a new one but i hsv another problem i csn use help with .i keep striping the thread off my right pedal this id my third one cant figure out why this is happening any clue?

So you used a low wrist pin piston just like I said instead of the high one.
The magnet is on the left side of the crankshaft! Remove the left side engine cover!

Communicating with you is difficult, you shouldn't have skipped school........

 

[Xboxbum]

So you used a low wrist pin piston just like I said instead of the high one.
The magnet is on the left side of the crankshaft! Remove the left side engine cover!

Communicating with you is difficult, you shouldn't have skipped school........

Dont be rude. Iam here for info not to be belittled.

 

[Xboxbum]

Mybe you should switch to decafe you scream in your posts.

 

[crassius]

if old piston was low, he should use another low - a pic would be REALLY helpful about now

 

[gary55]

About quarter inch its the piston i order a new one but i hsv another problem i csn use help with .i keep striping the thread off my right pedal this id my third one cant figure out why this is happening any clue?

Don't know why it's happening, but use locktite on the next one. that should solve the problem. Now are we talking about the dome or the outer edge sticking 1/4 inch abv. top of cyl.. Please show us a picture.

 

[Street Ryderz]

About quarter inch its the piston i order a new one but i hsv another problem i csn use help with .i keep striping the thread off my right pedal this id my third one cant figure out why this is happening any clue?

That's weird because when you use your peddles the pressure is tightning the threads so it shouldn't do that at all,does it tighten clockwise ? If you put the wrong piston in the total height from deck(top of cylinder)to the top of the dome(highest piont of piston)would be twice that roughly so closer to half an inch and really look wrong!the top ring would be close to or even at your deck height if pic is not an option then messure it really well as described and these guy's can help you chose where to add a gasket!