Snapped Piston Rings and Head Bolt

[HeadSmess]

rant rant rave rave.... like an olde hens nighte in here....

new rings, new studs, n crosss fingers the cylinders ok even though they are cheap...


just when you put the new rings in... note that theres a lil pin in the groove...all two strokes have these to stop the ring rotating and saying "allo to the ports at high speed...

 

[AussieSteve]

rant rant rave rave.... like an olde hens nighte in here....

But your post is an exception, of course.

 

[motorpsycho]

With all due respect sir , we are discussing a 2-stroke engine here. Gas and oil are supposed to get into the crank case. I think that you are confusing a 4-stroke operation with a 2-stroke operation.QUOTE]

really?
I do know the difference between 2 and 4 strokes, but i had no idea that gas and oil gets in to the crankcase of a 2 stroke. I thought that when the gas-oil mix enters the cylinder, all of the gas is burned and the oil is turned into a mist. this mist gets into the crankcase to lubricate the bearings.
I don't see how gas AND oil can get into the crankcase. Maybe i need to read a little more on the subject...

 

[AussieSteve]

..... but i had no idea that gas and oil gets in to the crankcase of a 2 stroke. I thought that when the gas-oil mix enters the cylinder, all of the gas is burned and the oil is turned into a mist. this mist gets into the crankcase to lubricate the bearings.
I don't see how gas AND oil can get into the crankcase. Maybe i need to read a little more on the subject...

motorpsycho, initially, the fuel/oil/air mix is sucked into the crankcase via the inlet port. While in the crankcase, much of the oil condenses and settles into the bottom of the crankcase, where it is thrown around by the flywheel. Then, the mixture is drawn into the combustion chamber via the transfer port, ready to be compressed and burnt.

Here's a page with a good description with diagrams and an animation:-
A Running Two Stroke Engine

 

[Skyliner70cc]

rant rant rave rave.... like an olde hens nighte in here....

new rings, new studs, n crosss fingers the cylinders ok even though they are cheap...


just when you put the new rings in... note that theres a lil pin in the groove...all two strokes have these to stop the ring rotating and saying "allo to the ports at high speed...

that little pin should be checked for security. On some engines it is loosely press fit and can fall out causing lots of engine damage when a ring catches a port. If you can pull the pin out with pliers, JB weld it.

 

[HeadSmess]

With all due respect sir , we are discussing a 2-stroke engine here. Gas and oil are supposed to get into the crank case. I think that you are confusing a 4-stroke operation with a 2-stroke operation.QUOTE]

really?
I do know the difference between 2 and 4 strokes, but i had no idea that gas and oil gets in to the crankcase of a 2 stroke. I thought that when the gas-oil mix enters the cylinder, all of the gas is burned and the oil is turned into a mist. this mist gets into the crankcase to lubricate the bearings.
I don't see how gas AND oil can get into the crankcase. Maybe i need to read a little more on the subject...

ok, ok, i cant believe i actually read this.

there is only ONE 2stroke design that DOES NOT utilize crankcase compression. diesels. which have ruddy great blowers instead.

otherwise EVERY 2stroke REQUIRES gas and fuel to get into the crankcase. its an inherent part of their operation

"blowby" oiling, what you seem to be thinking of...is used on model 4strokes. and is not recomended for petrol engines as its full of carbon! like the old sump oil in your car... you also need to run a 5:1 oil ratio to get enough lubrication....ie, smokey

 

[GearNut]

I got the extra money for the rings and stud. I'll be taking a trip to E-Z Cycles soon. Grade 8 right?

Grade 8 for the cylinder studs will do you right for sure.
Just be careful with the final torque. Too tight and you will pull the threads out of the crank case.

As for the other tangent that this thread has taken:
http://www.marinediesels.info/Basics/the_2_stroke_engine_explanation.htm
The 2-stroke diesel.

 

[echelonunit37]

Is there a specific technique for installing the piston rings? Never done it...

 

[motorpsycho]

ok, ok, i cant believe i actually read this.

there is only ONE 2stroke design that DOES NOT utilize crankcase compression. diesels. which have ruddy great blowers instead.

otherwise EVERY 2stroke REQUIRES gas and fuel to get into the crankcase. its an inherent part of their operation

"blowby" oiling, what you seem to be thinking of...is used on model 4strokes. and is not recomended for petrol engines as its full of carbon! like the old sump oil in your car... you also need to run a 5:1 oil ratio to get enough lubrication....ie, smokey

ok, i stand corrected. This only goes to prove that we can all learn something every day.
I was getting the operation of a 2 stroke confused with the operation of a 4 stroke.

 

[AussieSteve]

Is there a specific technique for installing the piston rings? Never done it...

What I do is hook each end of the ring with my thumbnails, then open the ring just barely enough to stretch over the piston without breaking or scratching the piston.

Often, it's best to work one end on at a time. ie. Open the ring slightly and then vertically separate the ends to allow one end to slip into the top ring groove, then carefully work the other end in. For the bottom ring, once it's in the top groove, it's easy to repeat the process to move it to the bottom groove.
Be careful to avoid scratching the piston or breaking the rings. They're very brittle.

Good luck, it's always a dicey process.

Once the rings are on the piston, you need to first hold the top ring compressed with your fingers, (or a ring compressor if you have one, but it's not really necessary), as you wobble the cylinder down over it, then repeat with the second ring, taking care that the ring gap stays aligned with the locator pin in the piston groove.
A good smear of 2-stroke oil on the piston and cylinder walls helps.

Once again, good luck. Be gentle and take your time. Don't force anything, or you'll break a ring.