Thread: Piston Rings

Tweet

I just did a rebuild on a 2 stroke engine and the piston rings are shot. It will take about a week to get new ones, so it is possible to test the motor without rings?? Does anyone know what piston rings do?

Also, I redid the electrical system on a motor bike and strangely, there is no alternator to generate AC. There are only 4 coils that are magnetically attached to a flywheel. Can anyone theorise how this system generates electricity?

To answer your questions......
1) maybe....with enough oil to seal the bore....but would run poorly....

Piston ring are the hinge that helps create compression....they help seal the bore so you make optimum power.....they take up the slack where the piston to cylinderwall leave it...

2) Magnetic Impulses.....when the flywheel turns it creates magnetic pulses which is electric or Alternating Current (ac)

Originally posted by gemcleod
I just did a rebuild on a 2 stroke engine and the piston rings are shot. It will take about a week to get new ones, so it is possible to start the motor without rings?? Does anyone know what piston rings do?

Also, I redid the electrical system on a motor bike and strangely, there is no alternator to generate AC. There are only 4 coils that are magnetically attached to a flywheel. Can anyone theorise how this system generates electricity?

gemcleod and this is not a smart answer, but if you don't know if a motor will run without rings or not, then i doubt if it will ever run again after you put the rings in it. there is not enough time or room on the board to explain everything you just asked about. you need to get you some good books on the subjects you were asking about and do a lot of reading or find a night class on auto repair or 2 stroke engines you could join. good luck

The question was asked because I want to start the engine briefly to see if the clutch is fixed. I really don't care if it runs smoothly or not.

I have read that the rings are required for engine pressure -- especially on 2 stroke engines. I find this forum interesting because many experts are able to explain the exact function of parts in an engine. I would have hoped that you would invite the question as a valid discussion topic.

Originally posted by gemcleod
The question was asked because I want to start the engine briefly to see if the clutch is fixed. I really don't care if it runs smoothly or not.

I have read that the rings are required for engine pressure -- especially on 2 stroke engines. I find this forum interesting because many experts are able to explain the exact function of parts in an engine. I would have hoped that you would invite the question as a valid discussion topic.

that is my answer no it wont. maybe somebody know something that i dont know.

Originally posted by DennyW
FREEZE!! Please put the tools down. Step... away... from the machine.
Sorry, couldn't help it.


Definition: An open-ended ring that fits into a groove on the outer diameter of the piston. Its chief function is to form a seal between the piston and cylinder wall. Most automotive pistons have three rings: two for compression sealing; one for oil sealing.

ps- and wont run without them.

Don't even bother to try fire the thing up without rings,,,,if any combustible gasses get passed the piston into the sump, it may ignite the oil and you will have an exploded case to deal with,,,,that is,,,,if it will start without rings to begin with.
your just asking for trouble,,,,,,so if you want to test the clutch,,,you can get a big drill and suitable socket attatchment,, and spin the motor with the drill,,,,and engage the clutch that way.
If your bound and determined to try fire the thing up without rings,,,,,,have a fire extinguisher ready,,,,,and notify your next of kin.

yeah listen to these guys, you do not want to dare try starting it without rings without causing serious problems to motor or self... just wait on those rings to test your clutch, its worth the wait... those magnetic parts that you were talking about are for charging the battery its how bikes do it, they dont require much power to run seeing that they've only got a few electrical systems, most likely your bike also has a magnito so that even if your battery is dead, when you kick it, it generates enough power to spark the plugs and thus start the bike... its a really inventive system.,... sometimes i wish my car had a kickstart with magnito

Alright, thats good advice -- I will wait on the rings.

The bike doesn't even have a battery in fact, it runs straight off the alternator. It is a '68 Vespa -- very primitive.

Vespa's are a pretty reliable little scooter,,,,and the magneto system is pretty simple,,once it's set up right they run forever.

Originally posted by gemcleod
Alright, thats good advice -- I will wait on the rings.

The bike doesn't even have a battery in fact, it runs straight off the alternator. It is a '68 Vespa -- very primitive.

These particular Vespas are absolute nightmares. I imported 3 from Cambodia and much of the engine had been built from homemade parts. For example, gaskets from milk cartons, clutch plates cut from corrogated iron, layshaft gears welded together. The builder also tried to smooth out the crankcase by applying cement glue.

The bikes are complete rebuild jobs, but what do I expect when I paid $300 each.

Yeah,,i've heard about those asian vespa's,,but i guess for 300 bux,,you get what you pay for.