Well buy yourself a Weisco and report back after it blows too! Anyone can blame what has happened twice on faulty parts but seriously you have another problem and if you wanna ignore it that's cool with me! You have more money to waste than me my friend!
my words with NAMURA!
- Thread starter blasty98
- Start date
Well buy yourself a Weisco and report back after it blows too! Anyone can blame what has happened twice on faulty parts but seriously you have another problem and if you wanna ignore it that's cool with me! You have more money to waste than me my friend!
it wasnt my freaking user error. i had locktite on my screws. like i said. i went for a whole year with no problems. when i put my reed stops in the screw fell out. i had locktite and everything. i said f**k it. i threw some longer thicker screws in and called it a day. i want to use some green locktite but dont have any
Blaner
Your Friendly South African Ambassador
your ring pins can become loose as a result of a clearance issue.
As the piston travels passed the exhaust port (which is the biggest port - thus more harzardous) Rings are pushed out of exhaust port due to spring nature of the rings - sort of like an expansion of the rings which are under tension causing a bulge when given the space of the exhaust port to do so. Poor chamfering or too square port shapes pushes the rings back into place harshly thus putting a shock force onto the locator pin as the rings are put back under their operating tension. Repetition results in worn or loose locator pins thus allowing ring rotation. you want your ports to gently guide the rings back into the cylinder and not have them jolt them back in.
this is a paraphrase of an extract of Gorden Jennings - 2 stroke tuning handbook.
As the piston travels passed the exhaust port (which is the biggest port - thus more harzardous) Rings are pushed out of exhaust port due to spring nature of the rings - sort of like an expansion of the rings which are under tension causing a bulge when given the space of the exhaust port to do so. Poor chamfering or too square port shapes pushes the rings back into place harshly thus putting a shock force onto the locator pin as the rings are put back under their operating tension. Repetition results in worn or loose locator pins thus allowing ring rotation. you want your ports to gently guide the rings back into the cylinder and not have them jolt them back in.
this is a paraphrase of an extract of Gorden Jennings - 2 stroke tuning handbook.
Blaner
Your Friendly South African Ambassador
Here are some other interesting notes i collected when researching what i did wrong after my engine failures, the last one involved rotated rings as a result of worn pins.
These are quotes from Graham Bells Performance Tuning book.
lots to read but these tips are VITAL to building a engine that will last.
“In this day of advanced metal technology, ring breakage is rare, and can usually be
attributed to one of the following causes: excessive piston to cylinder clearance
allowing the piston to rock and twist the rings as it passes TDC; worn piston ring
grooves that let the rings jump about; excessive bore taper causing radial ring flutter;
exhaust port widened excessively or ground an incorrect shape; sharp edges left in
exhaust and/or transfer ports; insufficient ring gap; ring grooves not properly cleaned
before fitting new rings”
“Generally, a two-stroke engine should be set up with groove clearances between
0.04 and 0.1mm. Tighter than 0.04mm clearance will cause the ring to stick in the
piston groove as carbon and varnish builds up”
“It is always a sensible practice to dress the ring ends with an oilstone. Chamfering
the outside edges reduces the chances of the sharp ends scuffing the bore. It is also a
good idea to stone the inside corners of the ring ends too. The slight radius formed
helps to stop any tendency the ring may have to pull the ring locating peg out of the
piston”
“When rings are being fitted, care should be taken to avoid fitting them the wrong
way up and to prevent damage by incorrect fitting technique. Piston rings can be
twisted permanently if they are fitted in the groove at one end and then gradually
screwed around until the entire ring is in place. Instead, they must be expanded
sufficiently to fit over the piston and then allowed to drop into the groove. Special
expander tools are available for this purpose but I prefer to use two 0.4mm feeler
blades held between the ring and piston. The blades provide a bearing surface and stop
the ring digging into the piston”
“When taking the barrel to a machine shop for reboring, have the base checked for
trueness. If the cylinder is not square to the base it will be necessary to mount the
cylinder on a mandrel and then skim the base in a lathe.”
“The cross-hatch pattern the hone leaves on the cylinder walls is critical if the rings
are to bed-in quickly and last for a long life. Personally, I prefer a 45° Crosshatch with
a finish of 10-12 microinches. This type of finish makes it necessary to run the rings in,
but they will wear well and not leak. A smoother finish does not retain enough oil and
consequently allows a glaze to form on both the ring face and bore wall. Power is lost
due to the poor ring seal, allowing gas leakage into the crankcase. A finish rougher
than 12 microinches will greatly reduce the amount of time required to bed the rings,
but ring life is shortened.”
“Each time the engine is rebored, or even just honed, it is essential that all port
openings be carefully filed and then dressed, otherwise the sharp edge formed will
damage the rings and piston. To the naked eye the openings may appear smooth
enough, but try running your finger around the edges and you will find just how razor
sharp they are. The idea is to smooth off the edges carefully
with a cigarette size oilstone”
These are quotes from Graham Bells Performance Tuning book.
lots to read but these tips are VITAL to building a engine that will last.
“In this day of advanced metal technology, ring breakage is rare, and can usually be
attributed to one of the following causes: excessive piston to cylinder clearance
allowing the piston to rock and twist the rings as it passes TDC; worn piston ring
grooves that let the rings jump about; excessive bore taper causing radial ring flutter;
exhaust port widened excessively or ground an incorrect shape; sharp edges left in
exhaust and/or transfer ports; insufficient ring gap; ring grooves not properly cleaned
before fitting new rings”
“Generally, a two-stroke engine should be set up with groove clearances between
0.04 and 0.1mm. Tighter than 0.04mm clearance will cause the ring to stick in the
piston groove as carbon and varnish builds up”
“It is always a sensible practice to dress the ring ends with an oilstone. Chamfering
the outside edges reduces the chances of the sharp ends scuffing the bore. It is also a
good idea to stone the inside corners of the ring ends too. The slight radius formed
helps to stop any tendency the ring may have to pull the ring locating peg out of the
piston”
“When rings are being fitted, care should be taken to avoid fitting them the wrong
way up and to prevent damage by incorrect fitting technique. Piston rings can be
twisted permanently if they are fitted in the groove at one end and then gradually
screwed around until the entire ring is in place. Instead, they must be expanded
sufficiently to fit over the piston and then allowed to drop into the groove. Special
expander tools are available for this purpose but I prefer to use two 0.4mm feeler
blades held between the ring and piston. The blades provide a bearing surface and stop
the ring digging into the piston”
“When taking the barrel to a machine shop for reboring, have the base checked for
trueness. If the cylinder is not square to the base it will be necessary to mount the
cylinder on a mandrel and then skim the base in a lathe.”
“The cross-hatch pattern the hone leaves on the cylinder walls is critical if the rings
are to bed-in quickly and last for a long life. Personally, I prefer a 45° Crosshatch with
a finish of 10-12 microinches. This type of finish makes it necessary to run the rings in,
but they will wear well and not leak. A smoother finish does not retain enough oil and
consequently allows a glaze to form on both the ring face and bore wall. Power is lost
due to the poor ring seal, allowing gas leakage into the crankcase. A finish rougher
than 12 microinches will greatly reduce the amount of time required to bed the rings,
but ring life is shortened.”
“Each time the engine is rebored, or even just honed, it is essential that all port
openings be carefully filed and then dressed, otherwise the sharp edge formed will
damage the rings and piston. To the naked eye the openings may appear smooth
enough, but try running your finger around the edges and you will find just how razor
sharp they are. The idea is to smooth off the edges carefully
with a cigarette size oilstone”
Blaner
Your Friendly South African Ambassador
Similar threads
