How far can the Cylinder base be shaved?

[SHSPVR]

and leaving it as it is will cause problems? worth a risk?

the new hole can be drilled anywhere?

what about the old hole, will it have to be refilled/closed or just let it be there?

Leaving it as it is will cause ring to broke "BANG NO MOTOR" that why you do not want the ring gap crossing over any open port.
Yes it can be any where but as I said you do not want the ring gap crossing over any open port.
What has to be done is replace it with a littler bigger aluminum dowel pin then CNC or Mill Turning the ring grove like should be as if it wasn't there that way the ring will seal then drill the new hole and install the steel dowel.

You know for what it worth Wiseco, Ross Racing Pistons, Arias Pistons, JE Pistons and min other can make you a custom pistons just for bike have thougth about ask them?.

 

[whenfoxforks-ruled]

You figure you have the port timing from the bottom up, back to what it was. What is the distance from tdc to the head? What are you going to do about the different port timing on the way down? The lower ring will hit sooner?

 

[SS109]

I advise giving the guys at Spec II a call as I'm sure they have run in to this bike before. They are Yamaha 2t street bike gurus. Spec II home page

 

[helio lucas]

thumper135, where are you located?
what is the diameter of the pin in piston?
i will look if i can get you another piston to fit. i bet there is many that fit that bike and are easy to find...

 

[whenfoxforks-ruled]

Because the ring land from top to bottom is different, it is going to effect the port timing in both directions. You have SEEMINGLY fixed 1 direction. For all I know, all that material should have been taken from the top? The ring centering pin, showing up in the port, thats a first, and an issue also for sure. There has got to be street bike people out there who have messed with this issue already? Vintage Bob

 

[SHSPVR]

My frist guest would be he from India
That bike is for the asian markets only there all base a round RX100 up to RX135 or in are case an old Yamaha Enduro 2-stroke from 70/80 in USA look up DT125 which by the way is being sold in min 3rd world countries.
Min 3rd world countries are start to ban 2-stroke in fav of more eco friendly 4-stoke road bike.
I belive in the asian markets is being replaace it with Yamaha YZF-R15 "150cc", FZ and Gladiator Type SS "125cc" / RS "150cc".

 

[thumper135]

You figure you have the port timing from the bottom up, back to what it was. What is the distance from tdc to the head? What are you going to do about the different port timing on the way down? The lower ring will hit sooner?

I will get the ring locating pin out of there and place it where there are no port passages on the wall for the 1st ring. its even more doable considering how it takes the most hammering due to constant firing/combustions.

the distance from tdc to head is yet to be determined since there is a little more shaving to be done on the cylinder base, the piston lip/edge does not sit just right at the liner deck, slightly short the piston still is (.50mm)

the head to top clearance on the other hand will be well taken care of as well as the squish band distance, that is once the piston is equal with the deck. :)

 

[thumper135]

Leaving it as it is will cause ring to broke "BANG NO MOTOR" that why you do not want the ring gap crossing over any open port.
Yes it can be any where but as I said you do not want the ring gap crossing over any open port.
What has to be done is replace it with a littler bigger aluminum dowel pin then CNC or Mill Turning the ring grove like should be as if it wasn't there that way the ring will seal then drill the new hole and install the steel dowel.

You know for what it worth Wiseco, Ross Racing Pistons, Arias Pistons, JE Pistons and min other can make you a custom pistons just for bike have thougth about ask them?.

I get your point completely, the new pin on the 1st ring groove will be moved to a location where it contacts no port passages.. also making sure the old pin is cleaned like it never was there.
now since the 2nd ring located end pin is on the right side, i should get the new pin tapped on the left side? since it goes approx 90 degrees away from the 2nd ring pin.

 

[thumper135]

thumper135, where are you located?
what is the diameter of the pin in piston?
i will look if i can get you another piston to fit. i bet there is many that fit that bike and are easy to find...

16mm is the piston pin diameter. they are easy to find, the stock options that is. infact I have another cylinder piston in backup to go ahead with the stock setup whenever. Its just the the willingness to go ahead with this setup and experience how it ends up as, especially when its almost just a lil teenie weenie locating pin that needs to sit and sleep where it is more in peace at. :D

thankyou. :-)

 

[SHSPVR]

I get your point completely, the new pin on the 1st ring groove will be moved to a location where it contacts no port passages.. also making sure the old pin is cleaned like it never was there.
now since the 2nd ring located end pin is on the right side, i should get the new pin tapped on the left side? since it goes approx 90 degrees away from the 2nd ring pin.

Yes that rigth thumper135

 

[thumper135]

Because the ring land from top to bottom is different, it is going to effect the port timing in both directions. You have SEEMINGLY fixed 1 direction. For all I know, all that material should have been taken from the top? The ring centering pin, showing up in the port, thats a first, and an issue also for sure. There has got to be street bike people out there who have messed with this issue already? Vintage Bob

Ring land as in the locating pin?
If that is it then it will be moved to a different location as planned already by moving it in a no port showing area, the 1st ring locating pin. the 2nd ring locating pin however sits pretty much fine without going through any port passages during its 2 stroke cycle.

the top of the Cylinder was to be shaved because? there was barely any material there to be taken off, approx .025". that too without compromising head gasket leaks would not have been possible to shave off.

 

[thumper135]

My frist guest would be he from India
That bike is for the asian markets only there all base a round RX100 up to RX135 or in are case an old Yamaha Enduro 2-stroke from 70/80 in USA look up DT125 which by the way is being sold in min 3rd world countries.
Min 3rd world countries are start to ban 2-stroke in fav of more eco friendly 4-stoke road bike.
I belive in the asian markets is being replaace it with Yamaha YZF-R15 "150cc", FZ and Gladiator Type SS "125cc" / RS "150cc".

Its a Malaysian Model, released from 1980's till to date in the asian markets, in 2004 started coming with a catalytic converter on it. these were considered after the RD series, pretty neat machines for their size..

# Engine: 2-stroke 135cc air-cooled engine
# Cylinder arrangement: Forward-inclined single cylinder
# Displacement: 133 cc
# Max power: 20 PS (15 kW) @ 8,500 rpm
# Max torque: 1.85 kgf·m (18.1 N·m) @ 7,500 rpm
# Max speed: 180km/h
# Bore x stroke: 56.0 x 54.0 mm
# Compression ratio: 7 : 1
# Transmission: 6-speed return
# Clutch: Multiple-disc, wet manual

 

[SHSPVR]

thumper135 the RD series where all twin cylinder even the small 125cc pre-80s but from 82 and up the DT, TZ and RD series 125 LC where all Liquid Cooled single cylinder model
Your is what I call old/new school tech as in old top end like from RS100 or DT100 but with newer buttom end like from newer DT, TZ and RD series Liquid Cooled model with 6-speed Transmission.

 

[whenfoxforks-ruled]

You think that the distance swept up is going to be the same. You have estimated that the piston difference removed from the bottom will fix it. You have not taken into consideration the new bottom end volume? Also, the distance from the bottom of the lower ring to the top of the upper is greater. This will alter the timing in both directions, fixing 1 is not fixing both. It may well be impossible to get exactly correct. Now if you had a software program, to plug in your parameters, you could see before you do it. Did you try any of the pistons from the models SHSPVR brought up? The cylinder is not toast yet. Vintage Bob

 

[SHSPVR]

You think that the distance swept up is going to be the same. You have estimated that the piston difference removed from the bottom will fix it. You have not taken into consideration the new bottom end volume? Also, the distance from the bottom of the lower ring to the top of the upper is greater. This will alter the timing in both directions, fixing 1 is not fixing both. It may well be impossible to get exactly correct. Now if you had a software program, to plug in your parameters, you could see before you do it. Did you try any of the pistons from the models SHSPVR brought up? The cylinder is not toast yet. Vintage Bob

Bob I belive the volume didn't change that much look like rigth around 2% or less which not enough to make that much of a over all diff to it.
When he dose get this all done the biggest change will be in the Compression ratio which should jump to about 8.5 due to dome piston vs his old flat top and that should push the hosepower up a bit.

 

[thumper135]

Bob I belive the volume didn't change that much look like rigth around 2% or less which not enough to make that much of a over all diff to it.
When he dose get this all done the biggest change will be in the Compression ratio which should jump to about 8.5 due to dome piston vs his old flat top and that should push the hosepower up a bit.

thanks for clearing that up. :-)

 

[helio lucas]

well, the dt 125 oversize will fit but i don´t think will be easy to find there. try polini, vertex or pro-x if you wish so. before 88? has two windows on the inlet side, after that just a plain skirt. and has the two ring pegs right on the place.

relocating the pin is a very hard work since has to be done correctly. if the pin comes out will damage the cylinder and the piston. has to be a very tight press fit...

the volume of the bottom end hardly change anything on that very low performance bike.

one thing to be very aware is the increase in compression ratio. that bike is air cooled and since it does 180km\h it will go wide open for a lot of time. while there is a nice increase in torque it may overheat. if that bike will see very long time wide open i do not increase the CR at all. just put a thicker base gasket and get the cylinder port timing a little agressive, towards high rpm power and overrev... it may return the lost timing because the overboring.
if is used only for small burts like in the city, go for it. it will be fun... maybe less top speed but lots of low end torque... :ride:

 

[thumper135]

well, the dt 125 oversize will fit but i don´t think will be easy to find there. try polini, vertex or pro-x if you wish so. before 88? has two windows on the inlet side, after that just a plain skirt. and has the two ring pegs right on the place.

relocating the pin is a very hard work since has to be done correctly. if the pin comes out will damage the cylinder and the piston. has to be a very tight press fit...

the volume of the bottom end hardly change anything on that very low performance bike.

one thing to be very aware is the increase in compression ratio. that bike is air cooled and since it does 180km\h it will go wide open for a lot of time. while there is a nice increase in torque it may overheat. if that bike will see very long time wide open i do not increase the CR at all. just put a thicker base gasket and get the cylinder port timing a little agressive, towards high rpm power and overrev... it may return the lost timing because the overboring.
if is used only for small burts like in the city, go for it. it will be fun... maybe less top speed but lots of low end torque... :ride:

the engine will not be used for long bursts, just very short ones, you're absolutely right on when you say lots of low end torque. :-)

Now that it seems re-positioning the 1st ring locating pin might be a difficult task to achieve, how stupid does the idea of running the piston with just the one 2nd ring sound? :coocoo:

for the overheating generated by the new bore size I plan to weld up some extra fins onto the cylinder, a few dampeners to help not vibrate. that should help the temperature come down. pretty much the same way i used to keep my amd processors cool enough not to shutdown by welding up extra fins onto the heatsink.. hehe

 

[thumper135]

well, the dt 125 oversize will fit but i don´t think will be easy to find there. try polini, vertex or pro-x if you wish so. before 88? has two windows on the inlet side, after that just a plain skirt. and has the two ring pegs right on the place.

relocating the pin is a very hard work since has to be done correctly. if the pin comes out will damage the cylinder and the piston. has to be a very tight press fit...

the volume of the bottom end hardly change anything on that very low performance bike.

one thing to be very aware is the increase in compression ratio. that bike is air cooled and since it does 180km\h it will go wide open for a lot of time. while there is a nice increase in torque it may overheat. if that bike will see very long time wide open i do not increase the CR at all. just put a thicker base gasket and get the cylinder port timing a little agressive, towards high rpm power and overrev... it may return the lost timing because the overboring.
if is used only for small burts like in the city, go for it. it will be fun... maybe less top speed but lots of low end torque... :ride:

I just read a post where you suggested someone to install brackets on the cylinder which will lead to the frame heating.. i was wondering if it will be feasible to attach the cylinder with brackets welded up to the frame so the heat transfers from the cylinder to the frame, which might help the cylinder remain cool?

 

[SHSPVR]

Ever hear of Air Ram
Just look up the old Suzuki GT250, 380, 500

 

[whenfoxforks-ruled]

You forgot the almighty GT750. At least it would have an excuse for blowing white smoke. Vintage Bob

 

[SHSPVR]

You forgot the almighty GT750. At least it would have an excuse for blowing white smoke. Vintage Bob

Oh that old Water Buffalo hehe that Water Cooled and dam thing where amazing fast they give new meaning to amazing heart pounding in good old days I ride one :yikes:

 

[thumper135]

*Update*

So the bike runs (approx 35 miles in belt) pretty strong in the low end (as Mr. helio lucas mentioned) lots of grunt and wanting to eat out gears (1st 3 especially) rapidly.. no issues other than a very small head gasket leak that is only noticeable on high rpms which hopefully will be done with by torquing the bolts down. a video of it running coming up after.

the cylinder base was shaved over 2mm to achieve the right piston to deck height. the ports were cleaned other than that no major changes. the squish band area was modified in the head to achieve proper clearance with the new bore and piston .

the locating pins for the ring end gap were left unchanged. apparently once looked at closely it became absolutely clear that both the locating pins on the new piston came in contact with the ports at some point of time.. now since i had a spare cylinder and piston from my spare engine i compared the stock to see where the end gaps line up in that cylinder, i was surprised to learn that the stock piston locating pins also do come in contact with the stock cylinder ports during their cycle. so understanding this and keeping in mind the complicated process of re-pressing new pins I decided I will just go with what I have without changing any pins. what damage can it really do afterall? the ring twists and breaks with some scoring on the bore, aah well.. :-)

 

[thumper135]

Bob I belive the volume didn't change that much look like rigth around 2% or less which not enough to make that much of a over all diff to it.
When he dose get this all done the biggest change will be in the Compression ratio which should jump to about 8.5 due to dome piston vs his old flat top and that should push the hosepower up a bit.

the stock cylinder and the new shaved cylinder measured at 97.4 and 94mm respectably. the measurement was taken from the base to the top of the fin. makes it just a little over 2% change..

any ideas how much the squish clearance be for this piston? (with head gasket installed and bolts torqued down)

 

[helio lucas]

no mr. here, i wish...

it´s pretty consensual from some 50 years that mirror finished ports don´t work. they are better finished smooth, but not polished. from my point of view it´s worse on four strokes but it´s really a "no no"! :nod:

thats the first cylinder i heard of ring gap pass a port. i´ve seen ring gap on exhaust side but not right on a port...

the squish clearance is mostly based on squish velocity. if you don´t have the means or knowlege to calculate it the best way to get around the problem is to get the compression ratio right. if you really want to go on squish clearance and forget CR, 1,5mm is a good start, i assume, for that engine.