Yamaha MT110 engine repair manual

If the engine the figures are required for is a re-ring using the original pistons it is important to check the amount of wear of the bore and of the piston groove clearance.

Once the ring gap is set to the minimum at an unworn part of the cylinder bore the gap should be rechecked at the most worn part and if the gap exceeds the maximum it indicates an excessively worn cylinder bore.
While this is not immediately detrimental it does mean the piston ring grooves will wear much more quickly and the job will have a shorter life and in some cases a high oil consumption can be worsened.

The piston ring groove clearance - side clearance between the ring and the piston should be 0.0015 inch maximum. It can be expected the top groove could be considerably worn and in that case new pistons would be beneficial or a Cord ring set.

worn ring grooves
cracked rings
top ridge not removed before fitting new rings and pistons
too much clearance between piston and bore
excessive compression pressures
detonation

Oil ring assembly always goes on the bottom. You really can't make a mistake there. Oil groove is always much wider than any other ring groove. Stock pistons with 4 ring sets????

As an engine wears the ring lands on the pistons wear also. In addition to ring land wearing on the piston, the bore in the cylinder develops a wear pattern. Has the engine been rebuilt?
If the pistons have worn ring lands and were re-used it may allow the rings (new or old) to twist in the grooves and catch on any ridge in the cylinder, thus breaking them.

When the engine is apart you must check for proper ring land wear. You need to consult the piston manufacturer for proper wear specs, typically around 0.006in.

If you're getting a visible amount of smoke/oil from the breather after the rebuild something is not right. The rings are not seating. I would definitely recommend boring/honing the cylinders and going with a new set of pistons/rings so you don't have to pull it apart again. A little more now can save a lot in the long-run.

Clogged PCV Valve
The main purpose of the PCV (positive crankcase ventilation) valve is to recirculate blow-by gases back from the crankcase area through the engine to consume unburned hydrocarbons. Blow by is a mixture of air, gasoline and combustion gases forced past the rings on the combustion stroke. The PCV system usually has a tube leading from the crankcase to the carburetor or intake manifold. Vacuum within the engine intake manifold pulls blow by gases out of the crankcase into the combustion chamber along with the regular intake of air and fuel.
Worn Piston Ring Grooves
For piston rings to form a good seal, the sides of the ring grooves must be true and flat - not flared or shouldered - and the rings must have the correct side clearance in the grooves. Normally, automotive ring groove side clearance should not exceed .002-.004. As the pistons move up and down, the rings must seat on the sides of the grooves in very much the same way that valves must seat to prevent leakage. New rings in tapered or irregular grooves will not seal properly and, consequently, oil will pass around behind the rings into the combustion chamber. Worn grooves are usually flared or tapered causing increased side clearances which permit more than the normal amount of oil to pass the rings into the combustion chamber. Excessive side clearances also create a pounding effect by the rings on the sides of the piston grooves. This promotes piston groove wear and, if the condition is not corrected, breakage of rings lands may occur.
Cracked or Broken Ring Lands
Cracked or broken ring lands prevent the rings from seating completely on their sides and cause oil pumping by a process similar to that described in #7. In addition to this, they also lead to serious damage to the cylinders as well as complete destruction of the pistons and rings. Cracked or broken ring lands cannot be corrected by any means other than piston replacement and this should be done as soon as there is the slightest indication of a crack.
Worn Valve Stems and Guides
When wear has taken place on valve stems and valve guides, the vacuum in the intake manifold will draw oil and oil vapor between the intake valve stems and guides, into the intake manifold and then into the cylinder where it will be burned. If this condition is not corrected when new piston rings are installed, an engine is likely to use more oil than it did before because the new piston rings will increase the vacuum in the intake manifold. When gum or deposits on the valve stems are removed - a procedure recommended when overhauling an engine - the seal previously formed will be removed and leakage will be more pronounced. This is particularly true on overhead valve engines where loss of oil may occur on the exhaust valves as well as on the intake valves. High oil consumption caused by too much valve guide clearance can frequently be cured by reaming or nerraling the valve stem. In some cases new valves may also be required. Use of a permanently bonded valve stem seal will give added insurance against oil leakage on complete engine overhauls or on valve jobs. Large Oil Leaks Leaking valve cover gaskets, leaking crankshaft front and rear seals.

your replacing the piston rings? are you using a spring compressor? when you compress the rings and set the piston down in there sleeves make sure to oil the cylinders the with the rings compressed and staggered gently tap the top of the piston with the wooden handle of a hammer. when i say stagger i mean the gaps in each ring are in a different position so as not to create a bypass of pressure or oil. if you use the compressor the piston should slide into the sleeve of the cylinder

It can be time consuming and the end result may not be desirable if you haven't done it before.
--- The following is just a sample of what to do once the engine is torn down: Pistons and Connecting Rods

1. Before installing the piston/connecting rod assembly, oil the pistons, piston rings and the cylinder walls with light engine oil. Install connecting rod bolt protectors or rubber hose onto the connecting rod bolts/studs. Also perform the following:
   1. Select the proper ring set for the size cylinder bore.
   2. Position the ring in the bore in which it is going to be used.
   3. Push the ring down into the bore area where normal ring wear is not encountered.
   4. Use the head of the piston to position the ring in the bore so that the ring is square with the cylinder wall. Use caution to avoid damage to the ring or cylinder bore.
   5. Measure the gap between the ends of the ring with a feeler gauge. Ring gap in a worn cylinder is normally greater than specification. If the ring gap is greater than the specified limits, try an oversize ring set. Fig. 5: Checking the piston ring-to-ring groove side clearance using the ring and a feeler gauge
      
      
   6. Check the ring side clearance of the compression rings with a feeler gauge inserted between the ring and its lower land according to specification. The gauge should slide freely around the entire ring circumference without binding. Any wear that occurs will form a step at the inner portion of the lower land. If the lower lands have high steps, the piston should be replaced. Fig. 6: The notch on the side of the bearing cap matches the tang on the bearing insert
      
   
   
2. Unless new pistons are installed, be sure to install the pistons in the cylinders from which they were removed. The numbers on the connecting rod and bearing cap must be on the same side when installed in the cylinder bore. If a connecting rod is ever transposed from one engine or cylinder to another, new bearings should be fitted and the connecting rod should be numbered to correspond with the new cylinder number. The notch on the piston head goes toward the front of the engine.
3. Install all of the rod bearing inserts into the rods and caps. Fig. 7: Most rings are marked to show which side of the ring should face up when installed to the piston
   
   
4. Install the rings to the pistons. Install the oil control ring first, then the second compression ring and finally the top compression ring. Use a piston ring expander tool to aid in installation and to help reduce the chance of breakage. Fig. 8: Install the piston and rod assembly into the block using a ring compressor and the handle of a hammer
   
   
5. Make sure the ring gaps are properly spaced around the circumference of the piston. Fit a piston ring compressor around the piston and slide the piston and connecting rod assembly down into the cylinder bore, pushing it in with the wooden hammer handle. Push the piston down until it is only slightly below the top of the cylinder bore. Guide the connecting rod onto the crankshaft bearing journal carefully, to avoid damaging the crankshaft.
6. Check the bearing clearance of all the rod bearings, fitting them to the crankshaft bearing journals. Follow the procedure in the crankshaft installation above.
7. After the bearings have been fitted, apply a light coating of assembly oil to the journals and bearings.
8. Turn the crankshaft until the appropriate bearing journal is at the bottom of its stroke, then push the piston assembly all the way down until the connecting rod bearing seats on the crankshaft journal. Be careful not to allow the bearing cap screws to strike the crankshaft bearing journals and damage them.
9. After the piston and connecting rod assemblies have been installed, check the connecting rod side clearance on each crankshaft journal.
10. Prime and install the oil pump and the oil pump intake tube.
11. Install the auxiliary/balance shaft(s)/assembly(ies).

OHV Engines CAMSHAFT, LIFTERS AND TIMING ASSEMBLY

1. Install the camshaft.
2. Install the lifters/followers into their bores.
3. Install the timing gears/chain assembly.

CYLINDER HEAD(S)

1. Install the cylinder head(s) using new gaskets.
2. Assemble the rest of the valve train (pushrods and rocker arms and/or shafts).

OHC Engines CYLINDER HEAD(S)

1. Install the cylinder head(s) using new gaskets.
2. Install the timing sprockets/gears and the belt/chain assemblies.

Engine Covers and Components Install the timing cover(s) and oil pan. Refer to your notes and drawings made prior to disassembly and install all of the components that were removed. Install the engine into the vehicle. Engine Start-up and Break-in STARTING THE ENGINE Now that the engine is installed and every wire and hose is properly connected, go back and double check that all coolant and vacuum hoses are connected. Check that your oil drain plug is installed and properly tightened. If not already done, install a new oil filter onto the engine. Fill the crankcase with the proper amount and grade of engine oil. Fill the cooling system with a 50/50 mixture of coolant/water.

1. Connect the vehicle battery.
2. Start the engine. Keep your eye on your oil pressure indicator; if it does not indicate oil pressure within 10 seconds of starting, turn the vehicle OFF. WARNING
   Damage to the engine can result if it is allowed to run with no oil pressure. Check the engine oil level to make sure that it is full. Check for any leaks and if found, repair the leaks before continuing. If there is still no indication of oil pressure, you may need to prime the system.
   
3. Confirm that there are no fluid leaks (oil or other).
4. Allow the engine to reach normal operating temperature (the upper radiator hose will be hot to the touch).
5. At this point any necessary checks or adjustments can be performed, such as ignition timing.
6. Install any remaining components or body panels which were removed.

Which Piston Ring Gap? First of all you need to purchase a Hayne's Manual for your car. It will give you the specifications under the Engine section of the book. The piston has three rings on it. From the top you have your first compression ring, then your second compression ring (these "clearance" specifications or "gap"), should be the same as measured on the piston insofar as the clearance between the "lands and grooves" or between the ring and the piston groove. The third ring is your oil control ring which will have a different clearance between (for example), the top of the ring installed and the piston's groove. Then lastly, you need to place the compression rings and place them in the bore of the cylinder WITHOUT being installed on the piston. A measurement is then taken between the opening gap of the ring while in the block. To make sure it's lined up properly, invert a non-ringed piston down into the bore from the top to make sure the ring is installed at the same depth all the way around.

If you don't want to buy the Hayne's Manual, just stop by your local Dealership and get the Specifications for the two compression rings, the oil ring and the "installed" clearance or gap on the rings.

Hope this Helps,

~00 Buck~

"Still living on the Right Side of Dirt..."

If you are that deep into things you will do poorly without a good manual. Are the pistons new or used?If they are used you need to completly clean the ring grooves in the pistons or the new rings will stick and gall.Did you remove the ridge at the top of the cylinders? If not there is a good the top ring will either break or bust the upper land off of the piston. Hopefully you had a machine shop go through the block. Check the ring manufacture's web site. I am sure they will have tips and instructions.