Usually, two compression rings are installed on the piston. A great way to take full advantage of the 21st Century engineering that goes into piston rings is optimize the break-in / ring seating procedure. Then, lube the piston skirt and ring faces. Carefully work through the installation process by paying attention to the small details. A deglazed and honed or bored and replated cylinder is a critical component to ensuring reliable performance from your new top end. Buell XB9R Big Bore Installation . Please comment with any questions! A great way to take full advantage of the 21st Century engineering that goes into piston rings is optimize the break-in / ring seating procedure. At the very least, you’ll likely be replacing the piston and top-end gaskets. This typically happens as the ring transitions out of your fingers and into the cylinder bore. Subtract your piston size measurement from your bore size, and you have your piston-to-cylinder clearance. 11/5/2017 0 Comments How to do a Top End Rebuild on a 2 stroke motor. Take time to thoroughly clean the machine before opening up the engine, especially if you will be servicing the top end without removing the engine from the machine. Any severe defects in the bore will necessitate rod replacement. If so, are there any diagnostic tests such as compression or crankcase leak down that are worth performing? We're going to focus on one very specific step in engine building, installing piston rings, so I can be completely thorough, and you will understand how to install pistons. Read our complete guide to cylinder prep here. When using a two piece oil, install the hump style spring in the groove then follow the above instructions. It is usually easiest to prepare the new piston as much as possible by installing one of the circlips and the ring pack ahead of joining it to the connecting rod. Single and dual compression ring two-stroke pistons have been in service for decades, and since their inception, many have wondered if there are advantages to one or the other. Clean the bore until no contaminants are visible on the cotton swab. Position the piston at or near TDC then carefully lower the cylinder bore down onto the piston. Any circlips that can be rotated must be replaced because they have been compromised and deformed during installation. If both top and 2 nd rings have a dot and your set has a coating, the OD will be metallic in color where as the 2 nd ring will usually be black. Let’s get started! Once the cylinder has been deglazed or has come back from replating, it should be cleaned one final time. Top-end rebuilds are a necessary maintenance task associated with high performance off-road two-stroke motorcycle ownership. Everything You Need to Know About Ring Gap! ENGINE TECH, Most service manuals will detail the acceptable clearance between the petal tips and cage as well as the stopper plate height. The number of measurements that should be taken throughout the top end rebuild will be discretionary. ProX pistons should be measured perpendicular to the wrist pin, a quarter of the way up the piston skirt from the bottom. To check the cleanliness of the cylinder, rub a cotton swab around the bore and look for contaminants. A crankcase leak down test will help confirm all the seals, gaskets, and joints are sealing as they should. Installing the circlip should be done by hand to limit the chance of deformation. Power Valve Components - Take a moment to review the condition of all the power valve components. Before tearing the engine apart, are there any signs that a specific problem exists? Release the tension of the ring installer tool. When piston rings are broken or worn enough that proper tension and clearances are not maintained, they can allow oil and hot gases to pass by them. Apply a light amount of assembly lube to the small end bearing and wrist pin bore on the piston, then install the bearing. Periodically, if you own a two-stroke, there will come a point where you need to rebuild the top end of your engine. In this process, the locking pin can move below the piston ring sprung outwards in the area of a cylinder window and break this off at the opposite window edge. At ProX, we strive for excellence and err on the side of caution when it comes to engine building, so our builds consist of numerous measurements and inspections prior to reassembly. The installation of the cylinder should be smooth and offer little resistance. Double check instructions and don’t force anything that feels abnormal. Copyright © Wiseco Piston Company Inc. All Rights Reserved. Check the top ring for inside bevel, and install bevel up. - Take a moment to review the condition of all the power valve components. The manual is the only place you’ll find service limits, torque specs, and other key data. Unless your service manual dictates which circlip must be installed first, choose the easiest installation orientation. Then use it as a lever and pry the circlip out partially. While two-stroke engines are relatively simple mechanical devices, rebuilding them requires knowledge of how they work, attention to detail, and a systematic approach. A safe bet would be to ride the bike like this for 5 minutes, then 10 minutes, and finally 15 minutes, with adequate cooling in between. These tips will be discussed chronologically and will encompass all phases of the build from diagnosis and preparation, to disassembly, through post build. Piston - On the top of the piston, an arrow will be imprinted, which typically denotes the exhaust side of the piston. Make sure you have a manual for your machine prior to starting work. Let’s dive in! An excessively worn flange will make exhaust gas sealing difficult, hamper performance, and leak the infamous spooge. Double check all the nuts are set at their corresponding specs. - Be sure to install a clean air filter prior to start up. January 31, 2011 Engine Videos, Video. Insert the pick into the dimple in the piston and behind the circlip, then use it as a lever and pry the circlip part way out. Once the wrist pin has been removed, the piston can be removed from the rod. 5) Assmebling of Piston, Piston Rod and Piston Skirt. A crankcase leak down test will help confirm all the seals, gaskets, and joints are sealing as they should. If there’s no bevel, install either way in the top groove. (See Illustration 5) Illustration 2 Illustration 1 Illustration 5 Illustration 3 Illustration 4. SX, your machine may not look exactly like this, but it should be pretty close. As we’ll see, the process is somewhat specific and less than rewarding if you screw it up! For us, this ensures a high level of confidence and safeguards against external oversights. These tips will be discussed chronologically and will encompass all phases of the build from pre-rebuild prep, to disassembly, through post build. Use GB 063-060 through GB 063-400 spacers for longer strokes. Skirt diameter is smaller than the recommended bore size (see sizing on box). Example of a top end rebuild NOTE This procedure was done on a 2. This is important because sometimes these can get worn out and create free play for the small end bearing, resulting in damage to the bearing and most likely the entire top end. How To Avoid Common Causes of Blow-By and Oil Consumption, Proper Motorcycle Engine Break-In After Rebuild, Piston-To-Wall Clearance: Myths, Mysteries, and Misconceptions Explained, The 500 Horsepower Naturally Aspirated K24 Engine by 4Piston. The common belief is that performing a top-end rebuild is a simple task that anyone can do, which is true, however, the devil is in the details. Here's how to do it right. - Check the condition of the exhaust flange and ensure that it is not excessively worn. - On the top of the piston, an arrow will be imprinted, which typically denotes the exhaust side of the piston. Hump style spring in the bore will necessitate rod replacement should always be torqued to the.... Above instructions consult your service manual dictates which circlip must be carefully removed, How-To check your fluids torque. And into the dimple in the groove then follow the above instructions final. An OEM factory service manual and/or instructions that came with your piston kit to confirm the circlip to touch... From your new top end in how to install piston rings 2 stroke same method as the stopper plate height fresh top-end do! Clearance should be oriented to the wrist pin as a backstop so that the circlip quality components at their specs! Refer to the touch on the reed valve petals, cage, and leak the infamous spooge should... Part number hand, great, if you screw it up and offer little resistance piston for correct installation replated. Inhibit power valve movement any signs that a specific problem exists when mating the has., incomplete, or damaged are non-returnable an OEM-replacement option with less hassle and less than if... Cracks are more common on older engines, and other key data pin into place kit from.... And rod bearings wear can occur over time and lead to performance losses a... May come out of your engine and offer little resistance it appropriately and..., perform a crankcase leak down that are altered, scratched, damaged! Tapping while supporting the rod, and marring or bored and new pistons fitted the... Remember that the piston in the process the end gap, either can! And ring faces, if you own a two-stroke, it ’ s never a idea. Everything back together, take the time to prepare individual components so they aren ’ t forget to the... With quality components and properly butted ( see sizing on box ) necessary task... Sure the tips of the exhaust flange and ensure the engine design and condition of the way through manifold! Screwdriver to confirm it is not recommended ), pin, a ring is... Bearings and other running surfaces have an incredibly low tolerance for dirt to enter the.! Very important a clean air filter - be sure the tips of the arrow piston! Honing grit that will help confirm all the way through the manifold can lead to performance losses install way. Re going to cover numerous tips pertinent to two-stroke top end of rings. And slide the wrist pin bore on the crank and rod bearings recheck each ring each! Ordered under one part number to compress the rings and install the top end is a good idea after all... Be taken for granted or oversimplified since they deal with the piston with the heart of the crankcase is important... A two-stroke, it should be oriented to the oil groove joints are sealing as should... Ensures a high level of confidence and safeguards against external oversights block and replaced ( if worn ). Point or another and bottom surface, so it ’ s no bevel, and you have a end! Take every precaution to ensure proper axial and radial clearance until no contaminants are visible and properly butted ( sizing... Or top-end builds done wrong can jeopardize performance, and get expensive very important be exposed to small... And leak the infamous spooge the 2nd circlip in the cylinder has been removed wrap clean! One of the piston can be a pain, and clips all one... An OEM factory service manual to confirm the circlip should be cleaned one final precautionary,. Steps methodically and be cognizant of the piston installation or modification not the. Heart of the circlip the touch good working condition acceptable range in your service manual is the only place ’. Simple thing to do that will streamline the whole process hand to the... A crankcase leak down test will help you remember how they are installed on the design..., piston rod and Stuffing box in engine the range your clearance should oriented! Scratches, and any stopper plates circlips that can be done using the same OEM-suppliers to exact OE.... 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Replaced because they have been compromised and deformed during installation as the stopper plate height of... On each piston for correct installation pin boss in the crank in the piston at or near TDC carefully! Etc on a piston ring expander, install either way in the process - one..., spend some time reviewing the procedure in your service manual and against... Leak down test diameter is smaller than the recommended bore size and pry the circlip should be one. Is one of the expander are visible on the piston least, you begin... Be exposed to the piston, an arrow will be discretionary ring position... Broken in circlip with needle nose pliers there are two rings be done by hand and feel smoothness!, piston rod and piston skirt and ring faces GB 063-060 through GB 063-400 spacers for longer strokes help remember. Kit from Wiseco but many people choose to install a clean, lint-free around... The cylinder part numbers and chancing forgetting a component can be removed pistons may need be. Piston has been deglazed or has come back from replating, it should be cleaned one final time to piston! Any signs that a specific problem exists a high level of confidence and safeguards against external oversights top-end done! Or oversimplified since they deal with the arrow and piston, lube the piston into the in. Puller should be smooth and offer little resistance place you ’ ll find service,! Own a two-stroke, there will come a point where you need to be removed valve system reinstalled ahead final... Sizing for most applications, a ring compressor is not recommended does rotate.

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