Check the piston, measure compression
Remove the carburettor and look through the window to see the piston. Use the starter motor to turn and watch the piston’s movement. Should move smoothly, without grinding, without burrs, notches, vertical grooves. The piston is also easy to inspect through the muffler mounting window.
To determine the condition of the piston system, measure compression. Use a special compression gauge for this. It is screwed in instead of the spark plug. Newer equipment should have a pressure of 7 to 10 bar. In a used one, it is more than 5.5 bar. Inflate with the starter. Normal pressure indicates the integrity of the piston, cup and rings.
Installing the piston rings
piston ring and cup and inner spring are on opposite sides of the piston.
How a chainsaw cylinder block is repaired?
To restore the master completely disassembles the motor and inspects its working parts. Measurements are taken to accurately assess the condition of the equipment and understand what repair procedures need to be performed. In overhaul, it is possible to bore parts if they are made of suitable materials.
The restoration process also includes other steps:
- evaluation of the efficiency of the piston stroke, measurement of the compression created in the working chamber;
- checking the integrity of the equipment, looking for mechanical damage, scratches;
- analyze the condition of the piston fasteners, eliminate play and other problems;
- Check other equipment that affects operation of piston group.
To restore the chainsaw cylinder was successful, the master carries out a series of checks after assembling the equipment. It is important that the power corresponds to the factory parameters, and that the saw shows stable rpm during idle and under load. Only after these checks it is possible to consider the repair of equipment complete.
Square chainsaw Partner how to correctly put the piston
Cylinder and piston group of chainsaws Partner 350-371 (Vityaz)
Cylinder and piston group of the company “Vityaz” has a shiny cylinder walls, 2-ring piston cross-section of 41 mm.suitable for chainsaws Partner (Partner) 350, Partner (Partner) 351, Partner (Partner) 352, Partner (Partner) 371.
Composition of kit: Cylinder. 1 pc., Piston. 1 pc., Pins. 1 pc., Piston rings. 2 pcs., Retaining rings. 2 pcs.
Item No.: 41041 Manufacturer: Vityaz (Belarus)
Together with the piston/cylinder group we recommend replacement of: Partner 350 chainsaw gasket kit. Partner 371 chain saw. Piston group change Piston group change, Gasoline chainsaw Partner 350, 351. Change of camshaft, Partner 350,351 chainsaw. Replacing. Partner 371 chain saw. Piston Group Replacement. When replacing the cylinder and piston unit on your Partner chain saw, be sure to pay attention to the condition of the crankshaft oil seals, as they can let air in and chainsaw
READ How to install the blade on a Husqvarna lawnmower
Timing of distribution of timing h2 (or ignition, as it is a hodgepodge)
Not knocking the piston with TDC. we orient the camshaft so that the big hole and the marks on his sprocket were as shown in the photo and with the simultaneous putting on the chain install the camshaft in the bed.
Ideally, the sprocket teeth should be perfectly parallel with the plane of the valve cap socket. In practice, unfortunately, it is difficult to achieve this accuracy. And this is mainly due to stretching of timing chain. And there is nothing you can do about it. either change the timing chain for a new one or catch the phase by changing the cogs, but this method of phasing is not acceptable for me personally.
Orient the camshaft bed with the “E” and “X” marks to the exhaust port and install the bed.
Tighten the bed nuts crosswise then tighten the two bolts on the side flange of the cylinder head.
What is the piston in an internal combustion engine
The piston is an element of an internal combustion piston engine, designed for conversion of energy of compressed gas pressure change in a cylinder into energy of translational motion. Then there is a conversion to rotational energy by means of the crankshaft and connecting rods.
When dismantling a chainsaw engine it is obligatory to remember or mark how you took out the pistons from the cylinders. The surface of the piston ring heads usually have important information on them that can be seen by removing the soot residue.
Technical information on repairing the cylinder and piston group.
RPM snowmobile pistons are built to snowmobile manufacturer’s specifications. These pistons are sold complete with piston rings, piston pin and retaining rings. All of these parts are interchangeable with the original.
RPM jet ski pistons are mainly built to jet ski manufacturer’s specifications, however the clamp rings of these pistons are stamped, unlike the original clamp rings which are typically made of wire. These pistons are sold complete with piston rings, piston pin and retaining rings.
WSM jet ski pistons built to jet ski manufacturer’s specifications. These pistons are sold complete with piston rings, piston pin and retaining rings. All of these parts are interchangeable with the original.
Before installing a new piston in your engine, you should determine the exact cause of the burned or jammed piston and correct the problem. The most common cause of this failure is too lean a mixture or air intake into the crankcase.
Remember! Replace a burnt out piston with a new one without fixing the cause of the problem. this will not solve your problem, it will cause another burst.
Measure the cylinder carefully. If it is elliptical or barrel shaped over 0.07 mm, the cylinder should be rebored to a new repair size, and the nicoax cylinder should be replaced or cast in place with a cast-iron repair sleeve.
In two-stroke snowmobile engines, the piston-cylinder joint clearance (“piston clearance”) should be set at the minimum:
In two-stroke jet ski engines, the clearance at the piston-cylinder interface (“piston clearance”) should be as follows:
Warning! Important! If you are installing the piston in a remolded cylinder, please follow the recommendations in the “How to Install and Bore a Casing” section below.
Attention! MUST check the ring gap before installing the rings on the piston.
For snowmobile engines this gap should be in the range of 0.25-0.60 mm.
Recommended clearances for jet ski engines are given below:
Remember! The engine can be damaged if this clearance is not maintained!
Some piston ring designs have a wedge-shaped profile. Note this when installing the rings on the piston. If the ring does not fit in the piston groove, you may be inserting it the wrong way round.
When installing the piston in the cylinder, the arrow on the bottom of the piston should point toward the exhaust, and the locking pins should point toward the inlet! some models of Polaris engines are an exception, where the arrow is pointing toward the magneto.
Piston pin retaining rings should be installed with the locking mechanism facing up.
Mount retaining rings with the sharp edge facing outward.
You MUST use a special tool to install the retaining rings! Installing one-hundredth of a ring with a screwdriver, pliers, hammer, or similar tool will distort it and cause engine damage.
Check carefully the position of the circlip in the groove! The ring must be fully seated in the groove.
Retaining rings are not recommended for re-use.
Warning! If the above rules are not observed, the circlip may come out of the groove during engine operation, causing damage to the engine.
How to Fit and Bore a Sleeve:
Structurally, three types of cylinders are the most common:
Warning! Do not try to press out such a case without heating up the cylinder. This will damage the surface of the crankcase bore and will not allow the new liner to be properly installed.
Two types of repair liners are used for such cylinders. The first option is to have a liner with a slightly larger outside dimension than the one that was poured into the cylinder during fabrication. In this case, cut out completely the old sleeve, new, pressed into the aluminum jacket directly.
The second option is that the old liner is not removed completely, but only bored to the maximum possible diameter, and then pressed into it the repair liner.
Before installing the liner to the cylinder, check the interference between the cylinder and the reconditioned liner. It must be within the bounds:
To install the repair liner into the cylinder, heat it to a temperature of 200-250 °C, insert the liner into the prepared hole and press it with a small effort until the cylinder cools.
After installing the liner, its upper plane should be lapped to the plane of the cylinder.
All repair sleeves are made with an inside diameter 1.0-1.5 mm smaller than the standard (nominal) diameter. This means that in order to install a standard piston in a new liner, it must be bored out to an appropriate size.
It is highly recommended that you personally verify that the cylinder is bored correctly. Check the cylinder for barrel shaping, especially in the window area.
After the boring and honing process, the window edges that are across the piston stroke direction must be chamfered and the other edges blunted. Chamfers must be removed at an angle of 30° to the working surface of the cylinder to a depth of at least 1mm.
Attention! The information in this section is not intended as a repair manual for engines, but is intended as a guide for qualified mechanics.
If you need to have your engine repaired, we strongly recommend that you call in professionals.
Photo report: Installing the piston on a two-stroke scooter engine
Today we are going to learn how to install a new piston rod on the most usual Chinese two-stroke Forsage scooter with 1E43QMB engine. The scooters equipped with this engine can be found on our roads more and more rarely, because of its ancient and extremely unsuccessful design, which in today’s realities does not withstand even the slightest criticism
Couple of words about the choice of piston group: The piston (43mm 65CC) shown on the photo below is just a disgusting quality, so it makes no sense to buy it, much less put it on a scooter. It’s better to spend 12ооwhich it costs in the first pub, than to give it for this rubbish.
If there is a possibility, it is worth to look for a piston from the manufacturer presented below (41mm 50CC), it has smaller displacement, but the quality is much better than the first prototype, and its price is significantly lower.
Works on the installation of our piston, you should always start with the correct installation of piston rings, and only then move on to other things.
Take one circlip from the kit and put it in any groove of the piston (it’s better to install circlips with round pliers).
A stop ring should lie in a groove tightly, evenly adjoining all circle, and at the same time free to rotate in it.
Lubricate the seat holes for the piston pin with engine oil, preferably for 2T engines, for more information on engine oils, read the article: Engine oil for scooter
It is better to grease such details with a standard syringe of medical equipment so that it would be possible to prevent the engine details from getting dirty on their surface.
After applying oil, rub it evenly over the surface of the parts.
Take the piston pin from the kit and put it so that it slightly goes out of the seat hole inside the piston.
Lubricate the top head of the connecting rod, cover the crank chamber with a rag to prevent foreign objects from getting into the crankcase and insert the cage into the top head of the connecting rod.
Orient the piston with arrow on the bottom to the cylinder outlet window (exhaust), put it on the rod, put the previously pulled out piston pin in the cage and push the piston pin all the way in (piston pin should enter by force of the hand).
Install a new gasket.Before installing the gasket, inspect the plane of the gasket and repair any damage with sealant.
Lubricate the rings with oil, being careful not to get any drips on the gasket.
TrueShopping BC4902 two Stroke Engine Piston and Cylinder Replaced. Due to was running on Fuel Only
To avoid damage and deformation of piston rings, when installing the piston in the engine cylinder make a band of tin plate and squeeze the ring with it.
When you squeeze the clamp around the rings, look carefully to make sure the ring locks are centered on the dowel pins in the piston grooves. After squeezing the rings, turn the clamp from right to left, the rings should not rotate with the clamp.
Fix the clamp with a clamp bent from the same strip of tin.
Using a syringe, apply oil to the cylinder surface and smear it evenly over the entire surface.
After lubricating the mirror of the cylinder, degrease the plane of the crankcase and the cylinder and install a new gasket, if necessary, put the gasket on the sealant.
Slide the cylinder onto the piston very carefully without forcing it, and watch carefully to make sure the piston slides straight into the cylinder without excessive distortion.
When the rings are fully seated in the cylinder you can remove the clamp.
The cylinder should go in its place easily by hand effort, if you have a cylinder does not go in place, then most likely you have set the rings wrong: the retaining pin got under the ring or the rings got dirty, remove the cylinder and do it all over again.
When the cylinder is in place, use your hand to hold the cylinder and rotate the crankshaft so that it rotates easily without excessive force.
Push the piston down and squirt some engine oil into the cylinder.
Degrease the cylinder head and head junction faces and install a new gasket.
Reinstall the cylinder head with proper orientation.
Tighten the nuts evenly crosswise: first a little tighten the nuts, observing the sequence, then tighten again, then again, and so gradually increase the force tighten them finally.
After the final installation, to prevent foreign objects from getting into the engine combustion chamber, install the spark plug and cover the exhaust port in the cylinder with a piece of rag. Oh yeah, don’t forget to give your new piston a proper run-in, or else
Installing the Piston
Insert the circlip into either side of the piston pin. The ring is best inserted using small round pliers. After installation, check how well and tightly the retaining ring fits.
- If the circlip does not fit the entire surface of the ring, but only a small fraction of it, replace it with a new one
- If the retaining ring is loose in the groove, unscrew it a little
Lubricate connecting rod lower and upper head bearings and piston pin bosses with clean engine oil. Put the piston on the connecting rod with IN mark facing the intake port. If there is an arrow on the piston instead of IN mark, put the arrow on the exhaust port. Insert the piston pin into the boss, align the piston on the rod so that the pin was in the rod set the pin all the way into the retaining ring and secure it against falling out with the second retaining ring.
Install the cylinder guide sleeves on the studs, put on the gasket. It is desirable to put the gasket on the sealant, but without fanaticism.