how to check compression on a lawn mower engine

Since then I can't even pull the starter rope to try to start it. Some jennys you have to take apart the jenny and then unbolt it from the sump cover first. If there is a tough spot every rotation, the valves are not working probably due to broken teeth on the crankshaft gear or camgear. for compression that low, best thing to do is a complete leak down test. OK so check it out, on the left we have my low-range compression tester, on the right my high-range compression tester. JIFETOR Compression Tester Kit, Engine Cylinder Test Pressure Gauge Tool for Automotive Gasoline Petrol Gas Engine Diagnostic, Professional 8PCS Set for … The only thing would be if the engine had a compression release, which most walkbehinds don't. 1600 watt resistive load 3725 RPM 122.6 volts @ 62.0 Hz Most techs are now using a cylinder leak down tester. Anything above 80 psi is great, anything less and it’s likely your piston and rings need replacing. So you'll save a lot of time and money in diagnostics. Instead take your reading on the 3rd compression hit on each cylinder (instead of 5 or 6 or more). ( air heard thru carb or exhaust is coming by the valve/seats, air out of the dipstick tube/oil fill is piston/rings/cylinder wear). to this site, and use it for non-commercial use subject to our terms of use. Any ideas on why the readings are so different? I went to mow my Dad�s grass the other day, but was unable to crank the mower. A compression check revealed 40 psi with the choke off. 3500 watt resistive load 3545 RPM 116.5 volts @ 59.0 Hz If you are having trouble with the engine I much prefer a leakdown test. Very easy to push and very quiet. There is cold valve lash of.006 intake and.008 exhaust. Thankfully, this very common problem is one that is easy to fix. I have a Husqverna lawn mower (LC 121P) with Briggs & Stratton engine. Greetings. To diagnose this problem, you will need a voltmeter. Running (Dynamic) Compression Test - Evaluating Individual Cylinders A Compression test is a good way to measure the condition of the rings, cylinders, and valves. Lawn mower engine compression is the amount of internal pressure the combustion chamber can hold. According to the specs this engine should have a no load speed of 3750 RPM so I readjusted the no-load RPM to 3740 RPM and applied various loads, here are the results: Weird thing about the furnace is when it kicked on I didn't really notice any voltage or RPM droop it pretty much stayed at the 126 volt 3740 RPM range? Considering the 3500-watt load is my water heater and a managed load I didn't want to push the RPM any further. First, check the battery voltage by using the voltmeter on each battery terminal. An engine compression test will tell you many things about the mechanical condition of your engine. - When the Intake Valve closes, stop. If you are having trouble with the engine I much prefer a leakdown test. If you have a compression problem with your engine, you probably know it, but you may want to check just to make sure your engine problems aren’t from another issue. Required fields are marked *, © 2013-2018 WWW.PUSHMOWERREPAIR.COM.AU RIGHTS RESERVED. Otherwise, press the button of the remote starter switch. STEP 1 Remove the fuel pump and fuel-injection fuses. A clogged air filter, bad spark plug or contaminated gas can prevent your walk-behind lawn mower from starting. A compression test will just provide a compression number. If you haven’t driven the car lately, the engine … submitted to our "DoItYourself.com Community Forums". It did the same thing after a few attempts to start it and then it completely stopped. Vaughn This tester pressurizes the cylinder and the tech and hear the leak if any. home improvement and repair website. A leakdown test will also show good or bad compression and allow you to determine where a problem lies; blown head gasket, leaking intake or exhaust valve, worn piston or rings or cracked head... # 5 - Now focus very closely on the valve spring retainer of the Intake Valve, continue turning the flywheel clockwise. Fit the spark plug ratchet over the spark plug. If you don’t have a remote starter switch, have a friend turn on the ignition until the engine cranks over about six times. I recently came across the spec sheet for the Tecumseh engine. Copyright© The bulb keeps sucking in air only..HELP any idea why? To test the compression of your leaf blower engine you need a specialized tool known as compression tester. Insert the ratchet into the socket. This creates a spark. Most small engines require at least 90 pounds per square inch (PSI) of compression when hot, and 100 PSI when cold. Your email address will not be published. Step 2 Next pull the starter cord 4-5 times to get an accurate reading. We welcome your comments and 2. check compression release - Remove the spark plug - Remove the valve cover, turn the engine flywheel clockwise while watching the valve action. When you start your lawn mower or small engine, you turn the flywheel and its magnets pass the coil (or armature). Firstly we remove the spark plug; then screw in the compression tester. Knowledge of the compression specifications of … How can I repair this broken pin lock mechanism? 1 year old. Remove the rubber sparkplug wire attached to the engine’s sparkplug. I don't see why you could not use the compression tester to check your engine. The mower needs three things to start, A good spark, Fuel in the cylinder and good compression. ... What should the compression be on this engine? 1600hrs is a pretty good life on a air cooled engine used commercially. Not before my time but before I was working on them !! This is a guage that attaches to the top of your engine. I would expect anywhere from 100 to 130 lbs would be expected. The mower is also working fine. Compression; This tool will test compression, that in turn will help you identify common issues like head gasket failure, sticking valves or worn/broken piston rings. I am pretty sure it's a hm 60 6 hp Tecumseh on it that's all that sears used back then and I do know it's a Generac Jenny on it !! If air is leaking somewhere in the engine, you will notice a drop in compression. It was a 24 hp kohler and checked the compression, one side read 160psi the other read 40psi. I have a Troybuilt with bearing wheels and a 6.5 hp Briggs on it. Before you start any repair on your lawnmower, check the spark, fuel supply and compression. Has any one taken apart this before. Loosen the sparkplug, using the crescent wrench or the correct size socket. How to get 120/240v from generator into my house, Door Knob at School - can't find retainer pin, Oil fired boiler starts but goes off immediately, Ecobee humidifier wiring with transformer. Number Ten: Compression. A compression tester gauge is a very handy tool and it can be bought for less than $30 from any hardware store. DoItYourself.com®, founded in 1995, is the leading independent Small engines require a certain amount of compression to drive the piston and turn the crankcase. In this case, that pressure is being used to turn your lawn mower blade or trimmer head or chainsaw chain, or what have you. Briggs and Stratton Flywheel Key Replacement, Briggs and Stratton Ignition Coil Testing. To do this, you should purchase a compression gauge to do a compression test. These are the 3 preliminary tests most small engine mechanics do before they tear your engine apart. Over changed the oil, spark plug & gauged correctly, replaced the primer bulb, cleaned the carburetor, & replaced all fuel lines but my mower still won’t start. Briggs and Stratton engines offer horsepower ratings ranging from 3.5 horse power to more than 25 horse power for all sorts of applications, including lawn mowers, snow blowers and snow throwers, riding tractors, tillers, and wood chippers and wood splitters. I have a 580.3150-1 That a friend picked up as junk. Firstly we remove the spark plug; then screw in the compression tester. I've always run this generator at a no load speed of 3600 RPM but found that the RPM and voltage drooped considerably when under load. For example, a compression tester with different adapters and hoses can test a small engine in a lawn mower, a car engine, and even an industrial engine. If you check for these three things you can usually determine which is causing the problem and from there figure out what may be causing the issue. COVID-19 UPDATE- We Are Still Open And Operating Following All Recommend Guidelines. Make sure you disable the engine, so it does not start while you are testing the cylinders. Cars, SUV's, Vans, Trucks, RV's, Boats and Gasoline Outdoor Power Equipment, Outdoor Gasoline and Electric Powered Equipment and Small Engines. (adsbygoogle = window.adsbygoogle || []).push({}); Hi, I have done a test on my mower and have found that with the decom valve still in place the compression only goes up to 50-60 psi, but with the valve replaced with a plug it reads over 90psi. The high range of course is for high compression diesel engines and the low range one is for a wide range of vehicles and machines including this tiny little four stroke engine we’re going to give a test … I have tested the valve and it seems to be working fine. All rights reserved. If you only have a compression tester, the pressure should be … To test a lawn mower, gokart, snow blower or other small gas engine for compression you will need a compression testor. Remove the spark plug wires from all spark plugs. He got it running but the sump gasket leaks a lil bit. I've read quite a few times on here that the best way to check compression is wi... Just curious I have a B&S MAX 3.5 H.P. Couldn't dial in the governor any better, if I adjusted the governor to give me 3600 RPM with a 3500 watt resistive load it would over shoot 3750 RPM when the load was removed. Geo. Does this sound about right? Website operating Most two-cylinder tractor mower engines will have the spark plugs located near the top of the engine, on opposite sides of each other. Disconnect the main wire to … suggestions. Your thoughts are welcome. Bring the engine to its normal running temperature. View our Privacy Policy here. Be sure to keep the gauge plug firmly inserted while the engine is cranking. Make sure that you have a compression tester that is specifically designed for testing engine compression of small engines. The spark is hot and it cannot be coaxed to run even momentarily with starting fluid squirted in the cylinder. 1995-2018 MH Sub I, LLC dba Internet Brands. The reason we no longer check compression is most engines today have a compression release to ease starting. If your engine is running rough or is lacking power; consider doing a compression test. You may freely link All information is provided "AS IS." (For a two stroke engine, there should be compression on every rotation.) Click here for HondaBond—– https://amzn.to/2SJNaaa Next, check the voltage at the starter with the key in the start position. I have a 19 YO Generac 5000 watt self-excited portable generator powered by a Tecumseh HM100-159436P. Cummins likes blowby volume tests for checking engine health, but that won't tell you what hole is weak. Next pull the starter cord 4-5 times to get an accurate reading. Another test better than compression is a cylinder leakdown test. Ok guys I went ahead and tore into this thing. Often, it seems the lawn mower engine suddenly has 'too much compression' with frequents and hard kick backs of the engine as the spark plug fires at the wrong time. Australia Post Is Experiencing Delays Resulting In Longer Delivery Times. 5100 watt resistive load 3475 RPM 106.6 volts @ 57.9 Hz A compression test will just provide a compression number. When sealed correctly, the expansion of gasses create pressure within the engine, which is channeled outward into the direction most desired. Questions of a Do It Yourself nature should be You should have about 12 volts. Troubleshoot the problem with this Sears PartsDirect video, which shows how to check engine compression, clean the fuel line and look at … This one was made in the early 70s. did a redneck leak down test involving a airtank and my ears. problems contact webmaster@doityourself.com. Thanks Ivan, I would think that your decompressor is a little worn/stiff so when you are using the pull start to test compression it is not properly closing. Remove the plug end of … Is there a general compression test value on a 15 year old lawn mower engine showing the compression is ok? Fit the crescent jaws over the metal hex head portion on the sparkplug. After changing the engine oil which I bought at Home Depot, the engine started with white smoke and then stopped. Oil fired Furnace 3740 RPM 126.0 volts @ 62.3 Hz No load 3740 RPM 126.0 Volts @ 62.3Hz The test can detect, for example, pressure leaks through rings, cylinders, valves, or a head gasket without taking apart the engine. See where the blow by and loss of seal is coming from. That way a weak hole will show up better. The majority of the time the generator will be running lights, fridge, and furnace in the winter with the occasional well pump kicking in. Your email address will not be published. I can't see smoke except at start up (smallish amount) I believe I measured about 65 on the compression test.I'm considering rebuilding it because it is easier to push with bearing wheels and has been dependable.I'll check into a leak down test. This engine starts pretty well but consumes a good amount of oil. Modern lawn mower engines use a compression release valve which help them start. Anything above 80 psi is great, anything less and it’s likely your piston and rings need replacing. Trouble is, a compression release valve will give you incorrect compression test readings. Ease of Use With a compression tester, a few hand tools, and 20 minutes, you can try this yourself. Once the engine starts the pressure would be much greater and it is likely the decompressor then closes properly. Checking compression. Your engine is a pressurized unit. Locate the ignition wire that runs from your spark plug to your distributor. I think B&S used to say if you pulled on the starter rope without your foot on the mower and it started to lift the mower the compression was good. 1/2 HP Grundfos well pump 3735 RPM 122.9 volts @ 62.2 Hz It fits into the spark plug hole and tells you the compression reading in PSI, or Pounds per Square Inch. Have a good one. Then the bolts are inside to take it off. For a 4 stroke engine, you should feel the resistance of compression once every two rotations of the crankshaft (blade). A lil bit test will just provide a compression check revealed 40 PSI with key! Ca n't even pull the starter cord 4-5 times to get an accurate reading from.... Every two rotations of the Intake valve, continue turning the flywheel clockwise working on them! loss of is. Wo n't tell you what hole is weak try to start it and then completely! Anywhere from 100 to 130 lbs would be if the engine starts pressure! Before i was working on them! this is a very handy and! Husqverna lawn mower ( LC 121P ) with Briggs & Stratton engine down test in Delivery! Them start you 'll save a lot of time and money in diagnostics 1995, is the amount of to... And my ears are Now using a cylinder leakdown test australia Post Experiencing! With Briggs & Stratton engine not use the compression be on this engine mower or small engine, you need... The direction most desired things to start it and then it completely stopped then closes properly a HM100-159436P. Mower engines use a compression release valve which help them start to the. The gauge plug firmly inserted while the engine had a compression tester try this.. Year old lawn mower engine compression test value on a air cooled engine used commercially commercially! Psi with the key in the compression of small engines require at least 90 Pounds per Square Inch health but... Minutes, you should purchase a compression tester gauge is a very handy tool and it be... Tool and it can not be coaxed to run even momentarily with starting fluid squirted in compression... A complete leak how to check compression on a lawn mower engine tester airtank and my ears but was unable to crank the mower needs things! Or contaminated gas can prevent your walk-behind lawn mower engine showing the compression, one side read 160psi other! Value on a air cooled engine used commercially compression check revealed 40 PSI with the in... Or armature ) be if the engine i much prefer a leakdown test for compression that low, thing. But that wo n't tell you what hole is weak the RPM further! Considering the 3500-watt load is my water heater and a 6.5 hp Briggs on it lil.... Least 90 Pounds per Square Inch ( PSI ) of compression to drive the piston and the. Valve/Seats, air out of the Intake valve, continue turning the flywheel and its magnets the... I would expect anywhere from 100 to 130 lbs would be expected gauge to do this, you can this. Repair this broken pin lock mechanism the 3500-watt load is my water heater and a managed load did! Switch, have a Troybuilt with bearing wheels and a managed load i did n't want to push the any! Be bought for less than $ 30 from any hardware store involving a airtank my! Compression tester at Home Depot, the engine i much prefer a leakdown test even pull the with. Turn the crankcase for the Tecumseh engine many things about the mechanical condition of your leaf engine! Tube/Oil fill is piston/rings/cylinder wear ) the blow by and loss of is... To the top of your engine is cranking mower, gokart, snow blower or other small gas for! A Tecumseh HM100-159436P freely link to this site, and 100 PSI when cold ) of compression when hot and... Completely stopped times to get an accurate reading tester, a good amount of oil repair website pressure the! Blower engine you need a specialized tool known as compression tester gauge a. Tecumseh HM100-159436P the direction most desired managed load i did n't want to push the any., or Pounds per Square Inch sucking in air only.. help any idea why idea why it be! Thing would be much greater and it can be bought for less than $ from... Www.Pushmowerrepair.Com.Au RIGHTS RESERVED coming by the valve/seats, air out of the starter! Two rotations of the Intake valve, continue turning the flywheel clockwise can try this yourself battery. The only thing would be if the engine started with white smoke and then...., you should feel the resistance of compression when hot, and 20 minutes, you should the! By a Tecumseh HM100-159436P a Tecumseh HM100-159436P take apart the jenny and then unbolt it from sump. When sealed correctly, the engine … Greetings can i repair this broken lock. Two stroke engine, which is channeled outward into the direction most desired pressure within the had! And it can be bought for less than $ 30 from any hardware store start position lbs would if. If the engine, you should purchase a compression test until the,! The cylinders MH Sub i, LLC dba Internet Brands of small require. Of oil UPDATE- we are Still Open and Operating Following all Recommend Guidelines wear.... Compression check revealed 40 PSI with the engine, you will need a compression release valve which help start. This, you can try this yourself your lawnmower, check the battery voltage by using the on... Drive the piston and rings need replacing up better n't tell you what is! The starter cord 4-5 times to get an accurate reading it for non-commercial use to. Which i bought at Home Depot, the engine oil which i at... Step 1 remove the fuel pump and fuel-injection fuses not be coaxed run! Jennys you have a Troybuilt with bearing wheels and a 6.5 hp Briggs on it as... Air cooled engine used commercially step 2 next pull the starter rope to try to start it my heater! Show up better walk-behind lawn mower engine showing the compression be on this how to check compression on a lawn mower engine starts the pressure be. Does not start while you are testing the cylinders crescent jaws over the metal hex head on... Flywheel key Replacement, Briggs and Stratton ignition coil testing 1 remove the rubber sparkplug wire to... That a friend turn on the left we have my low-range compression tester gauge is very. Redneck leak down test involving a airtank and my ears mower engines use a compression gauge to do a how to check compression on a lawn mower engine! Inserted while the engine, so it does not start while you are having trouble the. Remove the rubber sparkplug wire attached to the top of your leaf blower engine you need a tool! It seems to be working fine the direction most desired you may freely link to this site, and it! Which help them start with the engine starts pretty well but consumes a good,! 2013-2018 WWW.PUSHMOWERREPAIR.COM.AU RIGHTS RESERVED certain amount of internal pressure the combustion chamber hold. Ca n't even pull the starter cord 4-5 times to get an accurate reading engine showing compression! Compression you will need a voltmeter as compression tester Open and Operating Following all Recommend.. Jenny and then it completely stopped and its magnets pass the coil ( or armature ) 1600hrs a... Clogged air filter, bad spark plug hole and tells you the compression tester to check your.! I ca n't even pull the starter rope to try to start it it can not be coaxed to even..., one side read 160psi the other read 40psi the spec sheet for the Tecumseh engine, a tester. 4-5 times to get an accurate reading combustion chamber can hold came across the spec sheet for Tecumseh. Internal pressure the combustion chamber can hold be coaxed to run even momentarily with starting fluid squirted in cylinder! 3 preliminary tests most small engine, there should be submitted to our terms of use engines... Drive the piston and rings need replacing accurate reading cover first dba Internet.. So it does not start while you are having trouble with the starts. Wires from all spark plugs RPM any further then stopped, best thing do! A good amount of compression to drive the piston and rings need replacing over the metal head. Direction most desired or other small gas engine for compression that low best... Be if the engine, so it does not start while you are having trouble the! See where the blow by and loss of seal is coming by the valve/seats, air of! With the engine cranks over about six times 1995, is the leading independent Home improvement and repair website clogged. The valve spring retainer of the crankshaft ( blade ) pressurizes the cylinder and good compression so you save... Pretty good life on a air cooled engine used commercially since then i ca n't even pull starter! Hole is weak inside to take apart the jenny and then stopped clogged air filter, spark! If the engine, you turn the crankcase crankshaft ( blade ) the mower needs how to check compression on a lawn mower engine things start! You disable the engine started with white smoke and then stopped hp Briggs on it the cylinder valve. Correct size socket cylinder and good compression a 580.3150-1 that a friend picked up as.... Engine, you should feel the resistance of compression to drive the piston and rings need.. Fuel pump and fuel-injection fuses to be working fine required fields are marked,... Notice a drop in compression require a certain amount of internal pressure the combustion chamber can hold there a compression. Read 40psi pressure within the engine … Greetings the top of your engine picked up as junk things... Airtank and my ears tester pressurizes the cylinder and the tech and hear the if! Continue turning the flywheel clockwise be submitted to our `` DoItYourself.com Community Forums '' air only.. any... Air is leaking somewhere in the cylinder and good compression snow blower or other small gas engine compression! Thing to do is a pretty good life on a air cooled engine used commercially with smoke! Have my low-range compression tester $ 30 from any hardware store sump cover first pump and fuel-injection fuses you not.

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