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Re: no spark on my venox 250?
Possible failure of the ignition unit. you need to trace the voltage to the coil, the trigger voltage if absent then the ignition system is defective. Check the input and also the 12 volt to the coil , if coil is heating it can be faulty.
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Need Make/Model/Year/Engine Model/Deck Size, and hours on meter if you have one. A short description of the events preceding the beginning of the problem is also helpful.
1. Needs a valve adjustment or a valve job. Start with adjustment.
2. Needs new plugs. Start with new plugs.
3. Shear pin under flywheel is slightly damaged throwing off the timing. Remove flywheel examine shear pin for any damage. Just go ahead and replace it; if it even looks nicked or sliced.
4. Coil, or spark plug wire, is going bad. Very hard to test a coil for weakness without test equipment that the average person doesn't have. Check the first 3 problems, first. If it still backfires, then replace coil.
5. The other thing that causes backfire is fuel mixture too lean. On a small engine this is not usually an adjustment problem. It may be the fuel system/carburetor is dirty or partially clogged. It may also be an air leak in the gaskets of the intake manifold. If nothing else solves the backfire, remove the carburetor and clean or rebuild it. This is the least likely of the options so save it for last.
If compression is good and cylinder leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery or ignition problem (fouled spark plug or bad plug wire). A power balance, or cylinder balance, test should be run on a twin cylinder engine.
If an engine is hard starting, runs rough, misses or lacks power, run a cylinder balance test to determine if both cylinders are operating to their full potential. You will need an engine tachometer, a spark tester, and an insulated screwdriver.
1. Using the spark tester, with the plugs in, start engine and verify spark is equally good on both cylinders. Remove spark tester.
2. Connect engine tachometer.
3. Run engine at top no load speed. Note rpm.
4. Ground one cylinder spark plug with screwdriver. Note rpm.
5. Ground other cylinder with screwdriver. Note rpm.
The difference in RPM between the cylinders should be less than 75 rpm. If the difference between the two cylinders is greater than 75 rpm, the cylinder with the least rpm loss is the weakest and is a potential problem.
Note: If the spark plugs are new this could be an indication of a weak coil. Of course it could also be compression (rings), or valves.
There is a simple test you should do on this unit. first remove engine cover, then remove spark plug, then take soapy water and spray it around the base of the cylinder where it meets the crank case, if you have compressed air and a air gun, shoot air through spark plug hole and watch for bubbles around base of cylinder. be careful to only shoot very low pressure into unit. if you see bubbles there is an air leak, this is not repairable. new unit.
Do a compression test. Check for spark at the plugs BUT best to have new plugs.
on any four stroke engine, you must have three things for the engine to run. You need fuel, spark, and compression. The easy one to check is the fuel. Take your air filter off and make sure you're getting fuel to the engine. Then, check your spark. Pull the spark plug wires off the spark plugs in the head and insert another set of plugs in the wires. Ground the plugs against the engine, turn the ignition switch on and press the start button. Watch the plugs to see if you have spark. The next test is compression. With the engine cold, remove the spark plugs. If you have a compression gauge, connect it to one of the heads and spin the engine over with the starter. If you don't have a gauge, simply put your finger over the spark plug hole. Turn the throttle wide open and press the start button. You should show about a hundred pounds of compression if you have agaugeor the compression should blow your finger off the hole with a good deal of force if you're checking it that way. If you have all three of these and they're timed correctly, the engine should run. If the engine won't run, find out which of the three elements is missing and work from there.
Hi Anonymous, remove spark plug wires off of plugs, leave spark plugs in heads. Use a 3rd known good spark plug to check for spark.
Insert 3rd spark plug into any spark plug wire, ground the threads on bare metal like the edge a cylinder fin. Turn ignition switch on and make sure run/stop switch is in run position and the bike is in nuetral. Hit the starter button and watch for spark. Good luck
I don't know where it would have gone to...
On a more serious note: Your engine is an "Interference engine". What this means is that if the timing belt breaks, one or more of the valves will get hit by the pistons causing severe engine damage. The cylinders can be leak tested by removing the cams and putting compressed air into the spark plug holes to help assess the damage. In most cases, it can be fixed by removing the cylinder head and replacing a couple valves. In more severe cases, the pistons, the cylinder walls, or the cylinder heads can be badly damaged. It will be impossible to tell you exactly what needs to be done without some testing and disassembly. It is not likely to be cheap at any rate. It's more like if it is going to be expensive or is it going to be REALLY expensive?
Ok, let's troubleshoot that cylinder. Is this a 4 cylinder engine? If not, please tell me which engine you have. If yes, #1 is closest to the belt. Remove the spark plug and look it over. Is it clean and just a little brown? If it is dirty, clean it up.
Next push it back into the plug wire and hold it with an oven mit against the exhaust manifold. Make the threads contact the metal of the engine while someone briefly cranks and then shuts off the engine. Note, it could be loud if the engine actually starts. You can avoid that by taking the coil loose from the coil, but remember how it goes back. While the engine turns, watch for a spark at the plug. If the spark is strong and periodic, the ignition is working right and the problem is probably with a valve or injector.
If the spark is absent or not rythymic, the problem is the plug or wire. Try putting the plug into a different wire and redo the test to see whether it's the wire or the plug itself.
If the ignition system, plug and wire are all good, we need to troubleshoot the cylinder.
The first test to do is this case is a compression test. If you can borrow a compression tester from the parts store or a friend, etc. test all cylinders and write down the pressures.
If you get to this point, please get back to me. We'll get this figured out.
Hi Jeff when you say the engine will not turn over if your saying when you turn the key and hit the start button the engine will not crank over like its locked, if that's the case and you have a fully charged battery you may have a cylinder full of gas causing hydraulic resistance. You would have to pull the spark plugs out and crank the engine to push put the excess fuel from that cylinder,(caution move your plug caps away from the spark plug holes because fuel will spray out and a spark could ignite the fuel) and take note if that is the case you have a stuck float or needle that is stuck or worn on that carburetor.
If that is not the case and your saying the plugs are wet and won't start you can pull the fuel tank and use starting fluid to start it but be careful with that stuff highly flammable you don't need much.
In any case when you get it started your still back to square one there
is a problem that needs to be taking care of.
Since you are getting sparks to all the plugs thn the problem could be tht of fuel to those two cylinders 2 & 3.
What was the condition of the spark plugs in those two cylinders? ( 2 & 3 ), were they wet or dry?
Try te following,
Swap the spark plugs form the firing cylinders and fit them to the cylinder 2 & 3.
Try to block up the air intake side of those two cylinder carburator and start the bike's engine see if they would fire, if they do fire thn theres a problem to those two carburators, fuel is not going into the combustion chamber, the problem could be float level , or the jets may need to be blown with compressed air.
Hope this helps!
FIRST OF ALL YOU NEED TO RUN ENGINE FEW MINUTES DONT GET IT TOO HOT. TURN OFF ENGINE. THEN PUT ON SAFETY GLASSES. USE COMPRESS AIR BLOW DEBRI AWAY FROM SPARKS PLUGS.TO KEEP FROM GETTING INTO CYLINDERS.DISABLE YOUR SPARK IGNITION.AND DISABLE FUEL PUMP.BY REMOVING FUSE.NUMBER AND TAG SPARK PLUG WIRES.REMOVE ALL PLUG WIRES AND SPARK PLUGS.BESURE YOU NUMBER THEM AND TAG THEM SO THEY GO BACK IN THE ORIGINAL PLACE.THEN GET COMPRESSION GAUGE TESTER SCREW IT IN SPARK PLUG HOLE TO CYLINDER 1 FIRST.TAKE YOUR FOOT PRESS ACCELERATOR PEDAL TO FLOOR.PUT KEY IN IGNITION SWITCH CRANK ENGINE AROUND A FIVE TURNS.THEN CHECK COMPRESSION ON GAUGE.IT SHOULD BE NO LOWER THAN 100 PSI.IF SO SQUIRT SOME OIL IN THAT CYLINDER. IF COMPRESSION INCREASES.THAT CYLINDER HAS BAD RINGS IF OIL SQUIRT DONT INCREASE COMPRESSION. VALVES IS LEAKING. YOU DO ALL CYLINDER THE SAME.SCREW COMPRESSION IN PLUG HOLES.TURN ENGINE OVER 5 ROUNDS. WRITE DOWN ALL READINGS.
How to Test Engine CompressionAn engine depends on an equal compression reading in each cylinder to run smoothly. If poor compression exits in one or more cylinders it can cause a rough idle condition and low power. A compression test can be performed to check wear or internal damage. To start a engine compression test gauge is needed. There are two types of gauge styles, one threads into the spark plug hole which is more accurate. The other style of gauge is constructed with a rubber plug that is meant to be pressed against the spark plug hole, this style of gauge is difficult to use. To perform a engine cylinder compression test follow the steps below.
Remove ignition coil connector or ignition system fuse to disable power to the ignition system
Test ignition system to ensure that the power to the system has been disabled
Remove #1 cylinder spark plug and insert compression gauge, most gauges have a hose attachment that is installed into the spark plug hole with the gauge connecting to the gauge hose.
Engine Cylinder Compression Gauge
After the compression gauge has been inserted, use the starter to crank the engine over for about five seconds. Use about the same five seconds to test the remaining cylinders.
Record the compression reading as each cylinder is tested
Remove the compression gauge and reinsert the spark plug
Follow this procedure until all cylinders have been tested
Compare cylinders compression reading, all readings should be within about 5% of each other
If low compression exists a cylinder malfunction exits and further inspection is required. Possible causes for a low compression condition are: burned intake or exhaust valve, broken piston or piston ring, broken valve spring or a blown head gasket.