Question about kawasaki KX 250 Motorcycles

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I am working on a 2005 KX250F. It had a bad spark so the CDI was replaced. Still won't start. Compression is about 65 psi cold. Valves are fair using a leak down tester. Tried using starter fluid in the carb but still won't start. Not even a pop. I was told if the compression was under 88 psi then it's time to do a top end. Any ideas why it won't even try to run? David

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65PSI is way to low. It probably won’t run at 88PSI either. Put a small drop of engine oil (20w50 or similar) into the cylinder and do the compression test again. If there is a big improvement in compression it means the piston rings are worn and you will have to do a top-end overhaul. As a very rough guide you need 150PSI for a 4 stroke engine and about 120PSI for a 2 stroke engine.

Posted on Aug 21, 2010

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I have a 2007 Nissan Murano replaced all six cold packs all six spark plugs and it's me and it still missing really bad doesn't want to hardly at all and I has like a suction backfire

injectors are more likely the problem than plugs
clean/ replace injectors and check fuel pressure at the injectors
should be in the 50-65 psi range
run the fault codes first always and save money

Jan 08, 2017 | Nissan Murano Cars & Trucks

1 Answer

MZ360. What is compression in psi?

I have same generator. Will not start. Good spark, good fuel, good carb. Compression is 60 psi cold. Is this good? Bad? I can't find anything on what compression should be.

Oct 01, 2015 | Yamaha Electrical Supplies

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I have a 88 b2200. It shudder, jumps in all gears, has power loss and gains and poor milage. I've rebuilt carb, changed plugs and wires, disributer and pvc valve. Any ideas. Thanks

I would do a compression test of the engine. Spend about $40 for the gauge tester and do it yourself. Engine should be at operating temperature, remove all spark plugs, disable ignition by grounding the high tension cable from coil to distributor, screw in the gauge to one cylinder, hold the gas pedal to the floor-or hold the throttle at wide open, then crank engine for about 5 seconds. You will have a compression reading that should be somewhere between 100 psi and 200 psi. Anything below 100psi means not enough compression in the cylinder to produce power when running. Do each cylinder the same-crank the same amount of time for each cylinder( with wide open throttle). All compression readings should be fairly close-lowest reading must be within 75% of highest reading cylinder for a good, healthy engine.

If compression is low in any cylinder, it probably won't even fire the air/fuel mixture. Look for valve problems, valves not sealing (burnt valves cause this), or piston rings worn too bad, head gasket failure can cause low compression. Example, compression tested a Nissan, and readings were all 155-160 psi in all cylinders, so compression was excellent, engine was internally good. If you have good compression in each cylinder, look elsewhere like a plugged catalytic converter-won't let the engine breathe, or a problem with the ignition system-test for a snapping, blue spark when cranking the engine, on one of the spark plug wires. Others: check EGR valve for being stuck open, good luck, then.

Apr 06, 2015 | Cars & Trucks

1 Answer

93 Honda Civic dx will not start. new fuel pump igniter, has spark

sorry if you guess and guess wrong. really, must be expensive.

ok got spark (and timing is good, timing light test)

if test fuel ( use instant start in a spray can) fails, with spark

then engine is bad, compression is checked, see near 80 not 150+ PSI , the timing belt has slipped. if not changed by the book

they slip and the engine grenades (or bends valves)

this is an interference engine, never ignore the belt.

there is an acid test order.

1 compression good.

2 spark good, and timed

3 fueling is last. (if spark plugs dry add fuel, by hand)

cant burn fuel with no compression and spark. well with EFI it cant run right with bent valves either.

here is Chad running an engine (any) with no gas tank

even his battery is dead. and has external battery. for 12v power.

a real trooper.

ive done this 1000s of times. in 60 years.

his engine only makes 80 psi (old) and still starts.

but EFI will never do that not that low. compression

the cam slips and goes retarded compression drops to near 1/2

and the valve timing is so bad, the exh opens late and pollutes the

next last intake charge. the card house falls and then the valve bend.

take if from me, nostarts are a blessing on any honda

maybe it saved your valves.? do the service on time./

Dec 29, 2013 | 1993 Honda Civic 4 Door

2 Answers

I have a 99 sienna and the cylinders have low pressure what can i do?

If cylinder compression is too low, the car may not even start because of it. Have a shop do a compression test or a leak-down test to check the internal health of your engine. A good engine should have pressures of 150-200 psi in all cylinders and be close to each other. A worn or high mileage engine may have pressure as low as, say 125 psi, but if still balanced (close readings), would still run decent. Compression below that, especially below 100 psi, is serious trouble. ignition spark refuses to ignite the air/fuel mixture and you get a misfire-a non-working cylinder. Low compression can be caused by worn piiston rings or poor valve sealing. Low compression in 1 or 2 cylinders can be a valve problem, burned valves or valves not seating properly.
A leak-down test will check each cylinder and if there is a problem, the test will find the cause of the problem.

Dec 11, 2012 | 1999 Toyota Sienna

1 Answer

Engine turns over but doest start ive checked the spart plug its fine the batterys charged an all the elictrics are working petrol and oil is fine ? any ideas

you should first do a full inspection before you try to get it running. If this is the case, I'd do a compression check first because it's easy to do. First, check the quantity and condition of the engine oil. Hook up or purchase a good battery. Leave out the spark plug and crank the scooter for ~5 seconds. This helps to circulate the oil. Let it set for ~15 seconds and then do it again. It's not a good idea to continuously crank the starter because it can overheat and wear out prematurely. Most scooters need a minimum of 100 psi in compression in order to run start and properly. Compression should be checked when the scooter engine is warm. However, that's hard to do if your scooter is not running. So, just hook up a compression gauge and open up the throttle all the way. Crank the scooter until the needle on the compression gauge stops moving. This should take no more than 5 seconds. Very roughly, 100-125 psi is good, 125-150 psi is very good, and 150+ psi is great. If you don't have this level of compression, then you have bad valves and/or bad piston rings. If you want, you can add a teaspoon or so of oil to the engine through the spark plug hole. Then try the compression test again. If compression is higher, then it's likely you have bad rings. The oil will seal the rings and give you better compression. If compression is the same, then you have bad/misadjusted valves.

hope this helps


Aug 12, 2011 | Peugeot Sports Vision R3 Motorcycles

1 Answer

The Stihl 038 super won't start. It is getting too much gas on the spark plug when I try to crank it. Just replaced the carb hoping it was that but still it won't start. The saw was working fine a...

hi there mwb15
have you made sure the ignition coil is producing enough voltage to fire under compression load ?

you may get a spark at the plug unloaded but under load it may be breaking down / weak making you think its got a fuel problem ?

does your system use a cdi coil system or point/condenser system ?
spark usually falls into weak spark, no spark catergory

if compression , fuel ( you replaced carb) and exhaust are ok , and you have air and vaccuum tight c/cases only things left are timming and spark

remember F A C T S

F = Fuel A = Air & ( air tight c/cases ) C = Compression T = Timming S = Spark

compression should be about 130- 140 approx if in good running order

take a look and let me know

cheers pauly46

Jun 18, 2011 | Garden

1 Answer

How to test CDI unit for KTM65 2009 to diagnose if faulty or not.

If you are able to use a digital volt meter and work your backwards from spark plug wire to coil to cdi to stator you can figure out where voltage stops.thats a fairly newer bike unless you really submerged that bike under water i dont think its the cdi could be coil wire it could be want to check or change the cheaper parts before you go right to cdi because there not cheap.I have a yamaha banshee 350 and she was breaking up real bad.I thought because it was only happining on top end that the cdi was breaking down or stator was going bad.Found out with meter it was the coil wires and spark plug boots.These items have to have a certain amount of resistance or the do not conduct correctly.And spark plug wires and boots are not that exspensive.So thats why I say start from sparkplug boot and work your way back.Try that and Good Luck.

May 09, 2011 | 2009 KTM 65 SX

2 Answers

Number 8 cylinder has 65 psi in it and the rest

put a few drops of oil in the cylinder and check again

If the compression comes up then you have a cylinder issue, Time for a new motor.

If the compression stays the same then its a valve issue.

To have the heads done providing no parts are replaced cost about 200 a head (400)

The labor alone could cost 1000 bucks or more if a shop does this for you

Dec 11, 2009 | Heating & Cooling

1 Answer

2005 crf100f extremely hard to start when cold. A

If the bike has been in storage for any length of time, more than a year or so, the carburetor is plugged up and needs to disassembled and cleaned. If that's not the case do a compression check. You need to see at least 140 psi of compression for it to start reliably. If the compression is low, adjust the valve tappet clearances (tight valves will cause low compression).
Other than that, make sure the choke is functioning properly and that there are no air leaks between the carburetor and the engine.

Dec 04, 2009 | 2005 Honda CRF 100 F

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