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dubaholic2
04-10-2010, 04:31 PM
i just bought an older scag sw36-13ka walk behind from a friend of mine. the mower has been sitting for about a year, but was said to run fine prior to that. i tried starting it, but nothing. so, i started out by replacing the plug, all fuel lines,fuel, and fuel filter. i also took the carb off and soaked it in carb cleaner for about 24 hours. took it apart and made sure all passages were clear. i put it all back together and still nothing. i decide to check the woodruff key in the crank. pull it all apart, key is good. i notice some rust on the pick-up and what im calling the magneto. the part thats below the flywheel. i cleaned them both with emory cloth, put it back together and still nothing. i can spray starting fluid in the carb and after a few pulls it will backfire, but other than that im getting nothing. by the way, the engine is a kawasaki fc420v. if anyone has any ideas please share them. thanks in advance, ian

balreadysaid
04-10-2010, 04:51 PM
Is the compresion really low? If u got spark and u got fuel I'd look twards compresion. I also have seen a valve get hung up from some carbon and make it act like it has all sorts of issues when it had none at all. Hey good luck !
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topsites
04-10-2010, 10:56 PM
Compression test sounds like a good next step to me as well.

dubaholic2
04-11-2010, 02:37 PM
any idea what the compression should be? also, i know the intake valve is moving. i turned it over and watched it when i had the carb off.

DT Lawn Care
04-11-2010, 07:19 PM
90 psi and above is probably a good figure. Just because the carb passages look clean doesn't mean they are. I would go back and spray carb cleaner (aerosol can) thru the jets and passages and all around, then blow thru them with compressed air. I have worked on dirt bikes and mowers, and the carbs look perfect, clean it out and it runs/starts like brand new. I would also check your spark, if you don't have a tester, simply put a new/good plug in the coil wire and pull the cord, you should see good or bad spark.

dubaholic2
04-11-2010, 09:46 PM
when i took the carb off and cleaned it i soaked it in carb cleaner for about 24 hours and then sprayed brake cleaner through every orifice in the carb. all were open and flowed good. the plug is firing. i have checked it several times, plus if it werent it wouldnt be backfiring when i spay starting fluid in the carb. ill check the compression one day this week and see what that tells me. thanks, ian

dubaholic2
04-12-2010, 09:50 PM
checked compression today. nothing. didnt even move the needle. i dont understand. it if has absolutely no compression i dont see how it would even be able to backfire. im puzzled...

kenneth meals
04-13-2010, 12:18 AM
I'd pull the spark plug, using a small snake pen light inspect the piston dome. Also turn the engine by hand to verify the piston movement. to rule out broken connecting rod or a hole in the piston. Then remove the rocker cover and turn the engine to see if there's cam movement.

DT Lawn Care
04-13-2010, 12:42 AM
checked compression today. nothing. didnt even move the needle. i dont understand. it if has absolutely no compression i dont see how it would even be able to backfire. im puzzled...

Check your valves. You probably have one stuck open

topsites
04-13-2010, 01:04 AM
Are you sure, when you checked compression, that you got a good seal?
Because if you've got 0 compression and if it's a recoil start, you should be able to PULL
that string and the engine should spin with almost no resistance...

I'll put it this way, pull the plug then try to start it, watch how that feels.
Then put the plug back in and try it again, there should be a noticeable difference.
If such a difference exists it is quite possible when checking compression, it didn't seal tight.

dubaholic2
04-13-2010, 11:39 PM
i know it sealed tight. i always double check the tester when im using it. im hoping all ive got is a stuff valve. ive looked into the cylinder and from what i can see of the piston its dirty, but doesnt appear to be hurt (not that i can see much of it). i think im going to pull the head off of it and check the exhaust valve. i know the intake valve is free, but i cant see the exhaust. it doesnt appear to be too hard to pull the head. thanks, ian

dubaholic2
04-15-2010, 09:26 PM
got time to pull the head off today to check the valves... i pulled the valve cover and the exhaust push rod fell out. i looked at the valve spring and it was completely compressed. got the head off and the exhaust valve is stuck completely open. i filled it full of p.b. blaster and im going to let it soak for a couple days. hopefully i can get it to unstuck without taking it apart. if anyone has any other suggestions for getting it unstuck please share. i greatly appreciate all the help everyone has given. great forum. thanks again, ian

dubaholic2
04-18-2010, 10:08 PM
got the valve moving again. got a new head gasket and put it all back together today. starts and runs great. couple other problems to address now. first, the trans makes kind of a clicking noise when in neutral. second and most importantly, the mower dies when the blades are engaged. i figure it has to be some kind of a safety, but ive yet to be able to find it. if anyone has any suggestions please let me know. thanks, ian