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I have a Gravely 36" mower (about 4 years old) with a 12.5 hp Kawasaki FB460V engine. The engine will not start and when it did awhile back, it took 20 pulls to get it running. I just checked the compression and it came in at 25psi. I can buy a new motor for $550 online and install for another $100.
Does the engine need to be rebuilt? I think so but asking the experts now. Is it cheaper to replace the engine?
Thanks in advance.
02-10-2004, 02:03 PM
Once you get it started, how well does it run??Does it have a new air filter, sparkplug, and are the coils in good shape? If so, does it lose power when you start to cut grass?? If so, then yea, it may need to be replaced...I don't know what the compression is supposed to be, but a mechanic should be able to tell you...
02-10-2004, 02:29 PM
That series Kaw had two things you absolutley need to have if all that godbeus mentioned. Remove the air filter and look down the throat of the carb intake. Use a small mirror if you can't see the choke butterfly...Then, push the throttle all the way open, until the choke is supposed to close. Make sure it closes all the way...If it does not, just spread the throttle linkage rod a little further apart until it does.
If that was it, great...With 25 lbs of compression, I think it would be this rather than the choke.... Let me ask, does your compression tester screw into the head? Or is it one of the rubber fit all ends? If you got 25 lbs with a screw in, I would be more inclined to beleive it... You can check the next part with a leak down test...Screw in an air chick to the cylinder at TDC, then connect it to your compressor....Pre4ssureize the cylinder and listen to where the air is comming out,,,Check exhuast first, that valve was usually the one that would wear.
Being you engine is at the 4 year old mark, Kaw's had valve issues. Get a new set of valves, cost of about $75.00, install them and your problem will go away.
Yes, the compression tester is the screw-in type. I think it works well as my other mowers compression came in over 100. Would it be possible the rings are bad? Or just the valves?
02-10-2004, 05:22 PM
On that one, more likely the valves...Thats why the leak down test...You can either make one, or they got them at the autoparts stores for about $10.00. Snap Ons cost $60.00 and comes with a cool little case and a whistler for when the cylinder hits TDC.
02-10-2004, 07:59 PM
With pull start engines you are always better off doing a cylinder leak dowm test rather than a compression test. Most engine shop manuals say this. A gasket set and a set of valves are cheap enough and easy enough to do yourself. Also reringing it is no big deal either.
02-10-2004, 11:58 PM
A leak down test tells more about the mechanical sealing of the engine than a compression test. I dont know for sure on this model but many engines have a decompression feature that opens the exhaust valve just a little to make it easier to turn over. This will give a low compression reading. It is possible for the valves to be out of adjusment also. A valve with no clearance will not close all the way and leak compression. Verify valve clearance and check leakdown again. As stated above, listen to see where the air is leaking. If its leaking out the dipstick hole then you would assume the rings or cylinder are damaged. If you can hear air coming out the muffler then you would assume the exhaust valve is leaking and if you can hear air coming out of the carb that would indicate a leaking intake valve.
I appreciate all of the advice. I will conduct the cylinder leak-down test tonight. If I need to replace the valves, can someone direct me to where I can get a schematic for this engine?
02-11-2004, 10:22 AM
Usually a dealer can help there, but if you have a fair understanding of engines, this is pretty much a no brainer. Pull the air shroud, starter, flywheel, and cylinder head.
After you get those off, I'm not sure if the coil has to go as well, but the valve spring cover is there. Unbolt it, and there are the springs. If you don't have a va;ve spring compressor, you can use an open end wrench between the block and the valve spring retainer to pull the keepers. Wha la....This should get you started.
02-11-2004, 01:20 PM
Do these and also the 14 horse Kawasakis have a compression release for starting and if they do can you get a accurate reading with a compression gauge?
02-11-2004, 08:34 PM
This is a link to the FB460V on Kawasakis website. It shows the cam and valve mechanism. It does not appear to have a compression release. If you have the model and spec numbers you can look it up on their site.
You get a very accurate compression reading with or with out a compression release. The problem is that with the decomp you will have a reading the looks too low and makes you think that there is an engine problem when there isnt. Thats why you do the leakdown test.
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