Kawasaki FH721V Starter

[Mr Mower Man]

I'm working with a 25HP Kawasaki FH721V-DS23-R. The customer thinks it's blown up, but I really don't think so, even though it has nearly 1100 hours on it. Someone told him the rings were worn out, but my leakdown test invalidates that conclusion. It seems to have a slight exhaust valve leak on one cylinder, but the air escaping past the rings is low on both cylinders, according to my leakdown tester.

I ran a compression test, and I get 100 lbs. from one cylinder and 80 lbs. from the cylinder with the slight exhaust leak (makes sense). Kawasaki tech support tells me that compression should be at least 90 lbs. 80 is a little too low, but I think there's a reason for that which has nothing to do with compression.

I think the problem is the electric starter, which is turning the engine over at only 100 RPMs, which I don't think is fast enough for the engine to run. This is a "new" rebuilt starter that the customer got cheap from his buddy. By the way, it sounds awful. I took the plugs out to see how fast the starter would turn the engine without compression, and it was still only 200 RPMs. When I tested one of the new Kawasaki's on my new ZTR inventory, the starter turned over at 530 RPMs under compression! I think I've found my problem, boys! If the starter was turning the engine faster, it would start up and run a lot better for him. A faster starter would also make the compression readings higher, no? It's not engine drag, either. I can turn it by hand with no problem. Battery tests OK with 344 CCA. I guess it could be bad connections within the starter circuit, but I really feel that the starter's the problem. No need to replace the engine.

I wanted to run this past you guys, to see if anyone knows the minimum number of RPMs an engine needs to turn before it will run. Kawasaki has no spec for that. What do you think?

By the way, I checked ignition and carburetion as well. All seems to be well!

[Deere2me]

Since it's in front of ya, I would check the valve adj.,(could be too tight) and also verify the ACR is workin'.
In addition, It's lookin like the starter ain't up to snuff. Have you done a voltage drop test on it? Some ( DB Electrical) of the bootleg starters have a pretty good warranty, might wanna look into it.
Don't know the min. rpm for startin',but ya gotta figure, the more the better, right?
If you're the calculatin' type, ( I ain't doin' it for ya) You could figure the crankshaft RPM by counting the ring and starter pinion teeth and using the starter motor RPM as published by KAW. Should be avail inna manual.

[bobodu]

If you pulled the plugs and it still turned slow, I lean towards a low voltage condition. Try jumping straight to the starter lug off a known charged battery. BTW....an amp test has nothing to do with the voltage. You can have 1000 amps in reserve but only 7 volts.

[bgsengine]

If you pulled the plugs and it still turned slow, I lean towards a low voltage condition. Try jumping straight to the starter lug off a known charged battery. BTW....an amp test has nothing to do with the voltage. You can have 1000 amps in reserve but only 7 volts.

Actually , checking the starter's draw in amps is a valid test. If you remove starter and hook it direct to a fully charged battery to bench test it and get high amps draw compared to a known good starter, or published specs, then you found the problem.

But I agree battery amp test does not really tell you a whole lot except the battery can deliver x amps at x volts and would have nothing much to do with starter diagnosis beyond knowing whether battery is capable of cranking the starter over.

I would start with a Voltage Drop Test, as Deere mentions, and from there if it proves out, pull the starter and check how much it draws in amps - unloaded, it shouldn't be more than 60 to 80 amps or so I would think (dont have specs, but I am sure there'll be some somwhere) - if it is considerably more than that you got a bad starter, which would explain your cranking problem.

[bobodu]

But he didn't say he checked the starter draw.....he said the battery checked.

[Mr Mower Man]

A little update guys:

I took Dad out after dinner because he wanted to hear the starter turn the engine over. As I mentioned, it sounds awful -- it sings pretty loud. Dad took a look at how the starter gear meshed with the ring gear, and he said it was too close. I could see how the teeth of the ring gear had been bottoming out between the teeth of the starter gear, and vice versa. We loosened the starter and stuck a couple of washers between it and the block. Now it turns a lot faster and quieter. Not as good as one of my new ones, but much improved. I'll see if it'll run in the morning.

[Mr Mower Man]

Well guys, that did it! Using washers to put a little distance between the block and the starter cured it! Turns over just fine. Even better, it runs great! I think my customer will be happy that his engine doesn't need to be replaced after all.

Problem is, I broke off a torx socket in the valve adjusting screw as I was trying to adjust the valve lash. Oh well, don't sweat the small stuff, right?