Kawasaki 25 hp V-twin

Did you try testing the coils with a multi meter? I think the resistance thru the primary windings should be ~.5-2.5ohms and the secondary ~2500-5000ohms.

 

I don't like using resistance to test coils...VERY unreliable, doubly so on an intermittent problem like this.
You can do the test, might get lucky and get a difinitive reading like open, or continuity to ground, but usually what happens you get a reading that is just outside of their specs, and a new one doesn't fix it...that crap doesn't fly at a dealership (at least an honest one) so coils (of any kind, not just ignition coils) get condemned on voltage test instead...but sometimes those numbers can be hard to come by, Honda was tight lipped about voltages back in the day, heck the only way I found out that they actually had voltage specs was by going to their tech training, the American Honda guys shared the numbers with us that Honda Japan kept secret (and they wrote the manuals then) I think that info is much more available since then (I dunno, been away from it for over 18 years now)

 

Thought about it, but there are big warnings all over service manual stating "DO NOT TEST THESE COILS WITH MULTIMETER OR STANDARD OHMMETER. TESTING THESE COILS WITH ANY METER OTHER THAN JOHN DEERE XXXXX WILL CAUSE SEVERE DAMAGE."

 

Yep. Sorry, I should have been more clear. I have no problem using dino or full synthetic, although I usually stick to Deere OEM fluids for Deere machines, since they run some pretty tight specs.

My mention of it was not because I loaded full-synthetic, but because I had mixed the two, probably approaching 50/50, given how bad the machine was leaking dino thru front main seal, and how much it took to come up flush again. I've been told before to use one or the other, but never mix them. Not sure if there's any real merit to that thinking, but figured I'd mention it, in the spirit of full-disclosure.

 

New fuel pickup tube installed. but still exhibiting the same problems, so that wasn't it. The old one was soft, and did have a bit of a kink in it, so I don't regret replacing it, as it would have likely become a problem someday in the next few years. Just like the new heads and other items, they were showing their obvious age (2007 model), but they weren't the acute problem.

The new ignition coils are here, so I could do those next, but I'm wondering if that's the right path. I noticed today it's idling way slower than usual, to the point of stalling at idle. I had readjusted ungoverned and governed low idles just a week or two ago, during the rebuild, so it shouldn't be out of adjustment. It's also an intermittent problem, slow idle was just fine when engine was cold.

Does this point toward a carburetor problem or an ignition problem? I have all new carburetor and spacer mounting gaskets from rebuilding the top end, but did not touch the carburetor itself.

 

Does it sound rough when it's idling "too slow"? If so then I'd say it's running on one cylinder, which points to coil

 

Well, it was not running on one cylinder previously, at least in any fashion continuous enough to detect, I’d checked previously several times before by comparing exhaust and head temperatures. But this morning, I fired it up cold, and could tell right away it was one-legging it. First time it’s ever misbehaved cold.

Quick grabbed my little spray bottle of water, and could see left exhaust header tube was hot, but right was cold. Shut down swapped the old coils for the new pair I’d ordered, and it’s fixed!

Of course I need a chance to re-adjust idles and do a mowing with it, but idling in the driveway several minutes, and throttling up/down, it seems to be back to its old perky self.

 

BTW, the one unresolved issue is positive crankcase pressure. The result of this is that any small leak in any seal causes the engine to blow oil all over the machine... leading to things like overheating coils and heads, which is what got us here in the first place.

If you go way back to the beginning of the thread, you'll see I did a leakdown test, and the rough "good / bad" indicators on my gauge call the results of this engine's test "good". But I'm dubious of any "good/bad" indication that does not take at least the piston diameter into account, since small pistons should leak a lot less than big'uns.

Given that we have a new breather, new heads, new valves, new head gaskets... I'm coming to one of two conclusions:

1. These Kawi V-twins always show positive CC pressure, and the manual is just full of sh*t in implying otherwise. But many youtube videos seem to refute this, showing this is a symptom of a typically bad breather, albeit on versions of the engine with much simpler breather arrangements.

2. My pistons/cylinders are just so leaky that I'm getting that much blow-by. I would be surprised, as the machine was already pushing oil out around the oil cooler o-ring when I inherited it around 300 hours, indicating the engine was already showing positive CC pressure even back then.

 

Just my 2 cents on this and feel free to take it or leave it , that is up to you.
"IF" an engine is broken in with synthetic oil there is a chance that it will glaze the cylinders and the rings will not/ seal as they should. Without going back and reading this thread I do think you mentioned that the cylinder walls were very smooth.

Again take this for what is worth.

 

how were the pistons? maybe broken ring land?

 

Its been my experience that just in general V twins huff n puff out the crankcase a lot if you open while running. (Some more than others, depending on crankpin timing/etc) And all piston engines have positive crankcase pressure, unless measures are engineered into it to deal with that (I would expect that engine to have a hose going from a valve cover to the air filter box)
And all engines will leak oil out if given the opportunity, never heard of one sucking into the crankcase...if you think about it, all old engines would have vapors coming out of the breather (when conditions were right to see it) until the EPA mandated that be captured instead of vented to atmosphere.

 

You are 100% correct , there is no such thing as a piston ring that does not have some type of leakage. Ring gaps , cylinder bore being perfectly round and lets face it , a piston ring is a sliding seal made of ( lets just say cast iron for this application) that is trying to seal against a steel cylinder wall that has hone marks which are essentially controlled scratches.
This is why we have PCV systems , vacuum pumps and dry sump systems to control the oil vapor.
Granted this is just a mower; but an internal combustion engine is an internal combustion engine no matter what the application or the way you slice it. This would use the hose to the air box just like a PCV system works.

Again take it or leave it.

 

Engine would have been broken in on OEM Deere dino oil. It's a 2007, and original owner did none of his own maintenance, but just had local Deere dealer retrieve and service them each year. He was running about 70 hours per year.

Maybe. As noted previously, the leak-down looked reasonably good, although not equal on both sides. Bores no longer had much in the way of cross-hatch marks, and there was even one small spot of slightly different sheen, which I took just to be potential piston slap area at tail end of piston skirt, there was no associated divot or low spot... just slightly different sheen in that one area. There were also no measurable ridges, which anyone who's tried to extract pistons from an old cast-iron engine block would know well. These appear to be hardened moly sleeves in an aluminum block?

As to the rings, I didn't extract the pistons, so anyone's guess... but leakdown and compression both looked pretty good.

Old machines definitely puffed, running either side of neutral pressure on each piston stroke. Maybe I just got onto the wrong rabbit trail, with my thinking, here.

There is a PCV breather and tube, and I swapped the breather, as many reported it a likely source of failure. It was fine, but I swapped it anyway, since I was in there.

I can't remember how well I inspected the tube. Getting it back out will be a bit of work though, it's buried under the air cleaner and mount assembly, and the carb mounting bolts run thru that. Probably something I'd put off until winter service interval, at this point.

 

That should be more than good , first break in is what counts.
70 hours a year is next to nothing. Less than 2 weeks of work a year. (on a normal day if there is such a thing?)

Hope you get it straightened out. Something like can drive you nuts.

 

This is probably a long shot and may have zero effect for your situation, but, I'll go ahead and explain my experience with a JD tractor and a kawasaki engine. Mine is a GX335. 20 hp. It started running badly and it turned out it was the air filter. As in they came with two different filters depending on where the crankcase vent went. One was more free flowing than the other according to the dealer. I ended up with the wrong one and it was to restrictive. It caused it to run rich and draw oil into the carb through the crankcase vent. The trouble stopped with the correct filter for the internal crankcase vent that mine has.

The other issue, at a different time, was using a non oem, to small of micron fuel filter. It starved it for fuel despite seeing the fuel in the filter. I installed the oem filter and that problem hasn't returned either.

 

You probably wrote this before getting to the last post, the issue was fixed by swapping the ignition coils, with the right one being clearly bad. But to answer the issue:

This motor actually has the "heavy duty" air filter system, big canister filter about a foot long with dual coaxial pleated elements, like you'd find on larger diesel tractors. I blow out or replace the outer element yearly, and inspect the inner. The inner pretty much always stays as clean as new, it almost appears to be just a backup for a failed or defective outer.

I run OEM fuel filters in this machine, in fact I've taken to running that Deere filter in all of my OPE. It's the same 1/4" inline filter you find almost universally on all brands of equipment, but by buying it from Deere, I know I'm getting a part that meets their usually-relatively tight specs. I think Deere charges $3 for it, and I can buy the same for less than $2 from generic brands, but that extra $1 is cheap insurance... times four machines per year.

 

I'm glad you got it fixed. I finished reading the whole thread. What an ordeal.

 

Yes, the inner is an insurance policy for the outer, and also catches fines that may get through the outer...where most people screw up is taking that inner out when they are servicing the outer...unless you are gonna change it, leave it in place. Also, make sure they isn't a pile of dirt built up waiting to get into the intake when you have the filters out. Guys the work in shops that service a lot of commercially used machines will tell you that they see plenty of "dusted" engines where they basically destroyed themselves sucking dirt that got into the intake by "over servicing" the inner filter and/or pulling it out to change it without cleaning the buildup out of the housing first. If you are doing everything right that inner filter will outlast 2-3 outers.