Kawasaki 25 hp V-twin

Hey guys,

Long time no see. Still using my old username here, feels weird!

This one is right up MasterMech 's alley, but I know several of you guys are OPE experts, so let's see what you have to say about this.

The 25 hp Kawi V-twin motor on my zero turn started intermittently missing and exhibiting low power yesterday, and I noticed it's also leaking oil. It seems to have spark, and the fuel pump output is right on spec, so I did a quick compression test and found it's actually a bit high. Spec is 57 psi, I'm seeing 75 - 80 PSI... but it's an engine with 1200 hours that's never been scraped for carbon build-up, so probably not a surprise if it's a bit high.

I went to measure crank case vacuum, and found oil blowing out the dipstick hole. It's actually under a substantial positive pressure. So, figured it has to be the breather or the head gasket.

Leakdown test shows 17% - 23%, which isn't spectacular, but is still well-within the "good" (i.e. under 40%) range on my leakdown gauge. If I had a blown head gasket, I think I'd expect it to be worse than that, but really have no experience to tell me if that assumption is correct. It also wouldn't explain the intermittent aspect of the behavior, a blown head gasket is always blown, it doesn't come back and run fine for 30 seconds in between missing.

Lots of reports online about breather issues with these Kawi and Kohler V-twins, but oddly, none of the various photos and videos show a breather of the same type that's used in my engine. They all have a filter element with a cheap reed on the end, not the more complicated breather tube and screen with separate reed body that's apparently in my engine.

So, I looked at pulling the breather reed, but on this engine, that means a total tear-down. Rockers out, lifters out, cam out, flywheel off, split the crank case, etc. It's several days of work... not something I want to do if the problem lies elsewhere.

I spoke with the service manager at our Deere dealer (mower is a Deere) and he said they almost never see a failure of those breathers, but he sees a lot of breather cover gasket failures, the oil from which coats the cooling fins of one cylinder head. Yeah, I see that mess on my engine, but thought the leak was coming from the front main seal, due to crankcase pressure. He says the oil leaking onto the cooling fins of one cylinder causes grass and debris to stick there, and overheat that cylinder, the result usually being a burned-up valve on that side.

As bad as burned up valves sound, that's an awful lot easier to deal with than the breather, so I guess that's step 1. You guys ever seen this? Not sure exactly what I'll be looking for on the valve, other than possibly missing metal, as valves never look all that pretty when opening up 1000+ hours lawnmower engines.

 

My 2 cents.
If there is that much blow by it is blowing out the dipstick then I would look at two things you mention.
Breather being the first, if it is working properly then I would think about the ring seal . to me a 25% leakage seems like a lot but I am not a power equipment mechanic. In the car world that is a ton.
Kawasaki is known for overheating and either torching a valve or the seats fall out of the head when they get too hot. Biggest cause of this is clogged cooling fins , so if you run a Kawasaki keep the fins clean from debris.

 

With that low of a compression reading I'm guessing that it has auto compression release...does that need to be disabled to get proper readings? Or you just heard it leaking mainly into the crankcase at tdc when doing the leakdown?

 

I didn't even think about that but sure , great point.

 

Compression spec is 57 PSI, and I'm measuring 75 - 80 PSI, following the procedure outlined in the technical manual for this mower.

Crankcase pressure isn't necessarily a sign of blow-by:

1. Bad head gasket can allow exhaust gas into crank case via push rod channels.
2. Bad reed valve in breather can cause loss of crankcase vaccum, and thus relative high pressure pulse each time a piston travels down.

I think it's time to pull a head and check these valves, esp. with confirmation this motor tends to cook them. I blow it clean with a leaf blower after each use, but due to leaky blower cover gasket (known issue), one cylinder ends up caked in oil, and thus can't be blown clean. That was indeed the case when I pulled the shrouds from this one, although it's the cylinder with the better leak-down reading that was caked and clogged.

 

Got the engine degreased and hosed down in the rain today, back in the barn drying now. A hot job just came in that might keep me at my desk tonight and most of tomorrow, but I will definitely try to make time to get out there and at least pop one head off.

 

My God... I've had the heads off V8's quicker and with less work than this stupid little Kawasaki. A big part of the trouble was just cleaning the mess of oil grass and dust cooked well onto the cooling fins, but even beyond that, just miles of sheetmetal and linkage had to come apart to get the heads off.

Now that they're off, I'll admit it's not exactly new and beautiful, but I'm not seeing the sort of carnage I would have expected to go along with positive crankcase pressure and rough running. Let me know what you guys think:

Right head and cylinder:


Left head and cylinder:


Left valves out:


It's interesting the intake valve bore is half colored, but the seat itself is clean all-round. The service manager implied a burned and leaking valve would be the most likely cause of my positive crankcase pressure, but looking at the flow paths, I honestly can't imagine how. If a valve is leaking, I'd think it'd be leaking out the intake or exhaust... not into the crankcase, unless the valve guide were also blown.

Right head valves out:


The valves:


I know it's hard to see in the photos, but the contact surfaces of seats and valves are all clean and shiny, no obvious area of blow thru, and definitely no area of pitted or missing metal.

I'm swinging back toward my initial analysis of blown breather valve, but since that involves pulling the cam and splitting the crankcase, I think I may show this to a service tech before jumping into that.

 

OK , I will open my big mouth and say one thing after reading this. A leaking valve does not leak into the crankcase. I don't care if it is a lawnmower or a top fuel dragster it just doesn't. Think about it , it will either leak into the exhaust port and out the pipe or into the intake and out the carb. As far as leaking by the valve guide if it did it would be such a tiny amount , any leakage will take the path of least resistance and that isn't going to be past a valve stem. The intake is under vacuum so that valve guide will suck oil in if anything and exhaust under pressure so that valve guide would leak a tiny amount of exhaust if it was really bad. 99% of the race engines I do don't even get a seal on the exhaust side if anything a tiny amount of oil leaking by is actually a good thing , although it does not enter the combustion chamber it does keep the stem lubricated a little better under exstream conditions, just a seal on the intake since it will suck oil past the stem and into the combustion chamber.

Bottom line; I myself highly doubt it is a valve issue but my education is limited.

 

Hahaha...Got sucked in!!!

 

I'm here learning. I don't know these engines, but love the way they sound. Best industrial v-twin exhaust note in my book.

 

I have one on my ZT and it has been flawless , oil changes yearly and keep the fins clean. Never had to add a drop of oil between oil changes since I bought it.
Never even looked at a spark plug , for all I know it might not even have any.

 

Our Hustler ZT at work doesn't have 'em!

 

Exactly. And I have brought that point up with the Deere service manager, and then he changed his analysis to bad head gasket letting combustion gas down thru pushrod galley. I'm not seeing evidence of that, and I'm tiptoeing around the guy, as I know they don't love DIY'ers pestering them for free analysis. But I think he is wrong on both counts.

Yes, that was my first step, but there was positive pressure out of the dipstick tube. Almost broke my Magnehelic before I realized that.

No vacuum, it's quite clearly showing positive pressure. I also tried unscrewing the oil fill cap, and it blew off when I got to the last thread.

Also, remember engine is pushing oil out of breather gasket as well as rear main seal. There's pressure!

What's the take-away here?

Will-do. But also noticed valve guides have walked out a bit on each head, which dictates head replacement, as replacement guides are not available for this motor.

I'm leaning toward new valves. Heck, if I'm already doing new heads.

No worries on lapping in, been there done that, albeit only once every 10 years... just enough to be out of practice each time.

Dude... you have not seen the level of pizzed off I'll be, if I ever figure out this repair could've been as easy as a coil swap. lol...

Here's what we know:

1. Missing, low HP
2. Blowing oil out of every seam: main seals, breather cover
3. Seems to have high positive crankcase pressure
4. Valve guides pushed out
5. Signs of running hot... but no surprise with oil all over head fins collecting grass and dirt

My thinking is that I'm already 90% of the way to replacing the breather, and there's a reasonable probability that's the root cause of most of the trouble. If I put another 10 hours into reassembling this thing with new heads, valves, getting it all put back together just to find I have to tear it all back down to replace a $10 part I skipped, I won't be too thrilled with myself. Probably best to just split the case, pull the cam, and get that old breather reed swapped out, at this point. Then with the new heads and valves, hopefully the thing will be ready for another 1200 hours of work.

I did mention to the Deere tech and service manager I saw this morning, that it might almost be easier to just repower the machine with a new Kawi V-twin, but they said I'd have trouble finding one. That was a surprise, as I've seen motors that at least appear to be the same as this (minus Deere part number) for sale online.

 

Well, this is a 5 inch Magnehelic, not one of those super-sensitive 0.25" units that chimney tech's use. Spec was supposed to be well under that for a fully broken-in engine, so I thought it should be safe. But it's not a bidirectional unit, so it didn't love seeing positive pressure on the vacuum side of the scale.

This was with engine running. Should be seeing a few inches of vacuum (don't have spec in front of me now), but I'm seeing enough pressure to blow the dipstick out of the tube once I start to lift it, with the engine running.

Yeah, heads are toast, but I''m still not convinced it has anything to do with the original problem. Something caused this engine to go from "running great" to "barely running" in an instant, and something caused it to start building crankcase pressure and blowing oil out thru every seal. I'm not seeing anything on the heads that would correspond to such an instantaneous change in performance this week. Cooked valves didn't happen just this week, they've been on their way to that state for awhile.

Agreed, new heads already in the shopping cart, just gotta figure out from Deere's nearly-useless parts diagrams, which of the dozen-odd "tubes" and "fittings" I need to order along with the heads. I sure do wish they had pictures or drawings of the individual parts, so I know to what their super-specific "Tube" or "Fitting" description actually refers.

Just finished a 13 hour day at my desk, bidding some jobs. Headed out to the shop momentarily.

Will dial-indicate them on some v-blocks. I don't mind buying any parts that are truly needed, but with heads in the cart, this is shaping up to be a spendy rebuild.

I do plan to buy new valves, even though the guys at Deere said I could just lap these old ones into the new heads.

Hmm... guess I don't really understand the compression release mechanism. My concern with bent rods isn't so much initial lash, I dial that in with the rocker retainers anyway, but that they are weaker if not straight, and thus can continue to "shorten" themselves with runtime.

Deere is usually pretty damm good with parts, but they say the "engine gasket kit" for this engine is discontinued. Looks like I'm stuck finding and ordering each individual gasket.

 

Brand new one here: Kawasaki Vertical 25 HP V-Twin OHV Engine ES 13amp 1-1/8" x 3-5/32" #FH721V-JS09

 

Thanks! Yeah, lots more options in vertical shaft. But this is a special "heavy duty" variant with horizontal shaft. It was probably custom for Deere, although with a little dedication and effort, I'm sure almost anything could be made to fit.

Well, I had a chance to check push rods and valves last night. Valves took a bit of work to clean up, but surprisingly come in at spec, albeit right at the min spec, other than a little erosion of the stem right behind the valve flare. Since they don't give a min/max, I don't know how far above min they usually start, and since new valves are only $200 I just sprung for all new. I don't want to be tearing this thing back down in 3 years over $200.

But the push rods are remarkably straight. Spec is up to .020" runout at middle, spun between v-blocks under the ball ends, and I'm measuring only .003" to .004". So, it looks like I can reuse those.

I forgot to check the rockers for evidence of contact, but I can do that tonight. With the straight push rods, I'm guessing it doesn't matter, but I'm interested.

New heads, new valves, new breather reed, and a crap ton of new gaskets all on order. Should be a bit over $1000 when done, but that still beats a new $15k mower, or even $3k to wait on and then somehow retrofit a repower motor... assuming my fix works and this thing can last me another 1000 hours.

BTW... I'm surprised you called 1000 hours high usage. That's less than a year of work for a commercial mower, no? I've put triple that time on some tractors.

 

Didn't realize it was horizontal, here is one: Sorry about that, forgot to add the address!

FH721D-GH718K-R1

I have bought a couple small engines from this place. They know their stuff if you call and want to know compatibility.