Small engine repair (4–stroke air cooled v-twin gasoline engine)

[pinefall]

I have an Exmark Turf Tracer commercial walk behind mower (36”) for mowing our property which I bought used about 5 years ago. It has a Kawasaki FH430V engine. It had been trouble free but this summer have had some problems. We noticed it was gradually getting harder to start. Then we had a few unexpected stalls. Thought it might be result of getting shaken around (the power company was agreessive in clearing the right of way this summer with heavy equipment on wet ground, resulting in some very rough ground for the mower).

Found a loose connection on one of the interlocks. Did a regular service while I was at it (new plugs, fuel filter, air filter, oil change). The plugs looked fine with just a negligible amount of carbon. Seemed to run a bit better afterward but still not as easy to start as when we first got it. But then after a few weeks another unexpected stall then flooding trying to start.

We had some wet weather and it sat a few weeks while the grass grew. When I started it last weekend, it started suspiciously easy. Some blue smoke from the exhaust though but that cleared after a minute. After a few minutes of mowing, after it to warmed up, it started smoking again and lost power, barely running. Brought it back. While shutting it down I noticed oil leaking from the fuel pump. Blown head gaskets, I thought.

After some reading to increase my confidence in the diagnosis (and a few online videos) I decided to replace the head gaskets. First time repair, for me. Ordered head gaskets and rocker cover gaskets.

Before I started the repair I did a quick compression test. Spec is 57 psi at operating temperature. I did it cold, obviously since it wasn’t running. Cylinder 2 was about 50 psi; cylinder 1 about 40 psi, but in retrospect I may not have turned the engine enough to get a proper reading.

I also discovered the oil level was unexpectedly very high, and clearly had gasoline in it. I attributed this to be a side effect of the blown head gasket and drained the oil.

Following the engine shop manual, the head gasket replacement went fine, though the diassasembly to get to it was a bigger hassle than expected. I went for cylinder 1 first. When I got to it, it looked fine. No sign of a blow through. Cylinder 2, the same, no obvious problem. Big disappointment after several hours work. Replaced the gaskets and started reassembly.

While I was in there, no serious carbon deposits on the piston but some gummy oil which cleaned up ok. Cylinders looked fine. Valves were all in spec before dissembly. Cylinder 2 exhaust valve was a bit loose after reassembly but I adjusted to bring back to within spec. I didn't have the tools (or confidence) to go any deeper into the engine.

I didn’t complete the reassembly since I neglected to order the exhaust gaskets. So I don’t know if I made it better (unlikely given the state of the original gaskets) or made it worse (certainly possible fora first try at this repair). I’ll order the gaskets and complete the work next weekend.

So, my questions: if it’s not the head gaskets … then what? What to make of the gasoline in the oil? Before I order the exhaust gaskets, any other parts to try and fix or replace? (Carb?) What else to check?

Thanks for any diagnostics help.

 

[semipro]

Bad fuel pump? A bad diaphragm may allow fuel to be sucked into the crankcase.
Intermittent carb flooding?

 

[Riverbanks]

X2 on the pump, crank it over a few times, then turn key off, remove the vacuum line from the fuel pump, is it wet? or stink of fuel

 

[pinefall]

The fuel pump isn’t too expensive and easy enough to replace. I can’t test it now since the fuel manifold isn’t yet reinstalled (need additional gaskets before completing reassembly). But I’m willing to give it a try.

I’ve read that a stuck fuel float in the carb can also lead to fuel in the oil. Not sure which is more likely.

 

[Riverbanks]

If it was the float sticking, you would have not been using the choke to start it and probably holding the throttle wide open to get it to start, did you have that issue?

 

[EbS-P]

How much is a new carb? Can you bypass the mechanical pump with a cheap electric one for testing?

 

[Riverbanks]

If you don't mind a possible taste of gas in the mouth, pull a little vacuum on the pump on the line that runs to the crankcase

 

[Highbeam]

Less than 60 psi compression spec? Seems low, especially when compared to automotive engines.

If compression is at spec, and spark is strong (did you check?), then this fuel issue is the likely culprit. Check the air filter just in case. The carb and fuel pump are much easier than head gaskets!

 

[pinefall]

If it was the float sticking, you would have not been using the choke to start it and probably holding the throttle wide open to get it to start, did you have that issue?

Good point. It may have been running a bit rich but nowhere near enough to put that much fuel into the oil. If the head gasket was indeed blown I can imagine the back pressure damaging the fuel pump. But given that the removed head gaskets looked fine, I don’t know what caused what.

(And to your other comment, no I’m not willing to get gas in my mouth. But may be able to rig up something to produce negative pressure.)

 

[pinefall]

How much is a new carb? Can you bypass the mechanical pump with a cheap electric one for testing?

A new carb for this engine is about $265. I haven’t priced out a rebuild kit but on other engines I’ve opted to replace a carb rather then repair.

A new fuel pump is only about $30 and easy to replace. I’ll add the pump to my order with the exhaust gaskets and fuel manifold o-rings. Hope it all works when I finish putting it together.

 

[Riverbanks]

In hindsight, if you introduced a little oil to the cylinder before the compression test, that would have brought the numbers up, you had fuel washed cylinder walls, stuff happens, I have gone the wrong route on a repair also, just another life lesson

 

[moresnow]

May be worth verifying that the crank case is venting properly. No idea if there is a pcv valve of sorts on that model or not?

 

[pinefall]

May be worth verifying that the crank case is venting properly. No idea if there is a pcv valve of sorts on that model or not?

I don’t see a PCV. I’ll try to figure out how the crank case is suppose to vent.

 

[festerw]

Have you ever adjusted the valve clearance?

 

[pinefall]

Have you ever adjusted the valve clearance?

Not prior to this. All the valves were in spec when I opened it up. On reassembly, the exhaust valve on cylinder 2 was a bit loose but I adjusted to bring back to spec.

 

[pinefall]

I have an Exmark Turf Tracer commercial walk behind mower (36”) for mowing our property which I bought used about 5 years ago. It has a Kawasaki FH430V engine. It had been trouble free but this summer have had some problems. We noticed it was gradually getting harder to start. Then we had a few unexpected stalls. Thought it might be result of getting shaken around (the power company was agreessive in clearing the right of way this summer with heavy equipment on wet ground, resulting in some very rough ground for the mower).

Found a loose connection on one of the interlocks. Did a regular service while I was at it (new plugs, fuel filter, air filter, oil change). The plugs looked fine with just a negligible amount of carbon. Seemed to run a bit better afterward but still not as easy to start as when we first got it. But then after a few weeks another unexpected stall then flooding trying to start.

We had some wet weather and it sat a few weeks while the grass grew. When I started it last weekend, it started suspiciously easy. Some blue smoke from the exhaust though but that cleared after a minute. After a few minutes of mowing, after it to warmed up, it started smoking again and lost power, barely running. Brought it back. While shutting it down I noticed oil leaking from the fuel pump. Blown head gaskets, I thought.

After some reading to increase my confidence in the diagnosis (and a few online videos) I decided to replace the head gaskets. First time repair, for me. Ordered head gaskets and rocker cover gaskets.

Before I started the repair I did a quick compression test. Spec is 57 psi at operating temperature. I did it cold, obviously since it wasn’t running. Cylinder 2 was about 50 psi; cylinder 1 about 40 psi, but in retrospect I may not have turned the engine enough to get a proper reading.

I also discovered the oil level was unexpectedly very high, and clearly had gasoline in it. I attributed this to be a side effect of the blown head gasket and drained the oil.

Following the engine shop manual, the head gasket replacement went fine, though the diassasembly to get to it was a bigger hassle than expected. I went for cylinder 1 first. When I got to it, it looked fine. No sign of a blow through. Cylinder 2, the same, no obvious problem. Big disappointment after several hours work. Replaced the gaskets and started reassembly.

While I was in there, no serious carbon deposits on the piston but some gummy oil which cleaned up ok. Cylinders looked fine. Valves were all in spec before dissembly. Cylinder 2 exhaust valve was a bit loose after reassembly but I adjusted to bring back to within spec. I didn't have the tools (or confidence) to go any deeper into the engine.

I didn’t complete the reassembly since I neglected to order the exhaust gaskets. So I don’t know if I made it better (unlikely given the state of the original gaskets) or made it worse (certainly possible fora first try at this repair). I’ll order the gaskets and complete the work next weekend.

So, my questions: if it’s not the head gaskets … then what? What to make of the gasoline in the oil? Before I order the exhaust gaskets, any other parts to try and fix or replace? (Carb?) What else to check?

Thanks for any diagnostics help.

The remaining gaskets arrived a few days ago and I did the reassembly today. It went well for the most part although the governor plate and throttle linkage reinstallation were fussy. I expect I’ll need to readjust. I replaced the fuel pump (just in case) although no obvious problem.

To other question on this thread, no PCV and the crank case vent looked clear. Spark is fine; air filter is fine.

I have not yet tried to start it up. I’m still suspicious of the carb / float valve. I haven’t yet replaced the oil. So I opened the fuel valve and will watch to see if any gas finds it’s way to the oil reservoir. After a few hours, no sign of it yet but will give it a few days. If it still looks good, I’ll add the oil, reinstall the spark plugs and give it a go.

 

[brenndatomu]

Less than 60 psi compression spec? Seems low, especially when compared to automotive engines.

Many of these small engines have auto decomp valves...that makes the normal compression test numbers look low.

 

[Riverbanks]

If the float is sticking open, you should also see or smell gas at the carb. inlet

 

[brenndatomu]

If any part of the gas tank is above the carb, I try really hard to install a fuel valve somewhere so it can be shut off when not running...you just never know when one is gonna go n pee...either on the floor, or down its own throat...seen it happen hundreds of times at the bike/OPE shop. Sometimes its when being hauled (often) and sometimes its when the machine has been sitting for days...all of a sudden it starts to pee.
IME Mikuni carbs were good for this (but they will all do it with the right piece of dirt in the wrong spot...or just old age/wear/whatever) I can't tell you how many times I've drained a crankcase full of gassy oil...probably hundreds....and air box full of acorns, or dog food...danged varmint's!

 

[Highbeam]

If any part of the gas tank is above the carb, I try really hard to install a fuel valve somewhere so it can be shut off when not running...you just never know when one is gonna go n pee...either on the floor, or down its own throat...seen it happen hundreds of times at the bike/OPE shop. Sometimes its when being hauled (often) and sometimes its when the machine has been sitting for days...all of a sudden it starts to pee.
IME Mikuni carbs were good for this (but they will all do it with the right piece of dirt in the wrong spot...or just old age/wear/whatever) I can't tell you how many times I've drained a crankcase full of gassy oil...probably hundreds....and air box full of acorns, or dog food...danged varmint's!

Sure was nice to have those sight glasses on the side of the carburetor like on the big Holley double pumpers. You could see in an instant that your fuel bowl level was being properly regulated.

 

[Riverbanks]

I looked at www.engine-specs.net/Kawasaki, it said, engine compression is 56 p.s.i. at 500 rpm, that's cranking (starting)speed I think, so this one does have the decomp starting assist?

 

[pinefall]

I looked at www.engine-specs.net/Kawasaki, it said, engine compression is 56 p.s.i. at 500 rpm, that's cranking (starting)speed I think, so this one does have the decomp starting assist?

The Kawasaki service manual specifies 390 kPa (about 57 psi) minimum with a warm engine while cranking. No reference to the RPM.

The manual also states “Automatic compression release” but I didn’t come across the mechanism for this yet.

At this low pressure, I don’t have a lot of resolution on my gauge.

 

[brenndatomu]

The manual also states “Automatic compression release” but I didn’t come across the mechanism for this yet.

Its usually built into the cam...centrifugally activated...or deactivated, as the case may be...

 

[Riverbanks]

How goes it? Running?

 

[semipro]

If any part of the gas tank is above the carb, I try really hard to install a fuel valve somewhere so it can be shut off when not running...you just never know when one is gonna go n pee...either on the floor, or down its own throat...seen it happen hundreds of times at the bike/OPE shop. Sometimes its when being hauled (often) and sometimes its when the machine has been sitting for days...all of a sudden it starts to pee.
IME Mikuni carbs were good for this (but they will all do it with the right piece of dirt in the wrong spot...or just old age/wear/whatever) I can't tell you how many times I've drained a crankcase full of gassy oil...probably hundreds....and air box full of acorns, or dog food...danged varmint's!

Some Kawasaki engines have an electrically-operated fuel shut-off valve mounted on the bowl of the carb.
Ditto on the frustration with varmints. Old gas and rodents make my equipment maintenance demands a lot tougher.