Low Compression - Kawasaki FR730V

[scottchopchop]

Low Compression - Kawasaki FR730V

The engine is probably 10 years old.

Last mow of last season and suddenly one cylinder #1 stopped firing. (left, fuel pump side)

Pulled the valve cover off and the push rod was completely disconnected and also bent.

The bolt holding the rocker arm bracket to the head had become very loose, that bolt had almost completely backed out, and so the entire rocker assembly was flopping around.

Nothing else looked particularly dysfunctional.

Replaced the push rod and adjusted the valves on both cylinders.

However, it's not running quite right. It takes maybe 10 or 20 seconds for cylinder 1 to start firing. The engine starts up but with only cylinder #2 firing and then 10 seconds later before cylinder #1 finally kicks in.

Put on new coils and that didn't solve the problem.

Checked compression:
Cylinder 1 (low)
100 psi (cold engine) and it holds...doesn't drop pressure
125 psi (warmed up engine) and it holds...doesn't drop pressure

Cylinder 2 (within specs)
150 psi (cold engine) and it holds...doesn't drop pressure
170 psi (warmed up engine) and it holds...doesn't drop pressure

On that final mowing last season, when the problem began, I had been dealing with a bad bearing on a deck spindle, it had been grinding and that blade was rotating very slowly....just throwing this in the conversation because I suppose this could have been dragging the motor down and potentially caused overheating with my faulty cylinder #1.

The head gasket on #1 has been leaking just a bit of oil for a couple of years, but didn't seem to affect the compression or performance prior.

I pulled head #1 off and to my untrained eye, the only thing that seems obviously out of place was the blown head gasket...it was now blown in two spots.

To my eye, both valves seem to be seating fine and nothing with them seems loose, or sticky.

I do notice, when looking through the intake and exhaust ports on head #1, that the valve guide on the intake protrudes perhaps 1/8 inch, while the valve guide on the exhaust port protrudes perhaps 3/8 inch. I don't know the specs, perhaps this is normal? Or perhaps one or both of these valve guides got hot and slid out of place...and perhaps this is the source of the low compression?

Would that blown head gasket be enough to cause the low compression? Should I replace it and see what happens?

Or am I likely looking at something else wrong with the valves, seats, guides, etc etc...and I should go ahead and just replace the head/valves,etc with new ???

Pics of head attached.

Lastly, the cylinder itself looks great to me...no scratches, no scoring .... very smooth ...nothing obvious to indicate to me an issue with the rings.

My inclination is to just throw on a whole new head assembly, with new valves and seats and etc. Those complete head assemblies are about $300-$350 now....so a bit of an expensive experiment if it doesn't solve the problem.

Any thoughts or advice appreciated.

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• scottchopchop
• Mar 5, 2025

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• scottchopchop
• Mar 5, 2025

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• scottchopchop
• Mar 5, 2025

IMG_20250305_070347201 (1).jpg

• scottchopchop
• Mar 5, 2025

 

[txmowman]

If you have over 100psi compression, that is fine. It appears that the valve guide has slid due to the cylinder being overheated. Both heads should look the same. The loosening of the rocker bracket bolt is also likely heat related. This could cause a bent push rod but would not contribute to over heating. There is not a repair for the valve guide, head replacement will be necessary.
Not running the engine at full throttle will affect the cooling of the engine.

As far as starting on one cylinder and the other kicking in after short time, that could be an erratic ignition coil. I know you wrote they were new. Are they OEM or an Amazon/eBay, China knock-off?

 

[scottchopchop]

UPDATE: Thanks for all your replies fellas. I decided to try simply replacing the head gasket and see what happens...20 bucks and a couple hours of work. Got all the surfaces cleaned up and put the old head back on...adjusted the valves...and then re-tested the compressions on the cold engine.

Head #2 (the good cylinder) - 150 psi
Head #1 (the bad cylinder) - 150 psi

Ran the machine for 20 minutes or so, drove it around...good power...all seemed back to normal

No oils leaks observed.

Ran it for another 20 minutes the next couple of days. Again, all good. No leaks observed. Good power.

So far so good.

While I had the muffler off I went ahead and replaced the governor seal, which had been leaking just a little bit for a couple of years. The old seal was a booger to get out, took an hour to get it out...pick pick pick. Put the new seal in and ran it for 20 minutes. No leaks. Been sitting for a couple of days and so far so good...no leaks.

Again, I appreciate all your replies and input.

 

[slomo]

I wish you luck.

Most of the time you must lap the heads and block area where the heads sit. Typically they are all nicely warped. Leads to replacing head gaskets again later.

Must do even if you pull a head to decarbon the cylinder. Must lap the head and block. It's all in the prep.

 

[Auto Doc's]

If the guide had slipped, it would show a slight carbon ring where it was originally installed, I don't see that in your picture.

B&S engines were really bad about guides slipping, but Kawasaki and Kohler have not been that bad.

The guide and valve likely did get hot, and the valve started sticking/ scrubbing from the lack of lubrication.

If you did not level the block and head surfaces this time, you will need to the next time. Also replace the valve and of course another new pushrod, if it gets bent.

I wish you well and hope you get lucky this time, but I've had repeat issues a couple of times (in the past on my own stuff.)

 

[scottchopchop]

Kawasaki FR730V Gravely ZT HD60

The engine wants to bog down at maximum throttle when engaging the PTO. It recovers and has normal power and mows fine. But something is a bit off.

When engaging the PTO at idle it actually kills the engine.

Also, noticing that with throttle at idle the engine is not idling down enough, not to it's normal idle...staying a bit too high RPM. Holding the governor arm down causes the idle to be normal, but if I release the governor arm it goes back instantly to the slightly too high idle RPM.

Moving the throttle from slow to high, the engine is hesitating a bit, taking a little while to react to the throttle input. I'm not sure, but when mowing at full power, the engine to me sounds almost like it's running rich..but I might be off on that.

Lastly, it seems to me that sitting still, with no wheels moving, no blades engaged with PTO, the engine is wanting to rev too high RPMs. It's racing a bit.

Governor adjustment a bit off???

Fuel starved? Jets clogged?

In that image, the RED arrow, the governor shaft has a flat spot on top, it's D shaped, so there doesn't seem to be a way to adjust the governor arm and shaft like one could if the shaft was completely round.

I don't know what bolt is about halfway between the shaft and the springs, YELLOW arrow. Is that an adjustment bolt?

Thanks in advance.

 

[txmowman]

Kawasaki FR730V Gravely ZT HD60

The engine wants to bog down at maximum throttle when engaging the PTO. It recovers and has normal power and mows fine. But something is a bit off.

When engaging the PTO at idle it actually kills the engine. Have you checked spark on both cylinders to make sure the engine is running on both cylinders?

Also, noticing that with throttle at idle the engine is not idling down enough, not to it's normal idle...staying a bit too high RPM. Holding the governor arm down causes the idle to be normal, but if I release the governor arm it goes back instantly to the slightly too high idle RPM. Do you have a tachometer to see what the low idle is set to? It should be 1550 rpm. Possibly the low idle screw on the carburetor is out of adjustment.

Moving the throttle from slow to high, the engine is hesitating a bit, taking a little while to react to the throttle input. I'm not sure, but when mowing at full power, the engine to me sounds almost like it's running rich..but I might be off on that. Check your spark plugs to see if they have a black soot. If so, likely running rich. As far as the hesitation, the carburetor may need to be cleaned. Removing the two welch plugs on top. The larger one is the transition well. Make sure it is clean and the tiny holes are open. (3 of them)

Lastly, it seems to me that sitting still, with no wheels moving, no blades engaged with PTO, the engine is wanting to rev too high RPMs. It's racing a bit.

Governor adjustment a bit off??? A static governor adjustment may be necessary. Your local dealer can help you with that.

Fuel starved? Jets clogged? Possibly

In that image, the RED arrow, the governor shaft has a flat spot on top, it's D shaped, so there doesn't seem to be a way to adjust the governor arm and shaft like one could if the shaft was completely round. See the governor adjustment above.

I don't know what bolt is about halfway between the shaft and the springs, YELLOW arrow. Is that an adjustment bolt? This is a rivet that keeps the throttle panel assembly together. No adjustment.

Thanks in advance.

 

[Tiger Small Engine]

Kawasaki FR730V Gravely ZT HD60

The engine wants to bog down at maximum throttle when engaging the PTO. It recovers and has normal power and mows fine. But something is a bit off.

When engaging the PTO at idle it actually kills the engine.

Also, noticing that with throttle at idle the engine is not idling down enough, not to it's normal idle...staying a bit too high RPM. Holding the governor arm down causes the idle to be normal, but if I release the governor arm it goes back instantly to the slightly too high idle RPM.

Moving the throttle from slow to high, the engine is hesitating a bit, taking a little while to react to the throttle input. I'm not sure, but when mowing at full power, the engine to me sounds almost like it's running rich..but I might be off on that.

Lastly, it seems to me that sitting still, with no wheels moving, no blades engaged with PTO, the engine is wanting to rev too high RPMs. It's racing a bit.

Governor adjustment a bit off???

Fuel starved? Jets clogged?

In that image, the RED arrow, the governor shaft has a flat spot on top, it's D shaped, so there doesn't seem to be a way to adjust the governor arm and shaft like one could if the shaft was completely round.

I don't know what bolt is about halfway between the shaft and the springs, YELLOW arrow. Is that an adjustment bolt?

Thanks in advance.

Clean the carburetor thoroughly.

 

[scottchopchop]

Installed New Carb and new fuel filter. Problems resolved. Had replaced that carb two years ago with a $30 Amazon. If the old engine keeps hanging on, I think I will put it on my calendar to just replace that carb again in another 2 years.

I had asked here about that bolt on the governor control arm, located about half way between the shaft and the springs at the end of the shaft. I found a video where a guy confirms that this bolt is the adjustment for the governor. When trying to adjust this, my bolt stripped out and wouldn't re-tighten. We drilled the hole out a bit and replaced with a nut and bolt. Adjusted it to our liking, just a bit clockwise, and tightened down. So far so good. The governor shaft is D shaped, has a flat spot that marries with the flat section of the control arm, so there is no adjustment possible directly between the shaft and control arm. That bolt half way across the arm is the adjustment evidently.

Update on head gasket replacement. There's about 10 hours of operation on the new head gasket and everything is doing great so far. Compression holding and engine has good power.

This year, in addition to the items just mentioned, Also replaced:
- All idler pulleys. Drive idler, and both deck idlers.
- Electric PTO clutch. The bearings were shot on the old one. The new one, Xtreme brand, has to be at least 5 pounds heavier...mainly from the pulley I think.
- Rebuilt two of the deck spindles and replaced one entirely as the new bearings wanted to move around and not fit tightly into the old spindle.

Last year, the frame snapped in two. You can see it sagging heavily in the attached pic. Had a welding shop install square tubing under and between the front and rear sections. Extremely rigid now.

I appreciate all the input from everyone. Very helpful. Many thanks.

 

[Auto Doc's]

Never mess with a governor adjustment unless you had to remove the sump for and oil leak repair or conducting a full overhaul.

Too many people mess with a governor that have no idea what they are doing.

Your symptoms describe a possible dirty carburetor (inside).

Also, the cable adjustments need to be adjusted to verify proper travel, and the choke is not being partially activated. You had all that apart to replace the head gasket.

Lastly, you may need to replace the gaskets or O-rings for the intake to head mounting area, it is common for them to leak once they have been disturbed, and they are not reusable like too many people assume.