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Good morning,

I bought a used 150 pro-walk-behind with the Kawi 12.5 hp engine. The machine was sold as needing a carb adjustment since it would have trouble cold starting. I negotiated a good deal and have been trying to fix my cold start issues.

I started by buying a new carb and following carb adjustments from the FSM and carb adjustments also in the FSM. The machine will only start with starting fluid but ran well and I even put 3 hours on it cutting lawns.

I thought to check valve clearance and I wanted to check cylinder compression. I removed the cylinder head for a visual inspection, and one of the nine bolts was torqued excessively (supposed to be 25 ft/lbs).
I thought I was in over my head so I put everything back together and torqued the other 8 bolts to 25 ftlbs. When it ran, it sounded like crap, the worst it's ever sounded, I put a compression tester on it and got 30 PSI.

I suspect I have a warped cylinder head or I blew a head gasket. I committed to removing the over-torqued bolt and as expected the bolt snapped off and I need to drill it out. I ordered a new head gasket and new bolt when I get home tonight I will measure the cylinder head for warpage and measure the intake and exhaust valves.

Looking for advice on if there is anything I'm missing or maybe something I have overlooked.

Thank you all in advance,

You can't reuse the old head gaskets.

As for the broken head screw wait to order until you get the old one out as you might need to resize the hole which mean a different screw. Try your best not to damage the current threads if possible but that not always possible.

For hind sight next time you have a screw that is hard to get out, once it is out use a thread restorer or tap and clean up the threading. I just had a Briggs L-head that one head screw that came only part of the way out then got hard to turn. I applied my transmission/Acetone mix to the threads and run the screw back in then it came out easy. But doesn't work all the time either.

StarTech said:

You can't reuse the old head gaskets.

As for the broken head screw wait to order until you get the old one out as you might need to resize the hole which mean a different screw. Try your best not to damage the current threads if possible but that not always possible.

For hind sight next time you have a screw that is hard to get out, once it is out use a thread restorer or tap and clean up the threading. I just had a Briggs L-head that one head screw that came only part of the way out then got hard to turn. I applied my transmission/Acetone mix to the threads and run the screw back in then it came out easy. But doesn't work all the time either.

Click to expand...

if I cannot save the old threads I may go for a new engine. I don't know if it would seal the same if I did drill it out larger and I suspect there isn't a lot of meat left to upsize it. The bolt was 10 bucks on eBay and is no longer sold besides the one eBay listing we will find out tonight if I can remove it. I'm hoping ez out will save me If not I'm out 10 bucks for the bolt and 16 for the gasket.

it's a 20-year-old machine that really shouldn't invest a ton of money in but if I can get away with this repair I will.

I should have known better than to try and remove it dry but lesson learned. I did try to tighten and loosen it but it snapped right at the threads. I probably have an inch sticking out so maybe I can get some vise grips on it.

The M10-1.5 x 55 flange head screws are still available. Even can get them in aftermarket. It is the studs and that special head screw that are NLA.
For the broken if it moves at all just keep working it back and forth. Try to come out a little more each time. It probably got aluminum stuck in the threads.

No luck yesterday evening I tried grabbing it with vice grips and it wouldn't budge. I drilled with LH drill bits and nothing I then tried using a 1/4 screw extractor and the tip broke off.
Luckily it was the tip attached to my socket and I could back out the rest of the extractor so at least that didn't get snapped off inside too. Next, I'll get a beefier extractor set I'm looking at
ICON Multi-Spline Screw Extractor Set, 15-Piece from harbor freight.

Side note, I went to a lawn mower dealership and priced a new walk-behind model and 9 grand! that's more than what I paid for my Mitsubishi, Honda, and Lincoln put together.

No luck with the screw extractor it keeps spinning in place and I cannot remove that either. it didn't snap off or anything like that it just spins freely and won't back out at all.
FML. Not sure what I should do next I could bring it to a shop but I don't think a tech is gonna wanna fix my fuck up without a large asking price. I think a new used engine would be my best bet but I have a 20-30 year old machine and who knows what could be next to break.

Small update I removed the FB460V and replaced it with an FC420V-AS10. I bought a JD lX165 and robbed the wiring harness and engine. I was able to reuse the JD electric clutch and everything seems to mesh ok. I will need to extend the wiring and drill a spot for a couple of the switches. The engine is mounted with the original bolt locations and the PTO does clear the axle.

If anyone else looking for a replacement for a late 90s Gravley walk-behind 150 pro, you should find an FC420-FS15 otherwise you will need to weld an extension pipe for the exhaust. The AS10 exhaust will not clear the deck since it goes down but otherwise looks the exact same.