Miss firing

[SUKI]

Kawasaki FX751-AS04

After engine is hot it will after fire on shut downs and will back fire out the air cleaner on start ups. Lots of hours on this engine.

I have found the problem source and the root cause just wondering if anyone have come across a problem like this. I had three Kawasaki engines with similar problems and all had the same root cause.

[RoyM]

What do you see as the problem? Sounds like the engine is running overly rich.

[creia]

Yes, please share with us what you found out. That we can ALL learn.
Michael

[KE4AVB]

Suki is just pulling one my tricks. He just wanting to see what others think the problem was first. Since I was in on the troubleshooting I keep quite for awhile.

[KE4AVB]

I am surprised how few techs are willing to chime in on this. But I see this on other sites too as they only come for help and not willing to help.

But here is the causes.

Current cause is a sticking exhaust valve. Carbon build up. This last engine that SUKI has the carbon build up has even cause valve guide to move out of place damaging the valve stem seal. But the root cause is a blown head gasket. Only happening on his customer's engine after get hot so it not as bad as the last one I repaired

The FX-T00V I worked on was actually back firing on cold starts. I found the exhaust push rod off on it. When I re-install and was adjusting the valves I notice the valve snapping shout as I cycled the engine. Now of course the engine had over 3000 hrs on it and had already blew #1 head gasket last year but it was #2 this time around. No smoking just higher than normal oil usage. Even the valve itself was carbon up. And the darn service has two different valve specs listed for the guides. I got to get in a reamer for the next time but I had one that was close match.

I think when SUKI pulls the head apart he will find the same carbon build up. Between us that makes the fourth engine this year with problem.

Now carbon build up either valve will cause problems be it OHV or L-head.

But I got a major head of a repair in the shop now a JD Z925A that has the anti-rotation clutch arm that is now longer being held in position. I be removing the engine and all components to do the repair. First project however is the repair my air compressor. Pump failure after 40 yrs. Install a twin head pump in place the single piston pump. This give me a little more CFM. Just hope the HFT pump holds up well.

[bgsengine]

I am surprised how few techs are willing to chime in on this. But I see this on other sites too as they only come for help and not willing to help.

Methinks Suki's post might have been somewhat better worded to make it more obvious ... However, as you know I'm fairly well retired, and having said that, Ill also say I rarely ever had Kawasakis to deal with when I was in the business... But in a generic sense, given the backfire when hot symptoms I would likely have suggested a valve issue... Just wasn't really reading into it as one of those "can you figure out the cause from the symptoms I am listing" posts based on his wording, hence my opening suggestion to this reply (which I have done a few of those too)

[KE4AVB]

It sorta like the flywheel issue I had with the Kohler KT740. When I finally got to installing the short you probably would not had thought that the original engine had two blown head gaskets but it did and that wasn't even noticeable until the heads were removed. At least I got one re-assembled and a waiting the customer to pickup the $1366 repair. I only charged the customer half of the $200 shipping charge.

Or the CV20 with the pinhole in the cylinder head. The customer left the donor engine so I can reclaim the #1 cylinder head, crankshaft, hopefully the camshaft.

[SUKI]

Well since there no one with a faint idea of what this is here is what it is.

When hot carbon on the exhaust is randomly sticking the valve on closure just long enough to cause to allow unburnt fuel to enter both the exhaust and the intake passages. On this particular engine it has cause the valve to enough the destroy the garter spring and slight bowing the push is occurring. Root cause is a partially blown head gasket. AVB just had last month that the valve was hanging long enough that the push was falling out whenever the mower was hitting a bump.

On the engine AVB last worked both the stem and valve guide were heavily carbon up. At that engine didn't move the valve guide unlike the one I am working on.