7254 FD711D AS01 Engine Replacement

[tgunr]

I hope I can get some information here *** I have been looking on the net for hours to no avail. I have a Cub Cadet 7254 with a Kawasaki 25HP FD711D-AS01 engine. The engine has always been hard to start but about a month ago I started it up with no problem and used it for a couple of hours. Engine seemed as strong as it usually was before stopping for the day.

The next week I go to use it and it will not start. Period! Checked all the obvious, pulled plugs, had spark. Pulled fuel line, plenty of fuel to carb. It would try to fire but was acting like it just was not getting fuel. Pulled the card and tore it apart and cleaned it in an ultrasonic cleaner and pretty much the problem. Anyway, finally found a new carburetor at psep.biz (great people and even better prices than anywhere else so check them out!). Put on the new carb and gaskets now I finally got it to run but with only with full choke. Anything less will stall it out.

My neighbor who is a small engine mechanic come over this morning and we gave it a through going over and the only solid evidence we have is the compression check shows about 87psi on #1 and about 90psi on #2 and the manual says we should be seeing about 170psi. Put some oil in the cylinders and cycled a few times, and ran another compression check and only 2-3 psi difference so I don't think it is the rings. No evidence of blown head gasket, intake manifold looks ok, ran it and sprayed starting fluid around all the suspect areas and still ran as usual with full choke.

Valve lash and clearance all look good so the only other thing I can check is to pull the heads and check the seating. I looked all over for a rebuild kit as it is obvious I need an overhaul with this low of compression but could not find anything anywhere. Adding up all the parts required comes to about $800 including the $200 I already spent on the carb.

I can get a complete engine FD711D from psep.biz for $1600 plus $6 shipping but before I commit to just replacing the FD711 I would like to know if I could put in a FD791D with the EFI? Or even the FD750D which is a 27HP. I can't seem to find anything to tell me if this is possible although I tend to think it would be. If it requires a new wiring harness I'm pretty confident I could do that part as I have a background in electronic engineering.

Does anyone know if I can do this? Where to find specs on the output shaft, mounting points, etc?

 

[Maveric]

I don't know much about these engines but it seems like I heard once several years ago the Kawasaki's had a plastic gear that was prone to fail and the issue had at some point been adressed. I don't know that this is true, or which models were involved, but before I purchased another engine I would check the cam timing. If the alleged pastic gear story is true it could possibly be a gear that drives the camshaft and if so it may have slipped just enough to keep it from running normal. That may explain why the cranking compression is down on both cylinders. May be wishful thinking, but you never know. Good Luck

 

[Bob_Bainbridge]

Some of the older Cadets, like the 1450 with Kohler engine, had compression releases to enable easier starting. Make sure something simple like that is not responsible for the low compression.

Bob B.

 

[tgunr]

Guess i should have mention this was a 2003 model 7254. Another thought was maybe a blown head gasket between cylinders but there is no evidence in the oil or coolant.

 

[franmech]

The correct compression for this engine is 107psi, just looked it up myself. If you have a fuel solenoid on the carburetor, is it working properly, clicking on and off with the key, did this come with the new carb?? Also is the electric fuel pump working good? These FD engines have a complicated ignition system, could ignition timing be off? This engine should not have the plastic cam gear, that was other models of liquid cooled engines from KAW. A leakdown test would be good to confirm the rings/valves condition. Maybe get it to a dealer?? Even if just to diagnose it? Could make you scratch your had for a while.......Did you put in new spark plugs? I've seen strange things with spark plugs!

 

[tgunr]

Thank you very much for the information. The manual I have says 170psi which did seem high, a typo? So my readings of around 90 would seem consistent with the amount of wear I have on the engine which is around 1000 hours. But if 107 is the minimum I am probably due for a overhaul soon.

The carb is new and the electric solenoid does click, and the engine does run without missing or any other indication of timing problem as long as the choke is fully out. With the choke fully out it runs at about 1500RPM and sounds completely normal. It stays this way even when fully warm.

My neighbor also thought it could be the valve seating but I think 2 things rule that out, the problem happened suddenly almost overnight and both cylinders go out at the same time? Does not seem probable to me but stranger things have happened.

Also, put in a new fuel pump and filter last summer, I get about 150ml in 6 seconds so there is plenty of fuel flow.

Getting to a dealer for a leakdown test should confirm the valve seating problem but getting it down there (I live up in the mountains) would be quite a task. I suppose I could invest in a test kit.

I have not tried new plugs, worth a try I guess before I start to tear it down. I certainly am scratching my head over this.

BTW, did the manual you read from say 107 was the minimum or normal?

 

[Bob_Bainbridge]

One point that stands out is the engine was running normally, other than hard starting, until you replaced the carburetor. Are you sure you have the correct carburetor with the proper sized jets etc? Unless some mechanical problem like timing etc. occurred overnight, the fact that it only runs with full choke indicates it is running too lean and is starved for fuel.
One other thing that probably wouldn't apply to a tractor is the exhaust. I once wasted months and hundreds of dollars for diagnosis and computer replacement on a 1976 fuel injected Cadillac Eldorado. It would only run 50 mph at full throttle with a 500 cu in engine. I finally found the problem myself, getting a clue when an exhaust manifiold bolt broke. The catalytic converter was clogged creating back pressure. When the manifold vacuum dropped the computer fed more gas to the engine practically drowning it out.


Bob B.

 

[NassauEquipment]

We have those engines in commercial Toro Z's hitting well over 2000 hours. Take it to someone authorized by Kawasaki and get it fixed..........its a good engine.