Kawasaki water pump impeller shaft in FD731V fitted to X520 lawn tractor

[Griffin77]

Hello Everybody,

We're at wits end and are hoping that somebody knowledgeable here can please help with this. We have a leaking water pump in this FD731V Kawasaki twin and John Deere lists all the various seals and the pump cover and impeller, but the impeller shaft itself doesn't come up on any of their parts diagrams. Ours is pitted and we'll loose the motor if we can't rebuild the pump as no point putting new seals in with a bad impeller shaft.

Does anybody know even the Kawasaki part number for the impeller shaft in this FD731V Kawasaki motor? The full motor model is FD731V-DS02, but an impeller shaft from any FD731V series should fit.

Many thanks.

Griff

 

[oldnslo]

I have always just replaced the whole pump vs trying to rebuild.

If shaft is pitted what does the mating housing or bearing surface like?

 

[dfkrug]

Does anybody know even the Kawasaki part number for the impeller shaft in this FD731V Kawasaki motor?

I can't think of any maker that currently sells all the internal parts to a water pump. Even getting them apart to replace a seal, shaft, or bearing is often not possible without damage.

This is an aftermarket pump I put in an FD620 on a Gator. It was not expensive, tho not OEM, either. I am not thrilled by Kawasaki's extensive use of plastic on the drive gear, impeller, and cam gear (!). Might be the same as yours.

 

[Griffin77]

Thank you for the replies so far.

FD731V has the impeller shaft built into the engine casing and the pump components (3 seals and the impeller and impeller bolt) go onto the captive impeller shaft.

All the seals and impeller are still available from John Deere, but they don't even show the impeller shaft on any of their parts diagrams, hence being unable to order one.

The FD620 pump won't work unfortunately.

The mating housing is also pitted, but this is also readily available new. It doesn't make sense that there is a listing for every single water pump component except for the impeller shaft. It's not discontinued; it just doesn't show up on any parts diagrams anywhere and I'm stumped...

Hoping somebody who has experience with this motor might be able to chime in?

 

[dfkrug]

The mating housing is also pitted, but this is also readily available new. It doesn't make sense that there is a listing for every single water pump component except for the impeller shaft. It's not discontinued; it just doesn't show up on any parts diagrams anywhere and I'm stumped...

The only explanation I can think of is that the shaft is included with one of the other parts, esp a part that has to be pressed onto the shaft.

Do you have a friend with a lathe?

 

[Griffin77]

The only explanation I can think of is that the shaft is included with one of the other parts, esp a part that has to be pressed onto the shaft.

Do you have a friend with a lathe?

You're right. The reason the shaft doesn't come out is because it is part of the camshaft (extends out from one end)! A crazy design in terms of lack of serviceability, but efficient to manufacture. So, need to remove the camshaft just to rebuild the water pump by machining the impeller shaft that is on the end of it (or otherwise replace the entire cam if didn't have lathe access).

Once it is machined, how does one build up the shaft again to the original diameter for the mechanical and oil seals? Is there a specific material that should be used for a bushing or sleeve? The shaft itself would have been hard chromed when it was new.

Thank you

 

[TractorTech]

​

You're right. The reason the shaft doesn't come out is because it is part of the camshaft (extends out from one end)! A crazy design in terms of lack of serviceability, but efficient to manufacture. So, need to remove the camshaft just to rebuild the water pump by machining the impeller shaft that is on the end of it (or otherwise replace the entire cam if didn't have lathe access).

Once it is machined, how does one build up the shaft again to the original diameter for the mechanical and oil seals? Is there a specific material that should be used for a bushing or sleeve? The shaft itself would have been hard chromed when it was new.

Thank you​

I was going to suggest a speedy sleeve for the seal area if that is all that needs to be reconditioned. Otherwise, a machine shop would spray it and machine it.
​

 

[TractorTech]

BTW, Welcome to TBN!

Looks like the camshaft through Deere MIA10540 $150.00 or Kawasaki 49118-2157 (for spec FDV731V-DS01 OR 04; DS02 not listed) is about $120.

Kawasaki 4 Stroke Engine FD731V OEM Parts Diagram for VALVE + CAMSHAFT | Firedog.com

Buy OEM Parts for Kawasaki 4 Stroke Engine FD731V VALVE + CAMSHAFT Diagram

www.firedog.com

Welcome to Kawasaki Engine Store - Your source for Genuine Kawasaki Engines and Engine Parts

​

 

[Griffin77]

I was going to suggest a speedy sleeve for the seal area if that is all that needs to be reconditioned. Otherwise, a machine shop would spray it and machine it.
​

Thank you for the help, and for the welcome. This is a great place

 

[TractorTech]

Did you get a shaft yet?

 

[Griffin77]

Did you get a shaft yet?

Sorry for the slow reply. Have eventually tracked down a good used camshaft (the end of which functions as the impeller shaft) and split the casing in order to replace it.

The mechanical seal includes a stainless steel cup that is tightly pressed into the casing and had loctite applied to it at the factory. The trick was to heat around it until it smoked (to break the loctite bond), and to then drive it out from the rear with a suitable socket.

There is an oil seal behind it, and both the oil seal and the mechanical seal cup came out together easily once heated. Doing it any other way can easily result in damage to bore for this seal.

The new seal cup was pressed in using a suitable 12-point socket with a rim that only contacted the outer lip of the seal cup; i.e. without touching the fragile spring-mounted mechanical seal face.

Seal faces were cleaned with isopropyl alcohol and lint-free cloth to a mirror finish, and then lubricated with fresh coolant (with a few drops of dish soap mixed in with it) prior to them being mated together during impeller installation. Also drilled and tapped the weep hole and installed a 90 degree elbow and short length of tube so that it now points downwards, as I feel that the forward-facing weep hole had the potential to allow dust to eventually work it's way into the mechanical seal cavity and accelerate wear.

I'm running the standard green coolant that's recommended, but am now wondering whether a low-silicate or silicate-free coolant (e.g. pink) would be kinder to the mechanical seal (less abrasive) and therefore prolong it's life. Curious if anybody has changed over from the green stuff to one of these modern water-pump friendly coolants...but in a small engine vs the typical automotive application of such coolants?