26T Oil Pump Sprockets

[petert 554]

Has anyone else noticed unacceptable wear on XU10 26T sprockets, #051354? I went looking for a spare I had. I recalled I had one from an XU10J4 I'd dismantled. It had done approx. 150K, only ever touched by the factory. As I wipe the oil off it, I notice it has unacceptable wear from the chain. No problems I think, I'll just grab the one from my son's engine, a recently dismantled XU9J4, which I'd rebuilt 80K ago. To my surprise, it's also worn to the point of being unacceptable for a rebuild. Both engines had factory 52 link chains, not aftermarket. The 26T sprocket in my race engine looks like new, but it's only done 25hrs max.

 

Where I'm heading is whether or not this is a good idea. The 22T sprockets that I pull from XU9J4 engines are always as new. So what's going on? Poor metallurgy? Chain? You never see an XU9J4 with an oil light on at idle. Maybe it's better advice just to fit one of those? I'm certainly staying clear of 26T sprockets for now.

[JeffR 51]

Peter, your comments prompted me to have a good look at my chain & sprocket & compare them against the original. Mine also has the wear marks after no more than 4000 kms (admittedly at nearly full bore everywhere)!

 

I measured both sprocket thicknesses and the 26T sprocket is 0.002" thicker at 0.205", the 22T at 0.203". Would this account for the wear showing on the teeth? The smaller sprocket seems more rounded on the tooth profile too.

 

The longer chain showed signs of wear/scuffing on the outer links as well.

[JeffR 51]

....and one of the chain.

[petert 554]

My pic isn't quite as detailed as yours, but hopefully you can see the wear. 80K on the left, 150K on the right.

Edited October 19, 2011 by petert

[wicked 103 3 Cars]

I fitted a XU10J4RS pump on my XU9J4, but the chain (52link) tension does not look ok:

 

 

 

It turns out that the L-shaped spacer for a XU10J4RS is 1.1 mm thick, while the XU9J4 is only 0.7mm.

I ordered a XU10J4RS spacer, but it's on back order.

[welshpug 1,626]

could try two 0.7mm spacers?

[wicked 103 3 Cars]

First I want to try a 1.1mm spacer (just ordered it last week), 1.4mm might be too tight and make it wear even faster.

[mollisk 2 1 Cars]

I also fitted a 1.1 m/m spacer when I fitted a XU10J4RS oil pump to my XU9J4 engine. I also utilised the same 1.1 m/m spacer when fitting a 26 tooth sprocket onto a XU5 engine as the chain felt loose when the standard spacer was fitted.

 

Regards,

 

Kev M