Front Camshaft Bush

Front Camshaft Bush                    By  Peter Lawson

Do you wonder what that large square-headed bolt is for on top of the crankcase between the block and camshaft pulley?

I found out after cleaning in that area with a cloth-wrapped screwdriver.

As I forced it in the gap I noticed the pulley move forward slightly. I pushed it back and forth and realized there was about 5mm of movement. A quick call to Dave O confirmed that was not good.

Off came the cowl and radiator, dynamo, nose cone, and timing gear cover. It’s impossible to remove that square-headed bolt, which engages with a hole in the camshaft bush, without lifting the block. So some careful hacksawing took the corners off so that it could be undone.

Dave now came round to determine exactly what was wrong. We removed the camshaft gear and then prised out the bush. Sat alongside a new one you can see the problem in the photo. The other photo shows the camshaft shoulder against the bush.


A recess had worn where the camshaft shoulder sits against it, and also a washer had been installed between the two, which should not have been there and may have contributed to the wear.

If the wear was any greater there was also the chance that the petrol pump lever might slide off the cam lobe. I took the sump off too to check the situation from the inside. There was no need to remove the camshaft.

The bush retaining bolt head was turned to the round and a slot cut in for a screwdriver. The new bush was slid in place with a dab of Loctite Threadlock to the retaining bolt to ensure it didn’t come undone.

Ensuring the timing dots on the gears lined up, Dave tightened up the camshaft gear nut with an air wrench, ensuring the lateral end float had been all but eliminated.

With all the specialist work done, it was left to me to reassemble everything with new gaskets, paying particular attention to ensure the nose cone wasn’t finally tightened until the top faces where the timing gear cover mated up was perfectly flush using an engineer’s square.

After reassembly, it started first time, naturally, and even sounded, not surprisingly, a little quieter.


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