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From Crap to Scrap - part 2


Dave Parr

Now where were we, ah yes the removal of cylinder liners. The cylinder needs to be heated so that the aluminium expands sufficiently for the iron liner to drop out. A Propane torch, as used by felt roofing contractors can be used but I don’t have one of those. I do however have access to a fan oven, this will provide good even temperature control but will require some discretion with use. Mrs P goes shopping on Saturday morning – ideal opportunity I thought. Wait until the coast is clear set the oven to 120ºC, put the cylinder in to pre-heat, then wind it up to 180ºC and bingo the jobs a good un. I probably would have got away with this if I had cleaned the greasy crud off first. The ensuing miasma permeated the house and lingered for hours, in fact several more than my window of opportunity – it was a fair cop, I had to fess up.

A period of intense and meaningful discussion ensued.

Mrs P is not unreasonable however and permission was eventually granted for a second attempt this time under adult supervision… AND with everything suitably cleaned.

Here is a short clip with the cylinder heated to 180ºC and 200ºC

cylinder liners

The design of the new liners was finalised and Westwood Cylinder liners of Droitwich agreed to manufacture a special order - 2 off.

4 weeks later and here they are – Pistons 90.96mm Bore 91.005mm

The new ones are on the left. Points of interest.

**This is to resist crushing as the cylinder cools and contracts. When measured cold the original liner installed in the cylinder was 6 thou smaller at the top. Only becoming parallel at 120C. This is considered normal with these engines. The OD of the liner has increased 7mm so that metal has to be bored out of the cylinder, this will reduce the crushing force and combined with the thicker liner wall I hope to maintain piston clearance to 0 at 20C. Truth is, until it’s all together I just don’t know what the cold piston clearance will be and a cold seize is a distinct possibility. With this in mind I have increased the piston clearance from 0.04mm to 0.045mm, which is about +0.0003 in.

torsion bar valve gear

Nothing more I can do until the crankcase mouth is bored to suit the liners, so it’s time to look at more worn out stuff that I can work on in the meantime.

Torsion bar valve spring assembly
Torsion bar valve spring assembly

Torsion bar valve spring assembly

This sits in the cylinder head vertically as you see it. Oil enters via the hole just visible in the top casting. Oil just finds its way into the bottom half sits there forever and forms sludge, as a result the top half is worn but the bottom half is badly worn .

I plan do get a proper oil feed to the bottom via a tee off the head oil feed pipe.

The forked levers hook onto the valve stem and the preloaded spring pulls the valve closed. The valves are interconnected by the torsion bar. This system is often said to be desmodromic but is it?

The worn surfaces can be re-faced in a lathe and new bronze bushes made. One splined tube and one arm have gone to far and require replacement.

oil pump

Oil pump

The gears are a little scored but serviceable and the end face of the gears have been polished with wet and dry on a surface plate. The housing has been re-faced in the same way to remove excessive end clearance.

oil pump

Here the pump body is in position, the 7mm outlet port has been radiused for better flow but the cross drilling into the main gallery is miss matched and only 5mm diameter. This needs to be sorted but a drill will follow the old hole, which is off centre.

oil pump

Here is the original pump cover in position, the lift tube is marked red it is 6mm bore, the pump inlet port is 10mm. The only oil filtration was a gauze mesh to stop small bricks being ingested, so proper oil filtration is required. Poor oil quality and contamination caused lots of problems with these engines.

I want to get a filter into the sump through the hatch, a canister type can be mounted on the bottom of the sump hatch but they are a bit vulnerable to damage.

In order to get the filter to sit in the centre of the hatch, I need to reposition the lift pipe so a new pump base plate will be required. Bonus the new plumbing can be 10mm bore to suit the pump inlet port. I have some 12mm aluminium plate and a cunning plan.

oil filter selection

A raid on the spares department of the local bike shop provided some filter options the red one was my first choice. I then remembered the extension sump/oil cooler bought at Retromobile Paris this will add about 60mm the sump depth and make room for the Kawasaki filter on the left. Very pleased with that, it’s a good fit and inexpensive.


Here is a picture of Aardvark you can see the sump extension. This 1952 Panhard Dyna based 850cc car has been owned and raced by Don Racine for many years in America. Recently sold, it is now in Europe somewhere.

Here is a link to the Aardvark in action

Did you enjoy that? Back on topic, here is the thing, just balanced together.

and with the filter.

with the filter

Here are the new oil pump parts, the 1st one is cut from 3mm brass plate, the small grooves allow oil from the pump pressure side to lubricate the pump gear end face. The 12mm aluminium plate sits on top. I managed to mill the slot using a pillar drill and ordinary drill bits. Local Pembleton builder Graham Johnson has a band saw and very kindly cut it out, thanks Graham. A bit of fettling to do and the new lift tube to be TIG welded onto the back.

new oil pump parts
new oil pump parts

Well that’s all for now, I found these links interesting / informative.

Next time in part 3 - just more of the same. Shall I carry on or just call it a day?

Dave Parr

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