Thanks Doug, would you be happy to supply a copy of your drawing. Thanks Bruce

Somewhere in the middle of the wrecked +0.030 piston for a T5, the hope is that what there is can be cut down to make a +0.020 replacement piston, and here we continue with the salvage effort. They still have some way to go to get cleaned up properly, but as I inspect them closer, I found a disappointing situation at the top ring slot. These pistons are so rare, I thing us lucky that we have even these.

I find the oil return holes on the scored side blocked up with very hard carbon. I used a undersized drill bit in a pin vice to finally clear them.



More serious is I notice the top ring had a "wider region". The entire slot was quite far out of specification anyway, as also the ring that was in it. I had thought that that region might have been "bent upwards", but I have established it was all some kind of extraordinary wear damage just on that upper edge.



Measuring, we discover the ring slot is as the measurement shown in the picture.



The ring itself must also have worn, seemingly ending up kind of "slightly wedge shaped". It would have been nominally a 1/16" thick ring.



As to what to do about it, I don't yet know. I have heard of folk TIG welding busted pistons, but for this one, I am opting to simply cut the ring out to its widest existing measure, and just use a new thicker ring that has the right clearance. The book says clearance should be 0.001" minimum, and 0.003" maximum. It is entirely another question whether I should also change the slot on the other piston to make it look the same.

I have no idea whether it will matter much that I increase a ring size by 0.5mm or so into the space up to the top, but I guess I just have to risk it. Of course, if somebody out there has a better piston donor, then yes please. do tell.

No I don't. I was going to make some, but only got as far as a drawing. It is the same part number (9578) as used on the 350 EW from engine #19800 onward when they abandoned the screw in tappet guides, and all 250/350cc models until 1936. Also the same part number (now 9578-2) used on the 500/600cc Aeros.

-Doug

Hello Doug, Thanks for that, I don't suppose you would have a couple of spares? Cheers Bruce

Discussion about Douglas Aero 1936 cam followers has been split into a new topic and moved to General Discussion.

Douglas Aero 1936 Cam followers

Spring steel bridge clamp. Goes under the cylinder base nut between the valve and the legs bear on the edge of the tappet guide keeping them firmly pushed down into their tapered sockets. Very simple and effective. Beware some repros were made from plain steel and they just bend when clamped down and will not prevent the tappet guides from backing out. make sure they have a little bit of temper to them, like a spring lock washer.



-Doug

Douglas Aero 1936 Cam followers, can somebody tell me what holds the cam follower guides into the crankcase. Cheers Bruce

Hi Everybody, thanks for your help with the clutch cam lever, I have made a new one the opposite had to the damaged one I have.

I'm thinking just a smear right around the flange, to try first.

So just at the base of this pic (selected at random).
You don't want to block up any of the drillings or passages.
https://www.oldtimervergaser.de/images/product_images/original_images/AL-MKE-div1.jpg

You said it was loose in the body, so it might be that this isn't enough to prevent too much air
being able to be drawn in at idle - and bypassing the idle circuit.
In which case you might be right in hunting for another body.

But it can't hurt to try this ...

You are sure that all the gaskets are the same in both carbs ?
And the fuel levels are identical in both carbs.

Can you get the jet block out of the other carb ? 
To try swapping bodies over ...

Yes, I see what you mean. 925 area code is normally associated with parts of northern California. However, Arizona is adjacent to California and it may be a mobile number. Suggest to try calling it if you can.