Putting the Triumph Pre-Unit Engine back together pt 2

Published on 5 January 2024 at 19:21

Having had a sleep on the problem with getting my push rods aligned so I could refit the rockers I came up with a very simple solution. I got a bit of cardboard and cut it out so that one edge rested against the valve springs and two notches allowed the pushrods to sit in exactly the right position. It worked brilliantly, cost nothing and only took a few ,minutes to do. I was very pleased with that, both rockers went on easily with new gaskets fitted, I fitted new fibre washers to the tappet covers while I was at it. Adjusting the tappets was fairly simple although getting a feeler gauge in is quite awkward - the inlets are set to 2 thousandths of an inch clearance, the exhausts 4 thou. They will need rechecking once everything has bedded down a bit.

There seems to be pretty good compression there but I expect it to get better after an hour or two's running. My Motobecane had hardly any compression at al when I first rebuilt it but now it has loads, hopefully the Triumph will follow suit. Only thing I am a bit concerned about is that when I turn it over air is pushed back through the carbs. Ether it is running a hell of a lot of overlap or the valve timing is out, not sure which yet. I tried to look for the cam numbers but couldn't see any so I have no idea what lift, duration or timing it is running. I know it did run at some time though so I will leave it as is and see what happens. There is no clashing of pistons and valves, it turns over really smoothly, it should be ok.

what is not ok is the magneto, there is no spark whatsoever on either pot. I measured the resistance of the ht leads to ground, it should have been a few thousand ohms, it was open circuit. My big fear is that the winding has gone, that will be expensive to fix and an absolute pain. I checked the wires themselves, they are fine but there is no resistance at the output posts so it doesn't look good.

It's looking a lot cleaner now, I am not going to polish the life out of it, it's a 60 odd year old racer with a story to tell, I want to keep it as original as possible, warts and all.



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stephen lovett
6 months ago

Hello Dave, ad on Gumtree - in Woodhall Spa for anti clock Lucas k2f working mag for £75
Might help Steve