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For those of you who have read my posts, I am the proud owner of a functional Norton Combat with matching numbers, 202322. I bought it last August, after it had sat relatively well perserved and unused since about 1975. I know the original owner and was able to get the full life story of the bike, which made it an even more attractive find, as though it had a couple of owners since '75, none of them had ever done any thing with it. When I recieved it, there were about 9200 miles on the clock, only 1000 since a full rebuild in 1974. Although it is not an unusual time period for a Combat to detonate, this one grenaded the top end, not the bottom end. Pistons, cylinder barrels, head, camshaft, etc. all were replaced, as well as the main bearings, for good measure, all this at a cost of about $800 at the time. When put back together, she retained her 10:1 compression and 2S cam.
I was able to get her back on the road with a minimum of effort, and put about another 1000 miles her last fall. This past winter/spring, I decided to freshen her up as the years of sitting had taken their toll on the seals and the isolastics. To make a long story short, all the black parts were powder coated, all rubber bits replaced, all aluminum polished, all chrome re-chromed, new tires (the front was still original), carbs rebuilt, oil filter added, seat recovered, O-ring chain, blah, blah, blah,... and an oil pressure gauge installed.
Which brings me to the point of why I started telling this story. Last week, I finally was in a state of assembly where I was able to spark some life into the old girl. Once alit, all focus turned to the oil pressure gauge, which after a time, was still pegged at 0 (zero). Horror set in, then disbelief. A back-up gauge was connected, still zero. Rocker feed fittings were loosened, no stream of oil, just drip, drip, drip. The timing cover was pulled, then the oil pump. The pressure side looked okay, but the scavenge side had swallowed some shrapnell. A replacement pump was located and installed, still zero. The pressure relief valve was disassembled, a little sticky, but otherwise okay. Once the sticky was removed, it was reinstalled, still zero. After studying some detailed pictures of the timing cover in the parts book, I pulled the relief once again, and fished a piece of MIG wire up the gallery joining the pressure feed to the relief. There is supposed to be a 1/4" blanking plug in this location, and after feeding about 3" of wire up this hole, I was content to say that the plug was missing.
EUREKA!! Mystery solved. After pulling the timing cover (again, fourth time, I think. I can now time a Boyer in my sleep), I discovered that not only was the plug missing, but also any signs of any staking to hold it in place. I honestly believe that the plug was never there in the first place. This would explain why she blew in '74 and why it had always had a noisier top end than my dad's '74 850. Rather than just install a plug, I decided to put another timing cover on and save the cover with virgin hole as a momento.
I now have 50 psi at idle cold, 70 when revved, 40 psi at 3000 rpm hot, and 20 psi at idle hot. And the motor sounds alot happier. Thirty years and 10000 miles later, it is the first time it has had oil pressure!!!
Derek
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