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- Jun 30, 2012
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- 13,275
I was thinking about a topic on this forum which was about comp. ratio and carb jetting. I think the guy said that when he raised the comp. ratio, he fitted larger main jets. When I jet my carbs I always start larger and jet leaner.
A few days ago I went to a mate's funeral. He was Steve Oszko - in about 1965 he was the top A grade road racer in Victoria. Ron Toombs used to come from New South Wales with 500cc the Henderson Matchless which had a four valve head. At many meetings Ron would win the 3 main feature races. Steve was his main opposition with a 500cc Manx - he could always get up with Ron, but all he could ever do is put pressure on him and wait for him to make a mistake - which he never did.
Steve was a motor mechanic, educated in Hungary and a very logical thinker about motorcycle racing. His 500cc Manx was on 14 to 1 comp, on methanol. He made his own pistons.
Over the years I discussed a few things with him. When we talked about jetting, he said 'I run my jetting as lean as possible right down the needle'. When I asked him about ignition timing. he mentioned that with methanol at 12 to 1 comp. ,he used the same advance as for petrol, but at 14 to1 comp. he retarded the ignition by 2 degrees.
I had sometimes wondered about the effects of skinny exhaust pipes. Some guys had claimed that the fat exhaust on the 500cc Manx gave better power. I was once in Steve's workshop and noticed the exhaust pipe of his Manx. When I said 'that is a very skinny pipe', he said ' you bastard, you notice too much'.
A few days ago I went to a mate's funeral. He was Steve Oszko - in about 1965 he was the top A grade road racer in Victoria. Ron Toombs used to come from New South Wales with 500cc the Henderson Matchless which had a four valve head. At many meetings Ron would win the 3 main feature races. Steve was his main opposition with a 500cc Manx - he could always get up with Ron, but all he could ever do is put pressure on him and wait for him to make a mistake - which he never did.
Steve was a motor mechanic, educated in Hungary and a very logical thinker about motorcycle racing. His 500cc Manx was on 14 to 1 comp, on methanol. He made his own pistons.
Over the years I discussed a few things with him. When we talked about jetting, he said 'I run my jetting as lean as possible right down the needle'. When I asked him about ignition timing. he mentioned that with methanol at 12 to 1 comp. ,he used the same advance as for petrol, but at 14 to1 comp. he retarded the ignition by 2 degrees.
I had sometimes wondered about the effects of skinny exhaust pipes. Some guys had claimed that the fat exhaust on the 500cc Manx gave better power. I was once in Steve's workshop and noticed the exhaust pipe of his Manx. When I said 'that is a very skinny pipe', he said ' you bastard, you notice too much'.