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Old 13th November 2019
Tomcatt Tomcatt is offline
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I run premium. There's a Mobil gas station "mart" about a mile from my house with 91 octane (M+R/2) no ethanol. I've been seeing some detonation, the ECU (with Powervision) has the detection software but oddly doesn't have the software to pull timing. So, I've been tailoring my fuel and timing mapping around knock indications. I expect the detonation to go away when I get the top end off and tighten up the squish clearances.

I went thru the same process on my BT Evo. It also had .055" head gaskets as OE. Harley made a running change to .040" head gaskets to tighten the squish clearance to fix the detonation issues the earlier BT EVO's had. I did more, also shortening the cylinders. Here I am 30+ yrs later doing the same the same thing on my '17 Evo Sportster. My BT EVO was an '87.
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2017 XL1200C in Wisconsin, USA

Last edited by Tomcatt; 13th November 2019 at 19:26..
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