Wednesday, 17 August 2011

Heads off

Been trying to work out why the motor has been running rough, it started to need a bit of choke to keep it ticking over and seemed to be fouling the plugs all the time. At first i thought it might be the manifold nipple on the rear pot, they are as tight as they can go... So this morning i whipped the heads off, both James gaskets have blown between the head bolts and the cylinder. New copper gaskets on order!

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Location:Arthurs Terrace,Achnasheen,United Kingdom


  1. any idea what comp ratio you have there steve?

  2. Rowan, standard Scout is about 6:1 my motor is running pop up pistons, Bonneville spec. and skimmed heads so maybe nearer 7:1 ... I might check if I get a chance before the new gaskets arrive. I reckon the blow is more to do with not re torquing it again after the run to the Muir of Ord show. Also realised that I'd not used the right thick washers on the head bolts, so that might have been another cause , not spreading the load fully!

  3. i've blown so many of them james blue gaskets i cant count them... they say them blues dont need re-torquing, sounds strange but thats what they say .... definately go copper... i'd buy some pure soft copper and pierce them out meself i reckon... less work than doing it time and time again....

  4. Yeah, I was reading the build thread on Lars' Saltcracker 741 LSR bike, his James gaskets burnt out in a similar way on his last Bonneville attempt, rebuilt it with 1.7mm thick pure copper ones for this year's attempt.