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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Is it the valve guides, the cylinder sleeve or the piston?
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<blockquote data-quote="Ducvelo" data-source="post: 50862" data-attributes="member: 2564"><p>I had the heads and barrels off my Series C twin last year, and since I've put them back oil consumption has been enormous - c.2 pints in 100 miles. Based on the plugs, this seems to be confined to the rear cylinder. When I stripped the top end, valve guide clearance was large but not very excessive, 0.004" inlet, 0.008" exhaust. Rocker tunnels/bearings had had the usual treatment (dremel work on the valve well, and good grooves in the bearings) to improve oil drainage. Piston clearance about 0.004" at bottom of skirt (pistons/rings are from the mid-70s). Sleeves 'rang' well when knocked on the top - no sign of movement, but I don't have a press to really check. Little wear on the sleeves - I think the engine has only done 20,000 miles since the 70s rebuild. Was on a 0.030" oversize. Breathers are working well, and hardly passing any oil, and no leaks. The rebuild was to sort out the timing side - I swapped out badly worn Mk 2 cams and fitted the Gary Robinson 105s. I checked carefully clearance on the valve guide with the increased lift. Also fitted the restrictor disks for the cylinder oil feeds. I did remove the joggle wires, but now put one back on the No 1 inlet feed - hasn't made any difference.</p><p></p><p>Before I strip down again, any one got any tips on how to work out which is causing the problem?</p></blockquote><p></p>
[QUOTE="Ducvelo, post: 50862, member: 2564"] I had the heads and barrels off my Series C twin last year, and since I've put them back oil consumption has been enormous - c.2 pints in 100 miles. Based on the plugs, this seems to be confined to the rear cylinder. When I stripped the top end, valve guide clearance was large but not very excessive, 0.004" inlet, 0.008" exhaust. Rocker tunnels/bearings had had the usual treatment (dremel work on the valve well, and good grooves in the bearings) to improve oil drainage. Piston clearance about 0.004" at bottom of skirt (pistons/rings are from the mid-70s). Sleeves 'rang' well when knocked on the top - no sign of movement, but I don't have a press to really check. Little wear on the sleeves - I think the engine has only done 20,000 miles since the 70s rebuild. Was on a 0.030" oversize. Breathers are working well, and hardly passing any oil, and no leaks. The rebuild was to sort out the timing side - I swapped out badly worn Mk 2 cams and fitted the Gary Robinson 105s. I checked carefully clearance on the valve guide with the increased lift. Also fitted the restrictor disks for the cylinder oil feeds. I did remove the joggle wires, but now put one back on the No 1 inlet feed - hasn't made any difference. Before I strip down again, any one got any tips on how to work out which is causing the problem? [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Is it the valve guides, the cylinder sleeve or the piston?
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