TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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Figure 8-4. Figure 8-5. Checking piston position with brass rod. Figure 8-6. Borescope instrument in position for cylinder bore inspection. (6) Connect borescope control transformer (fig. 8-4) in 110 volt electrical circuit and insert borescope into cylinder (fig. 8-6), Visually adjust light intensity and mirror angle until a sharp clean image of the cylinder bore is apparent. Inspection of the cylinder bore should be made at three levels, lower, middle, and upper position of the cylinder to assure maximum coverage of the cylinder wall surface. Polish marks the length of the piston pin travel may be evident on the cylinder side walls on a line parallel with the cylinders. These lines normally are not serious and are caused by the movement of the piston pin allowing the pin end plugs to come in contact with the cylinder walls. Other wear lines, surface scratches, and wear patches that are not con- tinuous the full length of the cylinder bore are usually not significant. (7) A normal shiny area will often appear at midbore and usually on the anti-thrust side of the bore (below exhaust valve on left bank and below intake valve on right bank). This shiny area will not extend the full length of ring travel and should not be confused with scuffing of the cylinder wall. (8) Cylinder bores that show evidence of ΒΌ in. or more scuff marks, must be replaced. Re- hone cylinders and thoroughly inspect (para 6- 31 and 6-32), dimensionally check and clean thoroughly before reinstalling cylinders on engine. Replacement cylinders will require 8-9