Mercury 1976 340 S/T Service Bulletin Download

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Summary of Contents for 1976 340 S/T

Page 1: ...atio of 25 1 is required for the first one tank full during engine Break In period and or for Severe Service operation Refer to Operation and Maintenance Manual for Severe Service definition 2 For 197...

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Page 3: ...ified Sno Twister Snowmobiles that this balancer MUST BE INSTALLED installation instructions following IMPORTANT A simple visual inspection via the water pump belt channel in the bell housing can veri...

Page 4: ...s and 0 5 hrs labor per snowmobile will be issued upon receipt of a completed warranty claim One claim listing individual CHASSIS Serial Nos may be used to cover service to all snowmobiles D 71737 Wei...

Page 5: ...l to the front crossmember silver colored 5 8 diameter head 3 located inside lower cowl in a line on each side of crossmember be replaced with STEEL rivets Mercury Part No C 17 76047 or an equivalent...

Page 6: ...0 0 0 J...

Page 7: ...4992 DRIVE CLUTCH WEIGHTS Color Red Black Red Yellow Red Black CD Red No Stamped on Weights 0146 106 0146 105 0146 106 0146 286 0146 106 0146 135CD 0146 106 Gram Weight 5 958g 7 858g 5 958g 8 800g 5 9...

Page 8: ...Weight of Weight Part No Increase light 3 058g 0146 108 CD0 Yellow 0 406 D 71731 CD 0 Engine RPM 3 725g 0146 175 CD0CD Red 0 437 D 71735 CD0 CD 4 479g 0146 135 CD0CDCDCD Black 0 471 D 71737 CD 0 Q CD...

Page 9: ...1 Check timing 3000 RPM 100 005 BTDC 2 Adjust idle slow enough to allow clutch to reset Too high idle speed will cause partial engagement and belt drag resulting in a slower start off the line 3 Chec...

Page 10: ...your Operation and Maintenance Manual SLIDER TRACK ADJUSTMENT The track must be adjusted for proper tension as outlined in your Owners Manual The track will run smoother if the drive sprockets are lub...

Page 11: ...ail of latest information in Sno Twister Hi Performance Tipster bulletins on racing To compile such a customer mailing list via direct computer mailing it is ESSENTIAL that 1 you fill out all registra...

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Page 13: ...is centered directly over the cylinder Check carburetor float levels and adjust high and low speed mixture screws to specifications Reinstall engine assembly then check torque converter alignment driv...

Page 14: ...at the lines are secure on fittings and not pinched or crimped Check exhaust system Inspect for cracks broken parts and missing coupler springs Make certain that system is mounted securely Drive sheav...

Page 15: ...D 68440 1 D 71334 Carbide Sk eg Pair 10 Carbide Inserts Carbide Sk eg Pair 6 Carbide Inserts Badly chipped bent or broken carbide skegs should be replaced immediately Placement and length of carbide s...

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Page 17: ...CD CD CD Mag Mag 1 2 0 7 1 1 1 2 1 1 0 3 0 3 0 3 0 3 0 3 14 7 19 0 21 7 17 7 21 4_ 5 305 0 305 0 630 0 10 463 0 10 931 0 10 109 0 5 109 0 5 109 0 1 2 98 3 2 115 95 5 90 Q 1 5 95 3 1 5 92 0 75 1 0 84...

Page 18: ...9 70729 72006 66602 70238 68345 69869 66011 Suspension Slide Rail Slide Rail Slide Rail Slide Rail Slide Rail Bogie Wheel Slide Rail Swing Frame Chassis Length 1880 6 3 2235 6 2235 6 2235 6 2209 8 6 2...

Page 19: ...the driven shaft pillow block D 71007 has developed a small crack as shown in Figure 1 because of the torque load and stress to which the block is subjected Thus far complete breakage has not occurred...

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Page 21: ...ow speed mixture needles air pilot screws on both the 340 Sff and 440 Sff at 2 turns open from seat 4 Set carburetor jet needles as follows 340 S f E ring in 2nd notch from top 440 S T E ring in 1st t...

Page 22: ...e ski assembly to the spindle TETHER SWITCH Obtain and install a race proven Safety Tether Switch Type of switch and mounting location are strictly driver preference Safety Tether Switch IS NOT availa...

Page 23: ...Stud on every bar alternating from side o side 44 pes required t t t Scat Stud with spacer underneath to achieve 3 8 9 5mm maximum height allowed Attach to rack not on bar alternately after every 4th...

Page 24: ...side 44 pes required Scat Stud with spacer underneath to achieve 3 8 9 5mm maximum height allowed Attach to track not on bar alternately after every 4th track bar on centerlines of track drive lugs as...

Page 25: ...e damage Modifying 340 S T from Stock to Modified Stock CYLINDER A Exhaust Port Enlarge exhaust port of cylinder as follows 1 Raise top edge of exhaust port to a point 1 120 28 45mm below top surface...

Page 26: ...A modified stock 340 SIT will deliver maximum power when operated at 8 750 to 9 000 RPM Modify and adjust torque converter to increase full throttle engine RPM to this speed B Drive Sheave Clutch Ins...

Page 27: ...g exhaust pipes position pipes in snowmobile and rotate sections to attain best fit 3 Weld sections of exhaust pipes together Be sure that welds are smooth and do not restrict exhaust B Exhaust Pipe S...

Page 28: ...e converter to increase full throttle engine RPM to this speed B Drive Sheave Clutch Install Drive Sheave Modification Kit D 71711A1 Modify profile of drive sheave ramps to attain correct full throttl...

Page 29: ...xhaust Port Enlarge cylinder exhaust port as follows a Raise top edge of exhaust port to a point 1 120 28 45mm below top surface of cylinder Figure 1 DO NOT change bottom edge of exhaust POrt b Increa...

Page 30: ...t permitted for modified stock competition CARBURETION Adjust high speed mixtures adjust mixture needles and or rep lace fixed high speed jets to obtain normal coloration of spark plugs CAUTION When i...

Page 31: ...ding B Piston Modify piston Figure 2 as outlined in Modifying 440 SIT from Stock to Modified Stock preceding Squish Area Re Cut Squish Area out to Original Diameter Shape of Stock Cylinder Head ___ Sh...

Page 32: ...header pipe Figure 5 3 Weld sections of exhaust pipes together Be sure that welds are smooth and do not restrict exhaust _ eon Cones LV D Rotate for Best Fit in Snowmobile _ and Re Weld at Center Sec...

Page 33: ...carburetors Mikuni VM 38 and fixed high speed jets No 400 to No 480 contact DRIVE SYSTEM A Maximum Engine RPM Mercury Marine Hi Performance Products Department 20 Wisconsin Street Oshkosh Wisconsin 54...

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Page 35: ...ake certain that the FRONT END of both wear strips extend 4 10 16cm forward of FRONT wear strip attaching hole in chassis Failure to observe this dimension exactly may result in damage to the chassis...

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Page 37: ...ke certain that the FRONT END of both wear strips extend 4 10 16cm forward of FRONT wear strip attaching hole in chassis Failure to observe this dimension exactly may result in damage to the chassis t...

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Page 39: ...sheave ramp profile suitable for 340 S T and 440 S T Super Modified Snowmobiles see drawing below This ramp profile is intended to be used with green compression spring and optional weights 0146 135 f...

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Page 41: ...1 2mm 47 3 1 2mm 46 5_ 1 2mm 46 5 1 2mm 46 5 1 2mm Width of Transfer Ports 34 2 1 0 14 1 1 0mm 33 8 1 0 12 8 1 0mm 27 7 1 0 10 7 1 0mm 32 3 1 0 12 5 1 Omm 32 1 1 0 15 2 1 0mm Width of Intake Ports 42...

Page 42: ...l Slide Rail Slide Rail Slide Rail Overall Vehicle Length 99 44 500 99 44 500 89 875 250 89 875 250 Chassis Length 88 00 250 88 00 250 82 875 250 82 875 250 Ski Length l t 37 500 125 33 500 250 33 500...

Page 43: ...termine correct carburetor jetting ONLY CYLINDER HEAD SQUISH CHAMBER CLEARANCE A MINIMUM of 030 0 76mm clearance must be maintained between cylinder head and piston dome heads torqued to 225 in lbs 25...

Page 44: ...nt 1 Lubricate from ends of cables around core wires and or 2 Drill a 1 16 1 6mm hole in top end of cable junction block and lubricate through the hole CLUTCHING To obtain and maintain ultimate snowmo...

Page 45: ...spring curl as required c CARBIDE SKEGS Starting with Standard Carbide Skegs D 74783 1 ten 1 carbide segments numbered 1 thru 10 front to rear 1 Move carbide segment Nos 1 and No 2 behind No 3 Move N...

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Page 47: ...er Modified ENGINE A Cylinders 1 Exhaust Port Enlarge exhaust port of each cylinder as follows a Raise top edge of exhaust port to a point 1 100 27 94mm below top surface of cylinder Figure 1 DO NOT c...

Page 48: ...t to a point 3 779 95 99mm below top surface of cylinder Figure 1 DO NOT change top edge or chordal width of inlet port b Cut 4 inlet port corners at a radius of 0 20 5 08mm Figure 1 c Reduce boss at...

Page 49: ...d mixture jet needles and fixed high speed jets Adjust high speed mixture replace fixed high speed jets to achieve normal coloration of spark plugs NOTE Use fixed high speed jets which are 1 to 2 jet...

Page 50: ...4 D 69757A14 13 D 69757A13 Low MPH 12 D 69757A12 Standard factory installed 250 SITdriver sprocket BREAK IN PROCEDURE After modifying an S T Snowmobile and prior to racing the engine should be run in...

Page 51: ...RMANCE and could result in severe engine damage Modifying 340 S T from Stock to Modified Stock CYLINDERS A Exhaust Port Enlarge exhaust port of each cylinder as follows 1 Raise top edge of exhaust por...

Page 52: ...3 Reduce boss at top edge of inlet port to a minimum Figure 1 Boss must be large enough to completely cover piston ring when piston is at BDC bottom dead center 4 After grinding inlet port make a 0 06...

Page 53: ...1 Cut production stinger from each exhaust pipe NOTE Converging cone of exhaust pipes may have to be cut back slightly so that inside diameter ID ofcones is enlarged to 1 00 25 40mm same ID as replac...

Page 54: ...ns are supplied with modification kit C Sprockets Snowmobile may require re gearing because of increased horsepower a result of engine and exhaust modifications Installation of another driver sprocket...

Page 55: ...CREASE PERFORMANCE and could result in severe engine damage Modifying 440 S T from Stock to Modified Stock ENGINE A Cylinders 1 Exhaust Port Enlarge exhaust port of each cylinder as follows a Raise to...

Page 56: ...ge of inlet port to a point 3 829 97 26mm below top surface of cylinder Figure 1 DO NOT change top edge of port b Increase chordal width of inlet port to 1 772 45 00mm Fiigure 1 c Cut 4 inlet port cor...

Page 57: ...st system as follows A Exhaust Pipe Diverging Cones 1 Cut 1 00 25 40mm from diverging cone of each exhaust pipe directly behind header joint Figure 3 2 Weld header joint to diverging cone of each exha...

Page 58: ...achine lighter A certain amount of weight may have to be retained to meet minimum weight limit 3 Check synchronization of carburetor throttle valves and readjust as necessary CAUTION When in doubt abo...

Page 59: ...9757A14 1 13 D 69757A13 Low MPH 12 D 69757A12 Standard factory installed 440 SIT driver sprocket BREAK IN PROCEDURE After modifying an SIT Snowmobile and prior to racing the engine should be run in at...

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Page 61: ...m D 74492A1 failing on 1976 Model Sno Twisters The failure is occuring where track guide is welded to the control arm Reinforce rear suspension control arm as follows A If track guide has NOT BROKEN l...

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Page 63: ...member as follows 1 Remove 11 rivets which secure lower bulkhead to crossmember Figure 1 If any cracks in crossmember are evident weld as necessary before installing reinforcing steel strap 2 Position...

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Mercury 1976 340 S/T, Service Bulletin

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