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techtalk:evo:engmech07a [2019/11/06 23:14] hippysmack created |
techtalk:evo:engmech07a [2019/11/07 00:06] (current) hippysmack [Making 91-03 Breather Bolt Holes Smaller] |
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| ====== REF: Engine Mechanicals - Sub-07A ====== | ====== REF: Engine Mechanicals - Sub-07A ====== | ||
| ====== Making 91-03 Breather Bolt Holes Smaller ====== | ====== Making 91-03 Breather Bolt Holes Smaller ====== | ||
| + | This was done as a test to see if crankcase pressure would change with the smaller hole using a slack tube to measure the pressure change. \\ | ||
| + | The process is document here. \\ | ||
| + | 5/16" fine threaded bolts were screwed into the threaded holes in the breather bolts with O-ring seals. \\ | ||
| + | The stock air cleaner slides over the new bolt assembly with no clearance issues with the 1/2" hex head. \\ | ||
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| + | {{:techtalk:evo:engmech:making_91-03_breather_bolt_holes_smaller_pic_7_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) \\ | ||
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| + | The internal hole on the outside end of 91-03 breather bolts is factory tapped 5/16"x24. \\ | ||
| + | It's not known at this time why as the thread are not used on OEM Sportsters. \\ | ||
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| + | Below and for lack of having fine thread 5/16" bolts, course thread SS (5/16"x18) bolts were re-threaded to 5/16"x24. This works fine and re-threads easily. \\ | ||
| + | But it's easier to go and buy the correct bolts. \\ | ||
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| + | The holding block was needed to keep the bolt straight while boring a hole through it. \\ | ||
| + | You could use a block of wood, plastic or steel. The hole was drilled .2720" and tapped 5/16"x24. \\ | ||
| + | Each bolt was screwed into the hole, corner to corner lines drawn across the head to find center and the center punched to keep the bit from wandering. \\ | ||
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| + | {{:techtalk:evo:engmech:making_91-03_breather_bolt_holes_smaller_pic_1_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) {{:techtalk:evo:engmech:making_91-03_breather_bolt_holes_smaller_pic_2_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) {{:techtalk:evo:engmech:making_91-03_breather_bolt_holes_smaller_pic_3_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) \\ | ||
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| + | The small hole in 04-up breather bolts is 1/16" in diameter. However, as a test, 1/8" holes were drilled in these. \\ | ||
| + | An O-ring was added under the head to seal off the original hole. \\ | ||
| + | The factory threads were chased with a 5/16"x24 tap to straighten warpage and clean the threads for the new bolts to be inserted. \\ | ||
| + | Normally, marking center on both ends and sending the drill bit in just over half way from each end will make a more straight thru hole. \\ | ||
| + | But this just being a test, the hole was drilled thru from one side. \\ | ||
| + | The hole ended up off center in the thru end but this is not a critical point in this application. \\ | ||
| + | |||
| + | {{:techtalk:evo:engmech:making_91-03_breather_bolt_holes_smaller_pic_4_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) {{:techtalk:evo:engmech:making_91-03_breather_bolt_holes_smaller_pic_5_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) {{:techtalk:evo:engmech:making_91-03_breather_bolt_holes_smaller_pic_6_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) \\ | ||
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