Differences
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techtalk:ref:engmech05 [2019/08/22 13:08] hippysmack [Pics of Aftermarket Breather Valves] |
techtalk:ref:engmech05 [2020/03/01 23:29] hippysmack [Filter on End of the Vent Line] |
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| To stop a leak, you may be tempted to tighten the bolts even more. \\ | To stop a leak, you may be tempted to tighten the bolts even more. \\ | ||
| This could result in breaking the bolt. \\ | This could result in breaking the bolt. \\ | ||
| + | |||
| + | On 04-up heads, changing to aftermarket breather bolts means using bolts with the bigger I.D. (91-03) style bolts. \\ | ||
| + | The results of using the bigger holed bolt would be a slower rate of outflow and less positive crankcase pressure on a stock motor. ((Hippysmack of the XLFORUM http://xlforum.net/forums/showthread.php?t=2073932&page=4)) \\ | ||
| + | But the timing of the upstroke is the same which then pulls a vacuum. \\ | ||
| + | The umbrella valve will close down only when inside air pressure is lower than outside air pressure. \\ | ||
| + | If the inside pressure can't get out fast enough before piston upstroke happens the umbrella may 'float' or not close all the way. \\ | ||
| + | If the umbrella floats, X amount of extra air is pulled in until it does close. \\ | ||
| + | (on top of what didn't get completely out on the last downstroke = more air in the engine on the next downstoke = oil puking out the breather). \\ | ||
| + | How much slower the bigger bolt hole yields will vary with different engines. \\ | ||
| + | |||
| + | However, the smaller holed bolts were designed to OEM specs internally. \\ | ||
| + | If you've upgraded to bigger pistons, there will be more positive pressure displaced out the breathers on downstroke. \\ | ||
| + | This may negate the need for higher pressure generated by the smaller holed bolts. \\ | ||
| + | This may be something you'd want to watch since there isn't sufficient data to prove one way or the other. \\ | ||
| {{:techtalk:ref:engmech:breather_mod_2_by_hagen.jpg?direct&300|}} ((photo by Hagen of the XLFORUM http://xlforum.net/forums/showthread.php?t=146084&page=11)) {{:techtalk:ref:engmech:ds_breather_bolt_by_hagen.png?direct&300|}} ((photo by Hagen of theXLFORIM http://xlforum.net/forums/showthread.php?t=692845)) {{:techtalk:ref:engmech:broken_banjo_bolt_by_scout99.jpg?direct&200|}} ((photo by Scout99 of the XLFORUM http://xlforum.net/forums/showthread.php?t=28299)) | {{:techtalk:ref:engmech:breather_mod_2_by_hagen.jpg?direct&300|}} ((photo by Hagen of the XLFORUM http://xlforum.net/forums/showthread.php?t=146084&page=11)) {{:techtalk:ref:engmech:ds_breather_bolt_by_hagen.png?direct&300|}} ((photo by Hagen of theXLFORIM http://xlforum.net/forums/showthread.php?t=692845)) {{:techtalk:ref:engmech:broken_banjo_bolt_by_scout99.jpg?direct&200|}} ((photo by Scout99 of the XLFORUM http://xlforum.net/forums/showthread.php?t=28299)) | ||
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| The filter adds resistance to the vent pressure coming out of the engine. \\ | The filter adds resistance to the vent pressure coming out of the engine. \\ | ||
| This resistance can add to goop in the line / filter later. \\ | This resistance can add to goop in the line / filter later. \\ | ||
| + | It can also increase the vacuum inside the engine, which on a street bike, translates to weeping gaskets. \\ | ||
| The filter does not keep debris from coming back into the engine. ((Folkie of the XLFORUM http://xlforum.net/forums/showthread.php?p=2087347)) \\ | The filter does not keep debris from coming back into the engine. ((Folkie of the XLFORUM http://xlforum.net/forums/showthread.php?p=2087347)) \\ | ||
| Line 128: | Line 143: | ||
| If your breather valves are in good order, nothing can get back through them. \\ | If your breather valves are in good order, nothing can get back through them. \\ | ||
| - | The exception to this would be 91-03 engines with the middle rocker box umbrella valve with the tiny hole behind it. \\ | + | The exception to this would be small oil drainback hole that keeps oil from building up between the umbrella and the outlet. \\ |
| The tiny holes next to (and slightly lower than) the umbrella valves are for draining the separated oil back into the rocker box. \\ | The tiny holes next to (and slightly lower than) the umbrella valves are for draining the separated oil back into the rocker box. \\ | ||
| However, there isn't large enough suction back on the vent line to pull debris up and into the engine. \\ | However, there isn't large enough suction back on the vent line to pull debris up and into the engine. \\ | ||
