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| techtalk:ref:engmech01v [2025/08/06 16:34] – ↷ Links adapted because of a move operation hippysmack | techtalk:ref:engmech01v [2025/08/07 02:52] (current) – [Solids vs Hydraulics and Pushrod Types] hippysmack | ||
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| - | ====== REF: Engine Mechanicals - Sub-01Q ====== | + | ====== REF: Engine Mechanicals - Sub-01V ====== |
| ====== Lifter Comparisons ====== | ====== Lifter Comparisons ====== | ||
| + | ====== Solids vs Hydraulics and Pushrod Types ====== | ||
| + | Lots of folks have questions on the best type lifters to use in their Sportsters. The easiest answer is to do what the factory did. But in the case of upgraded engine parts, that isn't always the right answer. Below are some Q&As from XLF member, aswracing. \\ | ||
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| + | === When are applications where you can't use a stock lifter? === | ||
| + | When you run out of tappet anti-rotation pin clearance. Red Shift 585's have stock base circles and typically require an aftermarket tappet that has longer anti-rotation flats. SE 575's have almost as much lift, but they have a smaller than stock base circle, so they typically don't cause tappet pin clearance issues. ((https:// | ||
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| + | === What is the advantage of using non-adjustable pshrods? === | ||
| + | A non-adjustable pushrod is stronger at a given weight and also less likely to cause " | ||
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| + | === When do you stop using fixed pushrods and switch to adjustables? | ||
| + | The only good reason for adjustables is when you use a solid or travel limited lifter. These types of lifters require a very specific pushrod length that will vary literally every time you put the rocker box on. The only reasonable way to do that is with an adjustable. Quick install pushrods don't work that well on Sportsters, for a couple reasons. I'd avoid them at all costs. \\ | ||
| + | More lift in the cam doesn' | ||
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| + | Really you should base your decision on the type of lifters you use. If you're using a regular hydraulic lifter, you're better off with non-adjustable pushrods. With higher spring pressures I highly recommend a better set than the stockers, those things are flexi-flyers. But stay with a non-adjustable. A non-adjustable pushrod is stronger than an adjustable at a given weight, or conversely, lighter than an adjustable at a given strength. Plus you don't have to mess with collapsible covers. ((https:// | ||
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| + | If, however, you're using a solid or other travel limited lifter (i.e. Hydrosolids, | ||
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| + | === What is a proper argument for using hydraulic lifters? === | ||
| + | A hydraulic lifter self-adjusts within a certain range. In other words, if your pushrods are too long, the lifter automatically shortens, and if the pushrods are too short, it automatically lengthens. The hydraulic lifters used in HD motors have about .200" of plunger travel. As long as it's preloaded between about .050 and .150, it adjusts itself properly. So in other words, there' | ||
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| + | If you preload it too far (i.e. pushrods that are too long), for example, the valves won't land on the seats when the lobes are in the full down position, and as such, you'll suffer loss of compression and/or " | ||
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| + | The whole idea of a hydraulic lifter is to self-adjust, | ||
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| + | This 2007 Sportster had it's factory stock hydraulic lifters, no travel limiting washers, and non-adjustable pushrods. \\ | ||
| + | {{: | ||
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| + | 8000rpm with excellent valve train control. Tell me again what solid or travel limited lifters bring to the party? \\ | ||
| + | I also own a Buell XBRR factory race bike. 56 of them ever made. It came from the factory with a 9000rpm limit, makes 150hp at 8500rpm, and uses the same hydraulic lifters that came in all 2000+ Sportsters, literally the same part numbers. It's stock pushrods are also non-adjustable and it has one piece pushrod covers. \\ | ||
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| + | Another case in point: tens of thousands of Buell XB9 models produced from 2003-2010, every single one of them with a factory 7500rpm rev limit and a warranty, using the exact same hydraulic lifters that come stock in XL's since 2000. Same springs and locks and retainers and guides and pushrods and valves as the 04-up 1200's for that matter. I've never heard of one having a failure. And yet that same hardware breaks at 7000rpm with a different cam grind, as we've seen on the XLForum. The cam profile has a huge amount to do with it. ((https:// | ||
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| + | It's all about control. When you lose control of the valvetrain, a hydraulic lifter does what hydraulic lifters are supposed to do, it takes up the slack. But if that slack was caused by float or bounce, you're now holding the valve up off it's seat. Commonly referred to as lifter pump-up. | ||
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| + | Solid lifters, anti pump-up hydraulic lifters, and travel limited hydraulic lifters, are all just different approaches to dealing with this problem. | ||
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| + | But if you never lose control in the first place, the hydraulic works just fine. | ||
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| + | Hydraulics only have an issue with high rpm if you get slack in the valvetrain. When that happens, they do what hydraulics are designed to do, they take up the slack. So the lifter becomes too long and the valve doesn' | ||
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| + | But if you have good control of the valvetrain, which comes from a combination of lobe profile, spring pressure, and lightweight parts, then you don't get slack, and hydraulics work just fine. I maintain that travel limited lifters, adjustable pushrods, and collapsible cover kits are just more things to spend money on that have almost no tangible benefits and multiple disadvantages. Lots and lots of stuff like that out there for Harleys. \\ | ||
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| + | Solid tappets require frequent adjustments and they' | ||
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| + | === What is a proper argument for using solid or travel limited lifters? === | ||
| + | The one thing that a solid or travel-limited lifter brings to the party is easier starting, since they don't bleed down as the motor sits, thus shortening the intake duration which raises compression. They' | ||
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| + | You need to have a running clearance, which you set by adjusting pushrod length while using a feeler gauge positioned between the valve tip and rocker tip. Now it's true, you can slightly alter lift and timing by varying that running clearance, and racers sometimes do this. But you can't move it much without running into the aforementioned issues. Within the range you have to safely work with, it generally has very little effect on the dyno sheet. ((https:// | ||
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| + | The Hydrosolid is a nice solution for someone who wants the valvetrain control of a solid (especially at high rpm) with the self-adjusting convenience of a hydraulic. They do require adjustable pushrods and collapsible covers, but they' | ||
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| + | The quickest and surest way to determine if you have travel limiters is to take them apart. There' | ||
| ====== Tappet Flats ====== | ====== Tappet Flats ====== | ||
| **This is in consideration of induced noise from the use of high lift cams**. \\ | **This is in consideration of induced noise from the use of high lift cams**. \\ | ||
