Valve service interval ??
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Joined: Jan 2007
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From: along the shore of Mishigami
I remember recommendations to replace the EVO engine lifters at around 35K miles, has that migrated into the Twin Cam, because this is the first I've heard about the TC interval.
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Joined: Oct 2015
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From: Pine Flat Dam/South Bay Area, CA
The 110's developed a reputation for lifter failure due to heavy valve spring pressure paired with poor quality lifters.
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From: Upstate New York
So how often am I supposed to change the lifters in the M8?
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Joined: Aug 2020
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From: College Station, TX
I haven't seen anything specific about the M8 lifters failing, but I would tend to think about replacing them at about 25-30k miles, or if they became noisy. Reason being is that with the M8 engines, one cam lobe, lifter, pushrod and rocker arm is opening two valves and compressing two springs at the same time. That puts a lot of additional stress on the rocker arm down to the cam, when compared to previous HD engines.
The good news is that the M8 heads flow well enough that you don't need to open the valves .600+, which would require stronger valve springs, to get good performance out of it. But even lower lift cams with faster ramps still add to the stress on the valvetrain.
Paul
The good news is that the M8 heads flow well enough that you don't need to open the valves .600+, which would require stronger valve springs, to get good performance out of it. But even lower lift cams with faster ramps still add to the stress on the valvetrain.
Paul
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From: west Michigan
I haven't seen anything specific about the M8 lifters failing, but I would tend to think about replacing them at about 25-30k miles, or if they became noisy. Reason being is that with the M8 engines, one cam lobe, lifter, pushrod and rocker arm is opening two valves and compressing two springs at the same time. That puts a lot of additional stress on the rocker arm down to the cam, when compared to previous HD engines.
The good news is that the M8 heads flow well enough that you don't need to open the valves .600+, which would require stronger valve springs, to get good performance out of it. But even lower lift cams with faster ramps still add to the stress on the valvetrain.
Paul
The good news is that the M8 heads flow well enough that you don't need to open the valves .600+, which would require stronger valve springs, to get good performance out of it. But even lower lift cams with faster ramps still add to the stress on the valvetrain.
Paul
To engineer and build a production engine in which the valve lifters have to be replaced every 25K to 30K miles would be major mistake.
How many "miles" do you think the prototype M8 engines were bench tested for? My guess would be for well over 100K miles and to point of failure.
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From: OH
I`m sure that is correct and the same was done during development of the T/C , yet the tensioner issue came to light when the bikes went out into the "real world"
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From: west Michigan
When I swapped mine for hydraulic tensioners at 50K miles, the shoes looked like they could go for another 20K miles. I ran Syn3 in all 3 for all of those miles.
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From: College Station, TX
Yeah, there are lots of cases where people drove EVO, TwinCams and M8's 40-50-80k miles with no lifter problems. But there are enough reports where that was not the case, and the results can be catastrophic in terms of damage done. The early failures are likely due to riding style, like a lot of idle and around town riding time etc. So it is up to each owner to decide if and when they will be replaced, but for me I'd rather replace them too early rather than too late.
And yes, the M8 valve springs are a little smaller, but the seat pressure is not half of a TwinCam or EVO engine. So you still have more pressure on those parts, and you also have a different rocker support system that has had some failures where the rocker shaft mount point on the head breaks off on high lift, fast ramp cams.
Paul
And yes, the M8 valve springs are a little smaller, but the seat pressure is not half of a TwinCam or EVO engine. So you still have more pressure on those parts, and you also have a different rocker support system that has had some failures where the rocker shaft mount point on the head breaks off on high lift, fast ramp cams.
Paul
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From: Driftless Area
I remember a long time ago, when my Evo didn't "feel" right to me. When I dug into it, the rollers in one of the stock lifters started falling out into my hand. I counted them to make sure none of them went into the bottom end.
Then I replaced them all with a better aftermarket brand and rode another 100,000 miles (so far).
Then I replaced them all with a better aftermarket brand and rode another 100,000 miles (so far).