Compression release
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Elite HDF Member
Joined: May 2016
Posts: 4,130
Likes: 2,133
From: PSL Florida
Compression release
Got to thinking the other day, if I were to have head work done...
Saw a few different places that have different prices for ACR VS Manual releases.
Without coming off as an ***... Why do these bikes need compression releases? They aren't old kick start bikes. I know their purpose but why? Get away with a weaker starter, to cut manufacturing cost? If that's the case what about a higher amperage higher torque starter motor? Or do they not exist in the aftermarket realm?
I've built plenty of high compression small block Chevys for dirt oval racing and never used anything more than a cheap autozone starter for a truck and never had any issues... Some of the race cars I built I used heads without accessory holes nor did I fabricate brackets for them either so I just ran a belt for the power steering and water pump and made sure I had a good battery with a strong charge typically a higher CCA rating than need be say a battery meant for a diesel with 950-1200 CCA.
I know I'd run a heavier gauge wire to carry the amperage if I were to do such a thing and possibly stouter relay/solenoid. That isn't a problem. After seeing a few videos on the interwebs of some pretty sweet bikes, can hear the puffing of the compression releases as it's cranking and it just plain is an annoyance to me. Like I said I could understand if this was a kick start high compression bike (like the KX500 I had many moons ago) where the kicker could buck you up over the handle bars or slip and whack your ankle/calf and ruin your day without MX style boots on...
Saw a few different places that have different prices for ACR VS Manual releases.
Without coming off as an ***... Why do these bikes need compression releases? They aren't old kick start bikes. I know their purpose but why? Get away with a weaker starter, to cut manufacturing cost? If that's the case what about a higher amperage higher torque starter motor? Or do they not exist in the aftermarket realm?
I've built plenty of high compression small block Chevys for dirt oval racing and never used anything more than a cheap autozone starter for a truck and never had any issues... Some of the race cars I built I used heads without accessory holes nor did I fabricate brackets for them either so I just ran a belt for the power steering and water pump and made sure I had a good battery with a strong charge typically a higher CCA rating than need be say a battery meant for a diesel with 950-1200 CCA.
I know I'd run a heavier gauge wire to carry the amperage if I were to do such a thing and possibly stouter relay/solenoid. That isn't a problem. After seeing a few videos on the interwebs of some pretty sweet bikes, can hear the puffing of the compression releases as it's cranking and it just plain is an annoyance to me. Like I said I could understand if this was a kick start high compression bike (like the KX500 I had many moons ago) where the kicker could buck you up over the handle bars or slip and whack your ankle/calf and ruin your day without MX style boots on...
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Joined: Jun 2006
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From: san antonio
If you don't think one of these vtwins can generate a nasty heat soaked kick back at CCP of 200psi, you are mistaken; it can happen at 9.5:1. A real nasty heat soaked kick back can tweak a crank. Considering the fragility of the HD cranks since the supplier was shipped off shore, ACRs from the factor is just insurance for the MoCo, IMHO, to protect the shitty cranks. Aside from that, a set of manual compression releases is a much more cost effective way to deal with compression and extend battery and starter life than installing a monster starter. Hearing the puffing from the CRs is much less an annoyance to me than dealing with the potential downside of not having CRs. Both my bikes generate 190psi+ CCP and have manual CRs and I use them every time.........
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Elite HDF Member
Joined: May 2016
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From: PSL Florida
Makes sense in that regard. I would figure they cut cost by putting a weak starter in to cut production cost and increase profitability. Like ford does with alternators since 2012 with their load shed system to run all these high amperage devices such as EPAS and other amenities. You'd be amazed that they run such a wimpy output alternator for what they are running electronically...
Club Member
Joined: Jun 2007
Posts: 45,429
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From: Bedford UK
My S&S engine came with ACRs, 107" with 9.5:1 CR. The stock starter lasted a couple of years - it now has a much bigger one!
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