How much compression is too much?
Grand HDF Member
Joined: May 2007
Posts: 3,870
Likes: 499
From: Alberta
Last 4 builds friends and I have done have all used S&S E-Z starts. If you have kickback your gonna wreck stuff in a hurry; I did a long way from home and it cost me dearly.
As far as hard starting; I don't want to dis independent shops, but I think a lot of money is made selling parts to address SYMPTOMS afterwards; bigger starters, bigger batteries, bigger cables, heavy duty this and that...when all that's really needed is proper ignition timing and less cranking pressure via comp releases of some sort.
That's my two bits; been there, spent that.
As far as hard starting; I don't want to dis independent shops, but I think a lot of money is made selling parts to address SYMPTOMS afterwards; bigger starters, bigger batteries, bigger cables, heavy duty this and that...when all that's really needed is proper ignition timing and less cranking pressure via comp releases of some sort.
That's my two bits; been there, spent that.
Seasoned HDF Member
Joined: Aug 2007
Posts: 21,732
Likes: 17,569
From: Driftless Area
Remember that anything you do affects the rest. Harder on the starter to turn that compression. I keep mine dialed-in, so it doesn't turn over hardly at all before it catches and starts up.
Seasoned HDF Member
Joined: Feb 2008
Posts: 23,000
Likes: 11,441
Im getting ready to do a 95" v twin kit with 10:5-1 wiseco pistons in it. My indy swears that I wont need compression releases and that hes done this kit before with no problems, but I just wanted to get some others opinions. Afterall, that's a pretty big jump in compression from 8:9-1 to 10:5.1. Last thing I want is an unreliable bike that's hard to start. Thanks for your input.
find a skilled experienced shop to deal with.
Seasoned HDF Member
Joined: Feb 2014
Posts: 19,653
Likes: 835
From: North Carolina
The OP never mentioned cams with his upgrade. It seems we are assuming he is going to change those out as well. A lot will depend on that.
A lot of independent shops are run by guys who used to work for Harley and/or have been trained in working on them. It's just wrong to cast them all under a certain light.
Get your facts straight.
A lot of independent shops are run by guys who used to work for Harley and/or have been trained in working on them. It's just wrong to cast them all under a certain light.
Get your facts straight.
Seasoned HDF Member
Joined: Jan 2011
Posts: 157,518
Likes: 57,069
From: Michigan 15 Minutes East Of Hell
S&S Easy Starts are an option ... Doing the Compression Releases will hurt nothing and will DEFINITELY extend the starter life and ease of starting, especially on those hot summer days.
Seasoned HDF Member
Joined: Feb 2014
Posts: 19,653
Likes: 835
From: North Carolina
Yep, and probably add less than $200 to the total cost of the build.
Seasoned HDF Member
Joined: Aug 2009
Posts: 9,243
Likes: 3,266
From: west Michigan
I went with a conservative 95" build that doesn't look like much "on paper" but the additional compression definitely shows up when I crank it over, and it WILL shorten the life of the starter.
Seasoned HDF Member
Joined: Feb 2014
Posts: 19,653
Likes: 835
From: North Carolina
Last edited by LiiT; Aug 11, 2019 at 05:44 PM.
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Club Member
Joined: Dec 2007
Posts: 4,192
Likes: 168
From: Knoxville, Tn
Compression Releases
I did a 95" kit to my 06 Dyna SB and put high compression pistons in. I believe they ran about 10.1-1. The higher compression wakes the cams up. First rounds of mods put out, there again about 85hp and 93 ft pds torque. I did not have the heads drilled for crs but I could feel the bigger load on the starter. When I put different heads on the motor, they were already drilled for releases. Like a few folks said, they will not hurt anything so why not do it ? May save time and money later.
BTW When I use my manual crs, I always open them right after I shut the engine down...They will get hotter the longer they sit on a hot motor. The 211 cams have great low end torque so go for it.
BTW When I use my manual crs, I always open them right after I shut the engine down...They will get hotter the longer they sit on a hot motor. The 211 cams have great low end torque so go for it.