Detonation on 88” tc
Thread Starter
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3rd Gear
Joined: Sep 2008
Posts: 7
Likes: 1
From: maryland
Detonation on 88” tc
So I have a 05 88” tc that has 42k miles on it. I recently did cam tensioners on it. While in the motor I added se 203 cams and a set of Cometic .030 head gaskets. Motor now has serious detonation sounds like mainly on the rear cylinder. The bike has V&H slip ons and a K&N filter. It also has a V&H fuel pac but I’ve run it with it and without it and doesn’t effect the detonation. Anyone have any idea how to get rid of the detonation
Stellar HDF Member
Joined: Mar 2012
Posts: 2,019
Likes: 599
From: Columbus, OH
The older "in between" box or the newer phone based unit?
Can you post a pic of the fuel pac?
Short answer is the bike needs to be tuned to the newly installed cams
I'm going to assume it's fuel injected
Thread Starter
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3rd Gear
Joined: Sep 2008
Posts: 7
Likes: 1
From: maryland
Fp2
fp2. Yes it’s injected. Ive done this a long time and I have a hard time believing that a mild mid range cam and a half point of compression would cause this serious detonation. Already took it back apart and ck’d cam timing. There good together and to the crank.
Thread Starter
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3rd Gear
Joined: Sep 2008
Posts: 7
Likes: 1
From: maryland
Stellar HDF Member
Joined: Mar 2012
Posts: 2,019
Likes: 599
From: Columbus, OH
http://www.bigboyzheadporting.com/TwinCamComp.htm
As far as the FP2 it's very limited in what it can do
I found this
Install instructions
https://www.fuelpakfi.com/downloads/...pakSoftail.pdf take a look at the second page
and settings
https://www.fuelpakfi.com/fplookup_new_revb.php select the info closest to your bike and hit go at the bottom of the page, it takes you to a screen like this
https://www.fuelpakfi.com/cgi-bin/fp...7&TARGET=_SELF
You may be able to play with the settings but there is no option for spark timing
Thread Starter
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3rd Gear
Joined: Sep 2008
Posts: 7
Likes: 1
From: maryland
[QUOTE=Fat11Lo;21019590]Maybe plug your old cam and your new cam numbers into the Big Boyz calculator and see how much ccp has changed, things may have changed more than you think
http://www.bigboyzheadporting.com/TwinCamComp.htm
As far as the FP2 it's very limited in what it can do
I found this
Install instructions
https://www.fuelpakfi.com/downloads/...pakSoftail.pdf take a look at the second page
and settings
https://www.fuelpakfi.com/fplookup_new_revb.php select the info closest to your bike and hit go at the bottom of the page, it takes you to a screen like this
https://www.fuelpakfi.com/cgi-bin/fp...7&TARGET=_SELF
You may be able to play with the settings but there is no option for spark timing[reply ]
Thanks. I’m impressed with the effort you have put into trying to help me out. I’ll try those things and I’ll let you know how I make out
http://www.bigboyzheadporting.com/TwinCamComp.htm
As far as the FP2 it's very limited in what it can do
I found this
Install instructions
https://www.fuelpakfi.com/downloads/...pakSoftail.pdf take a look at the second page
and settings
https://www.fuelpakfi.com/fplookup_new_revb.php select the info closest to your bike and hit go at the bottom of the page, it takes you to a screen like this
https://www.fuelpakfi.com/cgi-bin/fp...7&TARGET=_SELF
You may be able to play with the settings but there is no option for spark timing[reply ]
Thanks. I’m impressed with the effort you have put into trying to help me out. I’ll try those things and I’ll let you know how I make out
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Seasoned HDF Member
Joined: Nov 2004
Posts: 8,129
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From: Ottawa, CANADA
The stock head gaskets were 0.052", so by going to the 0.030" gaskets, you've raised the compression ratio. You need to adjust timing, and fuel delivery, taking that into account. You'll likely need to use higher octane gas as well.
Cheers!
Cheers!
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Grand HDF Member
Joined: Sep 2017
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From: Dubuque, IA
He's still not going to see a ccp of even 170psi. Especially with 42000 on the rings. Hardly in the danger zone. Not even enough to need compression releases. Not sure what stock timing is on an 88".
Are you sure it's even detonation? What do your plugs look like? Sure you're not lugging it?
In fact the stock cams in an injected 88" is 34°. The 203s are 36°. Although it does have more lift, duration, and an LSA of 100.8. With a 9.0 compression ratio if you're lucky. A .030 head gasket MIGHT raise it to 9.3...if you're lucky.
You went from a cam with 6° overlap to one with 35° overlap making it lopey...
When I first put s&s 570 cams in my 103 is the first I ever heard my compensator clanging away. My initial reaction was detonation because it can sure sound like it.
Just a thought...
Are you sure it's even detonation? What do your plugs look like? Sure you're not lugging it?
In fact the stock cams in an injected 88" is 34°. The 203s are 36°. Although it does have more lift, duration, and an LSA of 100.8. With a 9.0 compression ratio if you're lucky. A .030 head gasket MIGHT raise it to 9.3...if you're lucky.
You went from a cam with 6° overlap to one with 35° overlap making it lopey...
When I first put s&s 570 cams in my 103 is the first I ever heard my compensator clanging away. My initial reaction was detonation because it can sure sound like it.
Just a thought...
Last edited by 60Gunner; Jan 13, 2023 at 08:35 PM.
