Top end big bore - compression not what it should be?

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May 29, 2022 | 04:39 AM

#71

Adam76

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From: out there

Quote:

Originally Posted by eighteight

I can not see nor interpret the O.P.s plugs

I`m just suggesting the following:

The OP and I have very similar specs , in my case ( 98" / 570 cams / 3cc domes ( for slightly raised compression ) DTT ignition / Both are carbs and jetting is similar and I also have the Sportster needle .

When I had DTT set at 2-2 the engine was "flat "

When I went to 5-7 the difference in response was considerable and the heat lines with a mag glass were in the right spot

It`s a 2 minute and zero dollar experiment

Well, I went against all my (very limited) understanding of timing and compression and set the DTT to 5 / 7 as suggested. Then went for a 20 minute ride.
I can't believe it, but the bike actually felt more responsive in part-throttle applications. I didn't have the ***** to test it at WOT (still breaking the motor in) but it was a noticeable difference in throttle response.... I listened hard for any pinging on acceleration, but couldn't really hear any.

I pulled the front plug to check for the timing mark on the ground strap, but it was exactly the same as before (still not even halfway up to the elbow). Probably not enough miles to re-read the plugs.

Thanks eighteight.

Last edited by Adam76; May 29, 2022 at 07:47 AM.

May 29, 2022 | 09:55 AM

#72

Max Headflow

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Joined: Dec 2005

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From: poway

Quote:

Originally Posted by Adam76

Well, I went against all my (very limited) understanding of timing and compression and set the DTT to 5 / 7 as suggested. Then went for a 20 minute ride.
I can't believe it, but the bike actually felt more responsive in part-throttle applications. I didn't have the ***** to test it at WOT (still breaking the motor in) but it was a noticeable difference in throttle response.... I listened hard for any pinging on acceleration, but couldn't really hear any.

I pulled the front plug to check for the timing mark on the ground strap, but it was exactly the same as before (still not even halfway up to the elbow). Probably not enough miles to re-read the plugs.

Thanks eighteight.

It will.

May 30, 2022 | 12:45 PM

#73

Harley1004

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Joined: Jun 2018

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From: WI

For what it is worth:
08 full dresser/classic
103ci bore/flat top
1.9 intake valve
head--intake and exhaust blended
heads not cc'd
.deck height not set
.030 head gasket
S&S 570 Easy start/TTS tune
Cobra 6450/ 2-1 Exhaust
It is not a slouch on the bottom. Starts pulling at 2450rpm @ 100 lb/ft. up to 119 lb/ft @ 5400rpm. Dyno chart said 104hp---119lb/ft total. Was told to set head cc's and deck height and would get more---somewhere in the 120/120 range. I like the 570 behavior, works good for my setup. With bike and both of us plus gear we weigh close to 1400 lbs. gross. If I keep it around 2900-3100 rpm. average around 38 mpg. If you need a quick 'out' somewhere, drop a gear at 80/85 mph and she will pull past 100 faster than any harley I have ever ridden 2up, even loaded down. I think the 570 is a good all around cam, city or highway. I have new SE 103 cylinders, SE flat tops. Will have heads cc'd, will get deck height set, and some more head work completed by next season. Gonna use my 570's. "If" I do get 120/120 that would be amazing.

May 30, 2022 | 06:14 PM

#74

Adam76

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From: out there

Quote:

Originally Posted by Harley1004

Thanks for posting. Sounds like you have a great set up - with a few more cubes and better flowing heads with the bigger intake valve, you're probably giving the 570s exactly what they need to shine.

How much do you think the 2-1 pipe is contributing to your great results?

I'm keeping my 570s, just trying to optimise what I alreadyalready Can't afford any head work, so I'd be happy with 90 / 90 the way things are going.
Cheers

May 30, 2022 | 08:10 PM

#75

Harley1004

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Joined: Jun 2018

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From: WI

I don’t know how much the two in the one contributed to horsepower and torque. Originally I had stock Exhaustwith 3 1/2 inch Reinharts mufflers. I was running the power commander five with the auto tune feature. It was all right set up that way. However, I never had it dino tuned so I don’t know what kind of horsepower and torque it was putting out. Once I got the two into one Exhaust from Cobra, I had a TTS master tuned to what I said earlier. It made a pretty good butt Dino difference. Quite a bit of difference. As long as it’s tuned good, pulls hard, gets decent fuel mileage, the numbers just fall in line… I’m happy with what I have right now

————— Knowledge is Power……

Last edited by Harley1004; May 30, 2022 at 08:15 PM.

May 30, 2022 | 10:50 PM

#76

Adam76

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From: out there

Quote:

Originally Posted by Harley1004

I don’t know how much the two in the one contributed to horsepower and torque. Originally I had stock Exhaustwith 3 1/2 inch Reinharts mufflers. …

I'm also considering a 2-1 pipe. The Python looks good and is reasonably priced, but trying to find the pipe for the 99-06 softail is proving difficult, as they are not in stock anywhere. Not a popular exhaust I guess.

Last edited by Adam76; May 31, 2022 at 12:39 AM.

May 30, 2022 | 10:53 PM

#77

Harley1004

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Joined: Jun 2018

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From: WI

Why don’t you look up the Cobra Exhaust systems. I just went on their website and they have several that you might be interested in. And just because they say it won’t fit your bike, doesn’t mean that it will not. You can call Cobra out there in California and ask them. My 6450 was designed for 2010 and up, however, in fit my 2008 great