96" compression
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Intermediate
Joined: May 2018
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From: WV
96" compression
Hey everyone, I have a 2009 Ultra Classic 96", it has 30,000 miles on it. When I bought it the power seemed to be lacking considerably. I did a compression check on the bike cold, I got 125 PSI on front and rear cylinders. That seems low to me, the touring FSM says minimum of 125 PSI. I plan on ordering a top end kit tomorrow, I just wanted to check here first to see if I am overacting. I already have it tore down putting cams in Wood TW-222, so doing the pistons and jugs isn't that much more. My pinion runout is 4 thousandths with a 1 thousandths play when lifting the pinion, so that would be 5 thousandths if I understand that correctly.
So some of you experienced motor folks, am I overacting or should I get a new top end minus heads?
Thank you, Jeff
So some of you experienced motor folks, am I overacting or should I get a new top end minus heads?
Thank you, Jeff
Thread Starter
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Intermediate
Joined: May 2018
Posts: 31
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From: WV
Ohio HD, it was a Matco gauge. The bike seemed tired when I bought it, that is the reason I did the compression check. 125 PSI seemed low to me and has been in the back of my mind since. When I tore it down for the cams, factory lifter rollers looked good, little wear as well as the tensioner shoes. But, there was a very foul smell to the oil and very nasty to boot. Like the service on the bike was neglected, it also had a trailer hitch on it, so they might have ben towing with it.
Jeff
Jeff
HDF Community Team
Joined: Jun 2006
Posts: 12,763
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From: san antonio
No disrespect to the OP and a bit too late now but three requirements for an accurate compression test; both spark plugs out, fully charged battery, accurate gauge and throttle held wide open. Doesn't seem right for compression to be that low with only 30K miles on the motor.
Just a passing thought. If new top end is the next step, OP should consider boring to 3.938", fitting appropriate pistons to increase displacement to 107" and maybe manual compression releases as well.
Just a passing thought. If new top end is the next step, OP should consider boring to 3.938", fitting appropriate pistons to increase displacement to 107" and maybe manual compression releases as well.
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Intermediate
Joined: May 2018
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From: WV
Loanwolf176, I did. I did so because I felt that the bike was sluggish. This is my first 96" bike though. I've had 88" and 103" bikes. I currently have an 05 Dyna with a carbed 88" that will flat scoot. It will put the Ultra to shame. I bought it from the local HD shop and it was the Owners bike. I don't know what they did to that bike. But it is a power house.
The Ultra came with Vance and Hines monster ovals and factory breather with a SE filter. At the suggestion of Fuel Moto, I switched mufflers to S&S Grand Nationals, Fuel Moto AC/DC breather with a Dynojet tune from Fuel Moto. It does run better but doesn't feel as strong as it should. I've been concerned with the 125 psi since I checked it. It is in spec, though the minimum by the FSM. But looking at a compression and motor displacement calculator with the cams I now have. Shows that I should have a static compression ratio of 9.30 :1 with a corrected ratio of 8.78 :1 and cold cranking compression of 176 @ 600 feet above sea level.
Jeff
The Ultra came with Vance and Hines monster ovals and factory breather with a SE filter. At the suggestion of Fuel Moto, I switched mufflers to S&S Grand Nationals, Fuel Moto AC/DC breather with a Dynojet tune from Fuel Moto. It does run better but doesn't feel as strong as it should. I've been concerned with the 125 psi since I checked it. It is in spec, though the minimum by the FSM. But looking at a compression and motor displacement calculator with the cams I now have. Shows that I should have a static compression ratio of 9.30 :1 with a corrected ratio of 8.78 :1 and cold cranking compression of 176 @ 600 feet above sea level.
Jeff
Last edited by wvmedic31; Mar 19, 2024 at 03:12 PM.
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Thread Starter
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Intermediate
Joined: May 2018
Posts: 31
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From: WV
Djl, no disrespect taken. I did the test that way by the book. As for the 107", I thought about going that route. Only problem is, I already bought the Wood TW-222 cams and would have to buy a new set of cams to go with the 107". I thought about going 103" because my cams would work good with it. Problem is, I don't want to mess with the compression releases manual or ACR's. Also I can get the 96" factory upper kit for $380.
Jeff
Jeff
HDF Community Team
Joined: Jun 2006
Posts: 12,763
Likes: 2,597
From: san antonio
Djl, no disrespect taken. I did the test that way by the book. As for the 107", I thought about going that route. Only problem is, I already bought the Wood TW-222 cams and would have to buy a new set of cams to go with the 107". I thought about going 103" because my cams would work good with it. Problem is, I don't want to mess with the compression releases manual or ACR's. Also I can get the 96" factory upper kit for $380.
Jeff
Jeff
I think you could get by without compression releases at 103", with a flat top piston, static CR would be about 190psi which is the point at which going past brings compression releases into question. You may be concerned about compression, which I understand as I used to be; however, I have come to learn that these motors, properly tuned can manage higher compression. I am currenlty running a healthy 98" motor at 11.25 static and CCP at 213psi with no issues; I do have manual compression releases and use them on every start up.
Please don't take my comments as anything but me trying to point out what I think is a great opportunity for you to take advantage of the situtation and maximize the benefit to get that extra power you are looking for. You may have considered everything I have pointed out and, if so, apologies for the redundancy.
Please keep us posted on the project and the results.
