Another cam question
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Road Warrior
Joined: Jul 2011
Posts: 1,327
Likes: 333
From: Central TX
Another cam question
I have gone on about a dozen rides since my big bore installation. You can see complete engine build in signature below. I kept build mild for reliability and had SE 204 cams installed about 8 months before the BB kit. I thought the 204's were a low to mid rpm torque cam, but my bike seems a little weak down low and pulls much stronger in the 3000-5000+ range. Bike is a lot of fun on highway at 70mph and I roll on throttle, but feels doggish when pulling away from stops unless I really get on it. When bike had stock cams it was really responsive down low, and I feel I have lost power in that area. Don't want to bump compression above current 9.8:1 or do any additional headwork - anyone have recommendations for other cams that come on earlier and still pull strong into low 5000 rpm range? If you have experience with the 204 and other cams, I woul really appreciate your input. Any advantage to 4 degree advance - I thought the higher compression would help? Running V&H 2-1 big radius - would a higher performance exhaust really make much difference?
Last edited by txphatboy; May 24, 2012 at 10:38 PM.
HDF Community Team
Joined: Jun 2006
Posts: 12,779
Likes: 2,609
From: san antonio
The pipes aren't helping you; there are much better systems like the Propipe, the new Bassani Road Rage, D&D Fatcat, Thunderheader or Supertrapp. Anyone of those pipes would help. Have you seen the dyno chart? Is there a TQ dip right off idle?
At 9.8 I would be wary of advancing the 204; they have 8* of advance ground into the base profile. I ran them at 9.8 in a 95" and had to pull them when temps exceeded 100*; the bike ran strong but detonation kicked in when temps warmed up. I didn't find the 204s soft on the bottom; 90TQ at 2400rpms 103TQ by 3500. That was with a set of BigBoyz heads; better heads would have made better numbers.
I would first be looking at the tune and possibly considering a second go with a different tuner to elimnate the tune as the culprit. I don't know anything about Dunn heads but they have to be at least equal to BigBoyz. A larger intake valve along with the larger TB could be slowing down velocity and impacting low end performance. If a second tune doesn't improve the situation, then you can start looking elsewhere, like exhaust
There are cams with earlier intake close events that might improve the situation but the fact that you aren't happy with the low end performance of the 204s is what is bothering me; that cam is a sweet cam and everyone I know running them, even in touring bikes, really likes the performance. I am not so sure that a cam change is the direction you should be headed, at least not yet.
At 9.8 I would be wary of advancing the 204; they have 8* of advance ground into the base profile. I ran them at 9.8 in a 95" and had to pull them when temps exceeded 100*; the bike ran strong but detonation kicked in when temps warmed up. I didn't find the 204s soft on the bottom; 90TQ at 2400rpms 103TQ by 3500. That was with a set of BigBoyz heads; better heads would have made better numbers.
I would first be looking at the tune and possibly considering a second go with a different tuner to elimnate the tune as the culprit. I don't know anything about Dunn heads but they have to be at least equal to BigBoyz. A larger intake valve along with the larger TB could be slowing down velocity and impacting low end performance. If a second tune doesn't improve the situation, then you can start looking elsewhere, like exhaust
There are cams with earlier intake close events that might improve the situation but the fact that you aren't happy with the low end performance of the 204s is what is bothering me; that cam is a sweet cam and everyone I know running them, even in touring bikes, really likes the performance. I am not so sure that a cam change is the direction you should be headed, at least not yet.
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Road Warrior
Joined: Jul 2011
Posts: 1,327
Likes: 333
From: Central TX
Thanks for the suggestions. Cannot attach Dyno sheet from my phone, but bike pulled 90 ft lbs at 2000 rpm and has torque dip from around 2200-2700 rpm. First time I have ever dyno'd bike - is this dip typically an exhaust issue? I gotta admit I like the look of the 2-1 BR on the bike and if an exhaust change is going to net a couple ft lbs, I'm not sure it would be worth it. What kind of gains could I reasonably expect from a 2-1 propipe, road rage t or fatcat? Are there any good 2-2 pipes that would give similar gains? I had bike dyno'd at very reputable shop and tuner spent all day tuning, so I don't think this a tuning issue. Also, bike is not a total turd down low, but definitely stronger in higher RPMs.
Club Member
Joined: Feb 2008
Posts: 18,575
Likes: 4
From: Norfolk, VA
Does your current exhaust have any kind of baffle?
I have gone on about a dozen rides since my big bore installation. You can see complete engine build in signature below. I kept build mild for reliability and had SE 204 cams installed about 8 months before the BB kit. I thought the 204's were a low to mid rpm torque cam, but my bike seems a little weak down low and pulls much stronger in the 3000-5000+ range. Bike is a lot of fun on highway at 70mph and I roll on throttle, but feels doggish when pulling away from stops unless I really get on it. When bike had stock cams it was really responsive down low, and I feel I have lost power in that area. Don't want to bump compression above current 9.8:1 or do any additional headwork - anyone have recommendations for other cams that come on earlier and still pull strong into low 5000 rpm range? If you have experience with the 204 and other cams, I woul really appreciate your input. Any advantage to 4 degree advance - I thought the higher compression would help? Running V&H 2-1 big radius - would a higher performance exhaust really make much difference?
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