Dip in power curve?
Thread Starter
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Road Master
Joined: Jul 2010
Posts: 1,045
Likes: 102
From: Waukesha, WI
Dip in power curve?
Hi everyone, a few people suggested I post here to try to figure out a strange dip in the power curve at 2900 RPM on my 98" big bore. The build has the following:
Just got my bike back from Suburban Motors in Thiensville, WI. Bike had 53k on it, and a nice running stock/stage 1 88". The original plan was to go with a cam swap to eliminate the chain drive cams and install a 2 into 1 pipe. Then one thing led to another. Ended up doing the 98" big bore high compression "Street Stomper" kit they offer. It consists of the following:
Bore stock jugs
Custom forged Mahle pistons
S&S 585G cams
45mm Mikuni carb
SE HD clutch spring
Adjustable pushrods
Daytona Twin Tec ignition controller
Ported & flow benched heads
Compression releases
1.9 Intake valves
10.5:1 C/R
Rinehart 2-into-1 full exhaust.
I'm wondering if it has anything to do with the cams or the exhaust?
Just got my bike back from Suburban Motors in Thiensville, WI. Bike had 53k on it, and a nice running stock/stage 1 88". The original plan was to go with a cam swap to eliminate the chain drive cams and install a 2 into 1 pipe. Then one thing led to another. Ended up doing the 98" big bore high compression "Street Stomper" kit they offer. It consists of the following:
Bore stock jugs
Custom forged Mahle pistons
S&S 585G cams
45mm Mikuni carb
SE HD clutch spring
Adjustable pushrods
Daytona Twin Tec ignition controller
Ported & flow benched heads
Compression releases
1.9 Intake valves
10.5:1 C/R
Rinehart 2-into-1 full exhaust.
I'm wondering if it has anything to do with the cams or the exhaust?
Road Master
Joined: Nov 2015
Posts: 1,236
Likes: 387
From: georgia
It's the exhaust. There is no air/ fuel graph probably because it would show a severe rich spot where you have the dip. Jetting won't cure it--only a different pipe. Having said that, do you feel the dip when riding or does it just bother you to see it on the graph?
Grand HDF Member
Joined: Jun 2013
Posts: 4,998
Likes: 875
From: Iowa
+1 The Rinehart 2:1 isn't much better than slip ons, but it looks good. You might want to look at a Thunderheader or a Fat Cat if you want performance. That is a pretty high compression ratio for a 98" with 585 cams, but I wouldn't think that would give you issues.
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,115
Likes: 7,638
From: Poolville
Yes without the afr graph it's tough to say... lots of times we have a little too much fuel on the accelerator pump and that combined with a 2-1 will cause that. Less back pressure in the pipe also contributes..
Thread Starter
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Road Master
Joined: Jul 2010
Posts: 1,045
Likes: 102
From: Waukesha, WI
Thanks for the quick replies, you guys rock! I haven't had a chance to ride it due to cold and salt so we'll see how it is going down the road. I did notice when revving it hard it does blow a little black smoke but no hesitation or stumbles. The builder was pushing a FatCat but it was too loud for my likes.
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