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Problem SE Stage IV kit/58mm Throttle body

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Old Nov 15th, 2009, 03:20 AM     #1
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Problem SE Stage IV kit/58mm Throttle body

Have just got my new SE Stage IV kit installed on my Street Bob 2008. It has been installed by some very experienced engine builders/tuning people. The problem is that they can not get it to run as it should even after spending a lot of time trying to tune it correct.

Acceleration is great, top hp and torque also, it runs a bit uneven when cruising. The problem is to start it, especially when cold. It does not start without giving a lot of throttle. They can not get it run run good on low rev, it sounds like it chokes it selves. They are speculating that it can be cauesd by the 58mm throttle body, that it is to big. It is a kit so it should work. Any ideas? Appreciate all support.
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Old Nov 15th, 2009, 08:05 AM     #2
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Re: Problem SE Stage IV kit/58mm Throttle body

The TB could very well be too big. Going to a TB of that size slows the velocity of the intake and can effect the performance at the lower end. At the upper RPM ranges it can use the 58MM but at lower end it suffers. You have to set the motor up to run properly where you ride the most and I doubt that's the upper portion of the RPM range.
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Old Nov 15th, 2009, 10:58 AM     #3
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Re: Problem SE Stage IV kit/58mm Throttle body

What I have installed is the SE Pro Stage IV kit - 103 cubic inch (part no 27516-08A) which has 110+ heads with intake valves at 2.120" diameter, SE260 cams, 58mm throttle body, super tuner etc. All in the kit.

What suprices me a bit if this does not work is that it is a kit that is put together by HD/SE just so you shouldn´t end up with this problems?
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Old Nov 15th, 2009, 02:07 PM     #4
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Re: Problem SE Stage IV kit/58mm Throttle body

and it does fly in the upper rpms.
You would expect that it should run decent in the lower and start easy when cold or what do you think? Maybe I just have to get used to the fact I need to give throttle when starting cold?
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Old Nov 15th, 2009, 03:50 PM     #5
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Re: Problem SE Stage IV kit/58mm Throttle body

yes, automatic
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Old Nov 15th, 2009, 03:57 PM     #6
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Re: Problem SE Stage IV kit/58mm Throttle body

yes they are activated
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Old Nov 16th, 2009, 04:36 AM     #7
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Re: Problem SE Stage IV kit/58mm Throttle body

get them to check the throttle stop screw the 58mm are hard starting stock the tps voltage that works i believe is .6V not .57 this wont change the idle it will get adjusted via the iac. this should work but i cant remember the exact voltage and am not sure where i had it written down hopefully this will help you.
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Old Nov 20th, 2009, 07:02 PM     #8
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Re: Problem SE Stage IV kit/58mm Throttle body

I had the Same kit on my 2008 streetglide. My 58 mm throttlebody was TBW. I had the exact same issue. Mine was dynotuned by a very well known tuner. Bike made good numbers, was hard to start sometimes unless you held the throttle open. Someone told me to hit the start button as soon as you turn on the run switch. It helped, but I didn't like doing that. I ended up removing the whole kit. It could be the high flow injectors injecting too much fuel during the startup sequence.
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Old Mar 14th, 2010, 01:08 PM     #9
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Re: Problem SE Stage IV kit/58mm Throttle body

The 58mm throttle body is defective. remove breather cover to expose throttle blade. Open throttle fully now grabe blade. The blade will move left to right about 1/16 of an inch. This should not happen this caises the the engine not to work at low rpm and hard to start. The blade is also flat along the edge. All blades on the other harley throttle body are beveled. If you release the throttle fast with cable throttle the blade can actually stick slightly which pevents the Ignition air control motor from opening the throttle blade to start engine. Its junk and must be replaced with the 50mm works ok or Zippers Performance 60mm works great too. This should be a harley recall.
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Old May 8th, 2014, 11:41 AM     #10
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Re: Problem SE Stage IV kit/58mm Throttle body

will the 50mm bolt on in place of the 58mm? I have this same kit. Mine runs fine. Tuned by doc's hd in St.Louis I was told I couldn't change because a smaller tb would not bolt up to the larger ports. My only reason for changing would be to see if I can get a little faster throttle response.
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