Lowering idle speed on FI bike.
3rd Gear
Joined: Nov 2010
Posts: 7
Likes: 1
im a 25 year harley certified tech so here is the deal on the idle of f.i. bikes. its easy to set the idle on a m.m. f.i. bike just a torx screw, but the delfi are different, you can use a scanaylzer and set the idle but the ecm has a chip to set the idle back to factory setting so it want do ya any good. this is for safety reasons (per h-d) all late bikes are electronics so when the voltage drops to low due to low charging at low rpm the bike can quit and you might get run over at a red lite when it changes, also the oil issue is no problem, these roller bearing motors work mostly off of splash oiling they can run over 800 miles with 1 pound of pressure (normal riding) befour causing any problems. i have seen this proven twice. everyone will tell you the hydralics will colaspe they might but they didnt in the ones ive seen, and all they will do is make some noise and not run as well. hydralics can operate off 3psi. the idiot lite operates off 5psi +/- 2psi. if you want to lower the idle get a thunder max ignition, if you want potato, potato, you need about 8.5 compression with hemi heads/domed pistons. they are alot of opions, hope this helps.
Elite HDF Member
Joined: Apr 2008
Posts: 4,718
Likes: 11
From: Back in the Good Ole USA. South Carolina to be exact.
im a 25 year harley certified tech so here is the deal on the idle of f.i. bikes. its easy to set the idle on a m.m. f.i. bike just a torx screw, but the delfi are different, you can use a scanaylzer and set the idle but the ecm has a chip to set the idle back to factory setting so it want do ya any good. this is for safety reasons (per h-d) all late bikes are electronics so when the voltage drops to low due to low charging at low rpm the bike can quit and you might get run over at a red lite when it changes, also the oil issue is no problem, these roller bearing motors work mostly off of splash oiling they can run over 800 miles with 1 pound of pressure (normal riding) befour causing any problems. i have seen this proven twice. everyone will tell you the hydralics will colaspe they might but they didnt in the ones ive seen, and all they will do is make some noise and not run as well. hydralics can operate off 3psi. the idiot lite operates off 5psi +/- 2psi. if you want to lower the idle get a thunder max ignition, if you want potato, potato, you need about 8.5 compression with hemi heads/domed pistons. they are alot of opions, hope this helps.
I have a question of the 25 year harley certified tech. How long does the bike have to idle to get this "voltage drops to low due to low charging at low rpm"? This probably isn't a poblem for me since I don't idling any longer than I actually have to. Guess I could test this by putting a voltmeter on my bike while it is idling at 800 rpm.
Ultimate HDF Member
Joined: Nov 2005
Posts: 5,926
Likes: 138
From: NE Ohio
+1 I can change mine also, but why try to put lipstick on a hog. To me a TC struggling to idle just sounds like a poorly tuned TC, doesn't sound cool just sounds like it needs worked on.
Elite HDF Member
Joined: Apr 2008
Posts: 4,718
Likes: 11
From: Back in the Good Ole USA. South Carolina to be exact.
I just think this is a non issue.
Elite HDF Member
Joined: Apr 2008
Posts: 4,718
Likes: 11
From: Back in the Good Ole USA. South Carolina to be exact.
I just like the 800 rpm idle better than 1k. 200 rpm diference, it certainly doesn't sound like it is struggling or poorly tuned.
I will put a volt meter on my battery at idle and report back on the voltage.
I've seen oil pressure as low as 5 Lbs. at 1000 RPM's, i've seen them down to 3 Lbs. at 800 RPM's, this is verified with an oil pressure gauge threaded into the oil senor unit port on the block, not the junk gauge that comes stock on touring bikes. (Don't trust that gauge, it's about as reliable as the fuel or air temp gauge). I personally wouldn't want my RPM's lowered under the 950 to 1050 idle that Harley wants it at. I figure thier engineers probably know a little more about it than I do so why mess with it.
Last edited by harleytuner; Nov 8, 2010 at 07:22 AM.
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Road Captain
Joined: Nov 2005
Posts: 720
Likes: 6
Things to be considered with a lower idle speed is not only the oil pressure but the alternator output with the extra load on a FI bike like the fuel pump and some other parts that would take more output to run properly than with a carbed bike.
I'm not sure that would be effected so much. There are a ton of people out there with all kinds of lights, stereos, etc. that eat up alot more juice than turning down the idle. I see some bikes that look like spaceships riding down the road with all the lights