Engine falls flat on its face
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Road Captain
Joined: Dec 2009
Posts: 512
Likes: 6
From: Minnesota
Engine falls flat on its face
This has happened about a dozen times over the time I have owned my bike. Under normal riding conditions it runs and drives great but, when I run through the gears hard (like racing someone) it will fall flat on its face when I get into into 4th gear or so. When I let up and throttle again then I can go again. I don't think it is the rev limiter because it usually happens right after I shift. Any ideas? Its kind of embarrassing when you are leading and then it dies. Thanks in advance.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
if a motor looses power at full throttle then you can look at fuel mixture ( likely too rich) and or spark timing- whacking open the throttle will drop motor vacuum and the timing should retard ( carbed bikes used a VOES switch- of which there are adjustable versions)- via a vacuum switch or sensor.
what you are seeing is more a sign of improper "tuning" rather than a mechanical problem beyond the basics of fuel pressure and clean filters
mike
what you are seeing is more a sign of improper "tuning" rather than a mechanical problem beyond the basics of fuel pressure and clean filters
mike
Last edited by mkguitar; Jun 2, 2016 at 04:40 PM.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
remarks are general- you don;t detail what your year/model/mods are.
whatever you have, system design and tuning are required to get optimal results- could be a setting or mis-matched "performance" parts
if you are going to contact FM or someone else about a performance kit, get parts which have been matched to a known result, a "package"- and then tune that
mike
whatever you have, system design and tuning are required to get optimal results- could be a setting or mis-matched "performance" parts
if you are going to contact FM or someone else about a performance kit, get parts which have been matched to a known result, a "package"- and then tune that
mike
Seasoned HDF Member
Joined: Jan 2006
Posts: 11,463
Likes: 2,990
From: Charleston, SC
Could also be a dirty air filter, dirty fuel filter, dirty injectors, low fuel pressure, faulty/intermittent Twist grip sensor or intake servo etc and etc.
Last edited by lp; Jun 2, 2016 at 02:29 PM.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,897
From: Bedford UK
Your signature suggests you have had your bike dynoed, if so the shop who tuned it may be better able to diagnose and solve the problem, unless it was FM who tuned your bike. Certainly you need a diagnosis of the problem before you can solve it.
Road Warrior
Joined: May 2005
Posts: 1,301
Likes: 24
From: Minden LA
It sounds to me like the fuel filter may be starting to clog and the fuel flow slows and it goes lean and fall on its face. Just a guess though.
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Stellar HDF Member
Joined: May 2015
Posts: 2,091
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From: mid Michigan
Try some Lucas fuel injector cleaner. I put some in last week & it actually cleaned my piston tops after two tank full & about 5 let-r-rip take offs( almost red line first 4 gears). Daught it's it but if it ever did run right this could bring it back. I'll be using it about every oil change from now on.
Last edited by xcbullet; Jun 2, 2016 at 05:27 PM.
Ultimate HDF Member
Joined: May 2008
Posts: 7,439
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From: 'Noke, VA
This, or possibly a hole's been rubbed in the fuel line.