TheOriginalEasyrider
Member
This sub-forum is pretty dead so hoping there is a fuel injection wizard on TC 96 motors here.
2010 FXSTC. Problem has existed since very early in this bike's life. I'd say since day one but can't honestly confirm that. The only change made early on was switching from oem to NGK iridium plugs. I can't remember what I did yesterday much less 13 years ago. There was possibly a set of Champion RA8HC plugs before the NGKs. I really don't think this is a plug issue but I'll go back to the bone stock plug as a test if I have to.
Problem is that the bike starts great when stone cold or fully up to temperature. If it's somewhere in the middle and especially on the cold side (like a two mile ride to the gas station) the engine mixture acts like it is way lean and starving for fuel. If you are old enough to remember having a kickstarter, if you didn't kick the panhead over three times with the ignition off the kickstart would launch you over the handlebars. That's what's happening here except that the engine turns over briefly, backfires through the throttle body and the starter jacking gear makes this horrible noise. Usually starts up (with persistent pressure on the starter button) after that.
Side note: I have not checked the fuel pressure, fuel filter or any of that mostly because this has been going on forever.
I have a V&H FP3 management tool installed now but of course it had this behavior back when the bike was bone stock. I thought maybe fooling with the low RPM, closed throttle cell might fix this but so far, no luck. There's probably a temperature range where these symptoms can be reliably reproduced. The engine is pretty cold blooded. I have a Jagg oil cooler on it but have it covered unless I am going on a long ride on a very hot day. For a typical short ride the oil temp gets up around 190F. Even on a very hot day it might only get to ~ 220F.
This is obviously (at least to me) a problem with a too lean mixture but only in a very narrow range of circumstances. The usual detonation and white smoke coming out of the throttle body. Other than that the bike starts and runs flawlessly. 20W-50 Mobil 1 full synthetic. Battery is fine. Plugs properly gaped and look fine. ~23k mostly gentle miles.
Various changes to the FI map for VE and likely suspects cells made no difference.
I don't see how this could be a timing problem and there is no way I know of to check the timing anyway. If it's a timing problem then it's in the ECM or whatever is telling the ECM what the engine temp is. I've not seen anyone anywhere complaining about this so I am inclined to think that the ECM and the engine temp sensor is probably designed and working correctly.
Thoroughly cleaned the throttle body, air filter and IAC sensor. The engine temperature sensor must be working otherwise the bike wouldn't run as well as it does, right? The FP3 app does display a lot of information but I don't really know what to look for other than the temp. As I said, there may be a small temperature band where this is most likely to happen but that really wouldn't tell me much as far as what I should be looking at to actually fix this.
I've been screwing around with this for years so I would be suitably impressed if someone was to just throw out the winning solution. What I am NOT interested in doing is shotgunning parts based on hunches and wild-assed guesses so please spare me.
What I'm hoping for are things I can check/inspect/measure or otherwise eliminate as possibilities or confirm as the cause. Whoever nails this problem cause will get my undying adoration.
2010 FXSTC. Problem has existed since very early in this bike's life. I'd say since day one but can't honestly confirm that. The only change made early on was switching from oem to NGK iridium plugs. I can't remember what I did yesterday much less 13 years ago. There was possibly a set of Champion RA8HC plugs before the NGKs. I really don't think this is a plug issue but I'll go back to the bone stock plug as a test if I have to.
Problem is that the bike starts great when stone cold or fully up to temperature. If it's somewhere in the middle and especially on the cold side (like a two mile ride to the gas station) the engine mixture acts like it is way lean and starving for fuel. If you are old enough to remember having a kickstarter, if you didn't kick the panhead over three times with the ignition off the kickstart would launch you over the handlebars. That's what's happening here except that the engine turns over briefly, backfires through the throttle body and the starter jacking gear makes this horrible noise. Usually starts up (with persistent pressure on the starter button) after that.
Side note: I have not checked the fuel pressure, fuel filter or any of that mostly because this has been going on forever.
I have a V&H FP3 management tool installed now but of course it had this behavior back when the bike was bone stock. I thought maybe fooling with the low RPM, closed throttle cell might fix this but so far, no luck. There's probably a temperature range where these symptoms can be reliably reproduced. The engine is pretty cold blooded. I have a Jagg oil cooler on it but have it covered unless I am going on a long ride on a very hot day. For a typical short ride the oil temp gets up around 190F. Even on a very hot day it might only get to ~ 220F.
This is obviously (at least to me) a problem with a too lean mixture but only in a very narrow range of circumstances. The usual detonation and white smoke coming out of the throttle body. Other than that the bike starts and runs flawlessly. 20W-50 Mobil 1 full synthetic. Battery is fine. Plugs properly gaped and look fine. ~23k mostly gentle miles.
Various changes to the FI map for VE and likely suspects cells made no difference.
I don't see how this could be a timing problem and there is no way I know of to check the timing anyway. If it's a timing problem then it's in the ECM or whatever is telling the ECM what the engine temp is. I've not seen anyone anywhere complaining about this so I am inclined to think that the ECM and the engine temp sensor is probably designed and working correctly.
Thoroughly cleaned the throttle body, air filter and IAC sensor. The engine temperature sensor must be working otherwise the bike wouldn't run as well as it does, right? The FP3 app does display a lot of information but I don't really know what to look for other than the temp. As I said, there may be a small temperature band where this is most likely to happen but that really wouldn't tell me much as far as what I should be looking at to actually fix this.
I've been screwing around with this for years so I would be suitably impressed if someone was to just throw out the winning solution. What I am NOT interested in doing is shotgunning parts based on hunches and wild-assed guesses so please spare me.
What I'm hoping for are things I can check/inspect/measure or otherwise eliminate as possibilities or confirm as the cause. Whoever nails this problem cause will get my undying adoration.