| Author | Message | ||
     Drhach |
Hi everyone, I have this strange intermittent issue. It happens when the bike isn't fully warmed up and only in first gear when pulling away from a stop. There are time when it feels like someone just whacks the clutch lever for a moment. It's a weird kind of stumble. It won't do it every time and more often than not it happens when I am accelerating a little more quickly than normal. By that I mean just a little goose off of idle. I'm pretty sure this bike doesn't have a TP sensor. I can only imagine it is something in the ignition controller. Anyone else experience this? Thanks, Dan | ||
| Harleyelf |
You don't have a throttle position sensor, but you do have a cam position sensor which can cause misfires and extra/unwanted firing of the plugs. It's under the timing cover and will probably smell burnt if it has gone bad. | ||
| Ratbuell |
Or the carburetor could need a good cleaning. Try doing the same thing, "not warmed up", with the choke knob partially pulled out. See if that changes it or helps it behave. | ||
| Drhach |
Thanks, I'll give the sensor a sniff. | ||
| Harleyelf |
You'll need to drill the cover plate rivets off and then unscrew the under-plate to access it. Mark the CPS mounting plate before you move it. Also, you might take the float bowl off the carburetor and see if there is anything in the bottom of it that looks like oil or dirt. While the air cleaner is off, look to see if your accelerator pump squirts fuel. | ||
| Ocbueller |
Could the front belt pulley be slipping on the output shaft? Have heard of these letting go, usually after they are totally stripped. Might be just starting to strip and is aggravated by high torque of first gear. SteveH | ||
| Drhach |
Hmmm, that's a good question. The bizarre thing is that it only ever happens in first gear. I'm trying to think of what happens in first gear only. The only thing I can come up with is that the RPM range from idle to say, 2500+ happens in first gear. After that, it's 2500+ to whatever. I managed to glance at the tach when it happened (once) and it the tach was at about 2K. They say most carburetor problems are electrical in nature. Very intermittent problems in my experience tend not to be fuel related. I'm wondering about the ECM. Maybe there's a vibrational frequency causing a stutter in the system somewhere. I'm definitely going to inspect the cam sensor. I think I need to inspect all wiring too. I suppose it would be worth inspecting the output shaft as well. | ||
| Ratbuell |
There are absolutely no wires going to a Buell carburetor. None. Nada. Nothing electrical whatsoever. You do not have an ECM. You have an ignition module - the only thing it controls is spark, and spark advance, based on a signal from the cam sensor. That's all. If it is only in first gear, it could BE first gear. You could have a chipped tooth in the gearset. Or, you could be missing a tooth on the drive belt and it only matches up to the "wrong" spot in first, once in a while. Conversely, if it only happens at one RPM spot and only when cold...have you tried the choke knob trick yet? While there's nothing electrical in one of these carburetors, there are very small passages for fuel and air that can get clogged up, and cause poor performance through poor air/fuel metering. A good visual check, and a quick experiment with the choke...are free. And easy. | ||
| Hootowl |
"There are absolutely no wires going to a Buell carburetor. None. Nada. Nothing electrical whatsoever." I think that was his point. In other words, most "carburetor" problems aren't actually carburetor problems. The VOES does attach to a vacuum port on the carb. If the hose has fallen off, or is cracked, timing is not adjusted by vacuum, which might cause low RPM issues. | ||
| Ratbuell |
Ah. That's not how I read it, sorry. Sounded like he was looking for an electric choke problem, or some sort of TPS problem. VOES is a possibility I suppose...but any time I leave the hose off after a rebuild (need to paint that damn hose orange on my bikes so I don't miss it!), all I get is a consistently flat low-RPM curve, not a skip/stutter. In my experience though...most low RPM issues on my tubers ARE fuel related, courtesy of our wonderful EPA and all the crap they put in our fuel these days. Consistent use of Seafoam has mitigated most of the issues, but sometimes one still misbehaves. | ||
| Harleyelf |
Have you tried raising the needle in your carburetor to slightly enrichen the mixture at near-idle? Your ECM has more wires going into it than a Sportster does. If it turns out to be irreplaceable, an early M2 ECM might be the answer. You'll have to rewire the plug to make the colors of all the wires you keep match. The sensor and its cup might have to be replaced to make this work. You can see the pulley without taking the cover off with a flashlight and a mirror (or your phone). Did you look for a head temp sensor on the rear cylinder? They can cause misfiring when they fail. | ||
| Natexlh1000 |
I don't think carbed bikes have temp sensors. | ||
| 1313 |
I don't think carbed bikes have temp sensors. If they have 'skip-spark' they do. So definitely '01 and '02 M2 would. A '98 S3 wouldn't as the lessons learned that brought about 'skip-spark' were just coming to light. | ||
| Drhach |
Yes, my point was that electrical issues are commonly misdiagnosed as carb issues. I understand that there is nothing electrical associated with my carb. Also, yes, I understand that ECM only controls spark and timing. That is still "Engine Control". It's just not much control. Semantics. I will try the "choke trick". I've been meaning to look at the jets anyway. it had a V&H muffler and still has a Forcewinder. It's pretty common for people to fiddle with carbs excessively when they do those things. Still, in my experience, something this intermittent would not (likely)be carb related. If it was more consistent, I might be more inclined to consider the carb first. Anyway, much food for thought and it won't happen this weekend unfortunately. I'll be sure to report back as I know more. I do welcome all suggestions. Thank you everyone for your input. If anyone has any direct experience with this, it would be appreciated. Dan | ||
| Screamer |
By "feels like someone wacks the clutch lever for a moment" - do you mean there is a brief uptick in rpm as if the engine is unloaded - and a hesitation in the bike's momentum? Does it do it in any other gear than first? | ||
| Harleyelf |
That's how I interpreted the statement, which is why I remembered my extra, unwanted sparking issue when my CPS went bad. Sometimes when starting the unwanted spark would kick the piston down while it was trying to come up. |
