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Running Rough at low RPM

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Old 02-22-2008, 01:00 PM
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Running Rough at low RPM

Rode to work today and about 25 miles into the commute, as I was going to pass a car rolling the throttle on in 6th, the bike starting sputtering. I pulled over to get my ipod out of my ears so I could get a better idea of what was going on and found it doesn't want to idle. I decided to limp it to work and noticed above 3.5k RPM it's seemingly fine: no coughing and power is smooth. Below it is coughing and sputtering like crazy.

I get to work and throw voltmeter on the battery thinking it's possibly the regulator as the bike needed a charge today after only sitting for three days. I get 12.2 at idle and 13.8 at 5k. At this point it would idle, but not for more than 15 seconds or so then it dies, sometimes with a pop from, I'm assuming, too much fuel.

In the last two months I have rejetted (182.5/185 mains, 45 pilot, 2.25 out, clip ins 2nd pos) and did the TPS mod (518 was as close as i could get, and I did have to modify the mounting holes to get it that close. Think it could be the TPS way out of whack?

Any other ideas?
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Old 02-22-2008, 03:50 PM
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My first thought, did you sync the carbs? That could lead to rough running, and the situation that you stated at idle.


Hawkrider has a TPS write up on his site.



Didnt you get the memo about the new TPS cover sheets?
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Old 02-22-2008, 04:08 PM
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+1 on carb sync
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Old 02-22-2008, 07:32 PM
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Thanks, guys. The carbs are sync'd, unfortunately. What's weird is the bike has been running incredibly strong and responsive for the 300-400 miles since the re-jet and TPS mod and was running just as well until halfway through my commute today. I'm really leaning toward electrical/ignition as the rectifier is the original (8 yrs. old) and the battery is almost three years old. Last I rode it was Monday after installing a new starter switch and I had to throw a charger on it to get it to turn over - same as this morning. The battery was basically dry, so I just filled it with some distilled H2O and it's sitting on a trickle charge right now. We'll see. I'll check the TPS next if necessary, then pull/inspect the carbs and re-sync if I'm still having issues. I'll have the wife bring me home a new rectifier from the shop tomorrow as a last resort - $106 at employee cost!!

I think I need a new clutch now, too; a bike that doesn't want to run under 3.5k + Houston Friday traffic is a good recipe for baked clutch. I'm sure everyone next to me on the highway thought I didn't know how to ride - squid city! LOL

Negative on the TPS memo (?). I did see Greg's writeup though, which is what I used to do the mod.
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Old 02-22-2008, 07:33 PM
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Well, sounds like this just started right? Had it been sitting for while? Bad gas? There must be a gas filter in there somewhere....replace it? Clogged idlejet/low speed jet, pilot/whatever it's called. One slide not shutting all the way? Sounds like a general inspection and cleaning of carbs etc should get you back on track.
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Old 02-22-2008, 07:59 PM
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Originally Posted by Motohead
Negative on the TPS memo (?).
Watch the whole thing as this is one of the best movies ever but 2 minutes and 50 secs and 4:30 into it will explain it all:

http://www.youtube.com/watch?v=FfY2q...eature=related

Last edited by superbling; 02-22-2008 at 08:02 PM.
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Old 02-22-2008, 09:27 PM
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Originally Posted by redman
There must be a gas filter in there somewhere....replace it?
I don't think there's a fuel filter anywhere on the stock VTR setup, but an inline one is a good idea to add.
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Old 02-23-2008, 09:42 AM
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LOL! I love that movie.

Well, apparently the cause was a dry/low battery. It has a non-serviceable Suzuki battery, but I pulled the caps off anyway. After topping it off and charging last night I dropped it in and she was back to her old self. I'm going to pick up a new battery today to be safe as I think this one is roached and I did dimple the caps on each end a bit prying it off.
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