Strange drop in idle.
Thread Starter
Light Cycle Expert
Back Marker
Joined: Mar 2011
Posts: 194
From: Tampa, Florida
Strange drop in idle.
The other day on the way to work, after half hour of driving, I noticed that the idle slowly drop to eventually stall the bike out after about 30-45 seconds at a dead stop. I adjusted the idle set screw to a higher setting to attempt to fix the issue. Even at 2k rpm idle it still did the same thing. I dropped it back down to normal settings and tried again after work. It still did the same thing but only once it was running for about 20 minutes. Almost home I was reaching the famous 100 mile refill mark so I fueled up.
The only thing that I have done differently to the bike on the past 48 hours was choose a different fuel to see if the SH performed any better. Not trying to restart the fuel war BTW. I went from 87 octane to 93 then back to 87. That's when it started acting up. I returned the fuel to 93 at the fuel station 2 mile from my house. Let the bike cool down. Checked it 4 hours later and it ran fine. Haven't had a problem since.
After doing some searching on here I saw a thread that said that the SH motor has this idle issue randomly with all the motors. Wondering if anybody else has had this happen. Maybe the same issue and not the fuel change? Or the other option is the R/R is original. I felt it when this was happening and it nearly burned my finger. I can see how it was a bad design. Thinking maybe it might be a symptom that it's going bad?
Any suggestions would be appreciated. Like I said it was a two time thing until the fuel refill. So I can't diagnose it any further with it not occurring.
The only thing that I have done differently to the bike on the past 48 hours was choose a different fuel to see if the SH performed any better. Not trying to restart the fuel war BTW. I went from 87 octane to 93 then back to 87. That's when it started acting up. I returned the fuel to 93 at the fuel station 2 mile from my house. Let the bike cool down. Checked it 4 hours later and it ran fine. Haven't had a problem since.
After doing some searching on here I saw a thread that said that the SH motor has this idle issue randomly with all the motors. Wondering if anybody else has had this happen. Maybe the same issue and not the fuel change? Or the other option is the R/R is original. I felt it when this was happening and it nearly burned my finger. I can see how it was a bad design. Thinking maybe it might be a symptom that it's going bad?
Any suggestions would be appreciated. Like I said it was a two time thing until the fuel refill. So I can't diagnose it any further with it not occurring.
Senior Member
Superstock
Joined: Jul 2008
Posts: 320
I doubt it's related to the R/R. The R/R will be hot even when it's working properly, and a slow idle reduction to stalling a couple times doesn't sound like any R/R symptom I've ever heard of.
I also can't imagine it being the choice of fuel.
Just a guess, but did you overfill the tank right before this happened? Could you have blocked the vent hose briefly? Not sure what else it could be.
I also can't imagine it being the choice of fuel.
Just a guess, but did you overfill the tank right before this happened? Could you have blocked the vent hose briefly? Not sure what else it could be.
Senior Member
SuperSport
Joined: Sep 2008
Posts: 805
From: Delmar NY
Does the vent get a slug of gas in it and then it takes a while for either the slug to evaporate and/or drain?
Senior Member
MotoGP
Joined: Mar 2007
Posts: 3,132
From: Phoenix, AZ
If you open the gas cap that should drain it.. but ya, there is some gas in the vent line, and the closed cap prevents it from going down (like putting your finger on a straw) and the suction of the carbs isn't enough to pull it up.. so the tank can't feed the engine.
Senior Member
MotoGP
Joined: May 2008
Posts: 3,452
From: San Clemente, CA
Follow your vent line from the tank all the way down to where it drops out the bottom of the bike. Make sure it's headed downhill for the entire length, not forming a trap, then it won't happen to you again.
Some have also had water get sucked up the vent line in the rain, causing a stall. That happened to me once, going 70mph down a long hill in the rain. My bike started cutting out, then stalled before I got to the bottom of the hill. I researched on the forum and found a tip about cutting the bottom end of the vent line on an angle (bologna slice) to prevent water getting sucked up the hose in the rain. Haven't had that problem since.
Some have also had water get sucked up the vent line in the rain, causing a stall. That happened to me once, going 70mph down a long hill in the rain. My bike started cutting out, then stalled before I got to the bottom of the hill. I researched on the forum and found a tip about cutting the bottom end of the vent line on an angle (bologna slice) to prevent water getting sucked up the hose in the rain. Haven't had that problem since.
Last edited by VTRsurfer; May 27, 2011 at 11:48 AM.
Thread Starter
Light Cycle Expert
Back Marker
Joined: Mar 2011
Posts: 194
From: Tampa, Florida
That vent line blockage makes perfect sense. I do always fill up the tank to the brim. Also I just washed the bike so maybe it's possible that water got there too. Thank you for your responses. I'm going to check the line for traps now.
Thread
Thread Starter
Forum
Replies
Last Post
thedeatons
Technical Discussion
14
Jun 21, 2015 09:11 PM
