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Technical Help Forum
Started by gamache at 07-25-2008 1:19 PM. Topic has 10 replies.
  
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 07-25-2008, 1:19 PM
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gamache
 
Joined on 06-18-2008
Cambridge, MA
Posts 87
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bike stopped idling, started popping
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Two days ago, I was slowing down towards a red light, downshifting, and suddenly hearing a bunch of exhaust pops. I put the clutch in and brought it to neutral, where it fought with a very low idle for a few seconds before dying out. I was unable to start the (totally warm) engine without choke. I ended up having to leave the choke out a little bit so the bike never revved under 1500, just to get me home. Along the way I noticed that there were many more exhaust pops on deceleration and even the slightest throttle backoff; also the throttle was sluggish coming off the line but felt pretty normal once I had a little speed/rev underneath me. No strange noises other than the pops I mentioned.
I haven't played with anything yet, due to the fact that New England was underwater for the past 48 hours. But I wanted to get some advice before I just start twiddling knobs.
Background: I got the bike about 1000mi ago, at 26kmi. I've changed oil/filter, drive oil, coolant (per Shep's Surefire Vinegar-and-Water Radiator Douche). The bike originally had some slight popping on deceleration, which seemed to clear up after I put some Seafoam in two tanks ago. I did the tappet and cam chain adjustment as prescribed. There is an inline fuel filter which doesn't look nastified. I have once adjusted the idle set screw, because when I bought the bike it idled around 1400 which was a shade high.
I was first going to play with the idle set screw just in case it came very loose, but if that isn't the magic touch, I could use some other ideas.
Thanks, greasy folk!
Pete from Boston
1979 CX500 Custom
WTB: Deluxe tank, engine bars.
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07-25-2008, 1:54 PM
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Anonymous
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Re: bike stopped idling, started popping
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sounds like the air cut off diaphram is bad.
it's on the side of the carb body, under the round plate w/ 2 screws. take it out and hold it up to a bright light to check for pinholes.
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07-25-2008, 2:33 PM
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hakko808
Joined on 05-25-2008
Fargo, ND
Posts 194
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Re: bike stopped idling, started popping
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In addition to the decel diaphrams as mentioned earlier, check for vacuum leak between carbs and engine. The rubber couplers tend to crack with age. Also the o-rings between the couplers and the engine can fail with age. Loose/cracked vacuum lines can also do it if equippped.
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07-29-2008, 5:05 AM
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gamache
Joined on 06-18-2008
Cambridge, MA
Posts 87
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Re: bike stopped idling, started popping
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Well thanks for those bits of advice, guys... Unfortunately I am not sure that's the problem.
I checked the cut-off diaphragm and it was un-holey. There were some cracks in the rubber engine-carb couplers but they didn't appear to go all the way through. There were no obvious leaks. What I ended up doing is just running it and playing with the idle set screw until it was idling about 1200 (1100 was a little feeble). I then let it warm up for a few minutes while I went inside and donned my gear for a test ride, then when I returned to the bike, its temperature was at redline. WTF. Shut it off and parked it again.
I noticed last week that it was running hotter than it should. Could a vacuum leak make the engine run so lean that it would overheat at idle so immediately?
I am interested to know people's thoughts, and also how to check for vacuum leaks effectively. Honestly there could be a leak that I'm missing. Thanks. -pete
Pete from Boston
1979 CX500 Custom
WTB: Deluxe tank, engine bars.
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07-29-2008, 8:45 AM
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Shep
Joined on 01-30-2007
Hull.East Yorkshire.England
Posts 1,713
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Re: bike stopped idling, started popping
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A lean engine can cause over-heating but 1st check the Radiator coolant level(Not via the overflow bottle as it's level is unreliable).
New Global CX/GL Forum,
http://globalcxglvtwins.hostingdelivered.com/
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07-29-2008, 10:59 AM
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gamache
Joined on 06-18-2008
Cambridge, MA
Posts 87
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Re: bike stopped idling, started popping
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 Shep wrote: | A lean engine can cause over-heating but 1st check the Radiator coolant level(Not via the overflow bottle as it's level is unreliable).
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Just checked it -- the radiator is full. I just remembered that after I flushed and replaced coolant, the radiator drew in the entire contents of the overflow tank over the next week or so. When I noticed this, I refilled the overflow tank. It wasn't soon afterwards that things went kerflooey.
Pete from Boston
1979 CX500 Custom
WTB: Deluxe tank, engine bars.
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07-29-2008, 2:32 PM
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Shep
Joined on 01-30-2007
Hull.East Yorkshire.England
Posts 1,713
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Re: bike stopped idling, started popping
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And there's no abnormal moisture coming out of the exhausts or coolant smell?
If you haven't already run the bike at idle with the tank pulled back and rad cap off up until the coolant flows to bleed the system
Could be a stuck/fualty thermostat?
Take old one to Autozone and match up.Get new Rad cap while there as well.Under the 3rd of Honda parts.
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07-29-2008, 3:01 PM
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gamache
Joined on 06-18-2008
Cambridge, MA
Posts 87
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Re: bike stopped idling, started popping
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| Shep wrote: | | And there's no abnormal moisture coming out of the exhausts or coolant smell? |
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aside from the two days' worth of hard rain that the mufflers blasted out the other day (after the problem occurred), nope and nope. The oil looks clean and the only smell is one of unburned gas coming from the exhaust, which I expected since the exhaust was popping.
| If you haven't already run the bike at idle with the tank pulled back and rad cap off up until the coolant flows to bleed the system |
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Could you explain this? It seems like you mean for me to take the cap off and run the bike until the coolant starts to circulate, but your use of the word "bleed" (and advice to pull back the tank) implies that coolant is going to exit the motorcycle.
Could be a stuck/fualty thermostat?
Take old one to Autozone and match up.Get new Rad cap while there as well.Under the 3rd of Honda parts. |
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This is good advice and I think I'm going to take it. Thanks for all your help, Shep.
-pete
Pete from Boston
1979 CX500 Custom
WTB: Deluxe tank, engine bars.
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07-29-2008, 3:14 PM
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RichNCT
Joined on 03-02-2006
Posts 2,079
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Re: bike stopped idling, started popping
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I think Shep means bleed the air from the system, maybe burp is a good analogy, since it's a gas, not a liquid (the air). The coolant can boil with the cap off, and might overflow a little, but in my experience will not erupt. Once you see it circulating for a minute or so, you have probably done the good deed. Cap it hot or when it cools the coolant level will drop allowing another air void in the radiator. Capped hot it will draw coolant in from the reservoir.
Born to be relatively wild
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07-29-2008, 7:25 PM
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gamache
Joined on 06-18-2008
Cambridge, MA
Posts 87
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Re: bike stopped idling, started popping
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I idled the bike until it almost hit temperature redline again. The coolant didn't move a millimeter. Looks like there's a new thermostat in my future... could it be anything else, practically? Should I worry about my water pump?
Pete from Boston
1979 CX500 Custom
WTB: Deluxe tank, engine bars.
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07-29-2008, 8:01 PM
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Shep
Joined on 01-30-2007
Hull.East Yorkshire.England
Posts 1,713
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Re: bike stopped idling, started popping
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| gamache wrote: | I idled the bike until it almost hit temperature redline again. The coolant didn't move a millimeter. Looks like there's a new thermostat in my future... could it be anything else, practically? Should I worry about my water pump?
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Yes.I would get the thermostat and RAD cap anyway but I'd have the water pump cover off.It could be that the impellor is not spinning correctly e.g spinning freely instead of attached to the cam shaft or similar
Just as a visual help and so you know the components in there click here,
http://www.geocities.com/sheppola/cx500/mechseal.html
PS
When I said pull the tank back it wasn't for any reason other than so you could keep fuel going to the bike but also get to see the open Radiator top.
If the cooling system is working correctly the thermostat would open and you would see coolant move across the top of the fins.This,"Bleeds" the air out of the system as per the manuals.Also the coolant transfer pipe on the side of the engine gets warm quickly after the the thermostat opens and if the impellor is working correctly :)
In some cases the coolant may rise to near the top of the radiator opening before the bleeding is complete but most times it just goes round once the cooling system is in full operation.
With your bike Red-lining as it is there's something definitly wrong.
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Honda CX500 & G... » CX500 GL500 Tra... » Technical Help ... » Re: bike stopped idling, started popping
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