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Author Topic: Bike won't idle properly or rev  (Read 3251 times)

plc

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Bike won't idle properly or rev
« on: May 11, 2009, 10:50:12 PM »
Hi Guys,

On the way to work, Thankfully almost there, my bike started misfiring and coughing. It would idle, but the tacho was reading zero rpm (not the only time it does this but rarely when warm). I got up the hill at work, but now the bike will start and idle roughly but no matter how much throttle the motor speed doesn't get above a rough idle.

I have checked and replaced the fuel filter, all good there, bike now has plenty of fuel, so that seems OK.  New spark plugs fitted also no difference. Also there isn't throttle response applying throttle at individual carbs.

What do you think guys? I checked dual coil, didn't seem physically damaged and looks newish too. A guy here said he has seen points bikes do this when the condenser is stuffed. Does that mean the trigger unit is stuffed? Yesterday I did about 100 km of freeway riding at around 110 km/h, so that may have accelerated (pardon the pun) some part failing.

I would appreciate the forum's collective wisdom.

Best to all,
Paul
« Last Edit: May 11, 2009, 10:51:34 PM by plc »
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Offline Justin B.

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Re: Bike won't idle properly or rev
« Reply #1 on: May 12, 2009, 01:04:00 AM »
This was exactly what the "Junkyard Dawg" was doing yesterday.  It would start, and sorta idle on one cylinder and wouldn't accept any throttle unless I choked it.  It turned out the idle jet was clogged...
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Justin B.

2004 BMW R1150RT
1981 R100RT - Summer bike, NEKKID!!!

steve_wicks

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Re: Bike won't idle properly or rev
« Reply #2 on: May 12, 2009, 01:07:41 AM »
I assume the tacho is a clue to an electrical problem ..... unless it is cable driven.
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Offline Justin B.

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Re: Bike won't idle properly or rev
« Reply #3 on: May 12, 2009, 01:14:21 AM »
I think all R65s used an electronic tach...
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Justin B.

2004 BMW R1150RT
1981 R100RT - Summer bike, NEKKID!!!

Offline MrRiden

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Re: Bike won't idle properly or rev
« Reply #4 on: May 12, 2009, 10:12:50 AM »
The usual suspects: drop the float bowls and verify cleanliness and fuel supply. Maybe remove the main and check for clogging. Then you can pull the tank and check electrical connections are clean and tight. Can you verify paste on the back of the ICU? Pull the front engine cover [remove battery connection first] Bean can on tight? Covered in oil, rust?
Connections clean and tight? The Tach is trying to tell you something I suspect.
rich
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Offline Lucky_Lou

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Re: Bike won't idle properly or rev
« Reply #5 on: May 12, 2009, 11:04:07 AM »
mignt be worth checking the spade connectors to the coils (this would tie in with the tacho) and if your pulling the tank off i would drop the fuel valve and check the inlet pipes........did you try it on reserve??
Lou
« Last Edit: May 12, 2009, 11:05:28 AM by Lucky_Lou »
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Online Bob_Roller

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Re: Bike won't idle properly or rev
« Reply #6 on: May 12, 2009, 11:26:15 AM »
The ICU sends independent electrical signals to the coil and the tachometer, they come off of different pins on the ICU.

You may have a hall effect sensor failing in the 'bean can', or the ICU may have issues.

I would check the wiring as mentioned, and if you have the ICU where the heat sink is removable, and renew the heat sink paste there as previously mentioned.

Until you have a complete failure, I don't know of any test method that can tell for sure which component it is, as it does still work, just not like it's supposed to.
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Offline Bengt_Phorqs

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Re: Bike won't idle properly or rev
« Reply #7 on: May 12, 2009, 12:58:52 PM »
Did anyone mention checking the carb diaphragms?  I had that condition in my 81 R65.  Even a pinhole leak can cause rough idling and no acceleration.
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Offline nhmaf

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Re: Bike won't idle properly or rev
« Reply #8 on: May 12, 2009, 01:28:07 PM »
It might be a red herring, but the tachometer thing seems to indicate an electrical gremlin that needs to be tackled.
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plc

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Re: Bike won't idle properly or rev
« Reply #9 on: May 12, 2009, 04:50:41 PM »
Hi Guys,

Thanks for all the suggestions. I am going to check the ICU first, because the bike runs on both cylinders, will run on either cylinder with the plug out and grounded, and neither carb responds to throttle. I want to see if it has a weak spark, obviously it has a spark as it runs. So if it is diaphragms it would be both, which I am sure is possible. I will also check to see if the bean can is mounted tightly and has not moved, last I checked it was fine but you never know.

I will keep you posted.

Paul
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plc

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Re: Bike won't idle properly or rev
« Reply #10 on: May 13, 2009, 12:14:26 AM »
Hi Guys,

I checked the flow to the float bowls, the float operation, the idle jet and the main jets. All seems OK.

I checked the coil resistances.  Primary winding is 0.9-1 Ohm. The secondary winding is 12.82 kOhm.  I am seeing mixed messages on sites and from my Clymer book. The Clymer book says that the primary should be 1.15-1.32 and the secondary should be 7.5-9.15 k? Yet some posts say 11 kohm is fine?

I have a spark at the plugs but it isn't great, looks a smallish spark.  Do you guys think the coil is in the death throes?

All the best,
Paul
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Offline Justin B.

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Re: Bike won't idle properly or rev
« Reply #11 on: May 13, 2009, 12:55:28 AM »
What color is the spark?  Yellowish/orange indicates a weak spark and blue usually indicates a healthy spark...
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Justin B.

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1981 R100RT - Summer bike, NEKKID!!!

plc

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Re: Bike won't idle properly or rev
« Reply #12 on: May 13, 2009, 01:45:38 AM »
It was bluish colour, I suppose I expected a bigger spark, that was brighter.

Paul
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DgM

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Re: Bike won't idle properly or rev
« Reply #13 on: May 13, 2009, 10:22:17 AM »
My 1983 R65 had similar issues. Check your coil.
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plc

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Re: Bike won't idle properly or rev
« Reply #14 on: May 13, 2009, 03:41:25 PM »
DgM, I have checked the coils but I am confused by the resistance reading which I listed in an earlier post. My secondary winding is 12.86 kOhms, which most sites and books say is too high but I have seen contrary comments on the web that say this is normal for the latest coils. My primary winding is 1 ohm, which is in no-mans land. I suppose I am curious if this indicates the coil is breaking down.

I have enquired with Rick from Motorrad Electrik about those figures before I order a Dyna coil from him.

I would appreciate any further input.

All the best,
Paul
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