CRAZY Tach. Help
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Author Topic: CRAZY Tach. Help  (Read 3113 times)
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JoeWannaB
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« on: June 23, 2010, 03:09:08 PM »

Last night, I was riding around town when my tach started to go haywire. It would register normally when it would suddenly start dancing around bouncing between 9000 and 6500 rpms. I noticed that when I pulled in the clutch lever and the motor returned to idle, the tach would respond by going back to normal showing the true speed of the engine. As soon as I took off and the motor got back up to around 4000 rpms, the dancing would start again. If I had to guess, there's something loose that breaks free during 3500 or higher rpms. Any ideas about where I should start looking to get to the bottom of this?  Has this happened to anyopne else? Thanks.  Joe
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« Reply #1 on: June 23, 2010, 04:07:56 PM »

Start at your battery and check all the connections.  I'm sure you'll find a loose wire somewhere.
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gunny
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« Reply #2 on: June 23, 2010, 06:13:32 PM »

check the wires on the coil and pull the cluster off and check the tach wires on the bottom of the cluster,
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« Reply #3 on: June 24, 2010, 05:21:36 PM »

Check the battery. And don't ask me why .
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JoeWannaB
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« Reply #4 on: June 25, 2010, 08:49:46 PM »

Thanks for the advice. I'm looking into it tomorrow morning before going out for a ride. I had the seat and tank off just the other day and could have messed up something under the seat. I'll report if I find something.  Hey Perrybwell, sounds like a lead in to a good story.
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JoeWannaB
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« Reply #5 on: June 27, 2010, 11:06:17 AM »

OK. New info and a very interesting observation.

Yesterday, the tach was really going crazy and I discovered that when I was on the highway, the bike was cutting out when I tried to cruise at highway speeds. I was heading to a friend's house to meet up to do some forest service roads. I noticed that the bike would cut out when the tach would bounce up to past the red line. I decided to press on to my friend's house just to tell him I wouldn't be riding with him that day.  To shorten the story a bit, I decided to try riding  a little with him to see if the problem persisted. While waiting for him to gear up, I jiggled the wires at the back of the tach but that is all I did. We rode the whole rest of the day including some very rough unmaintained logging roads and the tach behaved perfectly and the motor never cut out once.  The roads were rough enough that I managed to lose two bolts in the process.  So here's my theory. The bike has a redline limiter that was being activated when the tach was jumping past the red line. When I jiggled the wires, I managed to temporarily "fix" a short in the wires. I haven't had time to pull the instrument cluster out to check this out but it seems to make sense.  Question for those in the know... Does the KLR have a redline limiter that cuts power to the spark plug when you hit the redline?  Or am I totally off base?  Joe
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« Reply #6 on: June 27, 2010, 02:44:16 PM »

The KLR has no rev limiter.  Likely what was happening is the poor connection was causing a short which was reducing electrical power to the ignition system.  I've had a similar thing happen with a different connection which had nothing to do with the ignition system.  Once I got the connector plugged firmly in place, all was good again.
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« Reply #7 on: June 27, 2010, 03:50:26 PM »

On my '88 the tach goes nuts sometimes but only over 4k, runs fine always.
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« Reply #8 on: June 27, 2010, 08:28:26 PM »

Wonky tach is usually bad ground. The ignition is seperate from the tach and the other electrical.
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JoeWannaB
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« Reply #9 on: June 29, 2010, 06:54:34 AM »

Thanks for the help. My problem came back in the worst way yesterday when I was trying to get home on some superslab. THought I was going to get run over by a semi. Bike was cutting out really bad. I guess I'm taking everything off and checking the wiring tonight. I'll post up what I find.
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« Reply #10 on: June 29, 2010, 04:27:34 PM »

check your connections on the back of the cluster.
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« Reply #11 on: July 04, 2010, 12:10:02 PM »

OK. I have the tank, seat and side covers off and have removed the instrument cluster. None of the connectors on the back of the tach were loose and the wires look to be in good shape. (No chaffing or obvious shorts or breaks) I did disconnect each connector and cleaned them with sand paper til they shined. I also disconnected and reconnected the multi-connector that supplies the instrument cluster.

Following someone's suggestion that I had a ground problem, I went to every ground I could find and cleaned the terminals and retightened. I could not find any chaffed or broken wires.  I also cleaned the terminals for the thingy that connects to the spark plug wire. My battery connections are solid and clean. The wires to the rectifier are solid and clean.

I was hoping to find an obvious smoking gun but so far nothing has presented itself as the obvious culprit. I am about to button it back up and take it for a test run. I'll let you know how it goes. Is there something I'm missing?  Thanks,  Joe
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« Reply #12 on: July 09, 2010, 07:28:07 PM »

Here's an update. Over 300 miles and the tach is rock solid and the bike is running smoothly. No hint of the missing problem. I guess I got it somehow. I'll post up if anything changes. Thanks again for the help.  Joe
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« Reply #13 on: December 20, 2010, 01:39:49 AM »

I had exactly the same problem to the letter.
It was the 12v crimp connector onto the coil.
it was lose and arcing  Cleaned and crimped tight problem solved.
The taco gets its signal from the 12v coil pulse .the arcing sends the taco crazy
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