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Odd tacho behaviour


Boffin

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The tacho on my R1150RT has started behaving oddly. On the first start of the day all is well but after sitting in the bike shed at work for 9 hours it does not register until the bike is revved close to the redline. Once indicating all is well again. Park it for the night, next morning it works until I come to go home again.

 

The bike shed is covered on three sides, the weather is temperate and the bike stays dry and well aired.

 

Any ideas?

 

Andy

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Joe Frickin' Friday
The tacho on my R1150RT has started behaving oddly. On the first start of the day all is well but after sitting in the bike shed at work for 9 hours it does not register until the bike is revved close to the redline. Once indicating all is well again. Park it for the night, next morning it works until I come to go home again.

 

The bike shed is covered on three sides, the weather is temperate and the bike stays dry and well aired.

 

Any ideas?

 

Andy

 

Follow the wires, find the connector. Sounds like a loose/corroded connection that occasionally needs the vibrations and/or high voltage associated with redline to restore (temporarily, at least) good connectivity.

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Joe Frickin' Friday
Most people who have had erroneous tacho movements

say it is a prelude to a Hall Effect Switch failure.

 

I've seen spastic tach behavior after a dead HES leaves the engine inoperative, but if I understand Andy, the engine is still running fine.

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Most people who have had erroneous tacho movements

say it is a prelude to a Hall Effect Switch failure.

 

I've seen spastic tach behavior after a dead HES leaves the engine inoperative, but if I understand Andy, the engine is still running fine.

 

The engine is running just dandy and the tach either works or has no indication. The HES failure mode has the tach dancing around apparently at random.

What bugs me about this issue is that in the morning, after standing outside under a cover in the damp English summer weather there is never a problem.

I know that in 3 hours time when I get on the bike at the end of my working day, when the bike has been sat in warm, dry weather that the tacho will not work without being prodded.

 

Andy

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Andy, I would agree with Joe, It's a connection. Find the connection, clean it and I would put some di-electric grease on it. Your symptoms say it's a moisture related item, probably the moisture is "helping" to make the connection, then when it dries it can't until you get enough voltage.

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Could the needle be sticking on the stop or the shaft hanging up on its bushing?

Is the bike exposed to the sun in the 3 sided shed?

Anyway to rig up a temporary fan in the shed to see if cooling off the motor before it heats up the tach makes a difference?

 

Any way to temporarily connect a volt meter to determine if your fault is electrical or mechanical?

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  • 1 month later...

I'm still monitoring the situation..... tongue.gif

 

 

The bike is due to be given a brake service soon, I was going to chase this one down whilst I had it in bits for that.

 

Andy

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I know that in 3 hours time when I get on the bike at the end of my working day, when the bike has been sat in warm, dry weather that the tacho will not work without being prodded.

 

Andy

 

You should have lots of spare time to track it down with only a 3 hour work day! lmao.gif

 

It does sound like a bad connection somewhere, most likely at one of the plugs as stated earlier.

Good luck in tracking it down.

 

Andy.

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Andy,

I'm leaning towards Eric's idea....sticky needle at the stop. The Oilhead tach is one I've never had apart but maybe you could use a hi intensity light and a magnifying glass to inspect the needle and the stop?

I don't think a dirty connection would be so reliably intermittent.

 

Mick

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