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Buell Forum » Old School Buell » M2 Cyclone » Archive through July 23, 2010 » Crazy Tachometer « Previous Next »

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Scdobber
Posted on Tuesday, March 09, 2010 - 12:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I've got the service manual but it does not go into crazy stuff that happens like this.My tach works perfect in every gear except 5th.At wot throttle going through the gears it's fine but cruising along in 5th at say around 65mph and nail it the tach starts bouncing around when it hits 4000rpm but the engine never misses?? Any suggestions on this??
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Blks1l
Posted on Tuesday, March 09, 2010 - 01:19 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

That seems weird, since the signal for the tach. comes from the ignition coil. So it operates correctly in the 4000 range in all the gears?
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Scdobber
Posted on Tuesday, March 09, 2010 - 06:26 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Right,it does fine in all the other gears before and after 4000.I know it sounds crazy,my only guess is extra vibration in 5th gear.I checked the connections at the coil.Odd but I can live with it
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Buellistic
Posted on Tuesday, March 09, 2010 - 07:24 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

IMHO, my guess'es:

Never have these mystery problems as "i" am heavy into PREVENTIVE MAINTENANCE !!!

FACTORY SERVICE MANUAL and PARTS BOOK for your YEAR and MODEL are a "MUST" although they are sometimes wrong and do not have enough "INFORMATION" !!!

Learning to trouble shoot from you'll's mystery problems ...

Check you battery terminals for tightness(should check every 5K miles) ...

Check your voltage charging rate across the battery terminals at operating temperature ...

Wire'ing could be failing the wiring wiggle test(avoid this by Tie wrapping all your wiring) ...

If your engine was not rubber mounted, you would understand how bad a ridged mounted SPORTSTER engine vibrates ...

Check your coil and wiring to same ...

A high resistance open(dirty contact/terminal will cause mystery problems ...
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Devil_car
Posted on Wednesday, March 10, 2010 - 12:41 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Scdobber... I've got the same problem with my tach. I've cleaned the grounds, cleaned the tach wire connection on the coil, cleaned the connections on the tach itself, installed a new battery (old one was getting up there in the years), and thanks to my extended warranty (that just ran out in Feb) had a new tach installed by the dealership. The problem still persists though...

I've been wondering if the coil might be causing the problem. I've checked the coil resistance, but it meets the FSM requirements. Could it be caused by EMI? Is the tach signal wire bad? Who knows...

Since it doesn't cause any real issues, I don't focus on it too much, but every now and then I try something else.... I'll let you know if I ever figure it out.

-Craig
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Devil_car
Posted on Tuesday, June 22, 2010 - 03:15 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Looks like my problem was caused by EMI. I found a spark plug wire where the rubber plug boot did not fully meet up with the insulation. I was chasing down a different problem and while feeling around the spark plug wires at the coil, I got shocked.

Crappy thing is that the plug wire was only about four months old (screamin' eagle plug wires for sportster).

Scdobber, if you're still looking for a potential cause for your tach jumping around, you may want to perform a good inspection of your spark plug wires (or you can be lazy like me and just stick your hand near the wires while it's running).
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Maddanthony_59
Posted on Friday, June 25, 2010 - 07:35 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

This is CRAZY! And a HUGE Thanks to this thread for showing me an Easy Fix to my problem!

Last weekend I did the XB Rocker-box conversion on my '01 M2L. It went okay, and life was swell. I rode the bike to work Monday & Tuesday, no problems. I ride in Wednesday morning morning, no problems. I go home at Lunch and I notice the Tach is being a bit erratic. And the bike is starting to run pretty rough. I go home, eat, beat my dogs, etc...and go back to work. Bike is running Horrible! And the Tach is all over the place!

So I drive my Taurus to work Thursday, and login here, and found this thread. Hmmmm. I got home from work and looked at the spark plug wires, and anything coming off of the Coil. Hmmm...When I put my bike back together, I didn't pull the rear plug wire all the way back into it's "Tee", and I wrapped the Horn Wires around the Front spark-plug wire. Hmmm...So I put everything back the way it's supposed to go, and Wow! Tach sitting right at 1,000 RPMs, Solid as a Rock! I was so happy I went for a 100 mile ride, and enjoyed Every minute of the Smooth Purring of the engine!


So, this morning I ride to work, and as I'm going through town, I notice the Tach starting to jump a bit. So I pull into an Alley, and tinker with the wires. Nothing is really working. Then I pull the 2 Horn Wires as far away from the coil as I can, and the tach settles right down. Now I have a Tie-Wrap holding the 2 horn wires away from the coil, and all seems to be good. But is this the Beginning of an Electrical Nightmare?

But, yeah, the electrical interference was my problem, and it seems to be under control now. I still need to deal with the Pinched Rocker Box gasket...
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