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Old 07-26-2009, 12:23 PM   #1
Belgian Waffles OP
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Question Tachometer wont work...How to fix?

The tachometer on my 1989 Honda Transalp doesnt work anymore... A few days ago I was riding and it was sometimes working, then dropped to 0 when I was riding the twisties, then it "caught" again, and did this over a few miles until it just stopped altogether and now it just stays at 0. How could I fix this? Is there a chance that its just a bad connection somewhere in the guages? or could it be a bad connection somewhere near the engine? Where do I start?

Thanks all.
Belgian Waffles
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Old 07-26-2009, 10:56 PM   #2
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Don't know about the tach on the Transalp, but the ones on the Nighthawks ('91-'03) are well known for crapping out after about 25-30k miles. Maybe it's the same unit? Their problems are normally with connections of the electronic components inside the tach itself IIRC.
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Old 07-27-2009, 07:21 AM   #3
ZugBug
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Tach intermittent

Waffels, Check your CDI unit under your seat, just behind the gas tank.
I think the CDI on the right side of the bike is the one that sends a pulse to the tach. Take off seat, start the bike and jiggle the white plug, does the tach come on? A bad CDI more commenly causes the effected cylinder to cut out. If it's the CDI you need to do two things. 1st get a new CDI, 2nd find some means of keeping your seat from pushing down on the plugs of the CDIs. Aware of this common problem Honda made availabe a different rubber mount for the CDIs, the units are turned from upright to on there sides. My fix for this problem was to just glue a piece of alluminum bar stock 1/4"x1" to bottom of seat in such a way as it spans the sub frame. I did years ago and no CDI issues again. Good Luck with the fix. Paul
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Old 07-27-2009, 01:39 PM   #4
mas335
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Left CDI controls the Tach on Transalps. Swap sides with the CDI units and see if that cures the problem.

I would think if that was the problem you would have noticed the bike running poorly and on one cylinder.

Poor connections with the harness connectors would be my next item to check.
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Old 07-27-2009, 02:36 PM   #5
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If it is the same issue as the Nighthawks, here is a how to on fixing it. I think it would still need to be calibrated though.

http://nighthawk750.com/index.shtml

Can't seem to make a direct link but if you click on "Maintenance" on the left then on "Tachometer Repair" you'll see it.
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Old 07-30-2009, 02:28 AM   #6
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Awesome guys, thanks for the info! Ill look into all of that on the bike once it starts to cool off around here; its been in the triple digits in portland all week. Which is why I went riding to the coast on the Tengai today with a friend

BW
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Old 07-30-2009, 03:26 PM   #7
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I just took off the seat and checked the CDI boxes. That was the culprit. When I jiggled the right one, the tach needle started to move, so I switched the boxes and now the tach works. So this means I need a new CDI, and preferably the new rubber housing to lower the boxes into the frame more. Does anyone have information on the cheapest way to get CDI boxes? Do I have to get a Honda specific one?

Also, since one of the boxes are bad, doesnt that mean the bike has been running on only one cylinder? After riding for a few minutes, both cylinders and exhaust manifolds felt just as hot, is one cylinder still not working? Or working less efficiently?

Im also planning a trip next week with my dad (alainmax) up towards Canada. Will this cause any damage to the bike or engine if I ride for a week with a faulty CDI?

Thanks all.
Jordan
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Always chase your dreams. Even if you don't catch them, you'll have a hell of a time trying.

Current: 1989 Honda Transalp, 2006 Scorpa TY125F trials
Past: 1999 KLR 650, 1990 Tengai 650
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Old 07-31-2009, 03:19 AM   #8
mas335
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Quote:
Originally Posted by Belgian Waffles
I just took off the seat and checked the CDI boxes. That was the culprit. When I jiggled the right one, the tach needle started to move, so I switched the boxes and now the tach works. So this means I need a new CDI, and preferably the new rubber housing to lower the boxes into the frame more. Does anyone have information on the cheapest way to get CDI boxes? Do I have to get a Honda specific one?

Also, since one of the boxes are bad, doesnt that mean the bike has been running on only one cylinder? After riding for a few minutes, both cylinders and exhaust manifolds felt just as hot, is one cylinder still not working? Or working less efficiently?

Im also planning a trip next week with my dad (alainmax) up towards Canada. Will this cause any damage to the bike or engine if I ride for a week with a faulty CDI?

Thanks all.
Jordan

I have never tried any of the aftermarket products. The price difference has never been all that much and experimenting with a brand X product is not worth it to me.

Maybe you simply had a poor connection or a bad wire in the connector and not a bad CDI? We are dealing with 20 year old contact points. The temptation to "pull" on the wires and not on the connector body could cause a problem which would still exist after you install a new one. It may also have a affect on the Tach and maybe not affect the running of the engine?

It is possible that you have been running on one cylinder which would have been very VERY apparent, the bike will barely run. I wouldn't want to ride the bike for any unecessary reason just because it does run so poorly. It feels like you lost 75% of your power and not just 50%.

Inspect those connector wires for solid connections, clean the terminals and try it again.

Having said all that I aways carry a spare CDI unit and it may be wise to just replace both of them. If one does go bad on a trip you are SOL and its nice to have a back up. They run about $100.00 each and the new holder is around $10.00. There are plenty of places to order a OEM Honda CDI unit on line.
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