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A friend belonging to another site of similar bike, found a great repair for a tachometer that has suffered an overheat. The regulator/rectifier blew on the RD04 and blew the headlights and boiled the battery as well as frying the Tacho. It only worked up to 3.5 - 4000 rpm, no more no matter how hard you rev the engine.

The overheated resistor inside was the only burnt out item in the Tacho and the repair is quite easy as shown. Nearly 2 years ago mine blew, I checked everything, from spare CDI's and wiring checks, over and over... had to whittle down the possibilities, went mad, always eyeing the Tacho as the faulty part. After being told about this it took 20 mins and the thing was sorted, aint electrics a beast sometimes, and if you understand them its soo easy... apparently.

Not everything is the same in the tacho, but very similar, all electronic values must be very similar to @'s cos it worked.


QUOTE:

Hi,

This is a problem that affects many s10 and whose solution never met, until today.
I have to solve this problem for some time: the tachograph (aka rev counter) of my S10 does not run properly. Almost always works around the 2500 and does not exceed the 4000 RPM.

After inspecting the electrical installation (wires and connectors) and put a few of petroleum gely on the connectors (protection against corrosion), I decided to focus on the only element suspected: the tachograph.

You know about the lot of work we need to put the hands on the clocks: carenages and front lights surround, out.

Once the instruments panel free, it should be open to extract the rev counter. It is a delicate operation, to do without stress, and with the utmost care.

The Rev counter is composed by two parts: one electromagnetic and mechanical, and the other electronic (pulse converter).

If you do not feel with confidence to open the equipment, not to do so. Ask a tachographs technicien to do for you, and you ask him to deliver the electronic board (should dessold 2-wire, one red and one black). This is the board that we will be work.

To do it, you need some basic electronic skills, like operating a solder station, a multimeter, knowing electronic components, and take some measures.

Well, on the board, you will see various components. Focus on a resistor (perhaps blue and named R5 on the board), with the inscription "51O J" on the body.
Dessoldering one of the legs of the resistor from the board, and with the multimeter on the Ohmic scale 1X, read the value at the both legs of the resistor. If the readed value comes diferent of 51+/- 5%, take the resistor out from the board, buy and solder a new one (any value between 47 and 56 Ohm, 1W, 5% of tolerance).

The tacho board, the blow resistor (blue), and a new one (red) in place.
The board in place, just repaired.


Reassemble all in reverse order.

Explaning a litle more:

At this misfunction, the resistor R5 normaly after a blow, takes a higher value, reducing the voltage applied to the entire circuit.

How the resistor blow? Normaly, after a problem with the rectifier/regulator (another story), due to high values of tension on the circuit.

Notes :
1 - On the board, you will see another blue component (C6). Is a capacitor. Don't touch.
2 - On the board you will see a trimpot (something with a screw on the top). Don't touch. Its the calibration point of the rev counter.

Its my contribute to solving one of the electrical cheats of the S10, undocumented until now.

Problem solved on http://www.xtz750.com


 

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I had this exact same thing happen on my AT about 3 or 4 years ago after the recitfier died on the KKH. Looking at the PCB board we could see that there was heat damage around one of the resistors. We temporarily by-passed this resistor to test the tacho and it started working. So, about 3 years ago I popped into Maplins to buy an equivalent resistor - but they didn't have one so I haven't had a tacho for the last few years though every time I get on the bike I think "must do something about that you lazy buggar"!

So yes, the theory and practice appears to be the same whether XTZ or XRV.

Pete


www.horizonsunlimited.com/tstories/baird
www.garagenight.tv
 

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Discussion Starter #3
The original resistor is blue, the new one I bought (came with a second one) for about 15 pence, is light brown and stripey and about the same size. So I have a spare one if you want it Kiwi Pete. Give me your address and I'll post it. Easy fix and its soo nice to have a working tacho again, and bike back up to scratch.

Cheers
 

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Discussion Starter #6
Nice one Pete. Ta for the mention. Glad it worked for you too. Bike looks crap without some of its parts, nice to see what revs the bike will do at certain speeds, judge fuel consumption etc...

Just send us your KTM if you like, want one badly... but will keep the @ forever.

All the best mate.
 

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I had the usual problems associated with the regulator / rectifier going and that included the tacho ceasing to work all together. I tried this fix today and it worked perfectly. A couple of learning points though:

1. The resistor was marked 390 and so I took this as 39 Ohms instead of the 51 Ohms in the text above. Presumably the AT is a bit different (2 cylinder for a start).

2. Maplins only had a 0.6 Watt resisitor at 39 Ohms and nothing at 1 Watt. The 2 watt range started at 64 Ohms. So I bought and fitted the 0.6 Watt. It worked fine tonight throughout the rev range but it will be interesting to see how it fares long term.

This is a brilliant site for these sorts of fixes and I have saved a small fortune today. I might even have to subscribe!:happy3:
 

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Discussion Starter #9
Good on ya Fryupdale

Glad it worked for you too. Cant remember if I wrote that the bike the fix came from was an XTZ 750 Super Tenere, so a twin cylinder also, just with the cylinders side by side, and that tacho inside was very close to exactly the same as an RD04. The RD07 is very different though and if anyone needs one I have a spare... did think about trying to fit it to the RD04 when going mad try to repair mine, but not possible.
 

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Does any of you have a nice clear photo of the tacho's board? Mine was burned as well and never worked but I think some part is missing as there's a couple of holes where something used to be soldered into. RD07. Maybe photos of both sides? That'd be awesome!
 

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If it doesn't work out, I have a couple of tachometers in my spares box :)
Seriously? How much do you want for the "PC board" only? I've got a contact in UK who'll come visit SA in December. Probably worth while waiting...

Let me know if you ever come to Cape Town, you've helped so much with all my request. Pop in for a real South African "braai"...hope you like meat though :)
 

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I had the usual problems associated with the regulator / rectifier going and that included the tacho ceasing to work all together. I tried this fix today and it worked perfectly.
Do you have a RD07 or RD03/04? Took any photos during the repairs? I am sick of my not working rev counter, after 2 years having been too stingy to get it fixed...
 

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The RD07 is very different though and if anyone needs one I have a spare...
Well, I could do with one, Larry. As you can read I've been wanting to fix it for the 2 years I had my @ but didn't get to it, also parts seriously seem missing on the circuit board. How much do you want for a board?
 

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Discussion Starter #16
Well, I could do with one, Larry. As you can read I've been wanting to fix it for the 2 years I had my @ but didn't get to it, also parts seriously seem missing on the circuit board. How much do you want for a board?
Hey, sorry for not noticing your post. Aint been in here for a while. Are you still looking for an RD07 tacho board? I have the guts of one, you just need to fit it into the tacho housing and plug it in.
 

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Hey, sorry for not noticing your post. Aint been in here for a while. Are you still looking for an RD07 tacho board? I have the guts of one, you just need to fit it into the tacho housing and plug it in.
Great, but will you be able/willing to send to Cape Town? Otherwise, if you could send me a photo of the IC board so I can check what's missing on mine?
 

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Great, but will you be able/willing to send to Cape Town? Otherwise, if you could send me a photo of the IC board so I can check what's missing on mine?
Yes mate, no probs to send to Cape Town. I bought this from UK, when in New Zealand, and it got here fine so no reason it cant go right round the world. Its in good condition, £20 plus postage is what I paid. Same for you if you want it. I will dig it out tomorrow.
 

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so, looking at some tachos of other models, I figured I'd have to pry it open :(
I'm not very patient with this kind of job, so it's a little rough, I just hope I can get it closed again afterwards

prying:




disassembled:


tacho&temp assembly without the tacho:


internals out:


the blue thingy looks brownish as if burnt, so it seems I have the same issue as everyone else
now to find someone who can solder a new one in for me :)
 
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