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Pickup Coil Help Needed - Printable Version

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Pickup Coil Help Needed - samri79 - 22-01-2016

Hi all new member here


I have had a intermittent problem with my 92 TDM for a while, it felt like it was firing on 1 cylinder, so I would have the throttle wide open to compensate the lack of power, then when the other one kicks back in you take off like a rocket!


I've swapped the coil, plug tops, plugs, done the valve clearances as they were due and now I think I've tracked it down to the little pickup coil as I am getting a funny spark pattern when turning the engine over.


This has been tested as per the haynes book of lies and it apears its shorting out! however, you cant buy these little buggers on there own, you need to buy the whole alternator for 500 quid!!


Any help or info on getting one of these little blighters or refurbing the one I have would be great.


Thanks

Pickup Coil Help Needed - fixitsan - 22-01-2016

They're on the same harness as the alternator stator.

 

1 on ebay.... http://www.ebay.co.uk/itm/YAMAHA-TDM850-ALTERNATOR-AND-PICK-UP-COIL-TDM-850-3VD-ALL-PARTS-HERE-/221560709904

 

What I don't get is why one cylinder would run well and the other won't, they're controlled by exactly the same pickup coil and triggered by magnets on the rotor. Unless when it drops onto 1 cylinder it drops onto a different 1 and bounces between them but that's unlikely


Pickup Coil Help Needed - samri79 - 22-01-2016

Hi fixitsan


I did see that earlier however, it seems a bit odd you can't get these things seperatly and wire it in rather than changing the whole lot! I was thinking maybe the guys that rewind the alternators would be able to help?


As it stands the engine is at tdc as I have the head off renewing the valve seals, there is no resistance what so ever between the 2 cables from the pickup coil, as far as I can tell and from what the book says this would indicate a short in the pickup coil or, possibly the cable, but I haven't got that far yet.


So in my brain wouldn't this mean theres permanent power being fed to the coil and may explain all the funny little weak sparks I was getting at the plug, maybe trying to fire the cylinder to early or something??



I'm getting the bike ready for a solo spain tour in may and its not really filling me with confidence Sad

Pickup Coil Help Needed - fixitsan - 22-01-2016

I've never had to measure that coil....what value should it be, and what meter are you using ? It's only a low voltage coil, excited by a passing magnet, I wouldn't expect it to show a huge resistance



Pickup Coil Help Needed - fixitsan - 22-01-2016

Just measured mine... 234 Ohms

 

Reason I asked about your meter was in case the resistance to be measured was very low. The smaller the resistance the better quality the meter required to be accurate. 234 Ohms should be manageable with any quality meter (or at least give a ballpark value)

 

It may be shorted, but it's a passive component and doesn't carry much current. It's wires pass a couple of grommets. It would be worth taking it off and checking there's no short in the wiring, to themselves or to ground



Pickup Coil Help Needed - Rallyist - 23-01-2016

The Mk1 uses a wasted spark system so if it is running on 1 the problem is in the lead from the coil or the plugcap/plug assuming you are getting fuel into the relevant cylinder correctly :good:



Pickup Coil Help Needed - Studley Ramrod - 23-01-2016

:wifgeni:  or indeed a plug or coil on it's way out.  Coils can pass the multimeter test but still present problems when warmed up and/or under load.

 

Another problem could be wet weather rough running, esp. with the air being so damp.  HT lead can earth to frame.

 

Also worth checking that the thermostat housing isn't leaking onto the rocker cover when the engine is warmed up.



Pickup Coil Help Needed - samri79 - 23-01-2016

Hi all thanks for your replies.


It has a new coil with leads, new plug tops and new plugs. The carbs were the first port of call and they was clean as a whistle. It may not be just firing on 1 but with the power loss and noise from the exhaust that was my first asumption.

When taking the plugs out 1 was quite oily prompting me to check the valve guides which were fine. So while I was in there I thought I'd take the head off and do the valve seals as it does burn oil and it's something I wanted to do before the spain trip.


The thing that pointed me towards the pickup coil is that when I pulled a lead and put a spare plug on it, instead of the tick tick tick of a spark it was almost like a crackling of small weak sparks.


I will have a more thorough look into it tomorrow afternoon but it does seem to be shorting out.

Pickup Coil Help Needed - samri79 - 23-01-2016

Quote:Just measured mine... 234 Ohms

 

Reason I asked about your meter was in case the resistance to be measured was very low. The smaller the resistance the better quality the meter required to be accurate. 234 Ohms should be manageable with any quality meter (or at least give a ballpark value)

 

It may be shorted, but it's a passive component and doesn't carry much current. It's wires pass a couple of grommets. It would be worth taking it off and checking there's no short in the wiring, to themselves or to ground
Yes it should be between 184-276 @ 20 degrees centigrade according to the book of lies, I do have a decent meter and it was set on 200 but I'm going to give it amother go because I'm doubting myself now Sad

Pickup Coil Help Needed - TDMick - 23-01-2016

Self Amalgamating tape on the plug leads?



Pickup Coil Help Needed - muir1848 - 25-01-2016

out of interest where did you get the new coil? they seem hard to pick up -

 

cheers



Pickup Coil Help Needed - dablik - 11-05-2018

Dont you just hate an unhappy ending ffs.


Pickup Coil Help Needed - TDMRSA - 07-01-2024

Hi Guys

 

Could you sort the problem?

 

I'm having similar issues where the bike runs great in 1st gear and pulls all the way to 13k RPM (It's a little tweaked Big Grin), but in second gear it limits at about 9k RPM and from 3rd through to 5th, it limits at 6k RPM. It also sounds like a cylinder is being dropped and only firing on the left side. Keeping it under 6k RPM it runs without any issues.

 

I have changed the coil, new leads, new plug caps, new plugs, checked the plug gaps, rebuilt and synced the carbs.

 

I tested the pickup coil and also not getting a reading.



Pickup Coil Help Needed - drewpy - 07-01-2024

13k? mine would grenade at those revs. mine redlines at 8k but nothing over 7k really as no point usually stick to 5k and under



Pickup Coil Help Needed - TDMRSA - 07-01-2024

Quote:13k? mine would grenade at those revs. mine redlines at 8k but nothing over 7k really as no point usually stick to 5k and under
 

Mine redlines at 10k on the tach, but I have some hot cams installed.

 

What model do you have? 


Pickup Coil Help Needed - drewpy - 08-01-2024

Quote: 

Mine redlines at 10k on the tach, but I have some hot cams installed.

 

What model do you have? 
1996 model


Pickup Coil Help Needed - fixitsan - 08-01-2024

Quote: 

I tested the pickup coil and also not getting a reading.
 

Does 'not getting a reading' mean it's 'infinity' or at least above 300 Ohms ?



Pickup Coil Help Needed - TDMRSA - 08-01-2024

Quote: 

Does 'not getting a reading' mean it's 'infinity' or at least above 300 Ohms ?
 

It's not showing anything, just remains on 0


Pickup Coil Help Needed - drewpy - 08-01-2024

Quote: 

It's not showing anything, just remains on 0
have you got it on the right reading setting?


Pickup Coil Help Needed - leehenty - 09-01-2024

Zero ohms is a dead short