testing coil

[blackeagles]

i'm not sure if the coils are 'wrong' or not but having finished the bike i took it for a 'shakedown' and in the last few miles it went onto 3. it started straight away on all 4 and has been ok running in the garage since so i am assuming it only happens when hot so intermittent and maybe a sod to find.

prim - slight fluctuation prob. the gauge

coil 1/4 - 4.5 to 4.6 ohms
coil 2/3 - 4.7 to 4.8 ohms

sec.

1/4 - 14.70 ohms
2/3 - 14.60 ohms


plug caps

1 - 5.68 ohms
2 - 4.29 ohms
3 - 4.81 ohms
4 - 5.48 ohms

i have bought new caps.

these readings seem ok to me but electrics is a 'dark art' as far as i'm concerned so not sure. obviously the readings are for a cold engine and since the 'running on 3' was when hot i'm not sure if it makes a difference or if it can be checked hot.

only other thing to say, and i still feel a bit dumb mentioning it, was that just before the problem there was a odd noise like a demented bird tweeting - only way i can describe it - which i was thinking may be a plug cap resister giving up.....maybe?.

any suggestions?

[AshimotoK0]

I think your  secondaries were actually kilOhms so multiply your readings by 1,000 (typicaly they are 15,000 Ohms =15 kOhms

The readings look acceptable to me

yes  .. arcing over in the plug cap may have caused funny noises.

The main problem usually on those Honda 4 coils is the HT cable fatigues at the outlet from the plastic coil body and the central conductor multi-strand wire eventually breaks. Just ceck if it is 'floppy' at the outlet point on each HT cable

[JezzaPeach]

Yes I can’t express it as well as Ash, but I recently replaced my coils and caps. One HT lead was very suspect and since replacing the lot no issues.

[mike the bike]

If you can determine which cylinder is dropping out, then with a bit of swapping HT leads, plugs etc and noting if the problem migrates, you should be able to suss it out.

[blackeagles]

thanks all and yes, i had not noticed the little 'k' at the bottom of the display so it is in 1000's.

it would seem that they are alright, well when they are cold at least.  do coils break down when hot??? since there are no diodes/resisters etc in them to fall over  just windings and an iron core!!!!

i do not think these are the original as my old haynes says toyota denso and these are tek fl 703 so presumably they have been replaced at some time in the past.    they look i very good condition and the ht cables are reasonably supple - they are thicker then the modern stuff - and no 'waggle' where they go into the coils.  in fact the only thing to note was that the copper at the centre of the ht cable where the plug cap screws in was blackened on each one (quite shiny now as i've been pushing the probes in and out a lot) .  i would rather keep the original coils if i can so i will be cutting the ht back say an inch and using the new caps when they arrive to see what happens.

anything else i should check?

[AshimotoK0]

TEK is correct ...  they are original. Sounds like you just need to trim the ends of the HT cables  by the minimum amount to reveal a clean cable end and conductor.

[blackeagles]

ok.  given the 'apparent' good condition i am going to guess they were replaced some 12 years ago when the bike had a fair bit of renovation then stored until  i got it.

i see ds sells the same ones but i will try new caps and cutting back the ht first to see what happens.  i did buy a set of generic ones which only need the wires changing 'cos they have the wrong connectors but maybe i will get a set of ds ones if it continues.

plugs have only been run in the garage but for the cost a new set seems right.