Ignition coils.

[Deleted account 111026]

I've a 1980 R100RT which I'm converting into a cafe-racer. As standard it has points and two separate ignition coils. The coils are quite tatty and consequently need replacing. I'd rather use a plastic-bodied coil as all they ever need is a clean!
I'm leaving the ignition system standard as the bike will be used purely for weekend afternoon trips.
Is it possible to fit a later ignition coil which has a pair of leads, perhaps from a K series?
TIA.

 

[Voyager]

I've a 1980 R100RT which I'm converting into a cafe-racer. As standard it has points and two separate ignition coils. The coils are quite tatty and consequently need replacing. I'd rather use a plastic-bodied coil as all they ever need is a clean!
I'm leaving the ignition system standard as the bike will be used purely for weekend afternoon trips.
Is it possible to fit a later ignition coil which has a pair of leads, perhaps from a K series?
TIA.

According to the Haynes manual, your bike has a single set of points (so both plugs spark together - one on the top of the compression stroke and the other on the exhaust stroke). Your two coils are wired in SERIES (i.e if one fails you lose both).

I would have thought it OK to use a later OE BMW coil (the ones that crack with age) or go for something like an orange Dyna coil. Both are 1.5 ohm and both have twin HT outlets.

The picture shows an OE BMW coil on the left and a pair of Dyna Coils used for 'Twin Plugging' - you would only need one Dyna Coil.

Hope this helps.

Bob.

 

[BillN]

Hi Voyager,

You are correct in saying that the OEM BMW Bosch coil does crack and fail.........but it would be interesting to hear from other...........after how many years.

I have had two fail.......one after 22 years on an R80 and another after 16 years on a R100GS.........so although they do have this reputation....if think that it is only after a few years.

They improved the Bosch Coil a few years ago, so if you buy a new one today it should last longer..........but 15 to 20 years is not bad.

The Dyna coils are supported to be very good...but are more expensive and presumably you have to fabricate a bracket??

Cheers

 

[Deleted account 111026]

Thanks for the replies. My thinking is, because the points only have to earth the coils, hence generating the spark, and the power to the coils isn't routed through a CDI or similar, couldn't I use any twin lead coil?
I have a spare twin-lead coil from my R1100GS which would be ideal.

 

[Voyager]

Hi Voyager,

You are correct in saying that the OEM BMW Bosch coil does crack and fail.........but it would be interesting to hear from other...........after how many years.

The Dyna coils are supported to be very good...but are more expensive and presumably you have to fabricate a bracket??

Cheers

Bill,

I bought my '89 R100GS in November 2005 - the coil had about five deep cracks and one of the contacts was hanging off.

So, assuming that coil was the original (46,000 miles recorded), it would be 16 years old.

My neighbour has an '84 R80GSPD. His coil went the same way in 2004 (only 20,000 miles recorded) - making it 20 years old.


So yes, they do last a fair time.

Dynacoils - yes, a home-made bracket will be required.

I made one from a piece of angle iron - like this:

Alternatively, if your bike has the un-used square bracket welded to the top tube below the rear of the tank (to the rear of the relays) you can use that - it just needs a couple of holes drilled.

This is on an '88 R80RT, but my '89 R100GS uses the same technique for the second coil.


If I recall correctly, the spare (new) OE Bosch coil I bought for my R80 (back in 2005) cost nearly £90.


Bob.

 

[BillN]

Thanks Bob

Yes I think that the original OEM coil has only got a "bad" reputation because the original bikes are now getting old - so I think that it is just a normal life expectancy

What I am trying to get at is that there is nothing wrong with the OEM Bosch coil and if you buy a new one today, it should last 15 to 20 years - maybe more as they improved them a few years ago.

The dyna maybe better, but I just like OEM stuff and the Bosch coil looks better built, (I have not seen the dyna "in the flesh"), and I do not think that I could stand that colour, even if it hidden by the tank.

In that regard........I have now moved from Hawker Batteries to Westco, (Black cases), as I could not stand the red colour of the Hawker case, (just sprayed it black on my R80)

Cheers

 

[BillN]

Thanks for the replies. My thinking is, because the points only have to earth the coils, hence generating the spark, and the power to the coils isn't routed through a CDI or similar, couldn't I use any twin lead coil?
I have a spare twin-lead coil from my R1100GS which would be ideal.

Not sure about an oilhead coil on an airhead...............but I do think that in terms of performance stability and improvement it is better to buy and fit a new coil, if the one that you have is "old".

I have an R80, which I have had problems starting for the last four years.......I just thought it was one of the usual BM querks, I got used to it - it started eventually, but was temperamental and you had to "get to know the Bike" Last summer the coil went - classic symptoms........I fitted a new coil..........bingo the starting problems we also sorted.

My advice - FWIW - buy a new one

 

[Deleted account 111026]

Thanks BillN, the spare one is new. The price of the new ignition coils is mind-boggling! Why are bike coils so much more than cars? Profit with a capital 'P' perhaps?

 

[BillN]

Thanks BillN, the spare one is new. The price of the new ignition coils is mind-boggling! Why are bike coils so much more than cars? Profit with a capital 'P' perhaps?

Rob - The Mod of this "Airhead" section is the "electrics" man

He has Airheads and has had oilheads - he should be able to answer your question - 1100 Coil onto a R80/100 engine

I am surprised that he has not seen the posting - maybe PM him

PS - where are you in France - we are in Dept 33 - not far from St Emilion /Ste Foy La Grande

Good luck


Bill

 

[Ogmios]

fwiw,
i had an R65 with a coil the body was cracked on.
did a "temporary" repair.... shortly before i sold the bike / told new owner he'd need to get a coil Pronto!
a year later i was talking to him - he'd not bothered (tightfisted lawyer ).
the Bike ran fine! he had eventually got a coil, but not fitted it - as he said "it aint broke - why fix it?"

i'd repaired it by using araldite over the cracks and then laying a piece J cloth over that and more araldite to form a layer - like an old style plaster cast

alternative coils;
if i had the money - i'd get a dyna, i personally rate them highly.

 

[Deleted account 111026]

Opposite end of the country to you, I'm afraid, we're in 62. Five years in 56, then 2 years here. Easy access to England, but too cold in winter!

 

[Rob Farmer]

The two coils on the 1980 bikes are very reliable but are £46 each to replace new, however James Sherlocks suggest that they sell second hand coils for £10 each. I'd give them a call or put an advert on the wanted section of this site.

Motorad Elektric sell a pair for $90 http://www.motoelekt.com/ignition.htm or a Dyna coil for $80

There's so little space under the /7 tank I think you will struggle to mount a different coil with making pretty extensive modifications to the wiring harness.

 

[BillN]

The two coils on the 1980 bikes are very reliable but are £46 each to replace new, however James Sherlocks suggest that they sell second hand coils for £10 each. I'd give them a call or put an advert on the wanted section of this site.

Motorad Elektric sell a pair for $90 http://www.motoelekt.com/ignition.htm or a Dyna coil for $80

There's so little space under the /7 tank I think you will struggle to mount a different coil with making pretty extensive modifications to the wiring harness.

Hi Rob

but do you know if he can use his 1100 coil on an RT100, (which seems to be 3 Ohms primary resistance)....I would think not?

......presumably if he used the green 3 Ohms primary resistance coil he would need two

.....and he could NOT use the 1.5 Ohms primary resistance Brown coil as he does not have an electronic ignition.

so effectively he should stick to two 6 volt Bosch coils - maybe the VW Beetle fit ones are a little cheaper - but I would go for the correct OEM ones

Cheers

 

[Steptoe]

so effectively he should stick to two 6 volt Bosch coils - maybe the VW Beetle fit ones are a little cheaper - but I would go for the correct OEM ones

Cheers

VW coils are much cheaper. No need to pay the silly BMW price, as bosch make the coils anyway. The bike in the original question has the points with two coils fitted, unlike the later bean can electronic iginition with two coils, which you can't use the two six volt coils on. Not sure about using an oilhead coil, never tried it.

You can fit a K series coil in place of the later dual output coil with no problem, and they're a lot cheaper and more available second hand.

 

[Rob Farmer]

 

[Deleted account 111026]

Thanks again, after much thought, I'll buy a pair of the VW coils. It has also been suggested that later electronic ignition type coils require a shorter 'charge' time than the earlier type coils, and this may lead to them failing quickly when used on the points type systems.

 

[DevonianScotsman]

I may be too late - But I just bought a dual output Dyna coil for my R100GS - from these guys: http://www.tts-performance.com/catalog/product_info.php?cPath=223&products_id=436
Just short of £60 after postage.

Definitely worth doing. Give them a call if you are still after one

 

[toadjam]

elec ign coils

elec ign coils can be used with points . big fat blue spark but they burn your points out . i used vf500 coils on an shoc 750 honda .