Hi all,

I'm pretty sure I'm in the market for some new HT leads since #1 and #2 plug caps are full of white and green powder. I see RAM are selling kits at a semi reasonable price but I can't for the life of me find if they have resistance built into them or not? Anyone know? I can of course phone them up to ask but not at the weekend..

I also see some of you have had these fitted for a while, Dai I'm looking at you in particular! Any problems? All marvellous? Do tell  

They're also offering 10mm diameter leads for racing. Blimmin' RACING. In blue! I know it's stupid but the idea of big bore spark pipes is strangely compelling.. Shame they're £15 more. But what if..

they design the right things for our bikes

don't hesitate

I ordered a set of these leads too, they seem very efficient to deal with....

I just received a RAM SHOX from them and had quite a bit of trouble getting it delivered and Adrian really put himself out to get it to me.

I have a red colored set in my K1100 and they seem to work very well.

I have just ordered another set in black for my K1 as the old leads are very corroded.

The K1 already has a Ram rear shock and front springs

They do both types of leads (resistor for 16v and non-resistor for 8v) and are available on ebay

http://www.ebay.co.uk/itm/BMW-K100-ht-ignition-leads-/192114321425?hash=item2cbae7e811:g:ydMAAOSw6wRXAOxw

Yes I've seen them on ebay but they don't say if they're suppressed or not.. I have half a plan to collect some in person though, if they allow that. They're not a million miles away and a nice old Roman road will take me most of the way there, would be a nice day out. I have next week off work with no plans.. Just thought I'd find out anything I can from people here first

I had one fail - faulty manufacture (Realm don't make the leads themselves) but it was sent back and replaced within a few days with no argument. Otherwise, I've never had any trouble with them.

I phoned Realm yesterday and asked about the suppression, I was promptly laughed at and told that they've been selling these leads for years and no one ever has a problem so clearly they work. I know they work, that's not the question.. Anyway, apparently he gets asked this about once a year. There are no real alternatives to these leads other than Magnecor and they seem to lump all 8v and 16v K100s together (83-95??) so I don't trust them. So off I go down to Realm to get myself a set and put this to bed once and for all. The resistances are:

#1 - 3.04kΩ
#2 - 2.34kΩ
#3 - 2.22kΩ
#4 - 1.44kΩ

Clearly the resistance is down to the length of the lead, but it is what it is.. Should we be using resistive plugs with these or not? I don't know. Not that I'm going to change the D7EAs that have only just gone in there!

I don't suppose that it matters at all if you use resistive plugs or not. The energy for the spark is developed by the coils and that energy will jump a gap at the plug. If too much resistance would make more than 1% difference to the spark then I would eat my hat. That lost energy would have to be turned into heat energy and any significant amount would start melting things.
A spark with 99% or 100% of the coil output is still going to ignite the fuel air mixture which contains the energy to power the bike.

Looks like you better put some BBQ sauce on that hat Bob because it can make quite a difference.
The load and source impedance must be close to the same or you can get big build up of heat and a much lower current which is just as important if not more so than really high voltages to get what is referred to as a big fat spark.
I thought someone conversant with aircraft would have very good knowledge  about magnetos and spark and current V voltage in a circuit which has rapidly changing values.

Rick, for those of us who are hard of understanding, are you suggesting that this is a Bad Thing™? Not that my old originals will be in spec anyway..

Check out NGK plug wires.  They have resistor wires for the bricks at a reasonable price.

I can't find any of those, .75, and NGK's part finder doesn't know they exist. But interestingly their part finder did recommend D8EA plugs (which I immediately suspected after seeing the D7EAs were slightly shorter than the original Bosch plugs) and their blurb on plug wires reckons their own wires are a mere 8kΩ per metre while most are 16kΩ. Given the length of mine I guess they are around 16kΩ a metre, so perhaps we should indeed be using resistive plugs if this lead resistance is normal.

I also see the twist on nipple things can be resistive, and a new set of four are supplied with this Realm kit. But they are 0.7Ω, so they are not the key.

Snod Blatter wrote:Rick, for those of us who are hard of understanding, are you suggesting that this is a Bad Thing™? Not that my old originals will be in spec anyway..

I would say not recommended. If it didn't matter the manufacturers would just make the same leads for everything regardless of plugs or coils.
Usually the system will cope with a mismatch in impedance but it will shorten the life of coils and plugs and quite possible in a bad mismatch to actually cook the ICU output transistors due to heat build up.
Realm have a set of leads for each type of K so it is easy to get the right ones. Silicone leads are usually good when it comes to RF interference and don't cause problems.

All I can remember on this is that the 8 valve engines use resistor leads and non resistor plugs [D7EA/D8EA] and the 16 valve uses non resistor leads and resistor plugs [DR7EA/DR8EA].

I know that because someone on the forum reminded me.

But....my 8 valve K100LT did work with resistor plugs and I never noticed. It came with resistor plugs in it when I got it.

RicK G wrote:Realm have a set of leads for each type of K so it is easy to get the right ones.

I think we can be pretty sure that Realm don't have any leads that are actually the "right ones", they just have some made up that are the correct length and fit what they need to fit at both ends. People have lived with them and not died, so as long as my bike fires up fine with them then I'll keep them. Plus they're red

But! After this apparent revelation, might it be prudent to recommend the EnDuraLast kit to people instead? Or is that too high resistance? What a minefield. Plus it sounds like a product from Durex. Or perhaps recommend the Realm kit with resistive plugs? Argh!

EDIT: Our very own dark lord "Crazy Frog" has also suggested that big ICU trouble can be caused by too little resistance. Uh oh?

One of the tricky things about this is the use of the term "resistance". This generally refers to current restriction in a steady current DC situation.
When it comes to a varying current and voltage situation, other things come into play. This applies whether it is a regular change such as the 50Hz sine wave from a wall socket, the wild variations of an audio signal from the stereo or a pulsing situation from an ignition system.

In this case the correct term is impedance, though confusingly, it uses the same units, the Ohm. (Ω) Impedance is a combination of resistance, capacitance and inductance, though not a simple sum. To add to the confusion, impedance changes with the frequency of the varying current! This gets even weirder the more the changing current varies from a sine wave.

When we check a plug lead with a multimeter, we are measuring resistance, not impedance. However, it is satisfactory for checking whether something is way out of whack. As people have found, resistance generally increases with the lead's length. If one lead's resistance is strange compared to others and their lengths, it needs replacing. I'd replace the lot in case another one is going to go strange soon.

As Rick G says, an impedance balance between the source (coil) and the load (spark plug and leads) is essential for maximum energy transfer. The coil will always have an impedance because it is just that - a coil of wire which has inherent inductance, some resistance but little capacitance. The trick is to have a matching amount in the plug/lead combination. Pretty much universally, its either impedance in the lead and not the plug, or in the plug and not the lead.
If you have impedance in neither or both, it won't match the impedance of the coil.

Will this cause a problem?
In the short term, usually not. Longer term, it can, as Rick says, lead to coil failure. Not cheap on our toys!
With the less-than-optimum power transfer, as components deteriorate with age and use, the spark may not be as strong as desired, leading to misfires and less efficient combustion. 

Conclusion: Follow the manufacturer's recommendation of lead and plug "resistance". They've worked out what works best for the correct impedance, which in the situation in question, we can't easily measure with normal equipment such as a multimeter. They've also worked it out for the frequencies that will apply in the circumstances.

In an emergency, to get home, don't worry about a short term mismatch, but don't think that because it seems alright it will stay that way long term.

Bill

...



H'okay, so we can't actually measure what is important. But when the OE leads are reading 5-6kΩ, we should try and match it with resistive plugs if we use "straight through" leads and caps? This seems to be what is being recommended. Which is a bit of a bugger as these D7EAs have seen less than 4000 miles..

Thanks all, this has been a top thread so far.

Great stuff, thanks Bill.

This topic hasn't been clear to me for a while. I think I've seen reports the OEM 8v non-resistor plugs are hard to come by, but the resistor plugs can be found easily, so maybe a swap over of leads and plugs is in order.

I'll have to go back and read my previous research.

Thanks all!

nods wrote:Great stuff, thanks Bill.

This topic hasn't been clear to me for a while. I think I've seen reports the OEM 8v non-resistor plugs are hard to come by, but the resistor plugs can be found easily, so maybe a swap over of leads and plugs is in order.

I'll have to go back and read my previous research.

Thanks all!

I don't know about other places, but in Oz the D7EA isn't common in retails stores, but any decent parts place will be able to order them for you, and delivery is usually pretty quick unless you are seriously in the sticks. (DR7EA, the resistor one, is more common.)
Don't forget, though, that they usually come without the screw on nipples on the end, so keep your old ones or ask your supplier to get some. They can if they ask. Leaving them off results in deterioration of the plug cap of the plug lead.

Bill

heres something to confuse the matter even more still

the coils on the primarys of the 16 valve models are particularly low in value ...demanding more coil primary current...an a very much higher turns ration of primary to secondary output ..those output switching devices run red hot all the time  because of the current requirements

this in itself is not too bad ...but a (for me) very concerning option for producing an more aggressive spark at first strike of the ignition process

what happens with this low input resistance- higher current  (impedance at frequency  ) is a fatter spark ....but the coils are susceptible to back emfs (voltages )more markedly if the resistance - impedance is  terminated incorrectly   ..call it reflections ..for want of a better word .
these reflections can produce an extremely high pulse back to the ignition ecu ...and may weaken - break the silicon junction of the switching device inside the ecu ...
the general rule of thumb  for collapsing dc fields ( in coils ) IS THAT THE SPIKE REFLECTED AS IT TURNS OFF COULD BE 10 - 100 TIMES THE APPLIED VOLTAGE ..  in many cases  if things are right , more likely 10 times ...so we apply 12 volts for a split second and the resulting reflected spike to the efi computer could be as little as 120 volts ...but often more than that    for many reasons
and far more noticeable with a lower primary coil count (resistance ) as in the 16 valve ..motronic type ignition coils systems

on 8 valve machines the older coils with higher impedance (and lower coils ration ) don't receive this issue far too often unless we do something stupid ...like letting the plugs short out ...through poor connections , cable breakdown ..plugs without ferules fitted and the list goes on ...but for our European mates etc with very wet conditions throughout the riding seasons  the extra arcing events can cause break over of the secondary coils within the coilpack  resulting in (when measured ) possibly an open circuit .....funny enough that still works ...well sort of ...as the high voltage will jump the very small gap that has been etched across the coils within the coils tower  this however may crack the epoxy of the coil over time

heres the deal 
on 8 valve models
1> for those that use solid copper cables  the measurement along the copper cable is only a few ohms ... for those that use copper cables ..they need ngk type resistance plug tops  measuring about 5 k  (5000 ohms ) in addition to  cable actual resistance .

2> for those that know what they are looking for  and use magawire type leads ( a very thin and long resistance wire wrapped around a silicone core ) the expected resistance along the cable is a few thousand ohms per half meter (this one of the best ignition leads available - as it doesn't fracture along its length because it is a wound conductor with stress relief ) these leads  do not need a resistive plug top ...because of the resistance along the cable ...they have a higher  than copper reactance only because of the nature of the cable construction

3> standard production silicon leads ..these measure about 2000 ohms  (around about per 1/2 meter )  they are flexible but do not suffer stretching well and will often break down at the bends and crimp connections at the plug tops and coil top  mechanically and electrically   but commonly found and useful indeed for the right price  and they  have very low inductive ..reactance ) but you have to be careful handling these things when removing ..installing is a breeze .

so for k100 8 valve ...ngk d7ea  ...if you follow the above recommendations ...don't forget that many of these products were just not available at time of design

for 16 valve models with the motronic ignition systems with the very low impedance coils ...they need extra resistance ..and the best way is with resistive plugs as well as resistive leads because they develop a higher peak spark energy in voltage terms ..but a weaker spark energy in current terms so dr7ea might be the best deal  

its all about the loading of the plug wires .coil to spark gap ...of too low an impedance (resistance ) the returned spark energy from the ignition ringing  will reflect back to the coils and primarys creating an extremely high voltage at the ignition computer ...different results could be expected indeed .

remember that carbon resistance in the plugs carries no reactance at all  so does not add to the reflected spikes to the coil ,but acts as a current limit only ...funnily there was a concerted effort back in the early 90s to decrease the radiated spark energy into the radio receiving spectrum ..call it rf noise ..and resistive spark plugs became the flavour of the month type thing , knowing this, designers went for higher voltages rather than higher currents in the secondary spark and noise production designs

I hope that help a little bit ...not saying this is gospel but makes the perfect sense to me








for those that use
the

That's right, me again..

So these are proper boring..


And, as it turns out, have been arcing on to the plugs and actually eroding bits of the ferrules! I was in the market even more than I knew.


Ah there we go, racing leads. Bit strange that the coil connectors are naturally pointing downwards though, this means the leads are constantly twisted 180 degrees when connected. Also..




I'm not sure if it's clear in the pictures but these leads are miles too long. I know I could turn the caps on the plugs around to face the wrong way but they're so soft and rubbery I feel like I'll be massively stressing whatever connection is inside there. So I've had to try and tuck the leads into the space between the coils and the engine block. Ridiculous! And no way to fit the lead separators, it's all so scrunched up and boingy that there's no space.. I'm really unimpressed with these.

But! What I am actually impressed with is what a difference new leads has made. I feel like I've gained about 5 degrees of advance, there's loads more urgency at bottom and mid range, the tickover is slightly higher/stronger, gear changes are smoother, and I'll be surprised if this doesn't give a decent boost to economy too. Proper sparks are wonderful. But if I were to do it again, I'd make the leads myself out of NGK caps, maybe some of these (if they're correct) and a length of lead. At least then they could be cut to fit.

Has anyone else found these are really long? I do hope they won't melt on the engine..

Nice work there Mr Blatter.

For what it's worth, here is a photo of the leads on my bike (apparently fitted from the factory like this)




Oh, I should add, I've got a set of the red Realm leads on my bike now. Marvellous stuff!

Snod Blatter wrote:I know I could turn the caps on the plugs around to face the wrong way but they're so soft and rubbery I feel like I'll be massively stressing whatever connection is inside there. 

Has anyone else found these are really long? I do hope they won't melt on the engine..

I see nothing wrong with reversing the caps or making turns in the leads that are not tight turns. It just takes selecting the appropriate length lead for each plug and the best place to turn it back. Copying the style done in blakey's photo can work. The location and number of wires needing the turn might differ.

Thinking about it, perhaps I can use the cable separators to take some of the strain off the connectors if I do turn them around.

People who have these fitted - did you not find they were too long? It can't just be me..

I just twisted the b*ggers round, like Blakeys.

Ok, found the time to look at my 16v K, blown head gasket?? Started it up and running on 3cyl, header #4 cold, one dead spark plug, visit supacheapa new set ngk d8ea, now running on all 4 BUT after reading the forum properly they are the 8v spark plugs, new set of dr7ea plugs coming from Sparesbox, the leads were made for me by a local years ago not sure if they are the right type for a 16v, he is no longer around to ask, REALM' s website is under construction so no luck there, has anyone used the leads from Munich here in Oz, they have leads at $96 each or a aftermarket set for $160. Anyone know the price of the Realm leads.
https://www2.munichmotorcycles.com.au/product_info.php?products_id=6269

IIRC £54 - about AU$110? Plus shipping... well worth it though.

Thanks Dai, do you have a web link, cheers

I've had NGK resistor caps on my Brick from when I acquired it 20 years ago. When visiting a Tech who just does BM's and who was working on a mates Brick, I was asked to remove my plug cover.  I was told by BMW expert to remove the leads immediately or the computer would blow at anytime. He was prepared to sell me a set of OEM leads on the spot for I think was about $200.00Au+. I consulted another mate who was an ex BM tech and he said my leads were fine. I bought another set of these NGK leads for $70.00Au as spares. I do believe the original Tech and I am patiently waiting for Doomsday, OoooH woe is me I'm doomed. I was also told by another BM tech either NGK resistor caps or standard caps with resistor plugs.The NGK caps have worked for twenty years and I have a spare set so I'll not be changing anytime soon.
Regards Martin.

Well b*gger me - I actually remembered the price correctly!

For what it's worth these leads are still working fine, though they have covered a piffling 1500 miles so far.. Anyway, don't forget there is also the EnDuraLast alternative if that's any cheaper.

I realize this is an old topic, but I would like to run Iridium spark plugs in my 8 valve K100. The stock leads no doubt have the 5 K resistors and they won't work well with the Iridium resistor plugs. Can anybody confirm that the 16 valve K100's plug wires have no 5 k resistor and rely on the resistor plug. Over the years I've read about the loss of spark power when running both resistor plugs & wires together. It is not a lot of difference and with the better spark from the Iridium plugs they likely cancel each other out.

I know on my R100Rt with stock electronic ignition I switched to 1k resistor wires and the Iridium plugs and had no issues. In my view as long as the plugs/wires have the 5 k resistance somewhere in the line every thing should be OK.

Thoughts or comments.

cycleman wrote:I realize this is an old topic, but I would like to run Iridium spark plugs in my 8 valve K100. The stock leads no doubt have the 5 K resistors and they won't work well with the Iridium resistor plugs. Can anybody confirm that the 16 valve K100's plug wires have no 5 k resistor and rely on the resistor plug. Over the years I've read about the loss of spark power when running both resistor plugs & wires together. It is not a lot of difference and with the better spark from the Iridium plugs they likely cancel each other out.

I know on my R100Rt with stock electronic ignition I switched to 1k resistor wires and the Iridium plugs and had no issues. In my view as long as the plugs/wires have the 5 k resistance somewhere in the line every thing should be OK.

Thoughts or comments.

I tried the resisted iridum NGK in my '87 K100RS years ago and found it lacking in vitality, and a willingness to rev easily. Turns out the 'strain' on the coils is not worth it. Someone else will have to explain the exact issue, but in layperson's terms, the total resistance of leads, sparkies and coils will exceed the system's requirements/specs.

Two Wheels Better wrote:I tried the resisted iridum NGK in my '87 K100RS years ago and found it lacking in vitality, and a willingness to rev easily. Turns out the 'strain' on the coils is not worth it. Someone else will have to explain the exact issue, but in layperson's terms, the total resistance of leads, sparkies and coils will exceed the system's requirements/specs.

I've wondered about this myself. TWB, did you use the original resistance leads or change to no/low resistance?

Bill

indian036 wrote:

Two Wheels Better wrote:I tried the resisted iridum NGK in my '87 K100RS years ago and found it lacking in vitality, and a willingness to rev easily. Turns out the 'strain' on the coils is not worth it. Someone else will have to explain the exact issue, but in layperson's terms, the total resistance of leads, sparkies and coils will exceed the system's requirements/specs.

I've wondered about this myself. TWB, did you use the original resistance leads or change to no/low resistance?

Bill

initially stock K100RS ignition leads, then custom leads with 5K ohm NGK ends, replicating the original resistance. I think it might have been RickG who warned me off the resisted sparkies due to heat buildup in the coils. Pardon if I'm wrong that it was him - no one needs hate mail raining down upon our head. At any rate, it made the bike run all logy and sluggish. Reverting back to standard NGK D7EA restored the bike to full former glory, my faith in humanity, and the sage advice of those who have been there before.

Like snake oil products, there's often no magic silver bullet.

Thanks for the info.
It'd be interesting to see if anyone tried resistor iridium plugs with no-resistance leads.

Bill

To clarify the answer to Cycleman's original question, I note that both K11 & K12 replacement ignition lead sets from Euro Moto Electrics are supplied with 5K ohm suppressed leads, so it must be the coils we are concerned about, as was stated to me lo these many years ago.

+1 on plain vanilla D7EA or DR7EA plugs. My '91 K100RS came with brand new plugs of some sort with dual electrodes. It was hard starting and didn't run as well as it's 1992 predecessor.

I thought it was the result of being idle for 4 years and went through the injectors, temperature sensor, air filter, fuel pressure regulator, etc, etc. Nothing made it run better until I replaced the fancy plugs with the plain old NGK's I've been using forever. For some reason, my experience with these machines is that they are pretty fussy about the spark plugs I put in them. They have to be either Bosch or NGK and they have to be changed at 20,000km.

I tend to go with .75 in that "if it ain't broke, don't fix it", and if some pretty clever engineers designed something a certain way, while I consider myself reasonably cluey on things mechanical and electrical, I'm not in their league.

My exceptions to this run to my comfort and convenience in using the bike (custom seat from MJM, GPS, extra charging points . . .) or where improvements in technology since that time are useful and compatible such as modern oils.

Doesn't stop me being curious about the iridium plugs with appropriate leads, though.

(I had a couple of Mitsubishi Magnas with transverse 3.5L V6 engines. The back bank plugs were iridium because the intake manifold had to be removed to replace them, but the easily accessed front bank plugs were conventional.  )

Bill

In the realm (pardon the pun) of the really interesting, I'm itching to try that BSK fuel injection system on a 16V K, but the US dollar to Pounds Sterling is cratering at the mo'...
Perhaps after the channel is changed, from reality TV to serial drama, on 20 January things'll shift a bit in the other direction.

BSK Speedworks Fuel Injection

£1499.00 = US$2026.80

This is an interesting thread.

Cycleman, to save money and to keep life simple, I'd just leave the original leads in.

One of the things I don't like about bricks, you never see separators for the spark plug leads to minimise the potential to crossfire.

With a k100 two spark plugs fire at the same time, so it has to jump two air gaps, with a k75 it's only one, I guess this is why the k75 leads have an air gap built in. Using non k75 leads in a k75 might result in extra Volts or Amps, or sumnat like that, and increasing the possibility of power jumping the leads. This might be why some k75's suffer from backfiring or knocking. This could be a bunch of crap and another case of ridiculous wishful thinking from me once again, so I'd be interested in any feedback, whichever way it falls.

Anyway it would be easy for anyone with either of those problems to separate the leads so that they don't touch at any point, to see if it makes a difference.

(I drive a Magna now too, would like to have sat at the desk while the pencil pushers pushed that design, so a rat chews a lead and you need to remove the inlet manifold. It's the dumbest car I've owned to work on. On the positive, it's needed virtually no work)

BMW virtually admitted to the K75 backfire problem and stated that they all do it to some extent. However it can be drastically reduced by 1/ Eliminating all induction air leaks. 2/ Eliminating the pixie dust gasket leak between the header and the muffler 3/ Correct adjustment of the TPS 4/Correct mixture adjustment 5/ Correct injector spray pattern. 5/ Fully closing the throttle on over run. With all of the above done I did eliminate the backfiring for a while but eventually the occasional backfire has crept back in. I have always run NGK leads with 5 Ohm caps which were on the bike when I got it 22 years ago with no problem. I have a new spare NGK set as spare but as yet never needed them.
Regards Martin.

daveyson wrote:(I drive a Magna now too, would like to have sat at the desk while the pencil pushers pushed that design, so a rat chews a lead and you need to remove the inlet manifold. It's the dumbest car I've owned to work on. On the positive, it's needed virtually no work)

Mercedes did the same stupid trick on one of their V8s and used the same stupid solution.

I'm aware that the coils on the newer models, K1100/K1200 etc and older 4 v K100 models have less primary resistance, something in the area of 1.6 ohms or so, whereas the older K100 2 v coils had 2.6 ohms primary resistance.

If you check the parts fiche you can't really compare the 2 & 4 valve models because they use a different ignition module and lower ohm coil. I believe they changed the coil ends of the spark plug wire as well, likely so they would stay in place. Not sure who came up with the hooking the wires to the upside down coils. Would have been much better to let gravity help keep them in place.

When I had my 95 R100RT with the stock airhead electronic ignition I ran Dynatek coils ( with the right ohms resistance ) 1k ohm wires ( from the points airhead models ) and resistor plugs. Both Iridium and non Iridium and the bike ran well.

I don't see how the ignition system can determine if the resistance is coming form a resistor in the plug wire or in the spark plug. I also have been looking at retrofitting a pair of Dynatek 3 ohm coils. The only real issue I have with this route is making up a suitable mount.

The only reason I'm looking at doing something in the coil/wire area of the bike is that the bike has the original stock grey coils. The bike has low mileage and runs well, so not a real problem right now, and the coils from BMW when you can get them are really expensive. For new it would likely cost me in the neighbourhood of $ 500 Canadian for two of the newer coils and they are now where as powerful as the Dynatek ones.

Hi Martin, l realise my previous guess ties a long line of "ifs" together and the odds are long that it's right, but the point I was trying to make is that it's a quick easy thing to swap leads with OEM k75 leads, since there's a stack of bricks close together up in Queensland, just as a test. And I realise there are different faults that can cause backfiring or knocking, so this test might only benefit some, if any.

Can you get yours to backfire easily by deliberately not backing off fully on overrun? Because I can't get a bang out of mine even if I try, and two others I've ridden didn't backfire.

Let's say the leads wiggled around a bit after you got your brick until two critical ones touched, that might explain why it didn't backfire when you first got it.

I'm probably wrong but I hope I'm right, because that would be a good result with a minimum effort.

Anyway happy new years for tonight, it should go off with a bang! Heaps will be glad to say goodbye to 2020.

After I did all the things on my list, it stopped backfiring except for very occasionally if I didn't fully close the throttle down a hill. A lot of the previous backfiring came down to the header to muffler gasket leaking. It took a lot of playing around with various things to get that particular problem solved. The mica gasket is expensive and can turn to fairy dust if you look at it the wrong way. All of the things on my list did contribute  as either a minor or major source of the backfiring.

At the moment I suspect that the header to muffler gasket has developed another leak, but it's been quite few years since I've had to redo it. I developed a quick test for checking for leaks. I stick a vacuum cleaner hose set to blow, up the exhaust pipe and spray soapy water around the joint and leaks show up as bubbles. A compressor set on low pressure can also do the job. I've also found that it can backfire more if you start pushing it through the hills again only on over run. The occasional backfire doesn't bother me down hills it serves as a warning to oncoming traffic to stay on their own side of the road, hopefully. Happy New Year.
Regards Martin.

Use exhaust sealant instead of the mica gasket.  Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker

Or contact Bocutter Ed on the other K100 forum to obtain one of his exhaust gaskets.

Thanks Rob I've been using one of Ed's gaskets with no sealant for quite a few years with no leaks. I tried the ultra copper sealant and of all the sealant it lasted the longest but eventually blew out. I need to check for leaks just in case and will do so this week. I was running Ed's gasket with no sealant so I might have to add a bit of sealant.
Happy New Year regards Martin.