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51Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Thu Dec 31, 2020 7:10 am

MartinW


Life time member
Life time member
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.

    

52Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Thu Dec 31, 2020 3:12 pm

DadofHedgehog

DadofHedgehog
Silver member
Silver member
@indian036 wrote: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
Folks,

This post, and this entire thread, are why I am a happy member of K100-forum.com. I have learned quite a lot reading this entire thread, and it tied together a basket of independently gathered minutia in my head into a somewhat coherent whole.

KUDOS to all the contributors!


__________________________________________________
PRESENT:
1995 K75T.  I am the 3d owner.  Bought it in June 2019 with 6,242 miles on the odo.
1991 K100RS 4-valve attached to a 1990 Flexit sidecar. I am at least the 3d owner. Bought with 21,00+ miles on bike's odo.

PAST:
old (indeterminate age) Ural + sidecar
1997 Buell S3T Thunderbolt
1982 BMW R100CS
1974 Kawasaki KZ400
1970 Suzuki Titan
    

53Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Thu Dec 31, 2020 7:07 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
I have one of Ed's first bushings in my K75RT without any additional sealant and can't say how many miles it's got on it, but it's at least 20,000.  

I have learned to completely close the throttle when coasting, and along with Ed's bushing it's been years since I have heard a backfire from that bike.  The worst I get is some discrete burbling when engine braking at high rpm's.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

54Back to top Go down   Realm Engineering HT leads - Page 2 Empty HT leads on Thu Dec 31, 2020 11:27 pm

daveyson

daveyson
Life time member
Life time member
Hi Point-Seven-Five,

OK I'll bite. I'm assuming you also have non OEM k75  spark plug leads (with an air gap) in your k75. Am I right about that? If so, am I right in assuming there are two k75's on this thread with non OEM leads, that you have to fully back off the throttle on overrun to avoid backfiring?

I don't get it. I don't have to do that on any of my bricks, one of which is a k75.

Do you have to fully back off the throttle on overrun with your k100's?


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

55Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Fri Jan 01, 2021 12:13 am

MartinW

MartinW
Life time member
Life time member
Shutting the throttle fully activates the TPS switch which is supposed to cut of the fuel and reduce backfiring. The backfiring was a K75 problem which varied between bikes. Some didn't do it, some did it occasionally and some were prodigious back firers. BMW never came up with a sure fire solution to fix the problem and as much as said live with it, and it's part of the bikes character. By addressing all the things on my list it cured mine until recently. Mine when I first got it was a prodigious back firer. I checked for exhaust leaks this morning which I have found was a large contributor to my backfiring problem, and I've found a small leak. I will check the clamp for tightness and then pull it apart to see if the gasket has been effected.
Regards Martin.


__________________________________________________
K75s Hybrid
    

56Back to top Go down   Realm Engineering HT leads - Page 2 Empty HT leads on Fri Jan 01, 2021 12:35 am

daveyson

daveyson
Life time member
Life time member
OK I accept all of that, but what about my guess about the reason for the air gap? It's a total guess. For those who haven't worked it out, this thread is way over my head. If my guess is wrong why did BMW put an air gap in k75 leads? I'll guess they must have made them for a reason, so then I spose they shouldn't be swapped.

If I had this problem in my k75 with non original leads, I'd put originals in as a check, simply because it's so easy to do. I spose crossfiring should be worse with throttle on though, rather than off (which leads me to wonder about the knock)

Here's my guess, if a spark plug ignites at the wrong time (by jumping leads due to the increased Voltage or leads too close) that could cause backfiring.

If it is sparking at the wrong time, shutting the fuel off  possibly only masks the problem. The increased Voltage might affect both coil windings. All this sort of stuff is probably why I prefer to keep things simple, and go by what the manufacturer says.  

I'm happy to be corrected though, cause as I say, this stuff is way over my head.

Point-seven-Five is that 0.75 of a litre?


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

57Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Fri Jan 01, 2021 5:40 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Well it could be or maybe 0.75 of a normally functioning brain.

Ed's bushings have done a nice job of reducing the tendency of my K75RT to sound like a drive-by shooting when slowing for a stoplight. I had found that the fairy dust seals didn't successfully survive my attempts to install them leading to frequent backfiring after about one season of riding. For the first couple years I owned the bike their replacement was part of the annual maintenance ritual.

As far as plug leads, I still have the original OEM wires in my K75RT. After 94K miles they still work well enough that I can see no reason to replace them. The engine still runs very nicely, especially after I spoil it with some annual TLC. The only thing I do to keep it running well is to ride each of my bikes at least a thousand miles a month during the seasons when it isn't snowing, and to check the throttle body balance a couple times a year, mostly because it makes me feel like I'm doing something good for the engine without having to spend any money.

I did have a few issues when I first got it, but they were related to using the NGK plugs without the the terminal nuts. Mostly hard starting late in the season on damp days when the engine seemed to take forever to warm up and run as smoothly as it did with the Bosch plugs it came with when I got it. Getting a dozen terminal nuts from an NGK tech rep solved all my spark plug problems.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

58Back to top Go down   Realm Engineering HT leads - Page 2 Empty HT leads on Fri Jan 01, 2021 6:43 am

daveyson

daveyson
Life time member
Life time member
Goodo, that clears a lot up, thanks.

By the way I googled it and 0.75 of a brain is close enough to a litre, so your good to go. Coincidence?


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

59Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Fri Jan 01, 2021 2:11 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
At least I can't be called a HALF wit.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

60Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Fri Jan 01, 2021 4:43 pm

Snod Blatter

Snod Blatter
Life time member
Life time member
Ah yes this was a good thread, fun and interesting. While I'm here I'll say that these leads have now covered 6739 miles (pathetic!) and they still work fine, I've not touched them since I fitted them.


__________________________________________________
1989 K100RS SE ABS 8v  VIN: 0149214
Others: 1.5 x Honda CBX250RS-E, '94 CB250, '95 TRX850, '16 Z250SL
http://justbikethings.blogspot.co.uk/
    

61Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Fri Jan 01, 2021 11:48 pm

Two Wheels Better

Two Wheels Better
Moderator
Moderator
Here's some useful and clearly explained info from the BMW Motorcycle Tech Site:

"The K100 is originally fitted with Bosch X5DC (or can be fitted with the NGK D7EA). Both are non-resistor spark plugs and here is the reason: The original BMW spark plug cap already integrates a resistance of 5KΩ. Similarly, the connector at the other end of the original ignition cable also includes a resistance of 1KΩ (The total resistance is 6KΩ). If you replace the wires with aftermarket, non-resistor wires and caps and keep the original spark plugs, you will run into troubles and take a chance of damaging the output transistors of the ignition module (resistance of the wire/spark plug will be close to 0). It is possible to fit a K100 with aftermarket plugs and wires, but the spark plugs have to be replaced with a resistive type (Bosch XR5DC or NGK DR7EA). These spark plugs have a built in 5kΩ resistor. The X(R)5DC has a thermal index of 5 the D(R)7EA has a thermal index of 7. Even if the thermal index is different, both are suitable for installation in a K100 engine.... 

Why does the Bosch have a thermal index of 5 and NGK has a 7? Each manufacturer uses its own designation for the heat range: On the Bosch plugs the higher the number (from 4 to 8 ) the hotter the plug. NGK works in the opposite and goes from 8 to 4 (a lower number indicates a hotter plug)."


__________________________________________________
“A bike on the road is worth two in the shed.” ~ Anonymous

1970 R60/5, OZ '77 R75/7-R100, '85 K100'87 K75C, OZ '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R'04 R1150RT, '05 K1200S, '06 K1200R, '07 K1200R, '09 K1300GT & 2013 R1200RT-Polizei  - Beemers owned still or sold.

    

62Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Sat Jan 02, 2021 10:57 am

Dai

Dai
Life time member
Life time member
Just to state the obvious and for completeness: if you replace the HT leads with non-resistive ones, fit 5KΩ resistive plug caps (very commonly available) and continue to use D7EA/X5DC spark plugs.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

63Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Sat Jan 02, 2021 11:48 am

indian036

indian036
Life time member
Life time member
@Point-Seven-five wrote:At least I can't be called a HALF wit.
For those old enough to remember the Tumbleweeds comic strip:

The Colonel and the Chief are having a battle of wits.
"Who's winning?"
"Our half."


Bill


__________________________________________________
1985 K100RT  VIN 0028991  My original Very Happy   (Historic rego)
1985 K100RT  VIN 0029036  BOB the Blue Old Bike  (Historic rego)
1990 K100LT  VIN 0190452  Work in progress
1984 K100RT  VIN 0023022  Work needing lots of progress

1986 K100RT  VIN 0090542  Work needing lots and lots of progress
1993 K1100LT  VIN 0183046  Work in progress
1993 K75S  VIN 0213045  Newest toy, slightly non-original
    

64Back to top Go down   Realm Engineering HT leads - Page 2 Empty Re: Realm Engineering HT leads on Sun Jan 03, 2021 5:22 pm

Snod Blatter

Snod Blatter
Life time member
Life time member
@Dai wrote:Just to state the obvious and for completeness: if you replace the HT leads with non-resistive ones, fit 5KΩ resistive plug caps (very commonly available) and continue to use D7EA/X5DC spark plugs.
And what should you do if you've bought some Realm leads that vary in resistance from 1.44kΩ to 3.04kΩ? Adding a 5kΩ resistance makes it too much, leaving it unsuppressed is too little and just to top things off each plug will have a slightly different spark no matter which choice you make.

Actually, I see now that you can't buy these leads any more! Problem solved Cool


__________________________________________________
1989 K100RS SE ABS 8v  VIN: 0149214
Others: 1.5 x Honda CBX250RS-E, '94 CB250, '95 TRX850, '16 Z250SL
http://justbikethings.blogspot.co.uk/
    

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