Hi everyone, bought a K100RS a couple of months ago for some motorway use. Everything great until recently came off the motorway, stopped at the first set of lights, bike tried to stall. Got it home, could not do anything that night. Next day bike started fine, same thing again but worse. I've ordered a new crankcase breather pipe as lots of people say these fail, also the hall sensor. Don't really want to start spending lots of money so any suggestions would be good. Cheers, Chris

Hi Chris

Welcome to the forum and you are in the right place.

Little more information needed on which model, if you can pop your VIN and year into your signature it makes things easy for anyone offering advice as there are different engines etc on the K over the years. Early K100RS has 8 valve engine, later ones are 16 valve so a photo is even better.

Even though you have the K a while have a look at the home page and what to do if you have just bought a K. There are important things here like checking electrical connections and in particular the earths which being old bikes are very subject to corrosion and excessive electrical resistance. 

All in all a great bike but they have quirks and generally these are all well known. With the advice of the forum most are usually easy enough to sort.

Before you go buying Hall sensors there is a test as in using a hair dryer to warm up the T cover at the front of the engine. The Hall sensor does sometimes fail but its more usually after heating up so this replicates the conditions. I think too it usually causes a cut out rather than poor running but am open to correction on that. Do it when engine is cold and warm the Hall sensor cover up well.

If you don't know too much of the history fuel filters are also a weak point in that they are often neglected, getting blocked and causing fuel starvation.

Early model Ks as in up to 85 have an electrical 4 pin plug connector into the bottom front left of the fuel tank. This can give trouble with poor or intermittent contact with loss of fuel pressure. Its worth a check, if it very loose you can squeeze up the female side on the plug so you get a tighter connection on the tank.

Early coils are also not the best and these can be changed. There are only two coils so you could lose one coil and be down to 3 or 2 cylinders depending on the nature of the problem. If you can work out from exhaust header temperature which cylinders are your problem simply swap the coils and if the problem moves then its coils, if it doesn't then you should suspect plugs/leads.

Plugs can and do break down and new plugs are no guarantee against a plug issue. Had it happen twice, both times plugs only had a few miles before failing.

Crankcase breather is small money and well worth doing anyway. At some point you should look at replacing fuel hoses as they get old and hard and will leak. Being all under pressure they will spray fuel.

Olaf.

Sorry Olaf forgot to say bike is 1985 8valve can you tell me is it necessary to depressurise fuel system if engine is cold cheers Chris

I must admit I have always just left the bike overnight and gone at it next day. I don't like to work on fuel or tank near a hot engine. Other option is just pull the tank connector and then run the bike till it cuts out. When you pull the fuel lines chances are fuel will run out of the spigot on tank. Be careful not to break them off. If you haven't the tank off before then try not to have too much fuel in it. Have a good soft towel or soft card and lay it on right hand side.

The fuel systen usually doesn't remain pressureised for very long (15 minutes) so if you wait for the engine to cool then all should be OK.
The problem you are having does not sound like Hall sensors but more like fuel delivery. Replace the filter and service the injectors would be a good first step. Then clean the system and replace the hoses. All that probably has never been done and while the bike is being ridden often it all works well but leave then standing for a few years and lots of problems.

Stalling at low revs or idle when hot.... I'd also be checking your exhaust valve clearances. Better safe than sorry. Possible valve damage if they're too tight.
Have you been getting any exhaust popping etc on throttle off?

As Olaf mentioned, I vote bad coil(s) as a primary suspect.  Seen it before on 85s when they get warmed up.

And if you do replace the coils then I would highly recommend getting some newer ones that superseded the original ones.

chrisblake wrote:Sorry Olaf forgot to say bike is 1985 8valve can you tell me is it necessary to depressurise fuel system if engine is cold cheers Chris

Wear safety glasses and keep your mouth closed.  Seriously. As mentioned, any built up pressure dissipates rather quickly but if I'm in a hurry that's what I do.

Gas does not catch fire unless there is something to ignite it - like a spark or flame.  A hot engine block will not ignite it, just make it evaporate more quickly.

Replaced crankcase vent sadly problem still there I just noticed there is a vent pipe that appears to come out of the top of the gearbox but is not connected to anything and has had a pipe added by previous owner it was aimed generally towards tank.are the two vent spigots on the right hand side just left open IE no pipes attached it doesn't look as if the pipe would reach anyway just.looked at coils is there anyway to tell if they are replacement they look good on my r65 the old ones were grey and always needed replacing.one more thing the battery is showing 12 volt ignition on 13.5 engine running does that sound enough cheers Chris

The vent on top of the gear box normally has a vented plastic cap on it. That wouldn't affect the engine.
I take it the coil bodies are light grey in colour?

Images of parts you're mentioning will always help here so break out the camera!

chrisblake wrote:.......
one more thing the battery is showing 12 volt ignition on 13.5 engine running does that sound enough cheers Chris

12V static (at rest) is kaput. 12.45V is 75% charge and considered discharged. Your static voltage has to be above 12.45V. A battery in ok condition will read around 12.7V ±0.2V . Static voltage is measured across the battery terminals after a rest period of 12 hours after charging. Charging can be from a battery charger or the bike's alternator ie; after a run.

13.5V charging is not enough. A battery will start to take a charge at 13.6V. Charging voltage should be between 13.6V and 14.4V but typically is around 14.0V. This measurement is the voltage output of your alternator via its 'voltage regulator'. However, I suspect your reading may be incorrect if the engine was simply idling or there abouts. Charging voltage must be measured across the battery terminals while the engine is running at greater than 2,000rpm. The alternator only just starts to output above 1800rpm

If your readings are correct then your battery is no longer serviceable and should be replaced. If you try to start your bike with a battery in this condition you run the risk of permanently damaging the starter relay. Its a quirk, but the battery may turn the starter motor over and the bike may start but there's not enough juice to run the bike. Higher than normal currents are created at startup to compensate and damage can occur. Spark/ignition becomes weak and intermittent. The electrical system will fail and the bike will falter and stop. Other damage to the bike's electronics from high currents can also occur. 

Its likely that corroded connectors and earth connections are responsible for the poor charge going to the battery. This is a common problem. Alternatively, you may simply have an old or damaged battery.

You can get the battery tested under load at a battery shop. A good spec for a battery for a K100 is 30Ah 360cca. I would recommend a sealed battery like an AGM type because they are reliable and maintenance free provided you maintain your bike's electrical system (keep in mind that yours is now a vintage motorcycle). A few here use lower rated batteries down to 19Ah but I can't comment on the efficacy of that.

Cheers

Would a duff battery show these symptoms seems strange did wonder why bike required 30 amp hour when my r65 has 19 amp hour but I don't do electrics might try running bike on battery from r65 if I can get it secured on bike . Looked on motorworks website seem to list different size battery for same model

There is a fairly full discussion about battery amp hours and other characteristics in this thread, post 19.

In most situations, Amp hours is a relatively minor consideration if all is well with the bike. 

Using the R65 battery shouldn't be a problem for testing purposes, properly secured for a road test. 

Bill

Would a duff battery show these symptoms 

Certainly. If you removed the battery your bike would not run. Your battery is waaay past its use-by date, so as it runs down problems will start to show. Ignition starts to falter and fails and the bike stalls. It could well be that you could replace the battery and find the stalling issue remains. The problem could still be one of the issues suggested above by other member, but you won't have a hope in hell of troubleshooting any of those issues until you have a properly functioning battery.

did wonder why bike required 30 amp hour when my r65 has 19 amp hour

Go to realoem.com enter your VIN you'll find parts diagrams and specs for your model. Your bike started life with a 25Ah battery. Police bikes and LTs (I think) had a 29Ah option. R series BMs come with a 19Ah battery but the K100 is a bit of a beef-cake and was an advanced machine in its day with higher than normal electrical requirements.  4 cylinder electronic ignition, electronic fuel injection, a decent sized fuel pump, a number of sensors and senders, electronically controlled electric fan, electronic controllers for flashers and circuit monitors and a decent starter motor to crank compression on 4 cylinders. Add on top of that your own requirement like higher wattage H/L bulb, driving lights, power for navigation, phone, heated grips etc and the whole system is chewing up a bit of power. If you don't have these requirements then look for a 25Ah but make sure it got at least a half decent CCA rating.

Looked on motorworks website seem to list different size battery for same model

They're just offering options. Some owners are looking for cheaper options and others have cafe'd their machine and looking for smaller batteries. Check online with battery retailers for some good deals. Look for a sealed battery like an AGM and you'll have fewer problems.

Indian036 wrote:In most situations, Amp hours is a relatively minor consideration if all is well with the bike.

Bill, CCA may be a minor consideration but not Ah. jmo mate 


Cheers

hi chris

welcome to the forum

besides what everybody else has said ...which is important

make sure your high tension leads are scrupulously clean in all areas , from coil tower to spark plugs

we have seen many times that little things like the thimbles on top of the spark plugs have not been fitted by the last owner   and significant corrosion  has occurred in the plug tops of the leads ...coil connections inside the coil outputs corroded and green ....hint seeing a green output socket from the coil is a good sign that that coil has suffered a major calamity and is actually open circuit ....this wont stop the engine from running ...but gives weird "at load" type firing of the plugs because it is a wasted spark system ...if that also means something to you ..

also test the continuity ...( resistance of the high tension leads ) from end to end ...( you may need to build a probe to get into the back of the plug tops) just wrap a section of home electrical (stiff ) wire   around the probe to extend it by about 2-3 inches  expect resistances between about 2.7 thousand ohms on the shortest lead to somewhere 5.5 thousand ohms on the longest  (no 1 ) .

get new plugs ...they are cheap and always good value ....make sure you get the thimbles to suit ( second hand is good ) hard to find sometimes

ngk d7ea is what you should be aiming for  on a 8 valve type engine   ngk dr7ea for a 16 valve type engine.
hope it helps some what ...its what we all have done over time restoring our machines that are new to us

r

Ok thanks for all the tips busy weekend I guess short update ordered battery fuel filters air filters and plugs.removed tank bit of a mess on top frame rail IE rusty is that usual I guess if that's had water sitting there the wiring has had it as well.will test ht leads how expensive are they I nearly had a heart attack.what is the best way to clean the plug caps bit awkward to get to also need a good contact cleaner I guess any recommendations uk based if possible

Kaptain Holister wrote:

Indian036 wrote:In most situations, Amp hours is a relatively minor consideration if all is well with the bike.

Bill, CCA may be a minor consideration but not Ah. jmo mate 


Cheers

Thanks for the enlightenment Bill. I can see that a batteries Ah rating may not be as hugely critical as I thought. However, still worth giving it reasonable consideration especially if you have special power needs :suspect: . I still would not be going toooo low with Ah rating. Its a safety net thing for me. I do too many Ks out on the open road to find I have a dud battery. I have been caught.... never again . I installed a Motobatt MBTX30U 30Ah/360cca 

Cheers

Yes, Kaptain, as I said in my original post, bigger amp hours is a safety factor. Baby batteries are for those desperate to have light weight or those who like to live dangerously.   If all is going well, no problem with a small one, but with a 30 year old bike, who is going to guarantee that all will continue to go well?

Bill

chrisblake wrote:Ok thanks for all the tips busy weekend I guess short update ordered battery fuel filters air filters and plugs.removed tank bit of a mess on top frame rail IE rusty is that usual I guess if that's had water sitting there the wiring has had it as well.will test ht leads how expensive are they I nearly had a heart attack.what is the best way to clean the plug caps bit awkward to get to also need a good contact cleaner I guess any recommendations uk based if possible

Isopropyl alcohol (brake or electrical cleaner)  but for any corroded connections you will need to abraid them or use a product called DeoxiT (electronics retailer or online) to remove any oxidation. Finish off with a squirt of WD-40.

Its well worthwhile to pay attention to the earth connections. There's one under the tank on the side of the main spar and another on the R/H side of the gearbox housing. These must be clean and tight.

Keep the connector nuts for the tops of the SPs as new NKGs don't come with those. You have to reuse the old ones. The connection is not at all reliable without those nuts for the SPs.


When you grab the tang on the metal housing of the SP cap, don't twist, they'll break off reasonably easily being so old. Just pull straight out.

Can you fit coils from k1100 to a k100

Only if it is a 16 valve engine if you use the 16v coils on an 8 valve then you stand a good chance of cooking the ignition control unit and the leads aren't interchangeable either.

So what year can I go up to there are lots of later year second hand coils for sale which don't say if they are 8 or 16 valve can't buy new I'm afraid they cost half of what I paid for the bike

um ...88 I think   if your talking about an lt version ?

not sure about rs versions as the k1 was about then ...first of the 16 valve  and different ignition systems   I think the k100 rs 16 valve was not long after ? 

someone else will know the history in more detail ...but I have a feeling that it took a while to clear lt 8 valve stocks ?? (which might be the best model to chase for coils ?

Ok think I've found the fault tested plug leads as I said earlier don't do electrics but I'm getting the following reading no 1 6.46 no 3 6.36 no4 5.31 no 2 the culprit reading going from 19.3 to 6 .dothe other readings seem correct. I guess these leads can't be repaired like normal leads.so I will have to try and pick one up second hand does it have to be the no2 lead or just one that reaches thanks to all your help by the way although I've owned many bikes over the year's I've never really understood electrics so if I have cured the fault happy days cheers Chris

A #1 lead will also fit but is a bit longer due to it doubling back. If you can put a complete set in. You can get a set at a close to reasonable price from Realm engineering http://www.realmengineering.com/ram%20power%20leads.html

Glad to hear that answers seem to be coming. 

With spark plug leads, if one is suspect and they are all old, like Rick I'd prefer to see them all replaced. You can get the genuine BMW ones if you're rich, but I've never had problems with quality generic leads with the correct length and connectors.

(Make sure your plugs have the nipples attached as previously mentioned.)

I've not used the Realm leads Rick recommends, but their reputation is good.

Bill

Chris, Sounds like you are running on a tight budget.  If that is the case, take the bad lead to an auto parts shop and see if they have one the same length.  From your readings it sounds like you have resistor leads.  Make sure they know that when they advise a replacement. 

A single lead will cost more than 1/4 of a set, but will be a lot less than a whole set when you really only need one.

chrisblake wrote:Ok think I've found the fault tested plug leads as I said earlier don't do electrics but I'm getting the following reading no 1 6.46 no 3 6.36 no4 5.31 no 2 the culprit reading going from 19.3 to 6 .dothe other readings seem correct. I guess these leads can't be repaired like normal leads.so I will have to try and pick one up second hand does it have to be the no2 lead or just one that reaches thanks to all your help by the way although I've owned many bikes over the year's I've never really understood electrics so if I have cured the fault happy days cheers Chris

6 to 19.3 .....   I wouldn't expect an intermitant result on a crook lead. There's a chance you may have connected with some corrosion inside the lead plugs giving you higher resistance and an intermittant result of 19.3. Worth checking.