K75 Problem

[108281]

I have a 1992 K75RT with about 89,000 miles. It has run perfectly until this morning. The temperature was about 15 degrees F. when I started it up to ride to work. It started normally and I let it run with the throttle advance full on which I normally do for a minute or so in cold weather. This morning it was about 2 minutes when I got back to the bike and I heard it nunning roughly. I gave it a little throttle and it hesitated and backfired then died. After that it would catch a bit when I cranked it but wouldn't start and backfired again. The gas was near the bottom of the tank so I added some and waited until the temperature warmed up to slightly above freezing. I also put a portable under it for 15 minutes or so. It does the same thing, acts like it might catch but doesn't. Any ideas? I'm thinking a valve problem of some kind.

[gsmetal]

I had a K100RT that did that and it was the battery.

Does your battery have enough juice to run the Motronics?

[YB in IN]

Did the pitch of the sound the bike was making lower when you were trying to get it to turn over? If it did, then I would guess that it's the battery. I'd try to jump it once for good measure either way. If it's not the battery than I would take a look at the starter to see if you have some worn teeth, but I would guess that your problem is electrical in nature.

[108281]

Thanks for the replies. The battery is only a couple of months old and seems to have plenty of life. It makes the normal sound when being cranked. After thinking about it overnight I'm thinking it's a timing problem. I'm off work for 4 days after today and I'll do some trouble shooting.

[JetDoc]

I have a 1992 K75RT with about 89,000 miles. It has run perfectly until this morning. < snip > The gas was near the bottom of the tank <snip> Any ideas? I'm thinking a valve problem of some kind.

Sounds to me like you got some water off the bottom of the gas tank. In cold weather, moisture tends to condense inside the gas tank and will settle to the bottom. This is especially common if you don't keep the tank full. You may have also contaminated the fuel lines going to the injectors and the fuel filter.

Try draining the gas tank completely, change the fuel filter, bleed the lines, then refill the tank with fresh gasoline and a bottle of your favorite liquid fuel injector cleaner. It may run rough for a few miles until all the crud is run out, but should be OK.

[jgr451]

I would be inclined to agree with jet doc.
I don't know about fuel injector cleaner-the product I am familiar with for water in cold weather/gas tanks is methyl hydrate.It combines with the water that,it sounds like ,has gotten into your tank.Maybe that is the same thing.

Good luck!

[108281]

. . . Try draining the gas tank completely, change the fuel filter, bleed the lines, then refill the tank with fresh gasoline and a bottle of your favorite liquid fuel injector cleaner. It may run rough for a few miles until all the crud is run out, but should be OK.

Thanks guys. I'll try that tomorrow and give a report.

[dbrick]

It's pretty easy on Ks to flood the cylinders, which wets the business end of the sparkplugs; the over-rich condition prevents ignition. I'd remove the plugs, and make sure they're dry (or even replace them).

It's also useful to assure that the cylinders are dry inside and not coated with unburned fuel. With the sparkplugs out but connected to the spark plug wires, ground the plugs to the motor (to protect the ignition module), disconnect the electrical connectors on the injectors, and thumb the starter to pump air through the cylinders.

[PGlaves]

I think David is right. Usually when a cold K75 coughs and dies, it loads the spark plugs with fuel. It doesn't happen often ... but... The few times it has happened to me nothing, and I mean nothing would start the bike until I pulled and cleaned/dryed the spark plugs.

Paul Glaves

[kbasa]

I'm voting with the fouled plugs guys. I used to buy spare plugs in the fall so I'd have fresh ones to install when mine fouled itself. They're right, too, about pulling the plugs and allowing the cylinders to dry.

[riderR1150GSAdv]

If it was freezing when you started the bike it could have been that the water in your fuel system was frozen an blocking the line(s). When fuel runs through the system it will also cool off even more too. Just dump out all the gas and change the fuelfilter and clean/change the sparkplugs. Good luck! :wave

[108281]

I drained the tank, channel & lines and replaced the filter. The plugs look a little worn but the gap was okay. It stillwon't start. I'll get new plugs tomorrow but I'm about out of ideas. Wouldn't a good way of making sure the fuel pump is working be to disconnect the short hose between the filter and the final pipe and see if gas come out when I crank it? I think I hear the pump working when I crank it but I'm not sure.

Anyway thanks for all the advice.

Long Rider

[riderR1150GSAdv]

If you can make sure your motor gets gas then check to see if you have spark. Put a sparkplug into a plug wire and hold the plug against the engine while cranking. Be very sure you do NOT TOUCH the sparkplug or ELSE!! :hungover :violin . Use an insulated pair of pliers to hold on the plug and wire!!! Check all plugwires this way to see if any aren't working. If you see a spark it obviously works and something else is wrong :cry
Be carefull and good luck!!

[deilenberger]

I drained the tank, channel & lines and replaced the filter. The plugs look a little worn but the gap was okay. It stillwon't start. I'll get new plugs tomorrow but I'm about out of ideas. Wouldn't a good way of making sure the fuel pump is working be to disconnect the short hose between the filter and the final pipe and see if gas come out when I crank it? I think I hear the pump working when I crank it but I'm not sure.

Anyway thanks for all the advice.

Long Rider

That's certainly one way.. but were the plugs WET when you removed them? If so - your fuel pump was working.

You also can hear the pump better if you open the fuel cap when you're cranking the bike over.. and if you still have the flap inside the filler, push it open also.

Plugs that look a bit worn are worn out... DAMHIK (it was a long painful lesson.) K75's seem to have more difficulty with worn plugs than the K100 engine does (I suspect because of the difference in the ignition wires, a gap vs a resistive element), and once they are fouled - replacing them with a nice new dry set is really the only answer. And as others have pointed out - leaving them out overnight is a good thing so the cylinders can dry out.

Best,

[bobinillinois]

Last winter I had the same problem with my 1994 K75RT. During the winter I ran down the battery while trying to start the bike on half choke. After charging the battery I could still not get it to fire up. A friend with a K75 advised me to charge the battery again and then start the bike with no choke and the throttle wide open. I did this and it worked. After I got it started I slowly reduced the throttle and opened the choke half way. I let it idle for a few minutes and then rode it without problem. Not sure if this will solve your problem, but it is worth a try.

Bob

[kbasa]

Good point, Bob. Running a K75's battery down is a singularly BAD idea unless you like learning how fast you can disconnect a battery while the bike welds the starter relay shut.

[108281]

I got new plugs yesterday and skipped lunch today and put them in and it started right up. It smoked a little more than ususal the first minute or so but then it ran normally. In all I drained the tank, put a new fuel filter in and put new plugs in. It didn't show any signs of starting until it got the new plugs.

Now if I can get the fairing back the way it was I can start riding again.

Thanks again for all the advice.

[riderR1150GSAdv]

:clap :clap :twirl

[Joecubana]

Hello All,

I have been experiencing the same problem and went to remove the plugs. Of course, the fairing lowers seem to be in the way.

I didn't want to try and get into things until I found out:

1. Does the lower fairing need to be removed to replace the plugs on a 75RT?
2. If it does, I see the lower attachment point but in a quick search didn't see where else it was connected. I don't want to booger up the fairing and ask for guidance from more experienced riders.

Thanks,

Joe

[deilenberger]

Hello All,

I have been experiencing the same problem and went to remove the plugs. Of course, the fairing lowers seem to be in the way.

I didn't want to try and get into things until I found out:

1. Does the lower fairing need to be removed to replace the plugs on a 75RT?
2. If it does, I see the lower attachment point but in a quick search didn't see where else it was connected. I don't want to booger up the fairing and ask for guidance from more experienced riders.

Thanks,

Joe

Joe - nice numbered questions :clap

1. No. Simply remove the cover over the plug gallery - it's the back
cover in the center of the camshaft covers that has "BMW" in silver
on it. 3 allen screws. You'll find the plugs under the cover. The plug
wires do have the cylinder numbers on them - but to keep from
getting confused - number the caps with a sharpie, and take a
nice digi-pic of the ignition wire routing.

2. Since you don't need to - I'll just note - there are LOTS more
bolts/screws holding the lower on - most of them to be found under
the knee-pad (black thing ahead of your knee) and under the left
side radio/storage compartment, Also a few up front by the radiator
surround. Once you know how to do it - takes about 10 minutes, it's
just the first time - it's gonna take longer.

Best,

[Joecubana]

Thanks Don,

I will see if I can do it now!

Joe

[Joecubana]

Hey Don,

Things working well now. Old plugs were pretty wet. Previous owner had Autolie's in, gap was up close to .035...replaced with new Bosch's, right gap, aired out cylinders and the sucker took right off.

Now, once my final drive gets back from Bruno's next week I should be set, IF the weather doesn't snow on me anymore!

Thanks again

JOe :thumb

[deilenberger]

Hey Don,

Things working well now. Old plugs were pretty wet. Previous owner had Autolie's in, gap was up close to .035...replaced with new Bosch's, right gap, aired out cylinders and the sucker took right off.

Now, once my final drive gets back from Bruno's next week I should be set, IF the weather doesn't snow on me anymore!

Thanks again

JOe :thumb

Joe - glad it helped. Sometimes it IS the simple thing.. :-)