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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: pinhead on May 23, 2023, 02:58:07 PM

Title: 1985 bmw krt100 stalling problem
Post by: pinhead on May 23, 2023, 02:58:07 PM
I have been dealing with a problem that has been getting progressively worse.  When I first start bike up in when its engine is not warmed up, it starts ok but when I begin to drive it will stall out soon after and become hard to start.  When I do get it started it will run and when warmed up it won't do that anymore.   It also won't idle well and usually stalls when I come up to a traffic light.  I tried turning idle up but doesn't help.  Any ideas what could be causing this?  It runs good on the road at speed. 
Title: Re: 1985 bmw krt100 stalling problem
Post by: frankenduck on May 23, 2023, 03:12:09 PM
When's the last time that the fuel filter was replaced?
Title: Re: 1985 bmw krt100 stalling problem
Post by: The Mighty Gryphon on May 23, 2023, 04:40:59 PM
What does the famous Z tube look like.  Is it cracked where the clamps squeeze it?  Cracked Z tubes will mess up low rpm running when the throttle is almost closed. 
Title: Re: 1985 bmw krt100 stalling problem
Post by: pinhead on May 23, 2023, 06:44:08 PM
Now you got me wondering, what is the z tube and where is it on the bike?  thanks!
Title: Re: 1985 bmw krt100 stalling problem
Post by: frankenduck on May 23, 2023, 06:45:52 PM
Now you got me wondering, what is the z tube and where is it on the bike?  thanks!

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/ccb/ccb.htm
Title: Re: 1985 bmw krt100 stalling problem
Post by: pinhead on May 23, 2023, 06:59:08 PM
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/ccb/ccb.htm
good info.  I found the z tube and it appears to be ok.  Its not a stiff rubber though and appears to be a bit spongy.   but I don't see any cracks or tears.  I did replace the rubber caps on the throttle bodies as some were cracked and probably leaking.  but that did not seem to help
Title: Re: 1985 bmw krt100 stalling problem
Post by: pinhead on May 23, 2023, 07:10:22 PM
correction!!! I looked again and it is bad with a large crack at the crankcase.  Anywhere you can buy them preformed or do you have to by hose and cut yourself?  thanks!
Title: Re: 1985 bmw krt100 stalling problem
Post by: frankenduck on May 23, 2023, 07:17:51 PM
BMW Part #: 11151460480
Title: Re: 1985 bmw krt100 stalling problem
Post by: stokester on May 23, 2023, 09:30:40 PM
Or here at Beemerboneyard ->
Title: Re: 1985 bmw krt100 stalling problem
Post by: The Mighty Gryphon on May 23, 2023, 09:49:35 PM
Beemer Boneyard?  Is it out of stock and you need to register to be alerted when they get one?
Title: Re: 1985 bmw krt100 stalling problem
Post by: Past-my-Prime on May 23, 2023, 10:38:15 PM
I bought one from EME (Euromotoelectrics) for about $15.00.

Crankcase Breather Vent Hose - BMW K75, K100; 11 15 1 460 480 / EnDuraLast

To be found at

https://www.euromotoelectrics.com/searchresults.asp?Search=bmw+k75+crankcase+breather+tube&Submit=

They have 108 in stock.
Title: Re: 1985 bmw krt100 stalling problem
Post by: pinhead on May 24, 2023, 04:34:12 AM
I hope the boneyard isn't out of stock, I just ordered one.

On a different note, this weird bend hose with right angles is the second of 2 basic things that the K bikes suffer from.  All it took was the design to have metal 90 degree angle connector points for the hoses and you could almost use a straight hose with no collapse.

The other stupid thing on this bike is the driveshaft with no grease fitting.   In the 1930s they started putting grease fittings on cars where the drive shaft had to slip.  How they thought they would get away with no regular maintenance on it is beyond me.

Yet the bike is so well designed overall and reliable hard to believe that simple things they overlooked.....
Title: Re: 1985 bmw krt100 stalling problem
Post by: Past-my-Prime on May 24, 2023, 08:49:03 PM

The other stupid thing on this bike is the driveshaft with no grease fitting.   


Yes. Or maybe immersing it in some kind of lubricating jelly?!

Some of us went around 50,000 miles without realizing that the splines needed lubing. That was an expensive mistake.  But really, removing the rear final drive every tire change isn't that much effort and very rewarding, now! :laughing4-giggles:
Title: Re: 1985 bmw krt100 stalling problem
Post by: daveson on May 25, 2023, 04:23:22 AM
I thinks I read it in a sales brochure that the drive shaft and swing arm pivot around the same point, so there is almost no sliding of the splines. Another thing I thinks is hoses almost always have a bend, deliberately, for more flexibility.
Title: Re: 1985 bmw krt100 stalling problem
Post by: frankenduck on May 25, 2023, 09:53:10 AM
If you want to see how much the splines slide back and forth you can measure how this distance changes as the swing arm rotates:

(https://i.imgur.com/fm3Wixy.jpg)

(https://i.imgur.com/MhGmFaa.jpg)
Title: Re: 1985 bmw krt100 stalling problem
Post by: pinhead on May 25, 2023, 06:11:30 PM
yes every time I change rear tire I take rear drive off and lubricate splines with grease and my finger.  Last few times I was pleased that the splines were still well greased when I inspected but still I do it every time.  True, its not a big deal but wouldn't it have been nice to have known this before for the many who found out the hard way?  The prior owner of the K bike I own had this failure occur and it was an expensive experience for him. 
Title: Re: 1985 bmw krt100 stalling problem
Post by: stokester on May 25, 2023, 07:14:49 PM
yes every time I change rear tire I take rear drive off and lubricate splines with grease and my finger.  Last few times I was pleased that the splines were still well greased when I inspected but still I do it every time.  True, its not a big deal but wouldn't it have been nice to have known this before for the many who found out the hard way?  The prior owner of the K bike I own had this failure occur and it was an expensive experience for him.
I relube my splines every rear tire change as well using Honda Moly 60 and later Guard Dog and my '93 K75S splines look like new at 80K+ miles.  I'll be posting a source for a Guard Dog replacement now that it is no longer available.

According to the posted maintenance schedule it was to be an annual requirement up to 1990 after was every 40K miles.  Not sure if this was updated as the years went on.
Title: Re: 1985 bmw krt100 stalling problem
Post by: Laitch on May 25, 2023, 08:51:34 PM
True, its not a big deal but wouldn't it have been nice to have known this before for the many who found out the hard way?  The prior owner of the K bike I own had this failure occur and it was an expensive experience for him. 
There are 2V Brick maintenance schedules—both official and rider-created—all over the Web; finding them isn't much of a challenge if English is your first language. Attached is BMW's official schedule, but frankenduck's site at classickbikes.com (http://www.kbikeparts.com/classickbikes.com/ckb.tech/ckb.tech.toc.htm#m&o) is chock-full of tips and has been around for years. Ted Verrill also created a helpful site (http://www.verrill.com/moto/newkbike.shtml).

Back to lubing the driveshaft: unlike most autos, the Brick driveshaft receives significant protection by being located inside the swing arm, so lubrication is less likely to be compromised. That location also slightly impedes using a zerk fitting on its distal end; however, there are replacement driveshafts with zerk fittings for the u-joint. A significant development since the 1930s is the widespread availability of molybdenum paste that when applied correctly has a transmission input shaft/clutch hub lubrication life of tens of thousands of miles without replacement.

Replacing the z-tube is a nothing-burger; in a well-traveled Brick it also has a life of tens of thousands of miles, too. In a Brick that's mostly idle, it will rot.

Relative to stokester's observation, I'm using Ted Porter's spline lube—actual manufacturer not verified—but Loctite 8012 would be my next choice. The prices are similar but it would be another 60K miles before I'd need more than 2 oz from doing the driveshaft every year and the transmission input shaft/clutch hub at 30K–40K intervals.  Only Porter seems to supply small sizes. Staburags from Amazon sellers worked well for me during the first 80K. I believe it is a Barium/Graphite compound. Graphite and Molybdenum have some similar uses and lubricating characteristics.
Title: Re: 1985 bmw krt100 stalling problem
Post by: stokester on May 26, 2023, 10:05:13 AM
Relative to stokester's observation, I'm using Ted Porter's spline lube—actual manufacturer not verified—but Loctite 8012 would be my next choice. The prices are similar but it would be another 60K miles before I'd need more than 2 oz from doing the driveshaft every year and the transmission input shaft/clutch hub at 30K–40K intervals.  Only Porter seems to supply small sizes. Staburags from Amazon sellers worked well for me during the first 80K. I believe it is a Barium/Graphite compound. Graphite and Molybdenum have some similar uses and lubricating characteristics.
Yes, Ted Porter's BeemerShop spline lube is what I was referring to as a Guard Dog replacement and will start a new topic.

Title: Re: 1985 bmw krt100 stalling problem
Post by: frankenduck on May 26, 2023, 03:04:11 PM
Yes, Ted Porter's BeemerShop spline lube is what I was referring to as a Guard Dog replacement and will start a new topic.

There's already a topic about it:

http://www.motobrick.com/index.php?topic=14670.0
Title: Re: 1985 bmw krt100 stalling problem
Post by: stokester on May 26, 2023, 03:44:57 PM
There's already a topic about it:

http://www.motobrick.com/index.php?topic=14670.0 (http://www.motobrick.com/index.php?topic=14670.0)
Guess I'm behind the times...
New topic removed.