Author Topic: 1985 K100 RT That didn't run...does now!  (Read 11592 times)

Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #100 on: July 17, 2017, 04:01:27 PM »
It does bubble fairly vapidly when I give it some air.


Supershooter
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline know_fear

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Re: 1985 K100 RT That didn't run...does now!
« Reply #101 on: July 18, 2017, 12:27:28 PM »
Yours is the old style tank. The black "post" about 5 or 6 inches tall is the fuel level sender and is also where the wires to the fuel pump come through. The aluminum button just in front of it is where the fuel return comes in. It is a check valve so fuel doesn't pour out when you remove the return hose. Your check valve must have been partially plugged because the fuel return line should not build up enough pressure to blow out. Unfortunately I don't think that check valve is accessible. With luck. compressed air may have cleared it. 
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Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #102 on: August 27, 2017, 05:12:47 PM »
Frustration has returned, Grrrr!


I was noticing that the battery kept losing charge and was supposed to be "new" when I purchased the bike. So I grabbed the multimeter and started doing some basic checks.


First I charged the battery to a charge of 13.2/13.6 V. Then started the bike and showed a reading of 12.8, while running at idle. I sped the motor to 3k rpm, no increase in V. So I concluded that the alternator isn't charging.


Next I removed and evaluated the fuses and they all looked fine.


I go to fire the bike up again and it won't start.


Now I'm confused. I wiggled the wires going into the tank and they seem to gain and loses contact.


In the process of trying to start the bike it has back fired a few times with an extremely loud bang the first time.


I'm looking for direction again. Thanks in advance.


Supershooter
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Laitch

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Re: 1985 K100 RT That didn't run...does now!
« Reply #103 on: August 27, 2017, 05:30:05 PM »
I wiggled the wires going into the tank and they seem to gain and loses contact. I'm looking for direction again.
Thanks in advance.
Go in the direction of the wires that seem to have intermittent contact and find out if that is the case. Be certain your battery's transmission case ground connection is clean and tight and that your battery's cable connections are likewise.

I don't accept thanks in advance.  :giggles
  • Along the Ridley in Vermont.
  • 1995 K75T 60,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #104 on: August 27, 2017, 07:53:06 PM »
I charged the battery with the transmission ground, because it's easy to get at when the battery is in the bike. The bike turns over fast, I'm not concerned about it not being able to start he bike.


The back fires have me more concerned since it won't start. I'm starting to think it might to a fuel issue. I've just filled the tank full for the first time not so long ago. I think I'll syfin the gas back out of the tank so it's easier to handle.


The four wires that run into the tank, what do they control? Is it more than the low fuel lights and fuel pump?


Supershooter
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Laitch

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Re: 1985 K100 RT That didn't run...does now!
« Reply #105 on: August 27, 2017, 08:59:58 PM »
The four wires that run into the tank, what do they control?
The fuel pump and the fuel gauge. Do you have the float-type gauge?

If the four-pin plug that connects to those wires isn't clean and tight, the pump will operate unpredictably. Open the plug, gently clean the pins with electronic cleaner then be sure the pins are in tight contact with their sockets. It that doesn't help, there might be problems with the power wire at the point where it enters the tank, or inside the tank.
  • Along the Ridley in Vermont.
  • 1995 K75T 60,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline The Mighty Gryphon

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Re: 1985 K100 RT That didn't run...does now!
« Reply #106 on: August 27, 2017, 09:07:58 PM »
First, the four wires to the tank are only for the fuel pump and the low fuel indicators.  If they are intermittent the pump will not run.

Backfiring is usually from fuel being ignited in the exhaust system.  It can be the result of an overly rich mixture being injected and not firing until it gets to the exhaust system where there will be more air available.

You earlier had a problem with high fuel pressure possibly caused by a blocked check valve in the tank.  Have you put some air through the return line to see if it is plugged again?  As a test, you might try running a long hose from the fuel pressure regulator back to the tank through the filler.  That would bypass the check valve.  Then try to start the engine.  If the check valve is the problem the engine should start and run.

You haven't mentioned whether you have been able to check the fuel pressure in the rail.  That may also be something to do. 

I didn't go that far back in this thread.  What were the conditions inside the tank?  Was there a lot of junk in there that could foul up the fuel system?
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
"Dohn f wit me, honkey, cuz I dindu nuffin'"

Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'92 K100RS "Moby Brick"

Past:
'82 Honda FT500, '80 Honda XR185, '78 Honda XL125, '76 Honda XL125, '74 Honda XL125, '71 Ossa Pioneer, '68 Kawasaki 175

Offline The Mighty Gryphon

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Re: 1985 K100 RT That didn't run...does now!
« Reply #107 on: August 27, 2017, 09:21:21 PM »
If indeed the problem is in the check valve it can be replaced.  The part number according to the fiche at MaxBMW is:

16 12 1 455 348 and it costs $8.62 which is almost free in the BMW pricing scheme.  It looks like it screws into the bottom of the tank.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
"Dohn f wit me, honkey, cuz I dindu nuffin'"

Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'92 K100RS "Moby Brick"

Past:
'82 Honda FT500, '80 Honda XR185, '78 Honda XL125, '76 Honda XL125, '74 Honda XL125, '71 Ossa Pioneer, '68 Kawasaki 175

Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #108 on: August 27, 2017, 09:44:01 PM »
I blew some compressed air through the check value, it seemed to function fine. Nothing came out  of the check valve as far as I can see. I can post the video, if You'd like.


The odd part is that the bike had been running before I started investigating the charging system.


Then fuel pump is working, I can hear it run after I let off the starter button.


I haven't checked the fuel rail pressure.


Supershooter
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline The Mighty Gryphon

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Re: 1985 K100 RT That didn't run...does now!
« Reply #109 on: August 27, 2017, 10:31:35 PM »
I could be very wrong, but from my experience, backfiring can indicate an overly rich mixture.  You seem to have had pressure problems in the past possibly caused by the check valve.  That is the first thing I would try to definitely eliminate right now.  Try the hose through the filler test. 

A fuel pressure test may also be warranted.

Have you checked the engine temperature sender?

What do the spark plugs look like?  Are they all equally wet with fuel?

Another cause of non-start and backfiring is gross ignition timing error.  Have you messed with the Hall Effect Sensors? Plug wires? 
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
"Dohn f wit me, honkey, cuz I dindu nuffin'"

Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'92 K100RS "Moby Brick"

Past:
'82 Honda FT500, '80 Honda XR185, '78 Honda XL125, '76 Honda XL125, '74 Honda XL125, '71 Ossa Pioneer, '68 Kawasaki 175

Offline Martin

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Re: 1985 K100 RT That didn't run...does now!
« Reply #110 on: August 27, 2017, 11:35:44 PM »
A flaky temperature sensor or sensor connection can cause rough running or even non or hard starting.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline critter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #111 on: August 28, 2017, 03:45:42 AM »
is it possable there problem with maf have you tried starting and pushing flap open few mill as could be stuck as mine was when first tried to fire up and had about same issue as yours just a thought
  • australia
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Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #112 on: August 29, 2017, 08:45:43 PM »
I'll try and get back to the shop after work sometime this weekend start trying some of the suggestions


Supershooter
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #113 on: September 10, 2017, 10:20:25 PM »
Well the only common theme to working on the this brick, has to be that I continuously end up smelling like gas before I'm done.
I am fairly sure the wiring to the tank is working correct. When I press the starter the pump, runs and after I release the starter button it continues to run for a short time. 


I removed the return line and hit the starter and it rapidly pumps gas out of the return line but won't fire up and run. If I try to start the bike too many more times I'll empty the tank.


I'm just stumped, because it when from starting and running to not wanting to start, with an occasional back fire.
It looks like I can rent a fuel pressure test kit from a local auto parts store, how much pressure should this pump make?
Before I started tearing into things today, the bike seems to "run" while the starter was engaged, but wouldn't take off and run.


Any other thoughts?


Supershooter
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Martin

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Re: 1985 K100 RT That didn't run...does now!
« Reply #114 on: September 10, 2017, 10:33:30 PM »
Are the spark plugs wet or dry? With the spark plugs removed, earth all the leads and check for spark by fitting a spark plug to each lead one at a time and check for spark. WARNING failure to earth the spark plug leads while checking for spark can cause damage to the computer.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #115 on: September 16, 2017, 03:30:13 PM »
The plugs are wet and black, each plug made spark.


The bike backfires every so often when I give it the ol' come on baby just start.


Supershooter
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Martin

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Re: 1985 K100 RT That didn't run...does now!
« Reply #116 on: September 16, 2017, 05:18:39 PM »
Check the temperature sender and connection. A faulty sender or connection will cause an over rich mixture. If it happens while you are out in the boonies you can get them to start. It helps if you have two people but it can be done solo. First remove the fuel pump fuse No 6 Krafftstoppe. remove the spark plugs and allow it to dry out for 15 min. Replace the spark plugs, then start the bike, it should run on the residual fuel left in the cylinder. As the fuel runs out and the engine dies ram home the fuse, the second person is handy here while one does the throttle and start the other does the fuse. it should keep running albeit roughly, with manipulation of the throttle. It will run rough but should be able to be ridden with care. It has happened twice to me until I used Deoxit and dielectric grease on the connection. Due to where the connection is situated it is subjected to a lot of road scum and water. The sender can be tested and the various values are posted.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #117 on: January 13, 2018, 02:25:12 PM »

Update and Full Disclosure:


I did poked my multimeter positive lead into the alternator fitting and the negative lead to the frame, after testing the to see if the bike would charge the battery.  Is it possible I damaged something, doing this?


I am back I the saddle actively trying to fix the bike again, hopefully I can get it on the road again before the weather gets too nice. I'll gladly take suggestions and try to figure this out.


At this point I'm planning to check the temp sensor and keep checking things as I go.


Supershooter

Frustration has returned, Grrrr!


I was noticing that the battery kept losing charge and was supposed to be "new" when I purchased the bike. So I grabbed the multimeter and started doing some basic checks.


First I charged the battery to a charge of 13.2/13.6 V. Then started the bike and showed a reading of 12.8, while running at idle. I sped the motor to 3k rpm, no increase in V. So I concluded that the alternator isn't charging.


Next I removed and evaluated the fuses and they all looked fine.


I go to fire the bike up again and it won't start.


Now I'm confused. I wiggled the wires going into the tank and they seem to gain and loses contact.


In the process of trying to start the bike it has back fired a few times with an extremely loud bang.
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Supershooter

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  • Posts: 91
Re: 1985 K100 RT That didn't run...does now!
« Reply #118 on: February 13, 2018, 07:41:40 AM »
The motivation has been tough to come by, but here we go!


I finally took time to check a few things over the weekend.


I tested the EFI, Water Temp between pin 10 and ground- 2.5K ohms @ 20C my reading was 4.07 ohms at 10C (does the key need to be in the on position when testing the water temp?)


Airflow meter Pin 7-5 65 ohms, pins 7-8 320 ohms, Pins 5-8 360 ohms, pin 7-8 214 ohms


At this point, it looks like the temp sensor needs replaced, the Airflow Meter readings looks fine to me, of I'm mistaken please let me know.


I also oredered a new fuel line return fuel valve, to hopefully stop the return fuel line from bursting and spraying fuel on me as I ride.


Any other advice to help get this brick running again is welcome.


Supershooter

  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Laitch

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Re: 1985 K100 RT That didn't run...does now!
« Reply #119 on: February 13, 2018, 10:24:23 AM »
I tested the EFI, Water Temp between pin 10 and ground- 2.5K ohms @ 20C my reading was 4.07 ohms at 10C

Airflow meter Pin 7-5 65 ohms, pins 7-8 320 ohms, Pins 5-8 360 ohms, pin 7-8 214 ohms
Presenting accurate data is important. Was the Water Temp reading 4.07 Ω or 4.07K Ω? 4.07K is close to normal but that test doesn't indicate the sensor works throughout its range. If it were my bike, I'd be compelled to remove the sensor, clean its block grounding, check its wiring and connectors and run the boiling water test with it.

Regarding the air flow thermistor:
Two 7-8 values are recorded. Should the last one actually be for 8-9?
  • Along the Ridley in Vermont.
  • 1995 K75T 60,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #120 on: February 13, 2018, 09:36:37 PM »
Laitch,
My haste in posting before work caused error. The last air flow reading was between 8-9 at 214 ohms.


The multimeter I used was a auto read model, so all the readings I'm reporting are as read off the multimeter. The odd reading had me questioning whether or not I was performing the test correctly or if the sensor was faulty or if the sensor needed to be removed and tested.


Hopefully I can get some time to remove and test the sensor this weekend.


Dustin
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Supershooter

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Re: 1985 K100 RT That didn't run...does now!
« Reply #121 on: February 14, 2018, 09:09:24 PM »
Any advice on water temp sensor removal, I don't want to make a rookie mistake.

Supershooter
  • Liberty Township, O'brien County, Iowa
  • 85 K100 RT

Offline Martin

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Re: 1985 K100 RT That didn't run...does now!
« Reply #122 on: February 15, 2018, 02:18:14 AM »
There are two ways to do it. 1/ Remove the radiator to get at it. 2/ If you have large hands you might want to do the radiator removal method. Remove the air cleaner and MAF sensor housing. I normally remove the MAF, lifting the tank can help get a screwdriver onto the large inner most hose clamp or I use a 7mm 1/4 drive socket on a thumb wheel drive to undo the clamp. Once the clamp is undone you can swing the MAF out of the way. Remove the lower air cleaner housing two Allen bolts with washers on both sides. Don't loose the washers or forget to replace them tape grease or glue can be used to keep them in place when replacing the housing. Once both housings are out of the way use a small pick to remove the spring clip off the connector and remove the connector. Clean thoroughly around the sensor. If you have everything clean you can do the next step without loosing very much coolant. Using a 19mm socket remove until finger tight, have the new sensor at hand and quickly swap the sensors, make sure you have the seal on the new sensor. If you do it right and quickly you will not loose much coolant. Do not use thread sealant, thread tape on the sensor. The sensor relies on a good earth to work. Clean the plug with DeoxIT before installing on the new sensor. Replace the lower air cleaner housing making sure the washers are aligned. Smear a small amount of rubber grease around the MAF sensor hose and push it on it can take a bit of wrangling. Do up the MAF hose clamp with the 7mm socket and thumb wheel. Refit the air cleaner element. If you weren't quick enough swapping over the sensors you will have to top up the coolant.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Laitch

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Re: 1985 K100 RT That didn't run...does now!
« Reply #123 on: February 15, 2018, 02:39:50 AM »
There are two ways to do it.
What's the difference between 1/ and 2/, Martin?
  • Along the Ridley in Vermont.
  • 1995 K75T 60,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Martin

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Re: 1985 K100 RT That didn't run...does now!
« Reply #124 on: February 15, 2018, 03:47:59 AM »
Laitch one involves draining and removing the radiator the second method involves leaving the radiator in place and removing the air cleaner/MAF housing.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.