K100 cold start problems - K-Bikes.com - Excellence in Motion
 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old Oct 21st, 2009, 2:44 pm Thread Starter
Noob
 
Join Date: Oct 2009
Location: , ,
Posts: 19
K100 cold start problems

Hi,

I did a search for K100 cold start problems before starting this thread, nothing!

My 85 K100 has suddenly about a month ago started behaving like it needed choke to start it. I know that the choke is actually a low running speed control and nothing more. I was a profesional mechanic before electronics came along ( I stoped working as a mechanic in 1982!) so mechanically I'm OK, this is my first "vehicle" with electronic ignition and fuel injection. I presume that there is a temperature sensor that tells the injection to make the mixture richer when cold. If so where is it? Please enlighten me! I would be grateful for any suggestions and explanations.

Thanks in advance, Matthew
mattinker is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old Oct 21st, 2009, 6:30 pm
Senior Member
 
tg4360's Avatar
 
Join Date: Jun 2009
Location: Petersburg, Va, USA
Posts: 129
So what exactly is it doing?

My LT Will not idle when it's cold (even when the air temps are warm) without a few minutes of fast idle lever time.

There's a temp sensor in the water neck behind the left side of the radiator (as you are sitting the bike) that has two leads on it. One goes to the fan relay in the relay box and the other goes to the FI computer under the seat.

I left this connector off once while working on the bike and it would not start and instantly fuel fouled the plugs. My conjecture is that since the sender is a high resistance when cold, that infinite resistance looks like arctic temps to the FI computer and it goes full rich on start.

Check this page:

http://www.ibmwr.org/ktech.shtml

For a whole lot of leads on trouble shooting the FI, fan and other related stuff.

Tony G

'87 K100LT "Her Teutonic Majesty"
'79 XS750 "The Triple"
'72 A65T "The T-Bolt"
'68 B25 "The Blue Bike"
tg4360 is offline  
post #3 of 8 (permalink) Old Oct 22nd, 2009, 1:55 am Thread Starter
Noob
 
Join Date: Oct 2009
Location: , ,
Posts: 19
What it's doing.

Thanks for the link, that make things clearer, at least I now know where the water sensor is now. I can start checking out the connections (im-probable due to the suddenness with which the fault appeared), and the sensor, let's see if this old dog can learn new tricks.

The problem started this summer, I was working 7/7 12 to 16 hours a week to get a job done (no time to look into it sooner), suddenly, starting problems not helped by the starter not engaging part of the time. When the engine would turn over, it would try to run like a no choke start, too lean a mixture. A little accelerator (choke at maximum) gave best results, when running, cold, flat difficult to build up revs, once up in the 2000 plus range, better, but needs coaxing to keep running, it feels like a manual choke that does n't work. Once warmed up it runs normally. Three days ago, the weather turned cold, it fires weakly sometimes for a second then stops, the battery gets weak and the nothing. The bike will not push start, before, I could always push start easily (I've had the 85 K100 six years now with only minor problems).

Does that help?
mattinker is offline  
Sponsored Links
Advertisement
 
post #4 of 8 (permalink) Old Oct 22nd, 2009, 7:09 am
Senior Member
 
tg4360's Avatar
 
Join Date: Jun 2009
Location: Petersburg, Va, USA
Posts: 129
Back to basics

I think it's time to check that you don't need a new battery and that the starter doesn't need some attention.

Baseline the thing and see what happens.... You might start chasing your tail if it needs a new battery etc.

Also, check all the rubber parts... it's probably about time for replacement. Vacuum caps, the vac line to the fuel pressure regulator, the boots to the airbox etc. If it needs lots of fuel, there may be an air leak.

I sat down one evening and read almost every thing on that page and made a list of things to check on my bike. Some of it was good just for insight etc.

Tony G

'87 K100LT "Her Teutonic Majesty"
'79 XS750 "The Triple"
'72 A65T "The T-Bolt"
'68 B25 "The Blue Bike"
tg4360 is offline  
post #5 of 8 (permalink) Old Oct 22nd, 2009, 5:34 pm Thread Starter
Noob
 
Join Date: Oct 2009
Location: , ,
Posts: 19
So far

tg 4360

today I went through all the connections I could find under the tank, cleaned and made sure that all contacts were tight earth connections, battery terminals, the plugs are new, the plug caps are clean, visually I have a good spark, I cleaned the starter motor, I'll change the brushes, I'm now very aware of the problems that they can create! I'm leaning more and more towards temperature sensor, I managed to start the bike up using jumper cables, it took a long time, but once it was up to running temperature, it ran very well, better than before (I think, grin).

i think I'll have to bite the bullet and take the radiator out to get at the water temperature sensor. Good idea about checking the rubber parts, but i suspect that i would have seen a weak mixture on the plugs, they gave signs of neither too weak nor too rich.

Thanks for your thoughts and the link. When I bought this bike, I found the site you showed me, somewhere at the same time, I came across an article that showed how to bridge certain pins somewhere to get a diagnostic from the machine it's self, I wish I could find it now!

regards, Matthew
mattinker is offline  
post #6 of 8 (permalink) Old Oct 22nd, 2009, 5:59 pm
Senior Member
 
tg4360's Avatar
 
Join Date: Jun 2009
Location: Petersburg, Va, USA
Posts: 129
Don't yank the rad yet.

I have an LT so it's very much a pain but for you not so much.

I think if you take off the right rad shroud, remove the schnorkle and air filter and the bottom of the air box (two hex cap screws... if you have small hands it's a breeze... read here it hurts but comes off), you can get to the water neck from the right side.

BUT.... before you do that, while the tank is off, you can check one side of the sensor to ground via the connector to the fan relay and the other side you can check at the connector to the FI computer.

For your purposes the more critical side is the FI computer.

Check out the fan page on the kbikes for a diagram of the relay plug to see which pin to check.

Pin 10 is the one you are looking for on the FI connector... hold it with the pins on top and count from the left.

the expected values I have are 2.5K at 20C and 300ohms at 80C

I'd do that before tearing parts off.

Here's the trouble shooting doc I'm using.... it's more for bikes not starting but it's a gold mine of information:

http://hrsbstaff.ednet.ns.ca/bvogel/...20Starting.pdf

Oh... and the one thing I keep forgetting... there is supposed to be an air temp sensor in the air flow meter in the air box. I know on a T-bird I had once, the car ran better after I cleaned some smutz off of it. I've not gotten to mine yet but it can't hurt to take a look at it to make sure it's not crapped up in any way.

Tony G

'87 K100LT "Her Teutonic Majesty"
'79 XS750 "The Triple"
'72 A65T "The T-Bolt"
'68 B25 "The Blue Bike"

Last edited by tg4360; Oct 22nd, 2009 at 6:10 pm.
tg4360 is offline  
post #7 of 8 (permalink) Old Oct 23rd, 2009, 11:58 pm Thread Starter
Noob
 
Join Date: Oct 2009
Location: , ,
Posts: 19
Link http://hrsbstaff.ednet.ns.ca/bvogel...-wont-start.htm

tg4360

thanks for the http://hrsbstaff.ednet.ns.ca/bvogel...-wont-start.htm link, a mine of information. It shows the air temp sensor, lurking inside the air box!

Lots more nice clear testing stuff to do!

I'mgoing to have to put things on hold this w/end as my son and grandson are visitin from the UK.

I'll let you know how it works out.

Regards , Matthw
mattinker is offline  
post #8 of 8 (permalink) Old Dec 15th, 2009, 10:58 am Thread Starter
Noob
 
Join Date: Oct 2009
Location: , ,
Posts: 19
The end result!

Well, it's been some time! I was away on holiday, I got back a week ago. Finally, I got back to my starting problem. The tests in the K100 link http://hrsbstaff.ednet.ns.ca/bvogel...%20Starting.pdf are spot on! I had concluded that it was a cold start problem related to engine temperature sensors. It behaved like an engine with no choke. I have a spare block, which I took the water temperature from and tested with an ohm meter at 0C it showed 5,5K ohms, which is roughly what the chart said it should. Testing the N10 pin on the EFI unit lead to earth (not the EFI unit) showed no resistance. I was able to change the sender unit just by taking off the side of the faring (it has an LT faring, added i don't know when). The difficult bit was I didn't have a deep 19mm socket so I made a special spanner out of a cheap ring/open-ended spanner, bent to 90 near to the ring end. I didn't drain the cooling system, I lost practically no coolant whilst swapping things over. The bike started almost straight away once I'd changed the sensor!

thanks to those that contributed, I hope this will be of help to others. Regards, Matthew
mattinker is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the K-Bikes.com - Excellence in Motion forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
85 K100 won't start p85k100 Other K-Bikes Discussion 14 Apr 26th, 2013 3:36 pm
A ride tale Arr2Kay Bike Talk 8 Dec 1st, 2010 2:42 am
1984 k100 won't start !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! gabriel Other K-Bikes Discussion 2 Jul 21st, 2009 10:58 pm
idle problems k100 1985 gabriel Other K-Bikes Discussion 5 Feb 13th, 2008 10:25 pm
K100 with dead gauges and won't start Andros Technical, Repair and Maintenance 7 Sep 20th, 2006 1:22 pm

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome