Hi all,

My K100 sat at a mates place for about 9 months unused, and then wouldnt start back up. When we looked at it, all the rubbers in the tank were complete goo. He says he only put 98 in (and I believe him), but maybe previous owner was using E10 and it just never completely shat itself cos it was ridden more regularly. 

Anyway, since then I have:

• replaced fuel pump
  
• replaced fuel filter
  
• replaced fuel pump isolator and all hoses in the tank.
  
• cleaned the fpr
  
• ultrasonic cleaned the injectors, fit new o rings and filters
  
• replaced spark plugs
  

Now I finally have it starting, and it sounds ok when I twist the throttle, but it wont idle even for a second. The crank case breather hose does look cracked, but I sprayed around it with aerostart while revving it and there was no change, so not sure if its cracked through (i have ordered a replacement anyway). 

Now all the guides I've read on adjusting the idle assume that you can at least kinda get your bike to idle (just a bit too fast or slow), so I dont want to go adjusting things if the problem may be something else. Also it was idling fine before all this. Its blowing an arseload of smoke but it is on a side stand.

Any pointers on where I should start? 

Cheers in advance,
Chris

Keep looking for air leaks around the throttle body rubbers ans all the places hose clamps are used back to the air filter. also the rubber boots on the throttle bodies where you connect gauges.

z hose  ?  Behind the coil packs is often a good reason for poor - no idle , also note if the oil filler cap is off same or similar effect IF the z hose is ok

Are the insulators on the spark plugs black, white, tan, wet, dry after running?  Do they all look pretty much the same?

Are you absolutely sure the plug wires are on the correct spark plug? You would not be the first to mix up #3 and #4. The correct cylinder number is printed on the OEM cables.

Bobbins........?? If you have NGK plugs you need the screw on bobbins on the threaded tip.

Rick,
Is there a better thing to use than aerostart to find these leaks? I couldn't detect any. One of the vacuum caps on the throttle bodies was cracked, I replaced that one with another random cap I had. I got a new set of the proper ones in the post today with the crankcase breather hose. Will fit them in the next few days.

Charlie,
Is z hose the crank case breather? If so I just got a replacement and will fit soon and test. I'll check oil fill cap.

P75,
Plugs are wet and oily after running. Not sure if that's partly due to being on the side stand.

Olaf,
It didn't have bobbins when I got it back from my mate haha, but got them on it now. Couldn't buy any, luckily a local mechanic was nice enough to give me 4 floating around in his tool box.

Cheers guys,
Chris

Edit: I was thinking maybe something to do with the afm reading more airflow than actual, but no idea how to check it. I found some old YouTube links but they were all dead.

Get some new plugs and try running with the bike upright instead of on the side stand.

If they still come out black and wet you need to check the engine temperature sensor. When they fail or have bad electrical connections they will make the engine controls think the engine is cold and needs a rich mixture.

You can read the resistance of the sensor at the ECU plug under the seat. It should be about 2500 ohms when the engine is at room temperature and drop to about 150 ohms at operating temperature of 185-190 degrees.

mynameisrodney wrote:Rick,
Is there a better thing to use than aerostart to find these leaks? I couldn't detect any. One of the vacuum caps on the throttle bodies was cracked, I replaced that one with another random cap I had. I got a new set of the proper ones in the post today with the crankcase breather hose. Will fit them in the next few days.

I have used propane/Butane from a fire lighter the long snout makes it easy bur aerostart is good and does the job. Also check your valve clearances after a short run (10 seconds) and before you pull the plugs as carbon is dislodged and gets under the valve seat on the exhaust valves.

OK so crank case breather was torn through. Weird that spraying aerostart straight at it did nothing. Replaced this and the vac caps. The bike will now idle if I hold the choke it it's furthest position, but if I let go it goes to halfway and stalls. Maybe it will be OK now once it warms up, didn't want to run it too long and piss of the neighbours as its getting late. I'll try in the morning and report back.

Still smells like it's running rich as though. Will do more investigating as time permits.

mynameisrodney wrote: Still smells like it's running rich as though.

If the engine smells like it's running rich, intake air infiltration would not be the likely cause. Have you inspected the air filter and air box? A clogged air snorkel or air filter would contribute to that condition.

Another check, quick and easy, is to remove the vacuum hose from the throttle body at cylinder 4 after a bit of a run, it should be absolutely dry.

How did you clean the fuel pressure regulator? There's a rubber diaphragm inside, if it's broken, excess fuel will get sucked in the engine, which would not be as noticeable at revs.

Is fuel returning into the tank?

An arse load of blue smoke points to oil, black is to fuel. Maybe put on centre stand and check oil level, excessive fuel could get into the oil,  increasing its level.

Laitch wrote:

mynameisrodney wrote: Still smells like it's running rich as though.

If the engine smells like it's running rich, intake air infiltration would not be the likely cause. Have you inspected the air filter and air box? A clogged air snorkel or air filter would contribute to that condition.

I haven't, I'll take a look, cheers.

just a note , they run rich until reaching operating temperature 

check with the sniffer after 50 or so killometers , that way the oil will have burnt off , from residual build-up , and the engine should be at good running temps .

good luck

Thanks Charlie, unfortunately the bike Isn't currently registered, so will have to hold off on the 50km ride for now. 

I noticed that the oil in the sight glass looked a little cloudy, when I looked closer it was tiny air bubbles. After putting it up on the centre stand and checking again the whole site glass is full, so it looks like there's too much oil in it. I'm sure my mate had it on the centre stand when he filled it, but maybe his garage isn't level. I'll try to get to draining some out next weekend. Do you think too much oil could make it not idle due to extra drag?

Have you checked the resistance between pin #10 on the Jetronic plug and ground?  That is the reading of the water temperature sensor.  It should be about 2500 ohms when the engine is cold and about 250 ohms when the engine is at normal operating temperature.  

Those sensors have been known to fail and/or have dirty contacts that have high resistance causing the engine to run rich.  If you are smelling fuel in the exhaust, and fouling plugs it really is something you should check.

I haven't yet sorry. It is on my to do list. Unfortunately I'm pretty time poor at the moment. I'll see if I can check that in the next few days.

Ok just did some probing of the ECU plug
pin 10 -> GND = 2k @~28C

Following done with tank unplugged:
pin 7 -> pin 5 = 80
pin 7 -> pin 8 = 334
pin 8 -> pin 5 = 364
pin 8 -> pin 9 = 194

all look ok according to crazy frog's troubleshooting doc. I'll drain some oil over the weekend and see how overfilled it was.

ok so I just started it up and checked the oli level while it was running. It was maybe 2/3 the way up the sight glass, so cant be too overfilled, i doubt thats the issue. 

Just had a bit of a play. 

With the choke full on it will idle at about 1krpm.
If I give the throttle a twist up to above 3k and release, it will stay at about 3k until I release the choke back to the half position, then it will start to stall. If I then go back to full choke it will go back to 1krpm.

So I'm thinking now it might just be something in the throttle cable/idle adjustment now that the vac leaks are sorted? 

It's blowing a fair bit of smoke, but has done almost 250,000km so I'll give it a pass.

Hi Rodney,
you mignt be onto something with the cable.

The "Choke" on these bikes is simply that the throttle is hwls open slightly in order  to keep the revs up. As they are fuel injected, there is no "choke" as such. The fuel mixture is computer controlled.

I'd say focus your efforts on the TPS switch and where the throttle cable exits by the bank of unjectors/air inlet. Make sure all that is moving smoothly. But don't adjust any of the butterfly/balance screws on the bank of butterfly housings.

Make sure the TP Switch is engaging as you release the trrottle .You will be able to hear it click.

Focus on this area, and don't get sidetracked by oil levels etc. That is not going to cause the syptoms you describe, even if it was overfilled (which I'd say is unlikely).

Thanks, I'll take a look at that over the next few days, havent checked operation of the tps yet.

Not saying it's your problem, but on the bricks I've owned(all 5 of them) the oil level drops out of sight when the engine is running. I have to shut off the engine to see any oil in the glass.

ok so finally getting some time to spend on the bike again. I've adjusted the choke and idle and it will actually start and idle now. But, if I rev it and close the throttle the revs stay high. Killing it and starting the bike again it idles as normal. I'll do some more hunting for air leaks. 

Also, the spring that goes around the vacuum line to the fuel pressure reg is borked. Is it ok to remove it? Or anywhere I can get a replacement? I cant seem to find one in my searching.

Is the throttle cable or the butterfly linkage hanging up and keeping the rpm's high?  

Part number 13 54 1 461 531  SPRING  is still available from a dealer.  in the U.S. it costs only $2.72.

Awesome! Thanks heaps for the part number, should be able to chase one down now.

I don't think its the throttle cable, but will double check. I think at high rpm (higher vacuum) the rubber boots are distorting and opening up a crack which then stays open until the bike is turned off. I will check the cable and linkages though.

Cheers,
Chris

EDIT: Found the spring on ebay. $3.60 plus $26 shipping haha. Gotta love living in Aus sometimes.

Revs staying up after closing the throttle is an indication of lean at idle. You don't have to use that protective spring thing just using a thick wall rubber tube will do the job.

mynameisrodney wrote:Also, the spring that goes around the vacuum line to the fuel pressure reg is borked. Is it ok to remove it? Or anywhere I can get a replacement? I cant seem to find one in my searching.

There's always this.

Well I tried 3 times over the weekend and couldn't get it to replicate the issue. Blowing a crapload of smoke though. Time to check over the brakes then I'll take it to get rego so I can go for a ride and clear the cobwebs out.