Help Please,

I currently own 2 K100's a 2v and a 4v.
Recently decided to strip the head off the 2v to change the stem seals and give the engine a good clean strip and paint while I was at it.
To cut a long story short I managed to get a replacement engine with only 65k on it for $100 so decided that would be the easier job.
I rebuilt the bike up and tried to fire it up. The bike did run but very rough and with a distinct misfire.
As the wiring loom had been seriously hacked over the years I decided this could be a source of issues so changed that for a replacement in good condition.
Still no change misfire and rough running.
Timed the Hall sensor unit with a drop clock and led box all good
removed fuel rail and checked injectors( all spray well)
so started to change and check all the following:
Fuel side : Injectors (changed) , pressure regulator (changed) fuel tank and fuel pump (changed).
Ignition side: plugs (changed), HT leads (changed),coils (checked resistance etc), Hall sensor (checked)
Electrical side: battery (checked), Alternator (changed) earth connections ( checked) 

still the bike will not run well and on occasion will not run at all. fuel is def getting into the cylinders as 
after a while it will run out of the headers. def getting a spark as it will run on occasion but miss fire.

Really at a sticky point now just don't seem to be getting anywhere with this.
Determination is the name of the game but any pointers would be very helpful and much appreciated.
Thanks in advance

Air leak around the throttle bodies?

yes I thought air leak, so I tried searching for it with a can of easy start.

spraying around the throttle bodies with a spray etc while it was running but there was no hunting or pick up etc.
It could still be a possibilty though I suppose and will check in the morning again.

Thanks.

Check the three rubber caps on the intake body rail, also the vacuum pipe off the no 4 that goes back to the fuel pressure regulator. If you have an early 2v there is also a vacuum pipe at no 1 from the front of the throttle bodies to a fuel pressure sensor on the back, visible from the right between the air box and radiator. An issue with those can do quite funny things.

Hi,

Yes I renewed all three of the rubber caps and changed the tube to the pressure valve.

I must admit that I did pull one off and spray a little gas down it while the engine was running to see if I could get the engine to pick up or surge. It didn't seem to make any difference.

Do you think that could be an indicator of a larger air leak somewhere else?

not noticed this other pipe off throttle body one. I iwll look for that in the morning as well.
Thanks

andyldean wrote: not noticed this other pipe off throttle body one. I iwll look for that in the morning as well.
Thanks

The vacume switch was removed during -85, so you won't find it on your -87.

Make certain that the wires for plugs 2 & 3 aren't crossed.  The wire for #3 is longer than the wire for #2 and is folded back.

Point-Seven-five wrote:Make certain that the wires for plugs 2 & 3 aren't crossed.  The wire for #3 is longer than the wire for #2 and is folded back.

Does this even matter?  The K100 is "wasted spark" so 2 & 3 fire at the same time.

I don't think so on the K75.  I know I once switched those wires and the bike would barely start and when it did run there was very bad misfiring and wouldn't rev.  There have been others who crossed wires on a K75 and had the same symptoms. 

I think the wasted spark is a function of the K100 having two shared coils where the K75 has dedicated coils for each cylinder.

As said, one coil for each cylinder on the K75 no wasted spark.

On K100 one coil is for 1 and 4 and they both spark at the same time, they also spark on the exhaust stroke which therefore is wasted, the other coil fires for 2 and 3. You could mix up the leads to 3 and 4 with bad results......but mixing up 2 and 3 won't make a difference.

The injectors do likewise.....!

Is it possible to time it to the wrong TDC and have it run at all????. Either way have you considered reversing the hez leads or could it be poor contact to earth with the coils

Hi,

I have checked the coil earth , but not sure of the 180 deg out?

will re check timing tomorrow and report back it could be possible I suppose.

Have had old japs run 180 deg out but very roughly so its a thought.
Thanks

You cant time a wasted spark to the wrong TDC they fire every revolution.

RicK G wrote:You cant time a wasted spark to the wrong TDC they fire every revolution.

Also the HES plate only fits one way.

Yes i timed the bike with a led box and a drop clock in cylinder 1 so I am pretty sure its very close to right.

Throttle bodies are coming off in the next couple of hours so I will report back on what I find after that.

Its frustrating but hopefully I will get there soon.

Have you seen this bike running ok in the past?? If not, I'm thinking that possibly it may have the wrong FICU. There were quite a few L-Jetronics made for cars and motorcycles as well as airheads. Check you have the correct one.... 0 280 000 313

Ok so I have spent a few more hours on the bike now and completed the following:

Stripped the throttle bodies off the bike checked and cleaned everything and replaced.
New plugs
New coils
checked earth terminals
I restarted the bike and it fired straight away but ran very lumpy, and died on throttle.
I checked all four exhaust pipes and they were all hot which confirms it feels like a rough running not so much one cylinder down.
A suggestion from the shop I bought the engine from was to turn the timing plate slightly to see if it would smooth out, i tried this and it did run a little more smoothly and was able to run at 1000rpm without stalling but still not smoothly. The time plate slots now are a mile out of position so I am not convinced its right.
Ok so my next line of thought was valve timing?
The rest are observations, not sure if its right or wrong but if I give you the full diagnosis hopefully one of you guys may spot something to work with.
I decided to pull the rocker cover and timing cover to check the valve timing.
all plugs were dry but black.
On pulling the rocker cover the oil (synthetic) appeared dirtier and thinner than I expected. (all engine internals have been cleaned) and maybe a slight sniff of fuel.
timing cover off and next job is to check the valve timing, but at first look it appeared ok.

I have a rebuilt head and headgasket on the bench so not sure if I should throw that on.
Although cylinders check out well on compression.
any thought???

Holister wrote:Have you seen this bike running ok in the past?? If not, I'm thinking that possibly it may have the wrong FICU. There were quite a few L-Jetronics made for cars and motorcycles as well as airheads. Check you have the correct one.... 0 280 000 313

Sorry i didn't reply to this.

The engine block and head are new but all the other parts are from my bike.

I only stripped the original engine to replace the oil stem seals, but one job led to another and I decided to paint the block etc.
I managed to snap a oil control ring when stripping the block to paint so went on the hunt for a replacement. The Store had an engine he said he could give me at a good price so hence the new engine.

Have you checked the fuel pressure?

SPs black, running rough.... so it's on the rich side. If there was an air leak it would be running lean. Smell of fuel from the oil is not great. Sounds like its getting way too much fuel. Is the tail pipe coated with thick soot and smelly?
Is the vacuum hose from TB4 to FPR intact?
Temp sensor may be kaput. Easy to test. 2.5kΩ between FICU pin #10 and earth @20ºc (see trouble shooting page).
Fuel pressure as Inge suggested above.

Sounds very similar to problems i've had - i fitted a pressure gauge on the line before the pressure regulator and it was 70psi, i replaced the original regulator with an £18 adjustable one from ebay and set it at 33psi and she ran so much better still not perfect and ive changed pretty much everything.

Oh and when i bought the bike the oil had a wiff of petrol

Ok so I tested and cleaned all the temp sendor contacts checked resistance at the sendor and at the computer. temp was approx 25 deg C so guessing this is ok.

Checked valve timing and retimed the hall sensor all ok there as well.

checked the pressure at the fuel line 30psi and stable so assume thats ok.

then decided to try and balance the carbs.

This is when i discovered something interesting, when i remove the rubber bung to attach the vacuum gauge teh bike starts to run a little better.

when i attach the vacuum gauge its runs shit again.

so i remove all the rubber bungs and it runs even better.
no way i can balance carbs as everytime i attach gauge the bike starts to die.
only one vacuum point looked like it would alter with winding screw and vac gauge attached.
what is going on here ?

eventually stalled the bike and now it will not restart I assume its flooded.

Ok so I checked all the pin readings at the ecu and everything looked ok.

checked the airflow sensor and all ok there again checked at the ecu and all good.

Still the bike ran very rough and flooded after running for a few minutes.

I got another temp sender and wired it out of the bike and left it dangling in boiling water.
started the bike and it all ran well checked at the ecu plug and readings the same as the old sensor.

To cut a long story short it was a dicky plug on the temp sensor.

soldered up the break in the wire and she runs like a new one :-)

Thanks everyone for your help appreciate the time you have taken to assist.

Its often a simple and quick solution - after a long time has been spent working out what the simple issue causing the problem is!
Wouldn't it be wonderful if we could always go straight to the fault.  

Glad to hear all is now well, having followed the thread with interest.

Bill

andyldean wrote:Ok so I checked all the pin readings at the ecu and everything looked ok.

checked the airflow sensor and all ok there again checked at the ecu and all good.

Still the bike ran very rough and flooded after running for a few minutes.

I got another temp sender and wired it out of the bike and left it dangling in boiling water.
started the bike and it all ran well checked at the ecu plug and readings the same as the old sensor.

To cut a long story short it was a dicky plug on the temp sensor.

soldered up the break in the wire and she runs like a new one :-)

Thanks everyone for your help appreciate the time you have taken to assist.

Beers all round on anyldean. Trouble is we are so far away we have to ask him to drink them for us! Great to see it sorted.

It's always the last thing you look at, isn't it? 

Good to hear you have it running!

This bike is still having a few running issues and again it has me stumped.
There is a definite miss fire which seems to move around from cylinder to cylinder.
if  have the bike running and remove a ht lead as I push it back towards the plug and i can see the spark jump from ht lead to plug it runs smooth on all cylinders.
If i push the lead back on it misses again.
changed plugs and leads to give no chain.
Any ideas ?

Are the bobbins on the spark plugs?

+1

yes they are and I have tried it with new 5ohm leads that I have made up as well :-(

andyldean wrote:yes they are and I have tried it with new 5ohm leads that I have made up as well :-(

5 ohm ?  do you mean 5000 ohms ?   (5k)

Remove the bobbins.

Ok following the logic that .oving the cap away is increasing resistance. 
I have changed 1 plug for a R reskstance plug and all runs well.
What is wrong ?
This although runni h well is very strange

andyldean wrote:Ok following the logic that .oving the cap away is increasing resistance. 
I have changed 1 plug for a R reskstance plug and all runs well.
What is wrong ?
This although runni h well is very strange

Where I come from, a bike's running well isn't wrong, it's an invitation to ride it.

That is odd, so if you have a dr7ea in one cylinder and a d7ea in the other of the coil pac, and this makes it run smoothly. Then you've got a matched set in leads plugcaps and sparkplug? Now if this is right then one of the leads, plugcaps or  must be on the way out. Or the original spark plug wasn't a good one. So it would be interesting to know if you changed the new good spark plug for a new good non resistor plug, would it still run sweet??