Can you illustrate the air intake system you made?

Are you sure of your flow meter flap free movements?

Hope that makes sense, and yes the flap moves freely.

Poupy wrote:Can you illustrate the air intake system you made?

Are you sure of your flow meter flap free movements?

DBRMN wrote:So as I suspected air leak was one of the major sources of the problem. I narrowed down the air leak to one of the 3D printed parts I made (which supposedly isn't 100% air tight material but thats not a concern for now.)

You mean the material used for making the 3D parts before and after the air flow meter might not be air tight? 

How is realised the junction between your flow meter (where you placed it) and the new air box above throttles? Absolutely air tight?

On those k2s the air flow meter flap is supposed to very closely follow the throttles position, as it is it which monitors the electronic control. Hence the importance of reliable air thightness of the circuit between flap and throttles.

Poupy wrote:

DBRMN wrote:So as I suspected air leak was one of the major sources of the problem. I narrowed down the air leak to one of the 3D printed parts I made (which supposedly isn't 100% air tight material but thats not a concern for now.)

You mean the material used for making the 3D parts before and after the air flow meter might not be air tight? 

How is realised the junction between your flow meter (where you placed it) and the new air box above throttles? Absolutely air tight?

On those k2s the air flow meter flap is supposed to very closely follow the throttles position, as it is it which monitors the electronic control. Hence the importance of reliable air thightness of the circuit between flap and throttles.

Supposedly the material used to 3D is constructed in layers which air is able to pass through, however this effect is very marginal and is most likely having little impact. So I'm not worried.

If you have a look at my diagram, one end is silicon sealed and the other end has two o rings with grease. I have faith that they are both air tight.

That is why I asked the question: your sketch is not clear as concerns what comes between the flow meter and the throttles.

One rubber cover in poor condition on a depression plug can create a problem. So, a slightly porous material over a surface of a quarter of a square meter, why not?

Assuming of course that the junctions between your own air box and the various elements connected to it are perfectly air tight.

So large problem, after reassemble the bike won't run.

It turns over, it has spark and the airway is unblocked. However it seems the fuel injectors aren't working, the injectors worked before so I'm assuming they're not getting power.

I checked for continuity and found that there was no resistance across the tabs of one of the plugs that goes to an injector. This my friend informed me means there is somewhere in there circuit thats being shorted. So i've just opened a can of worms... 

I also checked the fuses and they're fine, except the "Side lights" which was burst.

Anyone have any other ideas what it could be?

This trouble shooting guide may help.

http://www.kforum-tech.com/electrical/EFI/bike-wont-start-EN.htm

Note that the diagram for the "Electronic ignition module female connector" is not correct. It should be per the attached. Bert is in agreement with this change.

http://forum.kforum-tech.com/members-upload/uploads/Corrected_Diagram_for_Female_EI_Module.pdf

So I'm now in Italy for a long time so all I can do is sit and try and work out every possible thing it could be.

There was an incident which I pray didn't have an impact but should mention. I was undoing my seat and dropped the screwdriver onto the battery and lets just say it hurt and there were sparks. Now my friend assured me that the current wouldn't have gone through the ECU because it shorted either through me or the frame and thats where the spike in current would be. 

But if the fuel injectors aren't working and they used to, it could be my ECU is broken...

Besides this I also think it could be some dodgy wiring on my part. However all I've touched is the gauge cluster, so can this interfere with the rest of the wiring on the bike? 

Also I had a look at the chart Glennpm what is the thermal resistance in the airflow meter? Do you think these symptoms would occur just from the air flow sensor not being plugged in properly?

Hi, 

I feel that you haven’t ruined the computer, agreeing with your friend.

I tested the air vane controller using a heat gun with caution. I measured the temperature with an infrared thermometer. I then measured the resistance at the measured temperature and checked it against the curve in the troubleshooting guide.

Did you run through the guide to this point with no issues found?

Glenn

So I'm finally back and got to spend the day on my bike. I hate to say it but its always the simple things. I feel like an idiot but I'm glad it wasn't something more serious. I also hope this information helps someone else even if I didn't end up needing it.

Turns out the fuel tank wasn't plugged in, so of course the fuel pump was doing nothing, and of course as soon as I plugged it in the bike fired up. So good news.

However, there's always a however, as the name of this thread implies the bike now needs tuning. I attempted that today with my newly bought carbtuner. But it seems I'm going to need more adjustment and will have to touch the blue painted adjustment screws. I know I need to be very careful and only tiny adjustments should be needed.

So thats tomorrows adventure.

You should never need to touch the blue painted screws.

If you can't sync the TBs then there's a good change you have an air leak in one or more of the boots between the throttle bodies and the cylinder head.

Also be sure that you're using the flow restrictors in the hoses to the Carbtune.

duck wrote:You should never need to touch the blue painted screws.

If you can't sync the TBs then there's a good change you have an air leak in one or more of the boots between the throttle bodies and the cylinder head.

Also be sure that you're using the flow restrictors in the hoses to the Carbtune.

I had been advised by a K100 builder that because I had such a radical exhaust and modified air intake system the brass screws may not be enough, which they weren't. Yesterday it was idling like a pig sometimes cutting out. However today i did fiddle with the blue painted screws and balanced it all and it now idles perfectly, I used the brass screws for fine tuning. 

When I was trying to track down an air leak I did check everything, I checked by boots. But I also made sure my seals where perfect. One end of the 3D printed part I made now, with greased o-rings, compresses when I tighten its bracket, and the other end is healthily silicon sealed.

I followed the instructions that came with it and did use the flow restrictors engine side as instructed.

duck wrote:You should never need to touch the blue painted screws.

If you can't sync the TBs then there's a good change you have an air leak in one or more of the boots between the throttle bodies and the cylinder head.

Also be sure that you're using the flow restrictors in the hoses to the Carbtune.

So Duck I think your right, and I can now explain to myself why. When i began tuning one of the cylinders was way off, which could mean it had an air leak of some description. This would mean in order to get them all in sync I would have to give the other 3 cylinders an "artificial air leak" which would mean the idle would be way too high. 

By the way thats more me writing out my chain of thought so I don't feel crazy.

Then I thought if only one cylinder, say, has an air leak, then in must be after the airbox. So I took it all apart and checked the rubber bookings where they meet the engine case.... hardly anything there in terms of liquid gasket.

So it turns out I applied the liquid gasket incorrectly, thus I have now applied it what I think to be correctly and tomorrow I will attempt to start and tune the bike again. (I also double triple checked everything was tight)

Good man for the methodical troubleshooting.

So thats it my friends, I've run out of steam... I'm throwing in the towel. Running the bike today it sounded and felt like the air leak had gone but at this point I don't really know. The idle was still way too high... at least it sounded nice.

At the moment I have no money and I'm just about to go to university so I'm going to save up and take it to a BMW specialist and ask them to fix it, make it road legal and ready to ride on the road. I know it going to cost me a lot... at least I tried.

Some fun videos for you:
1. The closest I'm going to get to riding it (Background noise is a lawn mower)


2. Some lovely engine sounds

So I finally get the bike home and it seems to have more issues than when I started and I can't even begin to think what issue is causing the revs to dip before I rev the bike. IF anyone can listen to the video and give me suggestions for what they might think is wrong that would be appreciated.
I suspect an air leak still but I didn't think this was a symptom of that but it might be.

Well a sluggish throttle response is typical of the flapper valve FI system, but it is worsened by poor throttle balancing. If you snap the throttles open as quickly as you are doing in the video, then you tend to ‘kill’ the engine before the flapper valve can catch up. How well have you balanced things? - that might be all that’s wrong?

chris846 wrote:Well a sluggish throttle response is typical of the flapper valve FI system, but it is worsened by poor throttle balancing. If you snap the throttles open as quickly as you are doing in the video, then you tend to ‘kill’ the engine before the flapper valve can catch up. How well have you balanced things? - that might be all that’s wrong?

+1 The Jetronic ECU prefers that you roll the throttle.  The Motronic, on the other hand, doesn't mind throttle "snapping".

Going back to the early 70's well before DBRMN was born, and before the advent of the vacuum carbs on bikes, you could get a similar effect on slide carbs. When you snapped the throttle open the engine would stall.

Mike

Look at the spark plugs; tell us what they look like—dry, clean, black, white, tan.

The reason I was snapping it was to show the problem, as I know in the past when I snapped the throttle the bike had no issue keeping up.

They aren't very well balanced at the moment so hopefully if this is just a result of that then that puts my mind at rest as hopefully it will go away once balanced.

I will have a look tomorrow and report back Laitch, I have read it could be a result of it being too rich.

I think my plan will be to remove the throttle bodies check all the rubbers and make sure the throttle bodies are all in sync.

To check the mixture ratio, with the bike warmed up at idle speed press the green starter button. The revs should stay the same or rise very slightly. If they rise significantly or drop the mixture will need adjusting. This can be done with either an exhaust gas analyser  or the lean drop method. Once done balance the throttle bodies.
Regards Martin.

Oh perfect I'll test that before I dismantle it, thank you.

So it has become very clear the bike is running too rich, I tried what MartinW suggested and the revs dropped. I also checked the spark plugs and they were black.

Dismantled the bike and had a look at the throttle body flaps and they are slightly out of sync, so I'm going to get as close I can off the bike then adjust tiny amounts on the bike (very tiny adjustments), and see how the bike improves. I am yet to check the rubbers for cracks etc.

Don't forget if you have just been starting the bike and not going for a ride then the starting baseline is a rich mixture. Keep doing that and it's a sure fire way to kill the spark plugs.

Good luck with adjusting the throttle bodies!

Mike

mike d wrote:Don't forget if you have just been starting the bike and not going for a ride then the starting baseline is a rich mixture. Keep doing that and it's a sure fire way to kill the spark plugs.

Good luck with adjusting the throttle bodies!

Mike

Very interesting thank you, do you know how long it runs rich for. Because if I can't ride the bike perhaps I just need to leave it running for a while?

Thanks I'm gonna need all the luck I can get 

Check the engine temperature sensor located behind the radiator.  When they fail, they'll give you a rich mixture because they make the ECU think the engine is never warmed up.

Point-Seven-five wrote:Check the engine temperature sensor located behind the radiator.  When they fail, they'll give you a rich mixture because they make the ECU think the engine is never warmed up.

Will do! Thanks Mike.

I have reset the throttle bodies so that they are now all moving together, I used a feeler gauge to check the gap with the throttle wedged open, then adjusted until all the gaps were the same. Hopefully that is a drastic improvement for the bike.

You need to synchronise the throttle bodies using a set of vacuum gauges or .75's home made method.
Regards Martin.

DBRMN wrote:I have reset the throttle bodies so that they are now all moving together, I used a feeler gauge to check the gap with the throttle wedged open, then adjusted until all the gaps were the same. Hopefully that is a drastic improvement for the bike.

Does this mean you didn't touch the air screws whilst the engine sat, oil warm, at idle - and only for idle? It's not a great idea to fiddle with the linkage between the throttle bodies since these can't easily be accurately measured for synchronised airflow at revs. Mercury sticks (now obsolete) or some sort of four column-type vacuum gauge such as what is shown above is required to get it accurate - again, at idle only.

DBRMN did buy a set of Morgan gauges, so I would think connecting them would be the next step.

Mike

Yeah Mike is right, anyone who follows this thread knows I was stupid enough to touch the blue paint screws and fiddle with them which is why I wanted to get everything as close to a good starting point as possible. Now that the blue screws are very closely in sync now I'm hoping the brass bypass screws will do the final adjustments with my CarbTune.

However I will not be touching anything until I am very sure I have no air leak, as this is the mistake I made last time (obviously they're never going to sync easily with a gapping air leak).

So I have a mini list of things I think it could be and will be slowly working my way through:

• On this thread I have been told that 3D printed parts are porous, so I have ordered some Araldite to line the outside of the part to hopefully prevent it leaking.
  
• Where the 3D part meets the air box I used to have an o-ring with a bit of grease, now I have put a bead of grease in the groove along with the o-ring, hopefully to help it it be air tight.
  
• Where the throttle body booting meets the engine case, I will replace the liquid gasket as I have never seemed very good at applying it and could quite easily be the problem.
  
• Cracked or perished rubbers, this is going to probably be one I do if the others don't word as firstly my rubbers look in very good condition, and secondly its hard to part with almost £200 just for replacement rubber.
  

Note: I also have the original exhaust on mainly for my neighbours benefit, but of course I will have to do a final tune with the new exhaust system.

chris846 wrote:"Don't forget if you have just been starting the bike and not going for a ride then the starting baseline is a rich mixture."


+1. In my experience you'll always have black plugs just running it in the workshop.

Thanks Chris, hopefully its not something to worry about too much, lets just hope I don't ruin the spark plugs before I'm finished tuning!

FWIW here's the way I've just balanced a set of throttles myself. Everyone will have their own equal/better way of doing this, but throttle balancing seems to keep cropping up on this project, so I though an extra 'take' on the whole topic might be of use to the OP:

Theory:

The sort of screw-twiddling balancing that we're doing is essential for smooth tickover and for pickup from low revs. Forget medium to high revs, the throttles will always be matched well enough for that anyway, and there just isn't enough 'twiddle' to unbalance things at high openings.

At small throttle openings (i.e. tickover - 2000rpm-ish) the vacuum on the engine side of the throttle plates is so high that inconsistencies between the tiny openings around the throttle plates can cause an imbalance. This is why, despite the best manufacturing tolerances, some manual adjustment is needed to get it just right. This also caters for wear during the lifetime of the bike. Two adjustments are provided, and these just about enable adequate balancing over the range required. 

1: Inter-throttle linkages: The 'do-not-touch' blue-painted screws. These are the main way of balancing the throttles. Their purpose is to align the throttle plates with each other so that they all open together by the same amount. The screws are factory set, probably using a flow bench to give an optimum setting throughout the tickover - low revs range. However, once the throttle plates are more than a quarter open, then the sort of small variations you can achieve with the DNT screws start to have no noticeable effect on air flow.

2: Brass bypass screws: at tickover the throttle plate mechanism comes to rest on the throttle stop screw. The purpose of the throttle stop screw is to leave the throttle plates fractionally open so's a tiny amount of air can get past and allow the engine just enough to tickover. If the DNT screws have already been correctly set to give optimum balance through the low rev range, then the chances are that they won't be perfectly balanced when the throttle plate mechanism is resting on the throttle stop screw. It is also the case that an acceptable, balanced tickover would be quite hard to achieve from an engineering perspective with the throttle plates alone. For this reason we have a set of bypass screws, whose purpose is to 'trim' the respective flows past the throttle plates at tickover. 

Practice:

Check and eradicate all air leaks as far as possible. Usual suspects are the throttle-to-manifold rubbers, especially if they have been dismantled. Sealant is usually necessary. The high intake vacuum, especially on tickover will exploit the tiniest of leaks and make the whole balancing thing impossible - but not until after you've wrecked all your careful base settings by trying to twiddle an air leak out of the system. That never works btw.

Close the brass bypass screws right down, you'll probs have to hold the throttles open by hand to keep it ticking over. You are now working only with the throttle plates/DNT screws and nothing else.
Rev the engine a bit to see how the vacuum gauges behave. Adjust the DNT screws - each screw controls the relationship between the two throttle plates adjacent to it. Don't worry about tickover speed, what you're aiming for is level readings across all throttles, particularly as you 'rev' the engine a bit. If one or more throttles doesn't behave, then you've got an air leak somewhere.

Once the throttles are all level the DNT screws are set forever and you'll not be touching them again. However, you are going to have to do something with the throttle stop screw. This is okay, because the throttle stop screw only moves the throttle plates in unison, which is fine and won't upset any balance. Anyway, you'll have to adjust it because at this point the thing will either be revving too high with the throttle closed, or not revving enough. Adjust the throttle stop screw to solve this, roughly.

Now it's the turn of the brass bypass 'trim' screws. Open them each by your favourite amount: either one full turn or one and a half turns or whatever. You might then have to back the throttle stop screw off a bit to get tickover back down, to offset the extra air that you've now allowed in by opening the brass screws. 

Twiddle away with the brass bypass screws to get even vacuum readings. Try to keep the bypass screws around one turn open, since this is the where their tapered seat principle works best. 

Next is tickover speed. What you are actually doing is combining the two air flows (air flowing past the throttle plates, and air flowing past the bypass screws) to give the correct tickover speed. If everything is working correctly, then it should be possible to set the throttle stop screw to achieve a correct tickover speed, with the brass screws each around one turn out.

Remember this: any difficulty/misbehaviour will almost always be down to an air leak somewhere, remember?

Thanks Chris
Nicely written and understandable. Twiddling is something I can relate to.
i am sure many will use this for future reference.

Yeah thank you Chris that is brilliant I will defo be using this once I'm sure the air leak is solved. Really appreciated.

So I have checked the rubbers, sealed the 3D part with araldite, added extra grease to the o-rings and balanced the throttle bodies as best I can off the bike. The liquid gasket is not going to arrive for 2 weeks so I might as well test what I have done.

If there is still an air leak, it could be the booting to engine case or the 3D printed part meeting the air box. If it's not that I will be a bit more stumped but perhaps it will be the rubber. But the amount I had to adjust the throttle bodies to sync them is encouraging.

This project just plays with my emotions it really does .

So I found a bunch of cracks on the rubber bootings.

Yayyy...

Nayy....

On the one hand that is very much my air leak. But on the other hand that's £140. Oh well I know I need to buy it and I know it will most likely fix my problem... hopefully.

It maybe worth giving Motorworks a call to see if they any decent second hand stock.

Mike

mike d wrote:It maybe worth giving Motorworks a call to see if they any decent second hand stock.

Mike

Well I was reading their website and the new ones they sell are upgraded rubber, so I thought I might as well. But I did think about that.

So the liquid gasket finally arrived, and yes the bike ran beautifully! but almost feels like I'm back to where I started at least with no air leak. Had a quick look at the balance and its a bit off but hopefully not too hard to fix. Haven't got a video as my phones broken. But all in all good news!

"almost feels like I'm back to where I started at least with no air leak"

No, you're actually back to post #11! 

Or post #137 because although I got the blue paint screws as close as I could off the bike, still think they'll need fine adjustments on the bike. Your post will be the perfect help for that, so thanks again Chris!

Suzi Q wrote:With the airbox & exhaust mods you've got, you should still be able to get the bike to run just fine with everything as standard. That's what you should aim for to start with - if it isn't running properly don't rush into thinking you need to 'tune' it to cope with your mods. It's much more likely to be a 'normal' problem that a K can encounter. This approach (and the guys on this forum, naturally) will help you troubleshoot anything you come across.

Once you've got it running 'normal', then you can explore the various tweaks.

Easy does it eh?

(And then we'll talk about swapping your crank for a lighter one - 1.2Kg makes a lovely difference!)

Ooooooo, lighter weight crank sounds excellent.  Where do you get a lighter weight crank?

Use a K75 one? 

Cheers, Rene