too many issues need help - '86 k75s Barely starts

[jimnto]

Hello - I bought this bike only seeing it turn over - never catch. It didn't run i took a chance.

There was very very thick varnish in the tank - fuel gauge sender was seized.  When i replaced the engine oil it was dark dark black and lumpy.  tachometer doesn't work.  After the steps (listed below) I got it to barely start.  I do think it sat for quite a few years.
 The brake reservoir had disintegrated from the UV.

Can I please get help finding my starting point.

I replaced the fuel pump, the hoses and filter and new (renewed) fuel injectors. Then! it finally catched.

It starts - but when I give it gas it bogs down. I need the choke to start it and when I turn the accelerator I hear a terrible metallic knocking (it seems like pinging but a lot louder).  In that moment I think i am going to crack the engine like throw a rod or something.  it mis-fires (sounds like) when I give it gas but when I let off - it settles down and almost idles politely.  At that moment it sounds like all cylinders are firing. No Tachometer but if i can coax it up to 4-5K all cylinders seem to kick in as well.

The plugs look... fine??  light brown and not crudded up.

I ACCIDENTALLY - when replacing the air filter - TURNED THE ALLEN KEY THAT ADJUST THE AIR BYPASS ON THE (is it the) AIR FLOW SENSOR THAT IS IN THE TOP OF THE AIR BOX. So far i have done nothing about this.  I turned it back to about where i thought it was.

I replaced the PCV hose - the old one was shreddies.

For the front cylinder i get good spark so i assume that for all of them.

When running it is very smoky and it seems like gassy. The smoke isn't white - but it isn't black.  It's kinda blue and smelly - not like coolant though.  It seems like it is running rich because of all the smoke.

I would appreciate a list of things to check - I don't know where to start.  Hey - i have horrible pictures of the crud in the tank - maybe the crud has to work it's way out.  Maybe some rings are a bit varnished up.  I am going to check the fuel pressure tomorrow - however when i take off the lines - it sprays pretty good so i think there is someeee pressure. Would a faulty pressure regulator cause this?

I am in Toronto, Ontario Canada.  I used to own another k75 and I missed it so here we are.  I am pretty comfortable doing brakes and replacing parts but I am a little out of my element.

[Scott_]

If your fuel situation is/was as bad as you describe, you may have to have the injectors cleaned, the regulator could be not working correctly(reason for pressure check).
The fact that you say the fuel line holds pressure when you disconnect it, at least indicates that you don't have an injector sticking open.
The airflow meter could be sticking, which could cause fuel mixture issues.

[Laitch]

For the front cylinder i get good spark so i assume that for all of them.
i have horrible pictures of the crud in the tank - maybe the crud has to work it's way out.

You cannot assume that all three coils are working correctly on the basis of one coil working correctly. Check the other two.

Did you actually replace the fuel filter, pump and hoses but not clean the tank first? That seems to be what you're writing. The only place the crud in the tank will work its way out to is to the new fuel pump, the new fuel filter, the new fuel hoses and the fuel injectors all of which you will then need clean or replace. You must clean the tank thoroughly. Remove the fuel pumps hoses, plug the openings. Fill with white vinegar and let it soak for a few day, shaking it occasionally during that time. Empty it and repeat. You can scrub it with a stiff bristle brush; a metal brush might gouge the interior if it's too stiff and you aren't careful.

You can remove the spark plugs and inject 10cc of oil or spray fogging oil into each cylinder then crank the engine in an attempt loosen the rings that have been partially seized and might be one of the causes of exhaust smoke.

[The Mighty Gryphon]

A ScotchBrite pad works well for cleaning the interior of the tank. 

Remove the injectors and shoot some cleaner through them.  There are lots of videos on YouTube showing ways to do it.  Find one that you are comfortable with.

Makes sure the plug wires are connected to the correct plug.  The number three wire is longer and is supposed to be folded back, and sometimes gets connected to the number two plug.

The rings are probably stuck and will need some running to free up.  A pint of Marvel Mystery Oil in the fuel and a pint in the crankcase will help speed up the loosening process.

I would also check the valve clearances. 

If the oil was as bad as you say, I would plan on doing a couple quick oil and filter changes once you get the engine running.  About a half hour of run time between changes would be good.  Replace one quart of oil with kerosene for these changes.  Use the cheapest oil you can find to keep the cost down.

I would also get a bottle of S100 motorcycle cleaner and tear the bike down and detail it very thoroughly.  This will get everything nice and clean so you can clean all the electrical connections with Deoxit and also allow you to give everything a close inspection to find any damaged parts.  As strange as it may seem, clean bikes do run better.

[frankenduck]

I use steel wool and paint thinner to scrub out nasty tanks.

[beemuker]

I use steel wool and paint thinner to scrub out nasty tanks.

my k11 tank was a nasty mess, 2 gal of vinegar really cleaned it .no scrubbing needed*

[jimnto]

You cannot assume that all three coils are working correctly on the basis of one coil working correctly. Check the other two.

Thanks I will do that

Did you actually replace the fuel filter, pump and hoses but not clean the tank first?

I did clean the tank pretty darn well - thank you.

You can remove the spark plugs and inject 10cc of oil or spray fogging oil into each cylinder then crank the engine in an attempt loosen the rings that have been partially seized and might be one of the causes of exhaust smoke.

Awesome - I see that my local Canadian Tire has some - I will try.  Thank you

[frankenduck]

Are you using the side stand or center stand?  If you park an early K75/K100(86-88) on the side stand after it is turned off then the oil behind the pistons will seep past the rings into the combustion chamber and generate a lot of smoke for several minutes after the next start.

If you're not using the center stand then this can be mitigated a fair amount if you tilt the bike to the right for several seconds between turning it off and putting it on the side stand.

For model year 89 and later the K75/K100 rings were updated to let less oil seep past them but if left on the side stand for a while (days, weeks, months) then any K will have some smoking on startup.

If the bike you purchased has sat for an extended period then it's normal for them to smoke quite a bit for several minutes. I've brought lots of K bikes back from the dead. I just ignore the smoking until I've had the opportunity to run the bike for a while.

[jimnto]

Fuel pressure is 34 - left gauge connected - kept pressure all night. So i think that is good?

I think the plugs look a little wet - tell me this - if I turn the accelerator and it chokes and back fires - then when i release it is settles down - does that seem too much fuel?

I can only get it to idle for about 5 seconds.

I replaced the PCV tube and sealed the rubber nipples on the air intake because they were cracked.  The vacuum line to the regulator seems in good shape.  Are there other vacuum lines?

[frankenduck]

The vac line to the FPR is the only one.

FYI: There's no PCV valve on a K75.  That part is generally referred to as the crankcase breather hose.

[rbm]

Backfiring could be indicating air leakage in the exhaust system - at the header/block interface, or where the collector joins the muffler.

Having the fuel pressure last overnight is not normal.  It's supposed to decrease over time, like a few hours.  Don't know what to make of that.

[jimnto]

Hello Hello again.
I seem to have spark and fuel.  I can get this thing running (shitty) and even idling (almost) but when I try to rev it - it seems to bog until i release the throttle.  My brother came over and said it seems starved of air.  Plugs (new and gapped nicely) are sooty.

Maybe the rings are letting stuff by.  Compression is about 110 in all three cylinders.  I am thinking of taking of the air plenum to see if something is going wrong in there.

Here is a video of the sound of it choking off.  Can't get above 3000rpm except if I luckily gingerly somehow rev it up.

[Laitch]

Maybe the rings are letting stuff by.  Compression is about 110 in all three cylinders.  I am thinking of taking of the air plenum to see if something is going wrong in there.

The rings aren't your problem. If you have a new, or clean, air filter, you need to look down the air snorkel to see if it's obstructed. You need to look into the air flow meter in the plenum to see if it's clogged with anything and that the vane inside it moves freely when gently pushed. You need to disconnect the meter's electrical connection, clean it with electronic contact cleaner—DeoxIT D5 is recommended but CRC is better than nothing—then reseat it snuggly. If the crankcase z-hose is ok and the throttle body manifold rubbers aren't leaking, try starting it again. Was the compression test done with a wide-open throttle on a warm engine with all the spark plugs removed?

Any moto neglected for as long as yours is bound to need a deep inspection and some treatment before running well again.

[jimnto]

I am grateful for any ideas.  I did de-oxit the connections to the Air-Flow sensor and i actually took it out and applied voltage to see that I get voltage all along the arc of the door and also resistance changes.
I sprayed carburetor cleaner all around the intakes and no jump in idle speed. 
After replacing the crankcase ventilation hose, and cleaning the connections to the air-flow sensor it does barely idle now.  I can get it to drive me up the underground garage ramp - but can't get it to go higher than (maybe) 4000 rpm.

And no - the throttle was not wide-open - thanks for that. And all plugs removed but it wasn't all that warmed up really - barely got it around the block. 

I am examining the air-intake very carefully today.

Thank you

[Laitch]

And all plugs removed but it wasn't all that warmed up really - barely got it around the block.

Idling for a while would have been enough; you can only do what's possible. You're likely to have different values with the throttle wide open. After seeing the first value with wide-open throttle, spray some oil in the cylinder and try it again. The value derived from doing that could give some idea of the condition of the rings if it rises.

[jimnto]

I don't have the words to express the gratitude to the excellent rbm (Robert) who drove down from North Toronto not once but twice and proceeded to get right down on the ground and start wrenching.
To recap - i bought a non- running bike and the whole fuel system was TRASH. even the varnish had varnish on it.  After replacing the fuel pump, hoses, filter - I decided to get upgraded 4hole injectors (FAILURE ALERT).  I expected everything to go so well but nothing.  New plugs nothing.  Robert came (and my brother lent support and a neighbour) we went over the Airflow Sensor, the Hall sensor, we established spark and checked the coils and fuel pressure.
I removed the air intake plenum and everything kept pointing to too rich a mixture.  Robert even swapped in his Air flow sensor and his computer thingy.

Finally - we couldn't ignore it was getting too much fuel.  My brother had given me rebuild orings (standard auto part) from his volvo injectors and new filters and Robert and I rigged up a 9volt battery and some carburetor cleaner and a bath in acetone.

AND SHE FIRED UP LIKE SHE WANTED TO! SHE VROOM VROOMED SOME BLUE SMOKE AND GAVE 'ER (in other words - pulled like a healthy beast)

So! I am furious at these 4 hole injectors.  They simply did not work. Too much fuel.  Dark sooty spark plugs.  No power 

[volador]

So! I am furious at these 4 hole injectors.  They simply did not work. Too much fuel.  Dark sooty spark plugs.  No power 

Some Chicom marketing genius selling the Chinese car version

Tills.de injectors

[frankenduck]

I've tried the four hole injectors in both 2V and 4V K bikes. They run about the same. Having better atomized fuel SOUNDS good but all fuel injectors do is spray gas onto the backs of intake valves, not directly into the combustion chamber. I've never found any actual dyno runs to show that four hole injectors actually improve HP.

I always just send injectors on to Mr. Injector to get them cleaned.