GK76a 1990 won't start

[djheard91]

Hi all,I'm at a bit of loss as to why I can't get this bike started. I've had it since February and as far as I'm aware it is a 1990 non-SP GK76a. When I picked it up it would start but wouldn't rev properly, it had been stood for a while so I thought that it may need new fuel and a carb clean. Since I've had it I have:

cleaned the carbs and replaced all the o-rings with the full litetek kit
checked the timing
honed the bores
compression checked cold (cylinder 1-145psi, cylinder 2 - 140psi, cylinder 3 - 120psi, cylinder 4 - 145psi)
valve clearance checked and re-shimmed (inlet: 0.13-0.23; exhaust: 0.2-0.3)
Pick-up resistance checked and is around 99ohms

Having put the bike back together when I first tried starting it, it sounded like it was close on a couple of attempts but since it seems to make no attempt to start - just turns over. I have checked and the spark appears to be decent. The plugs are wet when removed after trying.
I've noticed my CDI is not standard as the connectors are different. It has a green and yellow wire in the wiring loom from the gear indicator but the CDI has no wire connecting to it, pictures on link below. Not sure if this a correct CDI but I don't see how it would run but now wont start, surely if it's wrong it would never have worked.

http://s1065.photobucket.com/user/djhea ... t=3&page=1

I'm going to re-plumb the fuel lines as I'm suspicious that they are getting air locked, but the float bowls do have fuel in them.

Any ideas on what could be the problem would be gratefully received. Thanks in advance and sorry for the mass of text.

[willandrip]

Your p/bucket link is dead.

I'm pretty sure the green/yellow wire is the restriction circuit.

As you state; if it ran before it should run now on that CDI/pick up combination.

Pilot jet circuit is critical on these.
Have you also cleaned the air jets in the inlet side of the carb bodies?

[djheard91]

http://s1065.photobucket.com/user/djhea ... t=3&page=1

Don't know why the link doesn't work hopefully these do. From what I've read the green and yellow wire doesn't have to be connected as long as the cdi gets a resistance of around 1ohm then it will always think it's in gears 1-3 but I didn't realize the 1990 bikes were restricted and I would have to assume that the modification is inside this different CDI?

I sprayed carb cleaner down the air jets as I don;'t have access to a sonic bath. Can they be removed or is there any particular way to clean them?

[mattiec321]

I'm working from memory here but I'm sure the green/yellow wire is your neutral circuit which is also linked to the side stand switch.

On the 76 I've been working on there is a loose connection to he diode on the neutral circuit causing the neutral light to go out and also the bike to stop. As soon as the light is back the bike fires no problem.

That neutral circuit is a pain

[willandrip]

There is a colour coded diagram (translated)for this bike...I linked it up to another topic just a few weeks ago.
(It's in the documents section on the home page)

As you state ; restrictor circuit will not prevent starting.

You can unscrew one set of the air jets... the other appears fixed......well they were on mine anyhow.

I use a strand of copper wire from a bit of old wiring to run through the jets.... they are very small and even if you can see daylight through them they benefit from a good reaming (ooh arrh missus )

My 90 bike doesn't have that circuit only the neutral wire.

My 90 non SP 76a CDI looks nothing like the one in your p/b link.

[djheard91]

I have no idea where this CDI is from and if it will allow the bike to run properly, I'm hoping so.
I got the carbs off this morning and blew through the jets and can hear fuel bubbling in the float bowls, I think, but I'll try giving them a good clean when I split the carbs up again.
Although I have spark, I've bought new plugs which I'll fit.

Has anyone got any other ideas of what could be wrong and anything to check?

[rgvsp]

I'm no carb expert but I have rebuilt about 3 sets of these carbs now and here are a few things I ran into:

First I always just go logically. If it ran before, I check everything I could have messed up. And I mess up all kinds of shit! Any chance you ran the plug wires to the wrong plugs? I've done it.

Check the two vent tubes to the carbs. I had one pinched and that prevented mine from starting. The left one can get pinched from the choke lever moving.

Once I had nothing wrong and it just needed some starting fluid for that first tick over

Another time I had float heights all out of wack and it wouldn't start.

A carb sync also seems to do minor miracles for these carbs.

I'd replace that CDI just for peace of mind. Lots of standard CDI's around.

Just some random thoughts and ideas for you.

[Variablevalves suck]

Another biggy is forgetting to connect the vacuum pipe up if its been removed, easily forgotten and no start.

[stripes1976]

Most common one I've seen is throttle cable pinched holding the throttle open or the idle speed screw wound in too much enough to stop a bike from running.
Worth a check then can move to fault finding running issues. Especially since you have fuel spark etc

The 76a should always be started full choke no throttle from cold. They don't like too much air when cold.

[djheard91]

The vacuum pipe was attached and I tried attaching a longer pipe to suck on in case the vacuum wasn't working properly. I've also cleaned the tap.
The idle screw was not on very much. Is there a rough setting that I could try in case I had the screw out too much.
I'm also pretty sure the throttle cable wasn't caught as it all seemed to move freely but I'll definitely keep an eye on these.

I have found out that I have CR9EK plugs fitted so have ordered CR8EK replacements although I'm not sure how much difference this will make.

I've not adjusted the float heights but how can I check they are correct?

Is there anyway to check for correct spark timing and how can I check the coils are working correctly?