Starting and running issues

[Psychosomatic88]

OK so I recently bought a '93 GK76 which was known to have running problems. It would idle but as soon as the throttle was touched, die. It had previously to this been stood for some months.

So I get it back, remove the old fuel from the tank, drained the carbs and opened them up for cleaning and inspection. The carbs were a bit mucky, so I cleaned out the MJ's, pilot jets and the usual (soaked in carb cleaner for quite a while) and blew them through with compressed air. Opened up the slide covers, think all the needles were ok bar one, which was bent badly. So got that straightened. (I intend to buy a jet kit etc for it anyway, so this is only a temp solution untill I find some).

It was also missing 2 of the o-rings from the MJ holder - replaced all of them, plus the 4 by the slide as they looked a bit dry.

Fresh fuel in the tank, with an additive for cleaning out carb systems, and ... nothing. No firing.

So I pulled out the plugs and they were clean and dry, and producing a spark. checked the carbs again and the float bowls had filled, and were set at 20mm. Attached some clear pipe to the valve on the bottom of the float bowls and opened the screw. All carbs seemed to be supplying fuel from this drain valve quite successfully.

Looked back into the carb inlets and slides and they are all dry inside. So now Im stuck, where and what do I do from here??

[Psychosomatic88]

Bugger....

Its now leaking drips of fuel from around the fuel tap

[gixxerpaul]

what i did with mine that hadnt ran for over 12 months was squirt some petrol down the back of the carbs so it went straight into cylinders i new it was sparking new there was petrol in carbs just wasnt gettin to cylinders probablya silly question have u reconnected vacuum pipe to fuel tap

[Psychosomatic88]

Yeh I have tried 2 vacuum hoses that I had kicking around incase it was split or damaged.

I manually injected some fuel into the intake port (with out the carbs on) and fired it up, getting a few little firey pop out the back. So then re injected fuel in and put carbs on and repeated, getting pretty much the same but no joy.

Perhaps I should try again

[Awynn]

When you say you "fired it up" do you mean it started and ran a bit or that you tried to start it and all you got was "a few little firey pop out the back" and is that out the carb side? That would say to me that the fuel is igniting when the intake valves are OPEN, there are only 2 reasons I can think for that:
1)intake valves are not closing/operating
2)ignition leads are mixed up so there is a spark at the wrong part of the cycle

maybe there are more reasons that I cant think of at gone midnight

[Psychosomatic88]

Hi Awynn,

Sorry I meant fired up as in pressed the start button. It spat out some small flames out into where the carbs should be (wernt on at the first time I tried) so back out of the engine. The engine was recently replaced (alleged at 12K on it) as the old one had dropped a valve. The loom has lots of little tags on it suggesting whoever did it, put it back carefully. But I did wonder about the spark cycle thing.

Arent the centre cylinders leads longer than the outer cylinders leads? I will check this later when im home.

How would I check valve operation?

[6thgone again]

try to switch the ignition coils conector`s the same thing happenened my super4 backfiring ang flames sparking wrong well thats if it woz apart or u had it apart its worth a try switch two and that should let u know only need 2 to start it best of luck aren`t bikes gr8t lol

[Psychosomatic88]

Thanks for that 6th gone again, out in the garage fiddling now so ill give it a whizz.

I have the carbs off again now, looking at them there is 8 connections. 1 Throttle cable, and choke cable, easy to identify.

Then by the tops of the float bowls, 2 large pipes, one on each side of the carb bank. I think these the fuel lines and they go to the large brass looking connectors on the fuel tap, one connector being 90 degrees to the other.

Then by the top of the slide covers, 2 thicker still but shorter pipes, I think these are air pipes, and go to the top of the airbox.

So what are the 2 thinner (10mm? same thickness as what I think the fuel lines are) pipes that are roughly level with the cut out in the slide, and where do they go to? Are these breather lines? they dont appear to have the usual ringing on the ends from a circlip

I thought the vacuum hose was the hose from the cylinder to the small nipple on the fuel taps centre.

Sorry to sound stupid, but the carbs have been on and off more times than the barmaids drawersand you all know its a fiddle, plus I want to make sure its right

[wullvfr]

So what are the 2 thinner (10mm? same thickness as what I think the fuel lines are) pipes that are roughly level with the cut out in the slide, and where do they go to? Are these breather lines? they dont appear to have the usual ringing on the ends from a circlip

if the pipe goes nowhere then it sounds like they are a breather,do they attach to the carb above the throttle slides?

if so,they are similar to the ones on my 125.


william

[Psychosomatic88]

They are perfectly in line with the cut outs in the slides (the half moon part)