trouble starting

[SLIW]

Hi

My 79 GSX 750 is being a pain in the butt!

Recently had the carbs cleaned and it was running fine for a week.

I would go out in the morning, pull the choke out hit the starter button and after a little twist of the wrist it was running.

I go out this morning do the same and it turns over but will not fire. After trying a few more times i think i flooded it as i smelt petrol so i just left it.

There had been a light rain shower the night before but surely that couldn't effect it firing up in the morning could it.

I went home at lunch time thinking that the fuel would have cleared so i tried again and sure enough it turned over but would not start!

So frustrating i don't know where to start. Any tips?

Cheers
Scott

[chef1366]

Rust in the tank?
Bad spark plug wires?

[SLIW]

It could be rust in the tank as it does look a bit rusty..... the mechanic did say he cleaned it out but now you mention it some more bits could have blocked the fuel line.
Thanks i will check that out.
I don't think it could be the wires as it was working fine up until this morning but will also check out the plugs.

Thanks for the suggestions.

[jwhelan65]

Rust in the tank?
Bad spark plug wires?

Maybe a dumb question but how do you know if wires are bad? I checked I have a spark on all four but having the same problem.

[chef1366]

Maybe a dumb question but how do you know if wires are bad? I checked I have a spark on all four but having the same problem.

Try taking off the spark plug caps. They screw right in. Cut the wire till nice wire and rethread the cap.
Grab the wires while cranking and see if you get a shock!

[Steve]

A tip: Change your starting technique.

I would go out in the morning, pull the choke out hit the starter button and after a little twist of the wrist it was running.

Stop twisting the wrist when starting the bike.

The enrichener mechanism in these carbs (it doesn't really "choke" the carb intake like a car does) relys on the high vacuum created by a CLOSED throttle to lift the gas out of the float bowl to the air passage that is opened by moving the enrichener valve, then to the engine. Opening the throttle will destroy that vacuum, and therefore, the effectiveness of the enrichening system.

The other points made above are also good, but if you still can not start the bike when everything else has been tried, it's also possible that you need to adjust your valves. Can you remember when they were last adjusted? If not, they are probably past due. Suzuki recommends checking them every 4,000 miles. It's not that hard to do, just follow the directions in your service manual and use the help provided by BassCliff's tutorials. I also offer an Excel spreadsheet that will help you determine what size shims you need, based on what's in there, and it will also help you keep track of what you have from one time to the next. See ordering instructions at the bottom of my signature.

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[jwhelan65]

Try taking off the spark plug caps. They screw right in. Cut the wire till nice wire and rethread the cap.
Grab the wires while cranking and see if you get a shock!

Can I swap the coils from my 1100? I know those are good and I have them off the bike.

I went out this morning tried to start it and again it briefly rumbles like its going to start and than nothing but the smell of gas. No choke and no throttle given...

[SLIW]

Hi

Thanks for the tips re the throttle.

Just an update. i took the plugs out and they were black and that is only after 140km's or riding. I am guessing this is not right?

[Steve]

Black is not the correct color for the tips of your plugs.

That shows you are running VERY rich.

With the plugs that dark, you will be better of to start with NEW plugs.

When the bike is running correctly, put the black ones back in to clean them up.

.

[SLIW]

Thanks Steve.

Any idea what could be causing it to run rich. I have had the carbs out and they have been cleaned and the jets alligned.

[1150bob]

Aligned the jets? An Aussie term?

[SLIW]

haha Probably not, might be using the wrong term.

[SLIW]

Hi just an update.

It turns out the bike was running very rich which was causing the plugs to foul and only getting 140km out of one tank.
So now the mechanic has made it run much leaner which is a huge improvement.

It starts first thing in the morning with no problem and appears to be idling well.

It takes of well and appears to have no issues cruising at 60Km/ph
However when i get to highway speed (100km/ph) it constantly surges like it is being starved of fuel.
I am guessing this is because it is running to lean but why isn't it surging at the lower speeds as well?

Cheers
Scott

[Steve]

That would be because at lower speeds (lower throttle openings) you are using different circuits in the carbs. It is possible that the pilot circuit (idle circuit) is OK, the needle circuit (mid-range) might even be OK, but the main jet (over half-throttle) could still be a bit lean. That is why it is recommended to do plug chops and read the spark plug color after running at specified throttle openings long enough to color the plugs.

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