Can't find the problem; turns over but won't start

[BazookaFiero]

Okay, so I am still trying to get my 78 gs750E running, but me and the guys have hit a snug. It turns over fine, but won't start. It used to get going, but wouldn't run without the choke on, now it just won't start. We have:

- Replaced the breaker points (gapped correctly)
- Replaced spark plugs (all 4 are sparking well)
- Checked the petcock and fuel filter (both are good)
- Checked for vacuum to the gas tank (there is vacuum)
- Checked the carbs. Everything seems good there (Amazingly clean)

We have run out of ideas on what to check. Any suggestions would be much appreciated! Thanks

[Big T]

- Checked for vacuum to the gas tank (there is vacuum)

This could be your problem. The vacuum line runs to the petcock, not the gas tank

Have you tried turning the petcock to prime?
Have you pulled a plug and seen if it is wet with gas after you try to start it?
Did you actually take the carbs completely apart and clean them out? See the carb cleanup series

Running on choke only is a symptom of clogged carbs

[northwoods]

Squirt a bit of gas in the cylinders and put the plugs back in. If it runs or pops off for a little bit, you know you have a carb/fuel issue and then begin the carb rebuild fun fest.

[flyingace]

Could be a weak battery. Try jumping your battery to a car battery (car not running) and see if it starts. The starter motor can steal enough juice from your coils to produce a weak spark. A weak spark can look just like a healthy spark. If this doesn't help, at least you eliminated that problem.

If not the battery, try removing the plugs and turn the engine over. Do you smell gas coming out of the plug holes? You should. If not, there's some kind of carbueration or fuel delivery problem. Check for fuel in the float bowls - none there indicates petcock problems. Checked your fuel filter lately? (if you have one).

[robertbarr]

With the petcock on ON or RES, open a carb drain screw with a container beneath it. Examine the volume and quality of the fuel (if any) that drains out. Repeat with the other 3 cylinders.

[almarconi]

What is the voltage at the coils? Did you set the timing correctly? If the timing was way off it would not start.

[Suzuki mad]

If you have:-
Compression,
Fuel,
Air,
spark,

all at the right time you should have a running engine.

Suzuki mad