GS overhaul

[boy named suzi]

So, I'm at my wits end. Trying to get 1977 GS 750 running before the season ends (next week?).

I bought somebody elses head-ache, bike hasn't run in 10 yrs? 12,000 KM on the clock. I have cleaned, inspected, tested and overhauled everything I could without taking off the cylinder head. Totally stripped, soaked, cleaned, tweaked and set-up carbs, tank and pet-cock. Replaced ignition components (points, condenser, plugs and 1 coil), checked valve and ignition timing to manual spec. Had coils, wires and boots pro serviced. Replaced MISSING parts in starter clutch (warning- it's been open before), replaced damaged rotor and starter.

What have I missed? Using boosterpack and charger, lights come on. She fires on the ether (bad daddy) but dies, will not continue on (new) fuel. The bowls are receiving fuel (it drains at least), how does one find out if the carbs are drawing fuel (there is no obvious pump circuit like car). Spark is there but how good must spark be (orange - blue spark)?

Thanks for any help, this is a beautiful machine that should ride again.

[GreyGhost]

I'm not sure if you can see down the throats in a GS, but normally normally you can see a fuel mist inside the carbs. As a friendlier starting alternative, normally you can fire engines on propane. Start the bike cranking and then stick an unlit torch (with the fuel wide open) into the airbox. I wouldn't rev it up with this setup, but you may be able to let it idle until it gets up to temp. Sometimes getting it warmed up is enough to get things going the first time. My guess would be some sort of electrical issue (or an air leak somewhere around the carbs).

Good luck.

[BrianZ]

It sounds like a fuel issue. When you overhauled the carbs did you inspect all the jets? The main jets are fairly large and easy to clean. The pilot jets on the other hand are small and very difficult to clean. Sometimes its easier to just replace them. Recheck all carb passages, especially any passages in the float bowls. On a bike that has sat for several years the fuel will turn to varnish and plug any passages in the float bowls. I like to use bits of tubing to blow air through the passages to make sure that they are clear.

[boy named suzi]

Thanks for the tips. I have seen light through the jets, pilots aswell and will now recheck the passages, the ones in the bowls were really bad and may have overlooker a circuit in the bodies.

It seems odd that it wont fire at all, even in the summer when the air temp was higher. I did get one chug once when a plug was out for spark check.

[Scudzo_2]

I did get one chug once when a plug was out for spark check.

If it's sparking you've got a fuel problem.

(The old GS's are great, I had an '80 GS750E for my first street bike a few years back)

[02R6420]

You said it fired on ether(quick start) so it should fire with fuel, sounds like it's not getting any. I'd check the carbs, check all the jets, float level, and all of the little hole's in the carb body. Use compressed air to be sure all are flowing free.
Peace.

[Dilligaf0220]

Have you checked compression yet?