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1980 GS550E with CV carbs won't start

  • Thread starter Thread starter elkapower
  • Start date Start date
E

elkapower

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I have rebuilt my carbs, and so not have the spec on the air screw turns to back out. Does anyone have the CV carb spec? Have the pilot screws out 3 turns, but that seems wrong since this is a EPA bike, the screws were plugged.
Also, she won't start, have a NOS gas tank valve, new tank, even on choke, she won't fire. Plugs have spark on all for cylinders, carbs are all newly rebuilt, not passages plugged, compression is in spec. Where do I go from here? Have to run it in order synch the carbs, but she will not run> Not on choke, not without, or anything in between.
Anyone with any ideas?
[-o<
 
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If your new petcock is factory original (screwdriver slot type), it has to be turned to PRIME first. Turn the slot vertically. Then after some cranking, the fuel should fill the float bowls. If this is the problem and the bike starts, turn the petcock to ON in about a minute. The slot is horizontal when turned to ON.
Leave the slot turned to ON. Only if the carbs are serviced or the bike has sat a longer time do you need to prime again.
3 turns out on the mixture screws is too much for a stock bike. Try 1 1/2 turns out. Once the bike is running right and fully warned up, adjust the mixture screws to achieve highest idle, using 1,000 rpm's as a base idle for setting. Look up "highest rpm method" to set the screws.
 
Sucking

Sucking

You still need vaccum on these petcocks even on prime. When I service my carbs and the bowls are empty I have to apply vaccum manually for a minute or so to fill the bowls. Yeah, that means sucking on your vaccum line going into your petcock.:-)
 
Does she fire with starting fluid ?

Do the floats have fuel in them?

Are the valves adjusted properly?

Is the timing correct?

I'm going through a similar scenario with my 78 (non-CV carbs...sorry I don't have the specs). I've had to check and adjust almost everything in my list. Just thought I'd share in case you missed one.
 
GS550E won't start

GS550E won't start

Yes, the floats are set to 24mm height, float bowls are full. The obvious has been done, petcock on/pri/res. Have an IV bottle on it and it will also not start. Have not messed with the valves. Just tried setting the idle/ air screws to 1-1/2 turns and still nothing, not with choke on, or off.

Have not tried starter fluid figuring that when she is cold, I still want to have her start on her own. Have spark at all plugs. Plug wires were lifted to make sure they were not shorting out.

OK! Carbs are freshly rebuilt, spark plugs are new and gapped.
Fresh gas, no hose leaks. Boots tight with new clamps.

Can't synch the carbs until she runs. She is an 80 model, so it is electronic ignition, timing is set.

Any more ideas? I know, buy a new bike, but that is not an option I can afford for a casual driver. Too old to spend money on show bikes, enjoy, until she doesn't start the older style bikes.

Anyone with this model that has been through this before is welcome to chime in...certainly something is amiss.:?
 
You can still bench synch the carbs. If they're way off, it could cause hard starting.
 
Also, if you have spark, and fuel in the bowls, then check for fuel on the plugs.
Obviously, with good spark and fuel present, you'd have combustion. So with no combustion yet, I'm guessing you won't see fuel in the cylinders. That would mean a lack of vacuum from the bowls to the cylinders, a very low float level, which you say is correct, or the throttle plates are not synched/set correctly and may be starving the motor for air. Lack of air intake= lack of vacuum to draw fuel from the jets.
 
Still won't start

Still won't start

The carbs have been bench synched, all slides are adjusted the same. Even then you would expect the throttle when cracked open alot or a little to cause a blip of a spark.

The plugs are getting wet.

That is why this has me perplexed. Everything is there...but I have not checked the valves. Had it running last year on bad carbs, did not want to start, but got it started, when warm she would start everytime. Cold, no way. Actualy poured a bit of gas down the cylinders to burp it over. Have not done that since everything aught to be right.

So, hence the continued frustration.

Anything else you can think of. Should not be in the valves. When turning the motor over, I pulled off the gas line to see if pressure from #3 carb was pumping, OH YEH, what a mess, but that works. Last year before I abandoned the carb rebuild, she would start on the IV bottle, but not such luck, that is why I waited to get a new petcock, since the others I bought (3) were all bad also.

So here I am, virtually new everything, Do you know what the coil pack should read on a VOM. Maybe the spark intensity is not enough, that is where I am headed next.
 
It sounds like you're getting this sorted out. If you have fuel (wet plugs), and spark, all that's left is the air filter. Unless it's clogged totally, the engine should be pulling some air. The next to last variable is your choke, the cable of which is probably slipping by now so you're not choking off air to get a higher ratio of fuel. I have a 1980 GS550 that never needs choke (the pilot screws were freed), only a slight turn of throttle; and, for what it's worth, if I don't start it for two or three weeks, it's going to need starter fluid. ("I love the smell of starter fluid in the morning. It smells like...riding"--with apologies to Robert Duvall in "Apocalypse Now".) The gas in the bowls dries out by then and it takes a while for the vacuum in the petcock to suck in enough fuel to light that candle. The battery is a good question. That's often the problem because it's not strong enough to turn the engine over fast enough. The GS motor was very well designed and will start easily in most instances. Good luck and let us know how it turns out.
 
More info

More info

Just poured 5cc gas directly into the chamber, started up, no effect with choke on or off. The choke slide moves the chokes, so still no help.
But the good news it is not getting enough gas, screws in 1-1/2 turns to 3."
So why she doesn't suck fuel in don't know.
That means the boots are leaking, or the suction isn't enough to pull gas in.
Had it run for a minute, exhaust temp on pipe cyl 1 was 135, cy2 was 145, cyl3 was 98, cyl 4 was 120. Then she died out, and could not restart it.
Means the carbs are not balanced, right?.
SO, I am guessing they need to be tuned to get the temps equal. Right?
So more work to do. Battery is on charger, and has enuff to turn it over fast.
 
elkapower said:
The plugs are getting wet.
When turning the motor over, I pulled off the gas line to see if pressure from #3 carb was pumping, OH YEH, what a mess, but that works.
Click to expand...
I'm guessing when you say "to see if pressure from carb #3 was pumping", you really meant carb #2 ?
Carb #2 supplies vacuum for the petcock on your CV carbs.
If you do mean the above statement, then you have the petcock vacuum line connected to the floatbowl vent nipple that vents carbs 3/4. So you'd have no vacuum to open the petcock and you'd have two carbs with plugged venting which will not allow fuel to be drawn up easily (or at all) from the bowls in those two carbs. Also, it would mean you have an open vacuum nipple at carb #2 with or without a hose attached (doesn't matter) and this wouldn't allow the bike to start at all.
Also, fuel shouldn't flow from the petcock with these connections.
 
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