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Struggling with carbs here!

  • Thread starter Thread starter JimmyR
  • Start date Start date
J

JimmyR

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As some will know, I'm restoring an '82 GS1100G. The PO had the bike running with a really nasty rusted out 4-1 exhaust and no filter in the airbox. It ran and was enough to get me home when I picked it up last november but it didn't run too well.

So now I have cleaned the carbs extremely thoroughly, no residue anywhere and the little holes are all clear. I just rebuilt them and replaced the 160 with 170 pilot air jets as per the manual and I know I have #40 pilot jets. The rest I am not so sure about, but I will have a complete new set of genuine Suzuki/Mikuni jets and needles next Monday. I set the pilot screws to 2 1/2 turns out as recommended. As far as I can tell I have the floats set at the correct height. I have new boots between the carbs and engine with new O-rings and everything tightens up nicely and is clean. I have a stock style 4-2 exhaust.

Problem is, I can't get the bike to run! Well I can, but not for very long. Today after I had just got the carbs all back together again I installed them, attached the airbox with brand new filter and put fresh fuel in the tank. Primed the carbs and after a few cranks it started. Reduced the idle to around 2000RPM - any lower it didn't seem to like. Warmed it up, let off the choke, it ran for about a minute, making slight gurgly pops through the exhaust (I think the sound came from there anyway) but still ran ok. Then it stopped and I can't get it to run again.

The same thing happened last week when a mobile mechanic was around, except that he didn't have the airbox on. It ran well while he was here then the next day nothing.

So that's why I rebuilt the carbs. I did have them "cleaned and assembled" by a bike shop before the mechanic came around but was a little dubious of their rather sloppy work.

My plan now is to use all new needles and jets so I know what sizes they are and have a baseline that I know is stock. I can't see the markings on most of the parts I have except the air pilot jets and pilot jets. The Suzuki dealer - who is actually quite helpful - reckons the float heights are out and that I am running out of fuel in the float bowls. But that would mean that after a while of not running it would run again, I would have thought. This will run after I have put the carbies back on and then not again.

Does anyone have any other ideas? I really don't know much about carbies and feel a bit out of my depth. Plus I hate the smell of gasoline.
 
Did you check the spark when it died? How do the spark plugs look? Did you bench sync the carbs when you reassembled them? I guess you've not run them long enough to get a vacuum sync going. When you can get it to run, are all your pipes getting hot? Have you checked your coil voltage and coil impedances (including and perhaps without plug caps)?
 
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Yup pilot plugs are in. They're new, too. Yes I have sparks on all cylinders and the carbs are bench synched. All pipes seemed equally hot.

Now to the weird (but probably good) bit. Went out to the workshop this afternoon, pulled the airbox and carbies AGAIN, pulled the float bowls off, checked the float heights and values of the jets - everything was stock values. Put it all together again and managed to start it and it runs beautifully now. Very responsive to the throttle and it roars! Why didn't this happen before??

So I let it run for a bit and it blew a bit of smelly smoke before settling down, so I took it around the block a couple of times so it wouldn't get too hot. It rode really well, and if memory serves it seems a bit more willing than when I first go it. It isn't bogging down at all. It didn't even need much choke to get going. All I did was reduce the idle as it was idling at around 4000. Now it's just below 2000.

So what happened? Did I somehow dislodge some crud or something? I guess the real test will be if it starts tomorrow.
 
JimmyR said:
All I did was reduce the idle as it was idling at around 4000. Now it's just below 2000.
Click to expand...
When you get it to idle at the recommended 1000, you can call it a success.
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I try to keep my idle under 2000, even when using "choke" on a cold engine. :o

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I doubt it will idle at 1000! It's lugging by then. My Fatboy would probably idle at 1000 - heck it would probably run up hill at 1000!
 
Well, just so you know, the specs call for an idle speed of 1000 or so.

Not sure if it's 1000 +/-50 or 1050 +/-50, but that's where it's supposed to be.

All of my 850s idle at 1050, my son's 1000 is at 1000.

Just for reference, though, my Wing idles just fine at 650. :cool:

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Spec on my 8V 550 is 1100 +/-100, so between 1000 and 1200 RPM. Mine is set to probably between 1100-1200 when hot, depends how much to trust the tach :) Hot being 10-15 minutes of riding (not idling).

A good vacuum sync should help settle it down and keep it running around the target idle speed. You don't want to touch the throttle when starting the bike: just idle plus whatever air (+ extra fuel) your "choke" provides to get it started cold. If your throttle plates were that open it was like you were opening the throttle, not getting enough vacuum and thus fuel for the start.
 
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