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Only runs on choke now... what happened?

  • Thread starter Thread starter Anonymous
  • Start date Start date
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Anonymous

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My bike ('79 GS 1000) has been down all summer. I rode it in April to my new house from storage and then took it apart to paint. I just got it all back together today and it took a while to start but after about 10 shots of starter fluid she fired up on full choke ( it's about 90 degrees). The idle is now too low and it tries to shut off if I turn the choke off. Even after I let it run for about 15 min on choke and then took it down the road. I didn't touch the carbs at all. The only difference is a new battery and a new filter foam ( I used the foam from an A/C filter). How could I have changed the idle? Is there something I am missing?
 
That filter is probably the problem.

That filter is probably the problem.

That filter is probably the problem. Get yourself a UNI replacement foam filter that will fit in the stock filter holder. Then make sure its full of sticky filter oil. I bet you'll be in good shape after that.

If its still not right balance them and then set the idle. My idle was off and I couldnt find the right setting untill I balanced the carbs. Then it was easy to find the right idle.
 
Did you use fuel stabilizer with fresh fuel before the bike went out of service? Fuel turns gooey quickly in storage (put a couple of ounces of fuel in an open container where safe outdoors and see what is left when the volitiles have boiled off in a couple of days).

Failing to run/idle properly, especially when the choke must be on to run, is a common symptom of plugged-up idle circuits. If the carbs were sitting about on the workbench with fuel in the passages, I suspect that may be your problem.
 
is the stop screw not set properly? try screwing it in a bit, and see if that helps bring the idle up. 1000-2000 is 'the goal'...i dont mind 2500 myself. 8)
 
Um it's the A/C filter man.

Um it's the A/C filter man.

Um it's the A/C filter man. All the other stuff is important.... BUT..... Get that A/C filter off of it. Or re-jet it to handle it. Me personaly I would change the filter before I re-jet my bike to handle a rigged up filter.
 
A/C Foam Filter?

A/C Foam Filter?

I thought I had this figured out with foam from a seat also once :cry:
Save me some $$ and have the same thing:BONUS!! The only drawback is that it doesn't work either. Chris is right on target with this one. Bob
 
Let us know when you figure out the problem. Of course, it is important to try to adjust idle speed by way of the adjustment wheel. As to the filter, most bikes will run fine without a filter for tuning purposes, so a less restrictive filter shouldn't cause a problem of this magnitude. If a filter is more restrictive, I would have thought that would cause a too-rich mixture, which would not be solved by further richening the mixture with the choke, although a low idle rpm might result?

However, I'm big on theory and short on practical experience, and I usually get it all wrong, too. :(
 
Filtering

Filtering

Al,
Where the air filter comes in to play is with the jets. At idle, the pilot circuit is feeding the fuel with the restriction of the air filter figured in. Take the air filter out and it receives a gulp of air that the carbs cannot keep up with as the jet only feeds "X" amount of fuel. Think of it like this, ratio of air to fuel ideally is 14.7:1. If you lose the filter, now you have 25:1 ratio(number picked at random for illustration), effectively leaning the mix way out. With fuel injection and a lean condition, the pulse width of the injectors will lengthen(stay open longer) to add extra fuel until the ratio returns to normal.

Just my .02, Bob
 
Re: Filtering

Re: Filtering

cabinover said:
Al,
Where the air filter comes in to play is with the jets. At idle, the pilot circuit is feeding the fuel with the restriction of the air filter figured in. Take the air filter out and it receives a gulp of air that the carbs cannot keep up with as the jet only feeds "X" amount of fuel. Think of it like this, ratio of air to fuel ideally is 14.7:1. If you lose the filter, now you have 25:1 ratio(number picked at random for illustration), effectively leaning the mix way out. With fuel injection and a lean condition, the pulse width of the injectors will lengthen(stay open longer) to add extra fuel until the ratio returns to normal.

Just my .02, Bob
Click to expand...

The information you provided seems spot-on, but if I go out and pull my air cleaner right now, I'm still able to make the bike run/idle when warm despite the leaner mixture. In the described situation, the bike won't idle without choke even when fully warm. Wouldn't there be something else at work here, too?

By the way, the very first thing I'd do in diagnosing this problem would be to put in an OEM filter or equivalent! Why not eliminate the one variable that has changed since the bike last ran well? The Emgo filters I use cost less than $10 and are good for a couple of seasons.
 
Ok I neglected to mention that I do not have a stock filter or airbox. I have the equivelent of pod filters except that it is one big pod. It had a foam in the filter that started to crumble with age ( and frequent sprays of starter fluid) so I replaced the foam. It is the same filter housing I have always ran. The two foams are very similar, actually I think that the new stuff maybe a little more restrictive than the old crumbling stuff. The filter is not a rig up, it is made for the bike.

Now the fuel thing is possible, but wouldn't it eventually get to the good stuff? I ran it for a total of about 20 min with a fresh tank of gas.
 
djturnz said:
Now the fuel thing is possible, but wouldn't it eventually get to the good stuff? I ran it for a total of about 20 min with a fresh tank of gas.
Click to expand...

There are two issues related to gasoline here:

1. Is old gasoline causing your problem by failing to atomize or burn properly?

Perhaps. Drain the carburetor bowls and fuel tank - then add fresh fuel. Good luck, but it sounds like you may have covered these points.

2. Did the gasoline already in the teeny-tiny carburetor passages as the carbs sat on the bench turn into hardened muck?

If so, the prevailing wisdom says that the carbs have to come apart to be cleaned with special solvents. The gummed gasoline is called varnish because of its physical properties! Pour-in carb cleaners are not usually recommended, but some use them with good results (seek advice from those folks). From now on, use fuel stabilizer according to the instructions whenever your bike will be down for more than 6 weeks. My buddy adds it at each filling year-around in case he gets too busy to ride (a too-frequent occurrence).

Explore the air cleaner angle vigorously, too. As a general rule, stock bikes will run more reliably, and with less fussy tuning, than hot-rodded bikes. Perhaps that's why I have so little practical repair experience! My dozen or so bikes have all been stockers except for suspension upgrades, windscreens, luggage systems, or luggage rack/backrest.

Good luck.
 
I just picked up a UNI Filter yesterday Does it have to go in the stock carrier in the airbox or do i just put it in place?

Thanks
Michael
77 GS750
 
Well I just got the bike inspected. I asked about my idle problem. They suggested new plug ( I nneded them anyway). And also a carb rebuild.
 
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