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85 Gs 700 won't stay running

  • Thread starter Thread starter Ickaruz
  • Start date Start date
I

Ickaruz

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I need some help solving a mystery. I turned my bike over to a mechanic the other day because my 700 wouldn't stay running. He cleaned the carbs and synchronized them. He said the root of the evil was the little jets under the rubber caps inside the carbs, which were the ones that I neglected due to my inexperience when I cleaned the carbs the first time. So, everything was great! I drove for a few hours no problem. After I stopped for 2 hours I got back on the bike, started right up. Then half a mile down the road it starts hesitating and then dies. In this instances I find I can get it started only with a squirt of starting fluid, which I know is not the best thing to due. It will then run from anywhere from a half a mile to a mile max before it hesitates and dies. I took the carbs off again, cleaned all those jets including the ones under the rubber, installed an inline filter, and wa la. It felt all good again. Drove for an hour yesterday, shut the bike off, got back on, half a mile down the road, same thing. My first guess is vacuum but I did replace the orings and rubber boots that go from the carb to the engine. I did notice this morning when I turned the petcock to the right to directly feed the carb there was a lot of gurgling going on meaning the floats were empty. Still the bike won't start after doing that. I'm about to yank the carbs again tonight to check all the jets again but I hope someone gets back to me before than with a solution that doesn't require this. :) I appreciate any help!
 
First-choke the mechanic for taking your money and not fixing the problem.
The carbs must have dirt in them again...clean the tank, too.
 
I honestly don't think it is the carbs anymore

I honestly don't think it is the carbs anymore

Ok, this is why I'm pretty sure it's not the carbs. I cleaned the jets again, flushed the tank, and put an inline filter in. The bike starts and runs great. However after an indeterminate amount of time it stutters to a stop. After letting it sit for a minute it starts and takes off for a mile maybe two. It seems to me that the fuel cannot keep up with consumption. Just a guess. I also want to mention that I did coat the inside of the tank when I first bought the bike because of rust and a small hole. I was wondering if by any chance that goop sealed anything that needed to breathe that may effect the fuel. I cracked the fuel cap on the way home tonight from a friends, though, and it still stalled after a mile, so I don't know about that theory either. Basically I have no more ideas. When it runs it runs great, really smooth, but after awhile it just dies. Please help!
 
Last edited:
Drivers Test in three weeks!

Drivers Test in three weeks!

Sorry to be a nag but my drivers test is in three weeks so I really need to get this nipped in the but and get some more road time in. Please throw ideas at me as to what could be the problem.
 
Ickaruz said:
Sorry to be a nag but my drivers test is in three weeks so I really need to get this nipped in the but and get some more road time in. Please throw ideas at me as to what could be the problem.
Click to expand...

There is a running debate around here about whether or not to run an inline filter, and what type to use if you do. You should be able to go without, and they can exacerbate fuel flow problems.

When it dies and won't start, is there fuel in the bowls? What level of fuel is in the tank? Do you have the original petcock on the tank?
 
my vote is the vac line to the petcock kinked, inserted wrong, missing... this will cause the problems you are facing and dumb question is the fuel on (not res) possible problem there
 
I'll get rid off the inline

I'll get rid off the inline

I appreciate the help everyone. I think you all maybe a bit right. I'll buy the new petcock a a last resort. One of the most recent times it died I had a friend nearby who trailered the beast home for me. When I had it back in the garage I had the brilliant idea of turning the petcock to direct feed and I heard a bunch of gurgling as the floats filled. It was then that I put a new inline filter in. The next run out it died again. I then discovered that, yep, Ithink the vacuum line was run alittle funky an I believe as the bike ran for awhile it slowly kinked itself good because of vacuum. So I rerouted it with big bends only by running around some stuff. Yet after two hours of driving the bike died. But it was near the end of that ride that I was really getting into it. So, I think now that it has to be the inline. Any tips on attaching a new gas line to the carbs without moving anything?
 
After two hours of riding.... could you have been running out of gas? If you had less than a full tank and had the petcock set to the normal fuel position you could have just been getting low and switching to REServe might have solved the problem.

/\/\ac
 
Check to see that the fuell cap is venting properly. If it is not venting, vacuum will build up in the tank, flow to the carbs stops, and shortly thereafter the engine dies.
 
How do you check to see if it is venting correctly?

Also, my vote is a new petcock. My 79 GS750 did something similar. The petcock was bad, New petcock....and away I go!

Rick
 
To check, disconnect fuel hose from petcock, attach another hose that is routed into a suitable container, and set fuel valve on prime. Drain the whole tank if you have to; this will verify that the fuel cap is venting. If it is not, flow will slow to a trickle, then stop. Open the gas cap and fuel should begin flowing again.
Eliminate one variable in the equation.
 
Bad venting

Bad venting

Thanks Smokinapankake. I checked to see if the tank is venting like you said and it weren't. So now I need to figure out why. Like I said, I sealed the tank cause it was rusty so I assume I did something bad. I put a hose up to the first little hole that I saw beneathe the gas cap and blew through it and air came out under the gas tank from the nipple there. Is there somewhere else or someway the tank is supposed vent? Man I hope this is it so that I can ride care free tomorrow. Thanks all for your guidance thus far!
 
There could be crud in the tank that clogs the little filtre in the tank, then when you stop and put the bike on the side stand all the crud falls off the screen. Fuel flows, then it clogs up again. I would pull the tank and the petcock off and see if there is a bunch of crud in there causing my headache.
 
No crud

No crud

Thanks for the advice but there is no crud. There is definitely a vacuum issue in the sense that the tank don't vent and therefore the gas just slows to nothing more than a trickle if that when I open the petcock to direct feed.
 
This flow test has complications, as the flow should naturally slow down as the fuel level drops. Basically, more gas will come out of the petcock when there are a couple gallons of fuel sitting on it in the tank. When the tank gets low on fuel, there is much less hydrostatic pressure pushing fuel into the petcock. This is why in-line filters can be a problem.

If I were doing this test, I'd time it draining with the cap vs draining without. There should be only negligible difference. Of course, if the flow stops, there is a problem.

One thing I'd like to know, just to be sure: To initiate flow, did you have to do anything other that turn the petcock to prime, or did you also have to suck on the vacuum line?
 
Flow

Flow

There was a major differende when I popped the cap off. in itally with cap on it started flowing by itself when I turned petcock to prime, however, that soon slowed even though there was still plenty of fuel. I mean to say it slowed noticeably within thirty seconds. Then I popped the cap off and the flow resumed steady and strong. So i'm hoping now that that settles it and the problem is venting, which I have no idea how a tank vents. I understand the idea but as to where I need a little help..
 
Ok, that sounds pretty conclusive, then.

For the vent in my cap, there was a little ball in a chamber that made a check-valve which should close if the bike tips over. If you take the cap apart far enough to get into that, you should see where the vent passage goes from there. Assuming of course, that yours is similar to mine.
 
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