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Fast Idle and Won't start when hot.

  • Thread starter Thread starter joeadams
  • Start date Start date
J

joeadams

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I just got my 83 gs 750 out of winter storage to make the 150 mile trek to harrisburg. I got it down here today and along the way I noticed 2 things. Its idling at 2k rpm and the starter motor won't crank the engine when the bike is hot. I say hot and I mean hot like I just rode 50 miles down the highway in 65 F weather.

As for the high idle, I just changed the choke cable and I think I probably don't have that adjusted right and the choke is still partly open. I will have to re adjust it and that should fix that problem. Right??

As for the starting thing, I am at a loss. This is an entirely new problem. The battery has plenty of charge and it starts fine if I let it sit 10 minutes or so. The starter tries to start it and it sounds like it just isn't getting enough power to do so. The bike runs great once you get it started. Does it sound like a bad connection somewhere that gets amplified by extra heat?

Any input/help is much appreciated.
 
OK so I was just out and tried to adjust the chock cable. Where the choke cable is adjusted, on that little elbow there was a small brass nut and a larger brass fitting basically an elongated nut. They were both screwed down as far they would go and it seemed not enough to allow the choke to close comletely, I took the small nut off and just put on the larger one and screwed it all the way down. It seemed to help but perhaps I am seeing things. I didn't really look too closely at it previously but it didn't seem fully closed. I am going by there shiny parts of the brass choke rail being exposed. I didn't get a chance to take it for a ride and let it get hot again and see where its at tonight but I will tomorrow.
 
I doubt the problem is the choke or choke cable. When the motor is warmed up, a little leaking choke mixture will actually lower the rpm's on a correctly jetted motor.
If you just took the bike out of storage, the carbs could be gummed up, but that should cause hard cold starting too, not just hot. I assume the bike ran fine before the storage?
If the bikes idle rpm's rises significantly higher after warming up, say 1,200 cold, and 2,000 hot, that's a classic symptom of an intake leak. Most likely the manifold o-rings or the manifolds. You may try tightening the manifold clamps first, but it's more likely the o-rings/manifolds.
Intake leaks will cause the hard hot starting too.
 
If the bikes idle rpm's rises significantly higher after warming up, say 1,200 cold, and 2,000 hot, that's a classic symptom of an intake leak.
Click to expand...

This is what it does. When I first got the choke cable installed and took it for a ride back in March I heard what sounded like something sucking air coming from the carbeurator area. Pssh Pssh Pssh....in time with the motor. It was pretty noticable even when riding. Just this weekend, I just changed the oil and I charged the battery up. It was running rough without the air filter and making that same noise. I put the air filter on and it seemed to go away. I might be in denial and this will have to be reinspected. How hard is it to damage these boots? I just changed the choke cable and thats all I did down there but its possible I did something to cause this.

The bike ran good when I parked it and I don't think that it has gummed up carbs. I had stabil in the fuel all winter and started it a few times throughout the winter and ran it a while each time. Right after the oil change/battery charge it lit up within a second or two of me hitting the starter button and it had been sitting for a while(few weeks.) I had left the petcock on prime that whole time but nothing bad came (ie no crankcase full of gas) of it and I didn't start it until after the oil change.

As far as hard starting when hot is concerned, its not. It starts real easy when its warmed up. It will fire up when you push start it at little more than walking speed. The problem is that when you hit the starter button you are lucky to get 1 revolution out of it and it sounds horrible. It clicks but it just doesn't crank but only when it's hot. I tried it this morning after it sat all night (46 F) this morning and it canked. It cranked slowly and didn't start but I am not sure as to whether I should chalk this up to the battery being dead or the problem at hand.

It is very possible that I need a new battery. Its entering its 4th riding season and it's had a rough life. I got it from walmart when I bought the bike and the stator was failing. So I would ride it and the battery would die after a while because the stator wasn't doing its job properly. After it would die, I would push start the bike until I got a chance to re-charge the battery. I did this for 2-3 months (over 2 seasons) until it finally stranded me 20 miles from home and I discovered this website. I decided that it was time to fix it and got the new stator installed. I have been extremely impatient with the battery and have partially charged it and drained it many times. I have also left the key turned on all day a few times. It dried up once or twice as well, I didn't use distilled water. I had planned on buying a new battery this summer but this one still seems to take a charge. What do you think about this? I'm going to guess that you will tell me to buy a new battery.
 
My newest half wit theory...

The battery is toast and the engine is a little harder to crank when its hot due to expansion. So the battery doesn't have the juice to get the job done. Make any sense??

I know...I should get a multimeter and check everything out and I intend to. If not tonight, then tomorrow.
 
Yes, you need a new battery. Yours has been abused you might say. Heat creates resistance. More resistance equals less amperage flow. That's why a weak battery can start the bike cold, but not hot. You should also go through the entire harness and check/clean all connectors/grounds. You may want to check the brushes on the starter next and lightly clean the commutator with emery cloth if you still have trouble.
As for the high idle, if it fits my previous description, you have an intake leak.
 
Ok now, Intake leak.

http://cycleorings.com/intake.html

I did a search and found some stuff. It seems the big culpret for the intake leak is the o-ring featured in the website above. Is this what you are refering to? I assume this goes between the carbs and the head with this o-ring mating with the head.

Also I know that the tubes between the carbs and the airbox may be leaky as well. These seem to me to be in good shape though. Is that the case where you would do the WD-40 spray test?

I have no idea when these carbs were last serviced. Someone already replaced all the bolts in them with allen heads though. I wouldn't be surprised if the intake manifold bolts have been replaced as well.

I apologize for all the stupid questions. I should just get into it and see what's there.
 
Yes. Those are the o-rings, if your model uses them. It can be the manifolds themselves sometimes. Or loose clamps.
On a warmed up motor, a fine mist of water will sometimes expose an intake leak. The rpm's will drop for a moment. But it's hard to always get the mist in every spot. Don't use WD40, water is better.
Look up your model. If your model uses these o-rings, order and replace them. Apply some hi temp' bearing grease to help them last. Torque to about 6 ft/lb, or per your manual. They get bad much more often than the manifolds, but check the manifolds too.
 
So that picture from rhe Cycle O ring page didn't look familiar and now I know why. My bike doesn't look like that. I didn't get time to wokr on it tonight but I did snap some pictures and have a few more questions.



This is what she looks like. The screw I am pointing at with the screwdriver was semi loose. In fact every one of those 8 screws were like that. I tightened them all down. Most of them tightened until the ring was completely closed. I don't know if this did anything because I didn't do anything else with it.



The screw I'm pointing at in this one was not all the way tight either.

Basically, my question is, what's the deal with these things? Should they be totally synched up as I have made them?
 
The screws may have been a bit loose. Hard to say.
Whenever rubber is clamped down, there will be some give after some time. This would make you think the screws were loose. In my experience, the clamps commonly are closed or nearly closed after many years in service. New manifolds doesn't always help the clamps tighten more either. The clamps can fatigue.
Try the water mist test on the manifolds. On a warmed up motor, if the rpm's drop a moment, you've found the leak. This test doesn't always expose a leak though. It's hard to reach all areas. It doesn't take much of a crack to cause an intake leak.
Is the throttle cable adjusted correctly?
Did you try adjusting the idle adjuster knob?
How long since the carbs have been synched?
Does the idle rise once warmed up as I asked earlier?
 
To answer your questions:

The throttle cable is adjusted fine, it is definitely not the problem

I tried to adjust the idle adjuster knob but the engine was hot and I kept burning my hand trying to reach it. I then decided that it shouldn't have been moved and crossed it off the list.

I have no idea when the carbs were last synched. At least 3 years probably more.

Yeah it does just as you described, idle normal when cold and increases when warm.


Here is my plan of attack:
I got a new battery and charged it up last night. I'm going to install it tonight and get the bike running again. Then I'll be able to check if tightening those clamps on the manifolds did anything. Some were not even close to completely closed, there was up to a half inch between the two ends of the metal band. They all seemed to tighten significantly. I think they may have been loose but still had residual seal and when I was messing with the choke cable I broke one or more loose thus causing the problem. If it still Idles too high, I'll do the water spray test and see what happens. I may be in for some replacing.

I'll report back.

I also have to look into this oil loss I had. I hope it just got sucked into the filter but quite a bit had disappeared. That is another thread though.


Edit: I just installed the new battery and the bike lit up so fast it was ridiculous. Not even one full crank and its been sitting for a few days. Seems like the internals of the carbeurators are in good shape.
 
Victory is mine!

I got the new battery installed, put her back together and went for a little ride ~5 miles to get it up to temperature. It is now idling at what it used to idle at which is 1500 rpms. It must have been those clamps.I know thats a bit high but it's always idled there so I think its oK.

I also found out what that pssh pssh pssh sound was. It is the vacuum line from the petcock to the carbs. If it isn't seated right it makes that noise.

Thanks for all the help Keith, much appreciated.
 
Glad you got the bike running well! :)
Your second post about how loose the clamps were, made it more obvious that they were allowing the intake leak.
Your bike should idle well at about 1,100 rpm's. You should at least try to adjust it down next time before the motor gets too hot to touch. I mention this because an idle of 1,500 rpm's will cause needless stress on the gearbox when downshifting...it's harder on the clutch...it makes you wear out your brakes sooner... it makes the bike run MUCH hotter at stops...and it wastes gas.
If you can't make the bike idle at 1,100, you should have the carbs vacuum synched. That would most likely do it. But try to adjust the adjuster knob first. :)
 
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