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Need everyones help on this problem

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

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83 GS750 ES. Intermittent problem. Trying to figure out where to look next. Ever since I got the bike, it has had an idle issue. The person I bought it from said when its cold, it really doesnt like to idle, so I adjusted the knob thingie (sry I dont know all the part names) between the carbs, and got it running a bit better. Ive had it for abotu 6-7 months now. I ride it 4 days a week to work 40 miles away and back, so a total of 80 miles. Its never given me any real issues until now. Until about 2 weeks ago, the bike would either idle very high, around 5k, or it idles too low and dies at stop lights.. Either way, while running the bike runs great. Now (2 weeks ago) it started to idle perfect, but now backfires. It was backfiring thru the carbs just little pop pops while riding.. Now its getting worse. It for some reason will (while riding) just die. Electrical stuff all stays on, but the engine cuts out, then about a second later, comes back on, with a huge backfire out the pipes. As of this morning, after it did that, I pulled to the side of the road. bike died, started right back up, but had 0 power. prolly idled around 200rpm but wouldnt go higher. Choke on or off, throttle wide open or not. It would idle at the 200 for about 15 seconds, then cut out. Well, this was going on for about 30 min. So I got pissed and kicked it over. After laughing at what I just did, I decided to pick it up. tried to start it, waited for the few seconds to get the fuel back to normal, it started and ran better than it did in months! Got back home, about 2 blocks away, let it idle went inside, about 3 min later, back to same problem. Any ideas?!
 
Have you taken a look at your plugs? Maybe they're due for a replacement. Pull one out and let us know what colour they are.
 
Sounds like maybe some needle valves in the carbs may be sticking as well. When was the last time the carbs were taken down and cleaned really good?
 
I'll add to the already good suggestions...It may be as simple as a partially clogged or faulty fuel valve(petcock).
 
The fact that it ran better after being tipped on it's side sugests that the carbs need to be cleaned, there is rust/crap ? in them. Maybe the complete fuel system including the fuel tank needs to be cleaned
 
The carbs were bought 8 months ago brand new. I took them apart this past weekend. shiny shiny shiny. checked everything onthe carbs
I checked the intake boots. there might be a small air leak, but would that cause it to run like that intermittently?
 
the plugs are also new. Changed them the other day. Took them out just now, and they appear to be off yellow with what seems to be specks of something on the ceramic next to the gap.
 
A small intake leak wouls definitely casue an idling problem and it could be intermuittent it it leaks more some times than others, ie, hot & cold.
 
did you replace the o-rings between the intake and the motor? If those are leaking it will run lean and can cause some of the problems you describe (high idle, backfire).

Good luck!!!
 
just thought of something else, is the gas tank properly vented? check the vent tube to make sure it isn't pinched, or let it idle with the gas cap open, see if that makes a difference.

Don't run it on the street with an open gas cap, that can lead to bigger problems!
 
yeah, I checked all the venting. I also ran it with the tank open, and no not on the street :D
I did not replace the o rings on the intake. I havent taken the intake boots off. Hard time getting to them and I cant seem to remove the airbox.
 
Not sure if I mentioned this or not, but now it only starts in the morning if I use starting fluid. Never had this problem before. (started before all of the other issues)
Heres a rundown of what I replaced in the correct order

petcock
Stator (havent replaced the R/R yet)
clutch cable
choke cable
plugs
air filter
I dont know if that helps anyone.
 
My GFs 81GS650GL requires starting fluid when it sits for long periods of days or when the air temps are cold. I do need to rebuild her carbs, one in particular has a sticking seat or something that causes gas to pour out sometimes. That cylinder also runs very rich. Maybe this is a help to you.
 
Another possibility is an ignition problem. If the coils are a bit weak or on the way out I found cold starting was not good and idle was not consistent, but was ok when warm. One of my coils recently went, and caused similar problems to what you describe a while before one coil completely failed.
 
Good previous suggestions.
You may have more than one problem. The most common cause of a high idle after warm up is an intake leak. Spitting out the carbs is also a lean condition caused by an intake leak or low fuel level in the bowls.
I would replace the manifold o-rings, and manifolds too if they are getting hard or look questionable. Put some hi-temp brg grease on the o-rings and torque them down to 6 ft/lb. Make sure the carbs "pop" into the manifolds and tighten the clamps good. Of course, if you're lucky, you can just try tightening the manifold clamps first and see if that helps.
You should also clean your petcock and check for good fuel flow.
 
I had a similar problem with my GS750, but not as extreme. I eventually found that the fuel metering screws were incorrectly adjusted (the factory set ones you 'shouldn't touch' under the carbs). I set these to 5/8th turn out and the bike ticks over propery now.

Are you running standard jets and air box, are these new carbs jetted correctly?

Tony.
 
gs750es1983 said:
Not sure if I mentioned this or not, but now it only starts in the morning if I use starting fluid. Never had this problem before. (started before all of the other issues)
Heres a rundown of what I replaced in the correct order

petcock
Stator (havent replaced the R/R yet)
clutch cable
choke cable
plugs
air filter
I dont know if that helps anyone.

As far as starting in the morning with starter fluid... Starting procedure for most GS's is Full choke and no throttle. I personally put the petcock in Prime postition for a few seconds to insure fuel bowls have fuel.
Do you have more than 12 vdc at the battery?
Are you getting correct charging voltage from the R/R (~13-14vdc)?
What brand of plugs are you using?
You said you replaced the carbs. I would also pull the float bowls from #1 and/or #4 carbs(can do without removing carbs from bike) and check the starter fuel passage which has a tendency to clog.
 
Hmmm...sounds like the hell I went through with my Vulcan750 a year ago. Didn't know my left/front coil was going out and thought it was a fuel problem until I got on the highway to go to the salvage yard. That coil cut out and dropped me from 80 to 50 in about 3 seconds in heavy traffic.
Pulled over safely and checked out the bike after turning it off. Nothing. Started it right back up just fine. Got a few miles down the road and BAM, coil cuts out again. I figured then it was an electrical problem...something heating up and cutting out. I made it to the salvage yard and bought 2 new coils instead of a crash guard. Took off the tank and changed them on the spot. Bike fired up like better than new and has been running fine ever since. Of course my stator died a few months after that but that's another tale of woe...

:)
Dm of mD
 
sounds like several problems.
vacuum/air intake leaks need to be addressed.
small popping from carb intake could be a tight intake valve. could cause loss of power and low RPM too.
Big boom out exhaust means; ignition (spark) was lost, then came back and ignited all the unbuned fuel that passed through the cylinders into the exhaust system. Like ans "external" combustion engine. Poor ignition can also cause low idle and hard starting, and no power.
 
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