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1980 GS850l fuel delivery problems

  • Thread starter Thread starter JHook
  • Start date Start date
J

JHook

Guest
So, this issue has me wanting to punch a hole in my shed wall...Recently rebuilt top end,dipped,cleaned and rebuilt carbs, new petcock, resealed airbox, etc. Bike was running great no issues apparent, then I parked it overnight, came back out to start it and it fired up but barely ran off just one cylinder. Checked compression, checked timing at cams and crank, rechecked valve clearance, check for spark on all four-everything good and in spec. I then disassembled and checked carbs for any defective parts and hit each passage with compressed air and carb cleaner (again)..did this twice actually. Reassembled and engine did the same thing. Then after not running for several days, I couldn't get it to start. I took it to an experienced friend who has worked on many a GS and KZ. After a little bit of ether (i know, yikes, but it worked) he got it running good on all four cylinders. It was running great and I rode it home 15-20 miles, no problems. I parked it in my shed for the night and went back out to start it again the next morning. Started right up but again barely ran off one cylinder exactly as before. Any thoughts on what could be causing it to run great, but then just run off one cylinder after being parked overnight? Is my shed cursed?!
 
I think I'd try to figure which cylinder was firing and which ones were missing. After you get it running one one cylinder, kill the engine and pull the plugs to see which are firing, and you may get some indication as to why. Are some dry and white forms no fuel or.or they rich and wet? Rich and wet could be a fuel problem, spark issue or compression.

By any chance could you have gotten some bad or old gas?
 
Cylinder one is the only one firing. I discovered this when the problem first came up because it was the only exhaust pipe that wasn't cold. I've got big blue spark on all four and plug on cylinder one indicates rich. Again, this is happening as the bike sits overnight after running perfectly the day before on all four cylinders. I have tried draining tank and refilling with fresh gas, getting same results.
 
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Do you park it in shed on kickstand? Anyways, I suspect that your new petcock is leaking in its "ON" spot. Smell your crankcase oil. Disconnect fuel line from petcock next time you park it overnight and see if you spot fuel dribbles on engine.
 
Bring the bike (or just the carbs) over to my place, we'll figure it out.

Can verify proper assembly of the carbs, then put them on my bike to isolate whether the problem is carbs or something else.

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Steve, you're awesome. Thank you so much for generously offering to help me in person! Ok...removed the float bowls again and hit the passages in the bowls. Apparently some gunk got lodged in the passage for the enrichener pickup inside the bowl for carb #4, so I cleaned it out with smallest drill bit I had. I know I cleared these once before..anyway, reassembled and fired right up on all four. That will make 4 times total I think that I've had these carbs apart and cleaned to get it all right. Each time I thought I had them totally clear. Thanks to Grant at Rice Paddy Motorcycle Salvage for throwing out the suggestion for this and thanks to folks on here chiming in! Only problem now is idle is super high at start and doesnt want to drop no matter if I twist throttle and let off or dial down the idle adjust knob...stays at 3000ish rpms!?
 
Assuming that you have the choke/enrichment nob pushed in.;) Might be the enrichment slide isn't returning all the way back.
 
Idle hovers right around 3000. I had choke on at first..fired right up to 3k, after I bumped starter a few times to get the vac operated petcock going. Now it stays on really high idle choke on or off. If I pull choke out now it raises idle above that. The throttle cable seems to be functioning fine, and turning idle adjust knob doesn't seem to make a difference.
 
Steve said:
Bring the bike (or just the carbs) over to my place, we'll figure it out.

Can verify proper assembly of the carbs, then put them on my bike to isolate whether the problem is carbs or something else.

.
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When you bench synced the carbs, did you adjust all the carbs to #3? Does the idle adjustment screw close the plates completely when unscrewed? Did you vacuum sync the carbs?

Could also be a vacuum leak.

Have all the intake O-rings behind the intake boots been replaced? All the synchronize screws installed and tight? All intake boots screwed down? All intake boot clamps tight?
 
I worked on a 550 about a month ago that would not idle below about 3500. Carb sync was WAY off. #3 (the 'master' carb) was closed (the idle adjuster knob was not even touching it), the others were open almost 1/8". Did a bench sync to get them close, then a vacuum sync after it was running, it now works just fine.

Remember: every shortcut you take is just another opportunity to do it over and DO IT RIGHT. :encouragement:

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I did a bench sync, actually, following instructions I found on Bikecliff's site I think it was. I haven't vacuum sync'd, but again, the last ride I took it on it ran great at various different speeds. Is it possible my bench sync could have been thrown off? The high idle at startup is a new issue as of cleaning the carb bowls, wasn't doing this before.
 
Bench sync won't be "thrown off" unless you did not tighten the locknuts.

Have you tried turning the idle speed adjuster? With clean carbs, it's running better, so a higher idle is not unusual.

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Yeah turning the idle speed adjuster down made little to no difference
 
Weather looks decent this weekend, come on over. If you don't want to trailer the bike (or put it in a truck), just bring the carbs, we can test them on my bike.

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Thanks, Steve! I will see if I can't get this worked out in the next couple days. I will let you know if I can make it out there.
 
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