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Bogging at 4K..many steps have been taken (video also)

  • Thread starter Thread starter Roemy24
  • Start date Start date
R

Roemy24

Guest
Everyone,

1980 GS850L that I bought last spring and wouldn't run without choke on and didn't idle very well either. After much trouble last year getting the carbs apart and other misc. issues I have made some real progress this spring. I'll try to give as much detail as I can. I hoping to get this bike fixed to actually take a ride but at a loss again. Thanks in advance for any suggestions!

The issue right now is that it starts and idles great! After 45-60 seconds I can idle with no choke. After it warms up it will rev up to 4000 rpm but then die out like it's not getting gas. I can at the first time crack the throttle (multiple times) and hit 6000 with ease. After that though I can only get 4000 and if I try to stay on the throttle at a constent it will only reach 2500-3000. With the choke pulled at this point it will race right back up to 5000-6000 with backfiring out of the mufflers.

http://www.youtube.com/watch?v=wHdzaol-6yM

-new intake boots/clamps
-new intake o-rings
-new airbox boots/clamps
-coils test good
-valves verified (changed 3 shims)
-new spark plug caps (NGK) since the old ones had no resistance
-carbs have been cleaned 3-4 times (dipped each time) and the last time each sat in for 24 hrs. All jets also cleaned.
-new o-rings throughout the carbs
-airbox is sealed
-K&N air filter in stock box which was recharged but I ended up cleaning it again with concerns there might be to much oil on it.
-Bench synced and Morgan tuned
-All electrical connections cleaned
-R/R replaced from Duaneage (old one was shot)
-Stator tested marginal at 60-65 however I couldn't rev up to 4000 or keep it there for good readings
-New battery
-Fuse box cleaned
-Air screws are at 2.5 out from lightly seated
-Testing using a satellite tank with clear gas line (to eliminate petcock which is new as of last year anyway), vacuum line has been plugged
-Gas is easily getting into the carbs with no leaks anywhere
-Floats are adjusted to spec and needle moves freely to allow or stop gas
-When I posted my last video of the carb slides everyone said that they looked fine in operation.

The only thing I can think of is that there may not be enough of a vacuum in the system to raise the diaphram/slide/needle. This is the part of the throttle response where there is an issue. I can not find any air leaks or any signs of a leak in the system though. I can verify that the passage of air for the main jet is clear but as far as I remember it was fine when I checked them over after cleaning.

HELP PLEASE!!!!! :confused:
 
Last edited:
How volts at the coils?
Check the igniter. saltymonk had the same issue and we farted around with the carbs but it turned out to be a toasted igniter.
I have an extra one if you need one.
 
Chef....can you give me a little more guidance. How do I test the volts to the coils? Do I just check the pos/neg. of the wires going into each coil? Running, not running or just the key on? Also how do I test the igniter and even more important, where it is located :eek:. I can get readings tomorrow evening. Thanks
 
Roemy24 said:
Everyone,

1980 GS850L that I bought last spring and wouldn't run without choke on and didn't idle very well either. After much trouble last year getting the carbs apart and other misc. issues I have made some real progress this spring. I'll try to give as much detail as I can. I hoping to get this bike fixed to actually take a ride but at a loss again. Thanks in advance for any suggestions!

The issue right now is that it starts and idles great! After 45-60 seconds I can idle with no choke. After it warms up it will rev up to 4000 rpm but then die out like it's not getting gas. I can at the first time crack the throttle (multiple times) and hit 6000 with ease. After that though I can only get 4000 and if I try to stay on the throttle at a constent it will only reach 2500-3000. With the choke pulled at this point it will race right back up to 5000-6000 with backfiring out of the mufflers.

http://www.youtube.com/watch?v=wHdzaol-6yM

-new intake boots/clamps
-new intake o-rings
-new airbox boots/clamps
-coils test good
-valves verified (changed 3 shims)
-new spark plug caps (NGK) since the old ones had no resistance
-carbs have been cleaned 3-4 times (dipped each time) and the last time each sat in for 24 hrs. All jets also cleaned.
-new o-rings throughout the carbs
-airbox is sealed
-K&N air filter in stock box which was recharged but I ended up cleaning it again with concerns there might be to much oil on it.
-Bench synced and Morgan tuned
-All electrical connections cleaned
-R/R replaced from Duaneage (old one was shot)
-Stator tested marginal at 60-65 however I couldn't rev up to 4000 or keep it there for good readings
-New battery
-Fuse box cleaned
-Air screws are at 2.5 out from lightly seated
-Testing using a satellite tank with clear gas line (to eliminate petcock which is new as of last year anyway), vacuum line has been plugged
-Gas is easily getting into the carbs with no leaks anywhere
-Floats are adjusted to spec and needle moves freely to allow or stop gas
-When I posted my last video of the carb slides everyone said that they looked fine in operation.

The only thing I can think of is that there may not be enough of a vacuum in the system to raise the diaphram/slide/needle. This is the part of the throttle response where there is an issue. I can not find any air leaks or any signs of a leak in the system though. I can verify that the passage of air for the main jet is clear but as far as I remember it was fine when I checked them over after cleaning.

HELP PLEASE!!!!! :confused:
Click to expand...



maybe needs to warm up!! my manual says mine needs to warm up for 10 minuets!!!
plus it will need to warm up if its low on compression,
chk slides,to see if there in correct!! they will only go 1 way with the tab seated,and i rubber cemented mine so they were sealed, not a lot just enough around the ring, to seal them
pilots cleaned?? are yours under the (plugs)????
 
10 minutes seems awfully long to have to warm up. Well maybe completely but I should be able to drive it after a few minutes. I'll be really disappointed if I do actually have to wait that long. Compression was good, I don't remember it off hand since I did it last year but within spec. Slides function correctly with the tabs of the diaphragms in the correct location also. Pilots are clean. The air screws where under caps that have been removed for cleaning purposes.
 
cyclefvr2 said:
maybe needs to warm up!! my manual says mine needs to warm up for 10 minuets!!!
Click to expand...
WOW!!! :eek:

Good thing I have not read a manual. :o

Even though ALL my bikes are relatively quiet, I'm sure my neighbors would not care for a bike warming up for 10 minutes at a time. ALL of the bikes in my care start very easily, take between 30 and 60 seconds before they can be ridden out the driveway, then the 'choke' is turned OFF between the 1-2 and 2-3 shifts.

I think what the manual might mean is that it takes about 10 minutes of riding for all parts to get up to full operating temperatures. With that, I will agree.

.
 
Just a point of reference. I had a similar problem, plus some others, with my 1981 GS850GT a few months ago. Replacing the main jets to factory (#115) allowed me to get up to and above 5,000 rpm consistently. Also do the cylinders on the jet needles easily slide? You might want to look at some of the responses I got from my pleads for help. Bob Gibson
 
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