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No-start after carb rebuild

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

Anonymous

Guest
Last week, I completed a carb rebuild on my GS1100GL. I am now unable to start the bike. (I believe that it only ran before due to the extra gas dumping into the airbox from stuck needle valves.)

On full choke, it will catch, rev up for 2-3 seconds, then die. Sometimes, after long cranking, I can get it to sputter a little bit, but any throttle application kills it dead.

I did a complete rebuild, dipping the bodies, jets, and other assorted non-rubber parts. The pilot jets were completely clogged before the rebuild. The idle mix screws (on the engine side on these Mikuni CV's) are 2-1/2 turns out.

She's got spark, and I put in a new set of plugs to no effect. The air filter foam has some holes, so I wouldn't be suprised if it's running lean, but I'd still expect it to start!

Any ideas where to start troubleshooting here?

Thanks!

D
 
my bike was in a similar condition when I got it.. my 82 GS650G is very sensitive to the air filter and air intake leaks (if any). Check the condition of the intake boots from the carb to the engine.

Next check out your petcock valve on your tank. ensure the vac hose to the carbs works is intact and your petcock is working properly. (see if it starts when you put it on the prime setting)
Have you loosened up the screws on the bottom of the carb bowls to see if they are getting fuel?

When I tested my air filter, (mine is old too) I took an old t-shirt and stuffed it into the air-box, tried starting the bike, while I pulled the t-shirt out VERY slowly, gradually increasing the air intake to the carbs. Sooner or later you will get the air/fuel mix just right and if air is your problem it will start right up.

I dont know if you have done any or all of the above,
just some ideas..
Let us know
Tom
 
D,

Besides the carb cleaning, did you do "anything" else to the bike? As I understand it, you say it did run before, correct?

If the carbs are only thing that you touched, then are you sure hoses are hooked up correctly? If they are, then is petcock operating properly? If it is, then how are your carbs set up? Did you record screw settings before disassembly (if yes - did you try it with those exact settings?) Are float heights correct? Are floats moving freely? Are float needles sealing correctly? Did you look at plugs? (you said it 'started' to run a few times......if plugs are already black and fluffy, then you are currently too rich)...etc., etc., etc.

Don't know the year of your bike, so I don't know whether you have CV or VM carbs.......points or elect. ignition.......etc.

Quite a few questions here that need to be answered, :lol:
 
frosty5011 said:
Besides the carb cleaning, did you do "anything" else to the bike? As I understand it, you say it did run before, correct?
Click to expand...
Yes, it ran. Very poorly, and obviously super-rich.
frosty5011 said:
If the carbs are only thing that you touched, then are you sure hoses are hooked up correctly?
Click to expand...
Yup.
frosty5011 said:
If they are, then is petcock operating properly?
Click to expand...
Yup.
frosty5011 said:
If it is, then how are your carbs set up? Did you record screw settings before disassembly (if yes - did you try it with those exact settings?)
Click to expand...
No, I didn't. Stupid, yes, I know. The consensus around here seems to be 2-1/2 turns out, so that's where I put them when I was done.
frosty5011 said:
Are float heights correct?
Click to expand...
Not sure, will check.
frosty5011 said:
Are floats moving freely?
Click to expand...
Yup.
frosty5011 said:
Are float needles sealing correctly?
Click to expand...
Yup.
frosty5011 said:
Did you look at plugs?
Click to expand...
Yup. It hasn't run long enough to put any color on them at all. (New plugs -- the old ones were nasty black.)
frosty5011 said:
(you said it 'started' to run a few times......if plugs are already black and fluffy, then you are currently too rich)...etc., etc., etc.

Don't know the year of your bike, so I don't know whether you have CV or VM carbs.......points or elect. ignition.......etc.
Click to expand...
It's an '82. CV carbs. Electronic ignition, with good spark.
frosty5011 said:
Quite a few questions here that need to be answered, :lol:
Click to expand...
Hopefully I've answered them enough to keep getting ideas? ;)

D
 
MAGICTOM said:
my bike was in a similar condition when I got it.. my 82 GS650G is very sensitive to the air filter and air intake leaks (if any). Check the condition of the intake boots from the carb to the engine.

Next check out your petcock valve on your tank. ensure the vac hose to the carbs works is intact and your petcock is working properly. (see if it starts when you put it on the prime setting)
Have you loosened up the screws on the bottom of the carb bowls to see if they are getting fuel?

When I tested my air filter, (mine is old too) I took an old t-shirt and stuffed it into the air-box, tried starting the bike, while I pulled the t-shirt out VERY slowly, gradually increasing the air intake to the carbs. Sooner or later you will get the air/fuel mix just right and if air is your problem it will start right up.

I dont know if you have done any or all of the above,
just some ideas..
Let us know
Tom
Click to expand...

I'll definitely check out that t-shirt idea -- that's pretty cool! The carbs are definitely getting fuel. The petcock is working fine. I haven't looked at the boots yet, but now that I've resigned myself to pulling everything...again...I might as well. :)

Thanks!

D
 
I finished rebuilding my carbs a couple of weeks ago and experienced the same symptoms you have described. In my case I saw after switching to a clear fuel hose that the petcock wasn't delivering gas, even when on prime (you have no idea how much I hate petcocks). Make sure that your carbs are getting gas and that you have your vacuum and overflow/vent hoses hooked up correctly.

Good luck.

Jeff
 
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