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carbs cleaned and installed but bike don't want to run

  • Thread starter Thread starter Master077
  • Start date Start date
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Master077

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I have a 1982 gs750. Last week I pull and cleaned the carbs. After I installed the carbs the bike doesn't want to run correctly. It will only run with choke completely out and with petcock on prime. I set the screws 1 1/2 turns out. What should I do? Should I turn the screws out more? The manual says to turn them 1 1/2.
 
The odds are that if it's jetted right, and if you haven't modified the intake that you have an air leak between the carb and the cylinders. Spray starter fluid around the intake boot and if it surges then you know you have a leak.
 
I just tried that and nothing happened. What should I do now?
 
Your idle circuits aren't delivering- you are compensating using "choke" to make up for lack of mixture getting thru to carb throats. Try 2 to 2.5 turns out on mixture screws. Did you dip carbs? replace carb o-rings?

Your petcock is not to blame for this problem if it delivers fuel to carb bowls.
 
As Cowboy eluded to..a simple spray with carb clean is a waste of time and carb spray. A full 24 dipping for the bodies and parts is the only way to be 100% sure the passages are clean.

You must flush them with lots of carb spray and air after the dipping to further flush loosened stuff out. And also be sure to take a fine wire and poke the holes pilot jets and be sure to get the hole in the very end of the pilot jets, and poke all the holes clean in the mixture tube. Again flush them with spray and air.

NOTE.....Some pilots dont have the bigger holes around the perimeter, but they all have that tiny hole in the tip. Must be sure that is open.
 
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Did you connect the vacuum line between the port on #2 and the petcock?
 
If you are getting fuel to the carbs Id say the pilot jets or passageways are plugged up. Did the bike run before the rebuild ?
 
I dipped the carbs and I replaced the orings. The bike ran before the rebuild. I think the petcock might have a block in the vacuum line.
 
I wouldn't think that the petcock issue would cause the bike to not idle without choke once the float bowls are filled and the engine is warm. Putting it on prime should take the petcock completely out of the equation as from a fuel starvation standpoint. Try blocking the vacuum port on the #2 carb and running it on prime. That may rule out a vacuum leak at the petcock. Are you sure you didn't break off the tips on the pilot screws when initially seating them? Does adjusting the screws out help at all?
 
Master077 said:
I set the screws 1 1/2 turns out. What should I do? Should I turn the screws out more? The manual says to turn them 1 1/2.
Click to expand...
As much as we preach "read the manual", there are some times that it is simply ... not quite right. :-k

The 1 1/2 turn setting was to satisfy the EPA requirements that were coming through at the time. It ran like crap and took forever to warm up to the point where it would run without "choke".

Yes, you need to turn them out more. How much? That depends on who you talk to and how much fiddling you plan on doing when it gets running. Personally, I start with the concept that a richer mixture works better with a cold engine, so I start with the screws out three full turns from lightly-seated. Yes, that is actually too much for normal running, but you are only trying to start it so you can fine-tune it. The richer mixture also helps the "choke" a bit, so you can get off that circuit sooner. Of course, when the bike is warmed up, you will need ti fine-tune the screws. They might end up in the 2 to 2 1/2 turn range, but it will be easler to come down to that (from three turns) than it will be go up.

.
 
Remove the vacuum tube from the rear of the petcock. This is the smaller tube to the rear of the petcock. Block it off so that no air can enter the carburetor from this hose. Leave petcock in prime position. Try to start.

If you have any doubts about petcock have a look at the tutorial on Basscliff's site: Petcock Tutorial.

But if it was working before the carb strip it is likely to be working after. Therefore something has not been cleaned or correctly re-assembled.

The first time I did a carb rebuild, I put the carb to engine boots on upside down, the choke return spring between the wrong 2 carb bodies and tried to start the engine without blocking off the vacuum pipe that goes to the petcock (why would you need to connect that when you can just put it on prime!!).

Hey - you do have to learn by making a few mistakes. Keep going you are nearly there! Good job.

Here is my: Rookie Carb Instal Mistake

Greetings
 
Running on the choke only is a classic symptom of plugged pilot jets/ pilot jet passages. Maybe when you dipped them, crud just got moved around in the carb bodies and has found a home in your pilot jet passages. With the pilot jet out you should be able to shoot contact cleaner in the jet hole and see a stream come out into the throat of the carb. No spray= passage plugged.
 
I got my bike to run off choke, it will run perfect with petcock on prime. When I move the peacock to run that's when I start to have problems. The bike will ideal OK but when I add throttle and let off the throttle it will bog down run for 15 seconds then die. It sounds like it's not getting enough gas. Is there something I should adjust? I set the screws 3 x out? Should I pull the carbs a part
 
Set them at 2 1/2 out with the petcock on PRIme and see how it reacts there..if "better but still not quite right"..then you go 1/8 in from there and search out the sweet spot. have the airbox or pods on it just as if you are going down the street and start tweeking.

I can tell you that at 3 out its almost 100% assured it way to rich already and any more out isnt gonna change chit.
 
I will try that. Do you have any idea why It doesn't want to run correct with the peacock on run?
 
Youre petcock is junk or you dont have the vacuum line hooked up so it will work right. Your number 2 carb ( second from the left side ) has a brass nipple on it and thats the vacuum for the petcock. If its not hooked to the petcock and is wide open..then its a massive vacuum leak on that cylinder.

A vacuum line MUST be from that nipple to the small nipple on the petcock. There are 3 positions PRIme..which youve figured that out. Then there is ON..which will only work if the vacuum is hooked up. Then theres REServe..which work the same as the ON but only once the tank is low enough that it starts to sputter and you then switch to REServe. Yes the bike will run on REServe with a full tank also if the vacuum is hooked up.

When the bike isnt running you ALWAYS want it in the ON position to prevent fuel overflow that can contaminate the crankcase oil with raw gas..not a good situation .
 
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