Pilot screw turns: the saga continues

[Guest]

Need carb baseline pilot screw turns. Reinstalling and need to know where I should start

 

[cowboyup3371]

What bike are you talking about and are they CV or VM carbs? Put at least your model in your signature block so you don't have to remember to tell us

 

[Guest]

I used to have it there, im sorry. No idea where it went. It’s an 83 gs750es. I’m having trouble with cylinder 2 not firing so this question is kinda not important at the moment. I’m feeling stupid and frustrated.

 

[Steve]

Since a rich mixture fires more easily than a lean mixture, when I rebuild a set of carbs, I set the screws at three full turns out from LIGHTLY seated. When the engine is warm enough to run without the "choke" (only takes a minute or so), you can start turning the screws IN to lean the mixture for best running. They may end up in the 2 to 2 1/2 turn range, and they won't all necessarily be the same.

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[Big T]

Is the vacuum line attached to #2?

 

[Guest]

Ok diagnosing the idle circuit. Pilot jets look great. Screw looks good. I can shine a light down the bore and see it through the screw hole. However when I blow air into the pilot jet in the bowl im not feeling it come out either the air jet on the horn or the tiny hole under the screw in the bore. Am I right in thinking it’s blocked with this test. Air does come out the main which is closely connected to the pilot and out the hole in the horn opposite the air jet.

 

[Guest]

It’s doing this on all four which tells me it’s ok, however in studying the diagrams in manual and how the pilot jet is supposed to feed the idle circuit when the throttle is shut I would think some air should flow.

In case anyone has been following my issues I solved the dead #2 cylinder. It turned out to be a blocked pilot which occurred because i used a citrus cleaner on that carb in my ultrasonic. Don’t use citrus degreaser. If left on it will create a green oxidation on the brass which will plug if it’s not thoroughly rinsed afterwards. The carb body also lost its shine and developed white oxides which had to be wiped off. Hoping this isn’t also what happened in the passages. I bought berrymans dip after that to use instead. Lesson learned.

 

[Guest]

At this point I’m contemplating grabbing a guitar string and probing some passages

 

[Steve]

Ok diagnosing the idle circuit. Pilot jets look great. Screw looks good. I can shine a light down the bore and see it through the screw hole. However when I blow air into the pilot jet in the bowl im not feeling it come out either the air jet on the horn or the tiny hole under the screw in the bore. Am I right in thinking it’s blocked with this test. Air does come out the main which is closely connected to the pilot and out the hole in the horn opposite the air jet.

It is hard to judge air flow by blowing through the pilot circuit from either end. If you blow from the bowl end, you will have most of your air going through the passage into the main jet / needle jet area, as you have noticed. If you remove the pilot screw and blow back that way, you have to block the hole below the pilot screw, but then there are two or three more holes that are right at the top of the butterfly that you can not easily block.

Not sure how well Berryman's works with an ultrasonic cleaner, but a 20-24 hour soak will do wonders. I follow up a soak session with a blast of carb cleaner spray through the appropriate holes, and that is followed by a blast of compressed air to blow any blockage out. This usually works best if you blow from the pilot screw end to backflush the passages. When the passages are clear (no jets installed), you can definitely hear and feel air flow.

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[Guest]

im not excited about spending another week tearing them down and soaking again but it looks like im gonna have to. I have other bikes to fix in the meantime

 

[Steve]

Your other option is to not dip them and have it run like crap forever.

A little time invested now (even if it is a full week) will get you a LOT of smiles later. :encouragement:

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[Guest]

And that is why I do it! Thank you for the encouragement. This time I’m going to soda blast them as well to try to get them bright again

 

[Guest]

I must be getting good at this. I already finished cleaning the carbs again and even soda blasted a few that had taken a dullness from cleaning. I picked up Berryman’s carb spray and really made sure The passages weren’t blocked. I’ve got the internal circuits pretty much memorized now. Lol. So i put them back in and it’s still stalling out under 2k rpms. I notice that the rpms hang a bit when they should be coming down. I spent a lot of time consuming exhaust fumes while I played with the mixture screws. It’s really hard to read what’s going on there. I was able to keep it running while I turned them completely out. Of course there’s a lot of fumes coming out of the pipe and the plugs got sooty. The odd thing is there’s a lot of fumes with them turned out less than halfway as well. So I experimented with turning them all the way in and moving around under 1/2 turn out. I found it odd that I can keep the bike running with them all turned in. Fumes are not pouring out the pipe like before. I can actually get the idle down pretty low- 1k-1.5k but it’s very lopey and sounds like a diesel. I was checking plugs at all the settings and they did not look scary when The screws were in all the way. And that’s with the hotter B7EA plugs. I’m starting to think either my pilot jet or air jet need to be changed. I feel like I have too much fuel even while screws are turned in. I can’t explain the lopeyness of the engine at this point. But I’m just trying to get it to idle right now. I have it bench synced but I can’t do a dynamic sync until I can idle it without fiddling with the idle screw and being paranoid it’s gonna stall. If Im turning an adjustment screw and can’t get it to die then doesn’t that mean it’s time to go down a pilot or up an air jet?
If anyone can share what they think about my pilot and air jets I’d greatly appreciate some guidance.

 

[Guest]

Test signature

 

[Rob S.]

I must be getting good at this. I already finished cleaning the carbs again and even soda blasted a few that had taken a dullness from cleaning. I picked up Berryman?s carb spray and really made sure The passages weren?t blocked. I?ve got the internal circuits pretty much memorized now. Lol. So i put them back in and it?s still stalling out under 2k rpms. I notice that the rpms hang a bit when they should be coming down. I spent a lot of time consuming exhaust fumes while I played with the mixture screws. It?s really hard to read what?s going on there. I was able to keep it running while I turned them completely out. Of course there?s a lot of fumes coming out of the pipe and the plugs got sooty. The odd thing is there?s a lot of fumes with them turned out less than halfway as well. So I experimented with turning them all the way in and moving around under 1/2 turn out. I found it odd that I can keep the bike running with them all turned in. Fumes are not pouring out the pipe like before. I can actually get the idle down pretty low- 1k-1.5k but it?s very lopey and sounds like a diesel. I was checking plugs at all the settings and they did not look scary when The screws were in all the way. And that?s with the hotter B7EA plugs. I?m starting to think either my pilot jet or air jet need to be changed. I feel like I have too much fuel even while screws are turned in. I can?t explain the lopeyness of the engine at this point. But I?m just trying to get it to idle right now. I have it bench synced but I can?t do a dynamic sync until I can idle it without fiddling with the idle screw and being paranoid it?s gonna stall. If Im turning an adjustment screw and can?t get it to die then doesn?t that mean it?s time to go down a pilot or up an air jet?
If anyone can share what they think about my pilot and air jets I?d greatly appreciate some guidance.

EDDIE! The paragraph key! Find it. Use it. It's a good thing.

 

[Guest]

I like it BIG! Paragraph key?? You mean return? They’re over rated

...and I thought maybe someone had a reply

 

[Big T]

Let's see

No mention of proper dipping of the carb bodies or new O rings

How many times are you going to short cut the process?

 

[Rob S.]

I like it BIG! Paragraph key?? You mean return? They?re over rated

...and I thought maybe someone had a reply

We don't do rapping here. Or word wrapping.

 

[Guest]

Let's see

No mention of proper dipping of the carb bodies or new O rings

How many times are you going to short cut the process?

yes that’s all been done. You can eat off my carbs. Nothing is dirty blocked. As i said in another thread all the basics are covered. Valves, vacuum line, carb boot seals. This is a jetting issue. And definitely a carb issue

 

[Guest]

I’m trying to re-read everything I can on setting CVs up and another thing ive been resistant to is tuning for full throttle first. If the main is important for every stage then I’ll need to do that. It’s just counter intuitive for me to start up a bike that will die without choke or a lot of idle screw and wail on it down the road.
here in Michigan it’s been snowing one minute and sun shining the next. Not fun times to be tuning a bike on the road... maybe this weekend.
I’m just surprised no one has insisted I tune for the main before worrying about idle.