More carb adjustment questions

[dpcarson]

2000 standard.  Just pulled the carbs and rebuilt them cleaning all bodies and jets in the ultrasonic.  Still using the factory jets.  OK, when I am in neutral at idle, when I rev the throttle and then release it the rpms drop to 400-500 for a second and then recover to 900.  When revving up it will pop on the left side, when I am riding it and throttling down it will pop some.  Cylinder 4 is not hitting.  It is firing and I do have spark at the plug, but at slow speeds and starting off I can tell it isn't kicking, and at high speeds it feels and sounds like it is, as much as I can hear over the wind.  At idle, I can pull the plug wire off #4 and idle does not drop, so doesn't appear to kicking there either.  Have adjusted the idle screw on 4 everywhere from 1.5 turns out to 2.75 out and still do not have any kick out of 4.  Fuel is in the bowl.  Even pulled the bowl off and checked to make sure float valve was not sticking, blew out jets, pulled needle and checked diaphragm closely and movement of needle, and blew out all ports and jets.  Still no kick on 4.  After riding it plug showed like it was a little lean. 

Can one carb idle screw really be that different from all of the other carbs?  All the others are at 1.75 turns out.  Waiting on right angle driver to go through the manual's procedures for adjusting carb screws now, but any ideas while I am waiting.  Got a weekend to tinker before the new tool shows up.

So, far you carb wizards, any ideas?

[da prez]

Switch coils after checking to see you didn't knock a wire off.
 If miss goes to another cylinder , you may have a bad coil.

         da prez

[John Schmidt]

And those screws you're referring to aren't idle screws, they're mixture adjustment. You only have one idle adjustment on the entire carb set...that's the grey knob accessed from the right side in front of #3 intake runner.

[CoreyP]

To answer one question, no one carb should be that far off adjustment of the other carbs. If you sync the carbs, your air/fuel mixture should about the same on every carb.  

I have never done a 6 carbs rebuild so I don't have much more to say but I have done V twins and other bikes. It kind of sound like fuel starvation to me but why on one carb? Bad fuel line coming in, leak? Does that carb leak? Not sure what you have going on.

Not missing a spring or something like that? You have a few things which could be wrong and why I really don't want to rebuild my carbs.

Hey to cheery you up, the guys at motorcycle shops that know how carbs work is getting smaller every day. My local Honda dealer said "Honestly I don't have a guy who knows how to work on your bike. " I was getting some small parts and asked if I needed some major work done and that was his answer.

[dpcarson]

To clarify, yes, it is the mixture screws not the idle adjustment screws that I use for syncing.  Vacuum sync had all six carbs spot on. 

Corey, I probably need to start calling Honda shops and ask them how old their oldest tech is. LOL

I guess I will do yard work today and just wait on the motion pro screwdriver.  Or, I think I might have heard the IS miss when riding the other day.  Maybe I should go for a long ride on it so I can check the plugs afterwards!!

All I know to do is wait and try the full adjustment sequence in the manual when the motion pro gets here.  Anybody with other ideas please let me know.

[Foozle]

05-09

You say you're running stock jets (35 slows, 100 mains).  Are you also running factory needles, air box/filter, and factory exhaust?  If so, 1.75 turns strikes me as a tad lean.  2 1/4 turns is closer on most factory setups. Obviously, however, this isn't a perfect "one size fits all."

I had an issue with the front cylinders (1 & 2) not firing after a carb rebuild - which turned out to be a disconnected wire to the left front ignition coil.  I'm not sure which of the other two coils fires the #3 and #4 cylinders, but I'd examine this closely (as has been suggested).  It could also be a bad plug wire, poor connection, or even a faulty spark plug.  Check the easy stuff first.  

A good read on jetting, carbs, etc. can be found in the tech archives at:

http://www.valkyrieriders.com/shoptalk/jetting.htm

Terry

[98valk]

    NOTE: A rich problem gets worse as the engine heats up.
        If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.
    NOTE: A lean problem gets better as the engine heats up.
        If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!

http://www.factorypro.com/tech/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

[dpcarson]

OK< Additional question.  I pulled the jets out with the carbs still in place.  Got them in the ultrasonic.  I pulled the Mixture screw and and blew air through it with a hose attachment and had plenty or air come through the orafice at the butterfly.  Tried to hold my finger over that orafice really tight and could not hear or feel any air coming out anywhere else.  Does that orafice and the idle mixture screw port connect to the press in jet?  I also pulled the slow jet and do not seem to be getting any air through it.  Using the carb jet cleaning wires I cannot get it to go all the way through the jet.  I am guessing it should.

Any input?  I am not sure where the gas should be coming through at idle.

[Hook#3287]

OK< Additional question.  I pulled the jets out with the carbs still in place.  Got them in the ultrasonic.  I pulled the Mixture screw and and blew air through it with a hose attachment and had plenty or air come through the orafice at the butterfly.  Tried to hold my finger over that orafice really tight and could not hear or feel any air coming out anywhere else.  Does that orafice and the idle mixture screw port connect to the press in jet?  I also pulled the slow jet and do not seem to be getting any air through it.  Using the carb jet cleaning wires I cannot get it to go all the way through the jet.  I am guessing it should.

Any input?  I am not sure where the gas should be coming through at idle.

I'm definitely not a carb expert, but have replaced many a slow jet.  Every slow jet I've ever seen has a hole in it.

[CoreyP]

If you can't get something small enough (?) through the jet, it is clogged. I say small enough because are you sure what you are using is small enough? They make drill bits for jets and they are tiny. Put the jet over a bright light and see if you can see the light coming through. You should be able to see a pin point of light. Then you would be able to see for the next 15 minutes but.... 

[rug_burn]

   In my case, yes, one carb can have its mixture screw way different than the others, in my case, because I didn't get it totally clean, I believe.    One of mine is almost all the way out, where the brass is nearly level with the ring of the carb body around it.   But even with this, it runs pretty good  all in all.
     Actually I need to go back and check the vacuum sync and mixture again using that technique I told you all about, one more time.   That mixture may still be way off from when I was compensating for that hole in the vacuum hose, before I discovered it.

Also- check that other post about 'popping on decel'  sounds like you may have the same thing.

And as for those idle jets, yes, they should be clear all the way thru, you should be able to see  light thru them.     You can just replace them-  they're $6 apiece, because IIRC, the orifice is so small, it's hard to get a drill small enough.    I seem to recall it was about .012"

-Paul

[Forge]

OK< Additional question.  I pulled the jets out with the carbs still in place.  Got them in the ultrasonic.  I pulled the Mixture screw and and blew air through it with a hose attachment and had plenty or air come through the orafice at the butterfly.  Tried to hold my finger over that orafice really tight and could not hear or feel any air coming out anywhere else.  Does that orafice and the idle mixture screw port connect to the press in jet?  I also pulled the slow jet and do not seem to be getting any air through it.  Using the carb jet cleaning wires I cannot get it to go all the way through the jet.  I am guessing it should.

Any input?  I am not sure where the gas should be coming through at idle.

Your carbs need to be pulled to properly clean them. If you are blowing air into the hole that the pilot screw was in, and you held your finger over the pilot hole in the carb throat, you should have air come out of the 3 small transition ports just under the butterfly as well as through the air jet in the intake of the carb on the airbox side.

[dpcarson]

Thanks guys.  Soaked the jet for 12 hours in berrymans, then an hour in the ultrasonic, then 12 hour in berrymans, then another hour in the ultrasonic, now back in the berrymans until tomorrow afternoon.  After that I am going to reinstall and try again. 

The carbs were pulled last time (four weeks ago) and completely disassembled.  All carb bodies were soaked for an hour in berrymans and then spent 2 hours in the ultrasonic before being blown out.  I REALLY hope it is the jet because I do not want to pull the carbs apart again.  But what is a guy to do.  Everything else is running good and the plugs look like they are burning clean and just about right on the mixture.  Just #4 that wants to be a PITA.  Might try ordering a new jet before pulling the carbs again. 

[Forge]

Thanks guys.  Soaked the jet for 12 hours in berrymans, then an hour in the ultrasonic, then 12 hour in berrymans, then another hour in the ultrasonic, now back in the berrymans until tomorrow afternoon.  After that I am going to reinstall and try again. 

The carbs were pulled last time (four weeks ago) and completely disassembled.  All carb bodies were soaked for an hour in berrymans and then spent 2 hours in the ultrasonic before being blown out.  I REALLY hope it is the jet because I do not want to pull the carbs apart again.  But what is a guy to do.  Everything else is running good and the plugs look like they are burning clean and just about right on the mixture.  Just #4 that wants to be a PITA.  Might try ordering a new jet before pulling the carbs again. 

Read my above. If air is not going through anywhere (3 transition ports in the throat, pilot jet hole, and air jet) when you blow into the pilot screw hole and cover the pilot hole in the throat, you have plugged passages in the carb body.

[Ricky-D]

^^^^^ THIS ^^^^^

[9Ball]

Also, I always recommend replacing the jets with new rather than trying to clean them.  I find the cost to be less of an issue than pulling the carbs a second time and then replacing them anyway.  If there is a continuing problem, then it’s not related to the jets if they are new.

Just based on my experience and those that I’ve helped hands-on rebuild their carbs ( I’ve done five so far).

Most important next to replacing the jets is making sure the carb bodies and all the ports are scrupulously clean.  The last two rebuilds I did also involved testing and replacing o-rings and plugs on the air cut valves.  Aged elastomer components on the air cut valves contribute to the popping on decel that seems to be a common complaint following refurb. Many of our bikes are now more than 20 years old and it seems like quite a few have gotten to the problem point regarding our seals, o-rings, tubing and rubber components.  The lousy ethanol fuel has been an ongoing issue that won’t get any better moving forward.

Good luck...hope you get this sorted.

[John Schmidt]

As I recall(always questionable), I know the front coil on the left side under the tank fires #1 & 2. Then I believe the middle coil fires #3 & 4, and the most rearward coil fires #5 & 6.

I'm sure someone will correct me if I'm wrong. 

[dpcarson]

To go with that question, a coil is either all bad for both cylinders it fires instead of having one go out, is that correct?  Going to check plug wire as final attempt before pulling carbs again to clean the body.  Got the jet clean with air going through it finally.  Still didn't fix the issue.

[Hook#3287]

To go with that question, a coil is either all bad for both cylinders it fires instead of having one go out, is that correct?  Going to check plug wire as final attempt before pulling carbs again to clean the body.  Got the jet clean with air going through it finally.  Still didn't fix the issue.

My first experience with cleaning slow jets went like this.

1. Remove carbs.
2. Pull slow jets.
3. Soak jets in some cleaning chemicals (can't remember what) over a couple days.
4. Hand clean jets and use wire brush strands to clean out  orifice of each.
5. Reinstall jets.
6. Reinstall carbs.
7. Start bike, still running rough.
8. Get pissed off.
9. Repeat steps 1 & 2.
10. Install new 38's
11. Repeat steps 5 & 6.
12. Start bike, smile.


That was in 2008.

I don't do steps 3 & 4 any more because I don't enjoy doing doing steps 1,2,5 & 6 that much.

Just my personal experience.