Needle jet kit

[peter]

My Valk has truck stacks so the idle mixture needs to be enrichened or it will run lean and pop, spit, sputter, etc.., off idle.

I've turned the idle mixture screws out 3 full turns (vs. factory 2 1/2 turns) and it still stumbles ever-so-slightly off idle at low RPMs.  Nothing bad but noticable and consistent. I see 2 ways to go - either turn the screws out even more or go ahead and get a needle jet kit.

Which route would you take or is there something else to try?  Anyone have a kit to recommend?

Thanks,
Peter
'98 Tourer

[98valk]

3 turns is too rich for stock airbox and exhaust header pipes, which will cause a stumble. something else is causing the excessive popping.

[John Schmidt]

Agreed, mine are set at two turns out with stacks and stock airbox. I sometimes get a little burbling at low speed decel but I don't mind it. Actually makes it sound kinda powerful as you cruise by with that little rumble going on. There is no need for three turns or anything approaching that, something else is going on. We need more info on your complete setup.....type of intake filter, carb springs, trigger wheel, is it stock exhaust, what size slow jets.

[gordonv]

Unless you have done something else, my understanding, truck stacks are just a cosmetic cover. That means to me, that there is no change from stock pipes, so why would you need to adjust anything?

Popping to me, means an air leak, most likely in the header gaskets. I know there is more, but this is what I remember.

[Attic Rat]

Why don't you fix the problem and rebuild the carbs that is what is wrong with your bike. The o rings inside the carbs are worn out

[peter]

interesting responses.  To answer John's comments, the bike has a stock air filter, an IS ignition box, a 4-degree trigger wheel, stock headers with truck stacks, IS carb springs, stock slow jets, and needles have been shimmed.

The carbs have been pulled and gone through...twice. The o-rings on the idle screws seemed fine and I replaced the O-rings on the intakes.

I had the idle screws at 2 1/4 turns out and went back and changed it to 3 turns out, and it improved.  The popping stopped and there is just a small stumble off idle.

I greatly respect all those who have responded but there seems to be some discrepancies here.  maybe the aggressive timing makes it necessary to richen everything up.?


Thanks for your help.
Peter

[John Schmidt]

And why have the needles been shimmed? The rest of your setup pretty much shadows mine except I have a K&N without the prefilter. I do have 38 slow jets but they don't really change performance or mileage as much as helps keep the passages clear. What do the plugs look like, that can tell you a lot about how things are burning inside. Some stuff learned years ago on the drag strip; look at the end of the threaded body, if it's covered with black junk generally speaking your idle is too rich. The tip of the ceramic will usually tell you if you're running rich/lean at mid-range. The base of the ceramic is what you look at for how it's running under full throttle. A rich running engine won't burn off the fuel deposits and will leave the ceramic covered with it. Pull your plugs and post a picture.

When you went through the carbs, were the needle valves on the floats replaced? If not, it's kinda like turning up the radio to drown out the sound of a noisy lifter. 

[peter]

Dunno about the shims - previous owner.  But I do know the bike ran great for the 10 years I've owned her and the needles were shimmed and the idle mix screws were 4 turns out. Sounds crazy but it worked great.  The float valves were pristine and all the little plungers worked so I did not replace any of term.  I had a K&N air filter but changed back to stock as it was running too lean (when I checked the plugs)
I'll run it a bit and pull the plugs...

Again, the bike runs very well - I'm just trying to get rid of a very slight stumble at low throttle.

Thanks John

[big poppa pump]

Anything more than 2 - 2/12 turns is just way too rich. I have truck stacks on my Yellow Valk as well with a K&N without pre-filter, an IS ICM, IS Carb Springs, no trigger wheel but I've done the ECT mod and 38 slow jets. I have my screws out at 2-1/2 turns (might be a little rich) but my bike purrs like a kitten at idle and growls like a dragon when I take off. If you are having stumbling at idle at 3 turns, something is definitely amiss.

Turning out the screws anymore or adding a needle jet kit is definitely not the solution to your issue.

[Bagger John - #3785]

Anything more than 2 - 2/12 turns is just way too rich. I have truck stacks on my Yellow Valk as well with a K&N without pre-filter, an IS ICM, IS Carb Springs, no trigger wheel but I've done the ECT mod and 38 slow jets. I have my screws out at 2-1/2 turns (might be a little rich) but my bike purrs like a kitten at idle and growls like a dragon when I take off. If you are having stumbling at idle at 3 turns, something is definitely amiss.

Turning out the screws anymore or adding a needle jet kit is definitely not the solution to your issue.

Needle jet kit with a more aggressive taper - but with the e-clip set at the same height as the stock needles - will cure the annoying EPA-mandated flat spot around 2500RPM but will do little more with a "stock" exhaust and air filter.

My setups - Tourer and I/S:

Stock airbox, air filter and exhausts. Tips are changed but no baffle work to either system.
#38 pilots - air screws out 1 1/2 turns (both bikes)
Pro-Dyno jet needles - clips set second notch from top.
I/S carb springs (both bikes)
I/S ICM (both bikes)
Stock trigger wheel (both bikes)

Any more than 1 1/2 turns outward on the air screws with this setup gets things too rich, but they'll pull like no tomorrow. As they are, both are set up to run just a tiny bit richer than stock tune. It's the best balance between power and fuel economy, and power is definitely better than stock.

Agree with the other posters in the thread - you have air leaks and/or carb issues to find and correct.

[peter]

Thanks boys -  I did a carb sync at the same time I made the change to 3 turns out so I'll put the screws back to 2 1/4 turns out and see what happens. Maybe the carbs were way out of sync.

Is there a way to adjust the screws while the engine is running or with some test equipment so I don't have to keep guessing?

Thanks again - much appreciated.

[98valk]

it has a flexible spring head. been using it for yrs.
Honda tool.

07MMA-MT3010B WRENCH PILOT SCREW

[John Schmidt]

Peter, there's no guessing on adjusting the pilots. You turn the screw all the way, then mark your tool to correspond with a mark on something stationary. That way you can tell you've made a full turn each time your mark goes past, then turn another 90 deg. and you have the 1/4 turn.

[peter]

Yea, I get that part. I'm curious if there is a method of adjusting the screws based on actual performance, ie., adjusting the screws while the engine is running. How do we know 2 1/4 turns out is  any better than say 2 1/2 or 1 3/4 turns out?  Setting them all the same at an arbitrary setting is guesswork. 
Might be the best we can do, and I'm sure 2 1/4 turns out is close,  but it's anybody's guess what the peak setting is without looking at the performance of each individual carb. 

On my vintage bikes, you adjust this while the engine is running so you can determine the best adjustment based on actual performance.  But then again, it's easier to do with only 1 or 2 carbs. May not be feasible with 6.

[John Schmidt]

Pete, probably the biggest factor that prevents doing it while running....heat. A person needs baby size hands with 14" fingers to get in between the intake runners, therefore most end up removing at least one runner on each side just to get at the pilots. I've tried the Motion Pro doodad and got frustrated with it, even though I've cut a flat blade slot in the top of my pilots with a Dremel tool. Using the "D" shaped tool will drive a man to drink and often ends up messing up the head of the pilot screw you're working on because the metal is so soft. Granted, adjusting them while not running isn't a perfect science, too bad they're not the same carb as those on my GL1200. Those pilots are on the side of the carb and easily reached when running. And your fingers don't get blistered. 

After resetting those pilots, check your sync.

[peter]

Yea I agree. It's a curious design lapse in what is otherwise a wonderfully designed bike.
Thanks man.

[98valk]

Yea I agree. It's a curious design lapse in what is otherwise a wonderfully designed bike.
Thanks man.

as u mentioned your experience with other carbs, then u do know that u are only adjusting the idle and it doesn't affect much off idle. Most likely why the service manual doesn't instruct tuning while running. The tool I mentioned can be used while running if u desire.
www.factorypro.com has some great tech for CV carb tunning. I posted this over the yrs.
for your stock setup, what others have posted will be the turn setting to use. the manual gives info for altitude adjustment.