Another (can u believe it ) carb question.

I spose I should know this stuff, but I don't. Tried the search function and got no definitive results/answer, so here goes.

I decided to double check my carb tuning as I was doing the spring oil change/plug change maintenance thing. VooDoo has always idled low (900 or so) and I got some vacuum gauges to do it right. I used a home-made fluid gauge and I never felt comfortable with the results. Anywho....

I noticed when I pulled my plugs 1 and 4 looked pretty good, maybe running a tad rich, while plugs 2 and 3 looked to be running on the lean side, so I figured this would be a good tome to tweak the carbs. EDIT: I should also add that I was revisiting my carb settings due to adding baffles to my exhaust in an attempt to save my hearing in my advancing year lol

I made the flow restrictor found here, and hooked em' up to my vac gauges. Had the YICS ports blocked with my homemade yics tool, fans set up and everything good to go. At anything under 1600 rpm the needles are bouncing around like a kangaroo farm, but with higher rpms they settled down and everything looked to be right on the money..or pretty close.

So I tweaked 1&4 in 1/4 turn and 2&3 out 1/2 turn...she runs good but still has a low idle and this is where my issue starts. If I take the idle adjust knob and turn it so the bike idles in the 13-1500 range, it takes a looong time for it to idle down after I rev it up. If I turn the idle knob all the way out , it will idles down without hesitation. And in all this the throttle response is not what I would call 'snappy'.

So to put all the normal responses to bed before they arise.... valve clearances are in spec (or they were when I replaced the gaskets two yrs ago during the rebuild. ) I did a wet-set on my floats and they were all perfect when I did the carb clean during the rebuild. I don't think it has anything to do with the enrichment circuit as it seems to be dependent on the idle adjust screw only....

Anybody have any ideas on my idle issue? (short of pull the carbs , clean and rebuild) I'm pretty sure there's a simple answer to my problem... I'm just all thumbs when it comes to tuning carbs... thanks for letting me vent guys..

 

Air leaks in the throttle shaft seals or intake boots would be the first thing would check. How many miles have you ridden since the last time the valves were checked? With two years of riding it might be time to recheck.

 

-The bike wasn't fully warmed up for the attempt;

AND/OR

-Your bench sync is waayyy off;

AND/OR

-Your YICS tool wasn't sealing properly;

AND/OR

-You need to pull the pilot screws and replace the o-rings if you didn't;

AND/OR

-you need more restriction in your manometer lines. ***my vote.***

(you might want to double-check the valve clearances too, and then get a compression test.)

 

I'd say a colortune is in order
IMO you should play with the air mixture screws, reset the idle, play with the mixture screws.
I can do it by ear now, but a colortune is a wonderful tool. Any bike ive ever worked on (that ran great at first with no air leaks) where after a "tune up" the rpms hang, ive had to play with the mixture screws and Idle.
I would check for air leaks just for peace of mind
And yes, make sure your bike is at operating temp before sync and colortune
or else youre chasing your own tail
-Chris

 

Ok..lemme address these one at a time..

Realistically... less than 1k...

#1 . Bike was warmed up..
#2 . Wouldn't my vac gauges read a notable difference in draw?
#3. No way to know for sure on that one I guess...
#4. Didn't do that on the rebuild..
#5. Don't know how I would do that. Right now the restrictor is set up just like the quoted thread shows. Red tube epoxied inside the barbed adapter has an opening of approx .040 Suggestions on how to reduce it more?? Here's the restrictor setup..




Vac gauge is plugged into the left and the right is plugged into the port on the motor.

And yeah.. I have tried playing with the air mixture screws. I'm assuming those are the ones on the top just outboard (away from the motor) of the enrichment plunger. I have another set of carbs here that is missing some pieces and ...maybe I will tear that rack down completely and rebuild that...I can still ride the bike like she is (can't I?) and that way I can take my time...

 

so... no suggestions on how to make "more restriction in (my) manometer lines."???

 

looks like your using rubber hose on the manometer haven't tried this yet but wouldn't a small hose clamp restrict the line as you tighten it up. just a thought.

 

Well here's the predicament that I foresee, and I could be totally wrong...what do the gurus think.... If I am using 4 restrictors that are constructed the same way with the same materials, they should create equal restriction, correct? The problem I see with a hose clamp ( or squishing the end of the red tube in the restrictor was my initial thought) is that I have no real method of ensuring I am restricting each of the 4 restrictors by the same amount. Or am I over thinking this... i.e. a flow restrictor for a vacuum (a gas) isn't the same as a flow restrictor for a a voluminous material such as water or fuel...

knowhuttimean??

 

I use needle valves in my setup. I only need to unscrew them about 1/2 turn to get enough restriction without too much.

 

you can set them with a vacuum pump (not gauge) but i guess you would need one of those. And i was talking about going with the clamp straight to the hose. All of the responses that i have got have said to use what you are already using. I just haven't had time to do so yet. If u completely close off each clamp then back off a 1/8 of a turn than maybe. Like I said have never tried this and its just a thought. And i'm definitely NOT A GURU.

 

Another thing to check is that the vacuum port caps are on tight when you put them back on after syncing. If they are a tad loose, you'll get a air leak right there not even know it..............

Dave