I know it's been rehashed over and over again....

I have some questions on how to do it after futzing around in the garage trying to make SOMETHING happen.

I followed the carb clinic instructions to the T and I think something is adjusted wrong... Maybe you guys can help.

I have the idle speed screws to 1/2 turn past first contact with the arms

linkage disconnected

air bypass screws all the way shut.

all mixture screws out 1.5 turns

it'll start and run (slowly) and it'll get to what i think is around 450 rpm or something. really slow..

the only way I can get it to idle at 450 or so is by having the mixture screws in pretty far. two cylinders dont even react past a certain point! i can have them all the way in (lightly) and the engine doesnt change its note at all!

Please ask me questions so I can give the right info. I've never done this before but i'd like to believe these arent fiddly carbs.

When they say the engine should 'speed up' is it a really noticeable change? because mine's so subtle as to be not affected.

please help guys!

these are brand new carbs from jake's store. I have the box that says what the jetting is. i'll post that soon.

what are 'jets' and what do they do?

Jets control are brass 'screws' that have tiny little holes in them that let a precise amount of fuel pass through them. By changing the jets larger and smaller you can control the amount of fuel that is mixed with the air. The mixture screws only adjust idle mixture. Mid-range and high-rpm mixtures are controlled by main jets and air correction jets, there is no twist-a-screw-to-adjust for those. The Haynes manual on carbs is pretty good.

What's your timing set at?

Mark, I've tried to set my timing with the mallory as close as I can to 27* BTDC at 3200rpm, but the problem is I cant bear the sound of the engine when it's revved that High with these unbalanced carbs. i feel like i'm gonna kill the engine. the timing my be very off because I need someone to hold the gas down while I lean in with a timing light and do my twist & shout on the dizzy.

Is it possible it's my timing being too far off?
I was sitting on the john and that occurred to me that my timing may be off or my idle jets are too big.

all my best ideas come to me in the latrine, and I KNOW i'm not alone in this.

Also, is the engine speed up VERY noticeable for other people? I'm having trouble understanding how to tune this the way it's going with the screws not affecting the idle.

also, thanks mark for 'splainin what the jets are. In 2 stroke RC carbs you dont get those... Just a high needle, low needle and idle stop. if you're lucking with a slide valve carb you get a mid needle too! i love slide valve carbs! why dont cars get them?

You may have to turn the idle stop screws in more to raise the idle, the 1/2 turn is just a rough adjustment.

Here's my carb tuning proceedure from a March 03 post:

Assumptions: the carbs have the optimum jet and venturi package (good luck on this one), the float level in the carbs is correct, the cams are correctly timed, the valves are properly adjusted, the ignition timing is dead on, you have the proper spark plugs for your engine, the linkage is good, the fuel is good, the engine is good.

Remember that the mixture and air bypass adjustment screws are precision needle valves, not head gaskets. Use your fingers to tighten them, not your fist.
Start and warm up the engine.
Make sure the two drop links for the throttle linkage are exactly the same length, and disconnected. You can use a 8mm thin igntion wrench to snap them off.
Turn the mixture screws all the way in and then 5 half turns out.
Turn the air bypass screws all the way in.
Turn the idle speed screws out til it just touches, and then in 5 half turns.
Put on your hearing protection and start the car.
Use your STE and find the barrel that pulls the most. We'll call this one baseline.
Balance the barrel in the other carb that pulls the most with the idle speed screw. (if you have a Uni-syn, give it to someone you don't like and purchase a STE airflow meter)
Go back to the other carb, with the baseline barrel. You will have one all the way in, then use the air bypass screws and balance the other two barrels.
Go to the other carb and do the same thing.
Snug the jamb nuts on the air bypass screws.
All six barrels should pull the same amount of air at this point, if not repeat air adjustment proceedure.
Snap the throttle linkage drop links back on the carbs. If the idle changes then you need to barely adjust the linkage mounts so snapping the drop links on, doesn't change the side to side idle balance.
Use the hand throttle or a vice grip and rag to lock the linkage between 1400 and 1800 rpm.
Start back at the baseline barrel and adjust the mixture screw in or out, to get the smoothest running and highest idle, then turn it in 1/4 turn.
Do the same with the five other mixture screws.
If you have to turn the mixture screws more than two turns either way, you've got the wrong jets.
Recheck side to side and individual air balance, adjust as needed.
Road test the car.
If you get snapping and poping out the intake, it's generally a lean condition.
If you get heavy exhaust fumes, or pboofing out the exhaust it's probably too rich.
If you get a flat spot or popping out the intake at between 2800 and 3200 rpm, you probably need larger idle jets.

That's a rough, five minute draft of my carb tuning proceedure, hope it helps!

If it goes good it should take about 45 minutes, if not about three years.

PK

wow, that's awesome!

I think i have to wait for my flow meter to show up. It's the empi one that kinda looks like a snail. I get chumps out the exhaust when tuning one barrel, pops out the intake when doing another barrel, it's kinda maddening.

The valves are right on the money, i made triple sure of this.

The timing is iffy, i want the carbs to not make the engine vibrate so much before holding it at 3200rpm. i feel like it'll tear itself apart if i do that.

the plugs are brand new, and the right ones.
i'm getting huge blue spark off my ballasted promaster e-coil

I have done pretty much the above procedure except for the flow gauge. My burning question is

how noticeable is the change in engine speed when you're tuning the idle mixture screws? is it +-1 rpm like what I'm getting or is it +-100? i'm confused

oh, which weber carb tuning book do you recommend? there are like 4 of them out there

first, if you're trying to do this with the engine lid on, take it off. perry nails it but i don't quite understand setting the idle/air mixture at 14-1800 rpm. once you get the linkage near spot on it's easy to turn the idle up by just using one idle adj screw. the other side will follow suit. this method works well for me to fine tune the linkage. if the flow changes it's simple to bring one or the other carb in by turning the droplink rod in or out.

k

my lid has no rain tray, so it really doesnt get in the way. and i'm a fit 26 year old, so i dont need a whole lotta room anyway.

engine speed.....is it really pronounced, or subtle-like?

I start with the screw 1.5 turns out from closed. If I turn the srew counterclockwise in "5 minute" increments, then pause about 3 or 4 seconds, there may be a slight (50 to 100 rpm) drop. It may be just a slight change in tone unless you have turned 15 or 30 minutes worth. Plug fouling makes me crazy when I'm messing with the carbs. 15 minutes at idle speed will choke #3 plug, and then it won't behave right to complete the balancing process. I usually put in new plugs, fool with the carbs 15 or 20 minutes, put in new plugs, mess with it 5 minutes, then drive it for a while to burn of the carbon.
Also, check to make sure the throttle arms are holding the connecting rod to the carb in a perfectly vertical position. As those arms swing down, any difference in the geometry from the angles of the linkage wil become more exaggerated.
Unless the cilynder is not firing due to fouled plug or clogged jet, it will be pretty apparent when the combustion is decreasing.

Even at a rough, but equal adjustment on the four throats, you should run pretty smooth at high rpm (no misfiring). Grab a set of ear muffs, a friend and an adjustable timing light and get the timing dialed in. Revving an unloaded motor (i.e. not in gear) is pretty safe. Holding an unloaded motor at 3500 rpm isn't going to break it. Yer gonna have to get used to that. 914 motors like to rev, this isn't a Honda Civic that you can short-shift at 3000 rpm around town. You'll be revving to 4500 all the time while driving.

are you serious? 4500? christ.

I shift my mini at 3000 rpm to keep fuel economy up.

i feel like i'm going ballistic if i rev the mini up that high, like i'm trying to race people. what if my hydro cam balks at 5000rpm?

btw, the adjusted valvetrain really sounds good now. it's all quiet and such. starting to sound like a little german sewing machine, like the mini engine.

wait...I thought honda's loved to rev up?
I hear you though purple. I want to dance that line between performance and fuel economy. About to hook up a set of these myself. Quite a technique intensive thing to get these timed right. Especially (as I'm told) with an 009 dizzy and the stock cam shaft.
What did you put your valve gaps at for you car? I'm assuming it's a 1.7 or 1.8? I've got mine at .006 in/ex and i think they are still too noisy. I know some people suggest .004

sorry pete, cant halp you. I have hydraulic lifters and a webcam with a mallory unilite set up by jake raby.

to answer your question, 2 turns in past first contact. wow the valves are quiet after that. used be be real 'naknaknaknak' sound to it. now it sounds like a proper little sewing machine

Man, that's a pretty much ideal setup for carbs.
Enjoy

Took me long enough....but i finally got the Jetting spec of me carbs

MAIN:1.30
IDLE: .55
AIR: 200
VENT: 28

jake seems to have set em up nice, whatcha guys think?