Here's the issue. Went on a long drive about 300 miles with no problems. Took the car out a few days later and it's running like it has a bad valve or at least sounds like it. It does the same thing going down the road as well as at idle. Pull the air cleaner off that carb and you can see it spitting fuel out the one barrel. There is also what appears to be black soot on the throttle plate and inside that barrel. Called Redline and they said the idle speed screw it out of adjustment and can't be more than 1/2 a turn out. I said that doesn't make any sense because it does it going 70mph. After talking with several people, everyone thought it had to be a valve issue. Well it's not. So any ideas on what it could be?

How do you know?

You use the idle circuit up to about 3k to 3200 rpms.
So cruise on the highway could use the idle circuit...

It only takes about 10 to 20 hp to maintain 70 mph

Have you made sure the idle jets aren't clogged?

When you say it's dripping, is this when the car is idling, with the throttle plates closed? And can we assume you mean it's dripping at the top, center portion of the throttle body (the secondary venturi)?

Monkeyboy has a good, simple tip. Check the idle jets first. They're the brass screws at the top of the carb, on the sides. Be careful when you remove them that you don't lose the small o-rings. In theory, it's possible that the jet could become completely clogged and overpower the main jet circuit, forcing fuel to dribble out of the secondary venturi port. (Page 72 of the Tomlinson manual for those following at home)

While you're at it, you might want to pull the main jet on the offending barrel and check that it's not somehow plugged, both at the jet side and at the top of the emulsion tube holder. That one's a piece of cake.

I forgot to mail that thing we talked about. You still need it?

Do a leak down test if you haven't done it already. Then what the other guy's said.

+1

Easy enogh to check that idle jet, then valve adjustment. If it's OK then even a regular compression test should tell you what you need to know.

first, go to amazon and order "Bob Tomlinsons Weber Tech Manual". you need be able to identify each component and what function the component provides. the trouble shooting guide is straight forward and will point you in the right direction. you're wasting your time calling redline. while sort of correct with regards to which circuit does what at x rpm, once the throttle plates start to raise above the progression ports the idle jet is out of the equation

i'm confused with the advice you received. idle speed adjustment screw 1/2 turn out? they turn in to increase the idle speed. that's all they do. the idle air/fuel mixture needle screws affect the idle air fuel mixture @ IDLE. that's all they do. initially, the AIR by-pass screws should be set at 1/2 out off of seated. that's just a baseline setting as described in the "Bolt Em' On" chapter. once the throttle plates start to open you're on the progression circuits then the main jet circuits. get the book and study it! twisting and turning various unknown components won't get you anywhere. get the book, then discover what your current venturi size is (44-prob 36mm unless the carbs have been worked and pretty large), the idle jet size, main gas jet size, main air correction jet size, and emulsion tube size. fuel spilling on the top of a throttle plate is prob coming out of that IDF accelerator pump delivery jet.

k

I know the valves and head is good, pulled it took it a local engine shop. I realize that the idle circuit runs that high, but Redline guys thought that the idle screw is out of whack would not apply because the throttle plate at 3k would know longer be using the idle screw. One of the first things I did was clean the jets. The fuel is not dripping that I can see it spitting out the top of the carb. I may be wrong but I always thought carbs sucked air in, not blow air out. I was not really happy with the advise I got from Redline. I'll get that book maybe I'll find the solution.

Where exactly is it spitting out the top of the carb? A specific orifice, and pictures would be very helpful.

Also, is it doing this at idle?

Kevin is right - either way, you should order the book.

my guess is a cloud of vaporized fuel comes out of the top of one or more barrels on the snap back.

That's why i asked about the valves. Incorrectly set valves will do that to your engine ...

Andy and Kevin...


We need more specific descriptions of what's happening, but I think we're beginning to track this down.

Not only that, but at certain RPM's fuel with be pushed back toward the air cleaners. It's called reversion. It's normal with carbs.

That may or may not be what you are seeing.

valves were checked before the head came off and they were spot on. It's just doing it on the 1 barrel. It's spitting right up the and out the top of the barrel. if you placed your hand over the top of the barrel it would get wet with fuel. it does it at any speed. and yet I have ordered the book.

Sticky intake valve then?

The only reason you will see fuel (and air) coming out of the top of the carb is if the intake valve is open while the piston is moving upward.

update.

Well it turned out to be the carb. Don't know what in the carb it was, but after having it run through a Ultrasonic Cleaner the problem went away:)

Sounds like you had a clogged idle jet or the idle jet circuit. This is a very common problem as the jets are tiny. I was having problems with this with the K&N filters I was running. The filters would allow little particles into the bowl vents which would eventually clog the idle circuits. So I made some little filters for the bowl vents themselves out of this material,

http://www.motorcycle-superstore.com/2/9/4...CFWNp7Aod7FAAqA

It is a cheap and effective solution. The bowl vents are in between the two main jets on the top of the carb housing. Just cut out some of the material and stuff it over the whole vent. Now I rarely if ever have idle circuit problems.

Just gonna say it cause the cap'n seems to be less frequent...

Little pieces of dust are getting past your kn filters?
Shocking!

Can you imagine? All the hype but in the real world they cause so many problems. They were also shedding. I would find fibers in the idle jets as well.

+1 A store-bought solution: CB Jet Doctors. Comes from off-road buggies that live out their lives in places made of things that clog jets. Not that expensive but really effective. Ditch the K&N's, use paper filters, and add a sealing line of high-temp grease (wheel bearing or such) to the filter tops and bottoms, will all help keep the crap out. That or learn to love cleaning idle jets by the side of the road.

I also use outerwears around my filters. I know many say they are not needed on the street, but I rarely have problems with my jets after using them.