Carb pilot screw question - sort of

I have been tinkering with this bike (82 650 Maxim) for awhile. Float heights have been the bane of my existence. However broke down and bought the gauge from Len. All floats are 3 to 3.5 mm at the meniscus. Pilot screws at 2.5 turns out. Bike started right up ran smoother than ever.

Then I discovered what appeared to be a dead cylinder on #4. How did I know? No color with ColorTune on cylinder #4. Checked coils, and spark all are good. It turns out that cylinder 4 doesn't want to run until I get to 6.5 turns out on the pilot screw.

I am a tard when it comes to carbs. What should I be looking for?

By the way all carbs were broken from rack. Taken apart and ultrasonically cleaned. All new seals, float needle valve assembly, pilot washer and O ring. Polished throats to insure clunk test. New butterfly screws. Diaphragms are good, no pin holes. Checked all passages with guitar strings and blew through with compressed air. Carbs are synched with CarbTune


What

 

did you try a running sync?

 

yep. Its all synched and colortuned. Just the #4 pilot screw is at 6.5 turns out. That can't be right.

 

Try using a bit of choke and see if cylinder #4 comes alive............if so, then the pilot circuit for that carb is still plugged.

In our experience ultrasound is not a very good way of cleaning the tiny internal passages within these carbs....they are, of course, tiny, and they make a lot of bends, too. It has to be a mighty powerful ultrasonic cleaner to produce any results in there. Carb dip and pressure (i.e. air compressor and//or carb or brake aerosol cleaner pressure) is about the only way to insure that the pilot circuit internal passages are truly cleared of all blockage (i.e. fuel varnish, which can turn hard as a rock).

 

EDIT ::

Choke just kills the engine

---------------------------------------

I'll give it a whirl! Thanks for the suggestion.

I'm getting real good at pulling em off and puttin em on. 15 minutes both ways heheheheh

 

Re check float level on no. 4 pot

 

Rechecked float height off the bike, its dead on. Put back on the bike and checked it again against all the others. All were within 1 mm of each other.

While off the bike I cleaned all passages on the carb with guitar wire and carc cleaner. All passages allow a steady stream of cleaner through them. #4 still wont run until its 6.5 turns out.

Also put a different float in just in case.

 

Are the valves in spec?

 

valves are all in spec

 

It sounds like possibly a leak around the intake boot, or gasket causing the #4 cylinder to run extremely lean. If there are any cracks in the intake boots. Coat them with RTV sealer, and apply a bead of sealer around the boot where it meets the head.

Ghost

 

I'll look into it but I had glued all the cracks then gave the boots 4 coats of Spray Liquid Electrical Tape.

Looks like I am going to pull my carbs off my other Maxim and give them a whirl. I might have a spare carb boot around here.

The problem bike is a parts bike I used for various parts to finish mine but am putting it back together for my brother. He cant afford a bike so getting this going will be a big surprise for him.

 

Did you take the pilot mixture screw, spring, washer and o-ring out, and clean thoroughly, check for wear, clean the shaft, squirt carb cleaner down the hole, on the #4 carb?
Did you put them back in the right order: i.e. o-ring, washer, spring, screw, in that order?
Only asking this because it is very easy to reassemble wrongly.....
If not, it could be the reason(s) why you are having to turn it out 6 and a half times (a wonder it hasnt popped out!?) to get it rich enough to fire....?

 

Did you take the pilot mixture screw, spring, washer and o-ring out, and clean thoroughly, check for wear, clean the shaft, squirt carb cleaner down the hole, on the #4 carb?
Did you put them back in the right order: i.e. o-ring, washer, spring, screw, in that order?
Only asking this because it is very easy to reassemble wrongly.....
If not, it could be the reason(s) why you are having to turn it out 6 and a half times (a wonder it hasnt popped out!?) to get it rich enough to fire....?

 

Assure Pilot FUEL Jet is Correct SIZE and Clean.

Pull the Pilot Screw.
Remove ALL the Parts.
1. Screw
2. Spring
3. Micro-flat
4. O-ring.

Shine a Light down into the Hole.
You should see the SHINY HOLE that's open to the Intake Neck.

Probe the Hole with a LONG DARNING NEEDLE.
See if there is any debris or ---> A Flattened-out O-ring down in there.

Heat the Tip of a Darning Needle or a LARGE Safety Pin.
Hook the End with Needle-nosed Pliers.

Go fishing.
Extract anything in the Hole not part of the Pilot Screw Assy.

::: There might be an O-ring squished flat. There might be a Fragment of an O-ring loose and stuck in the Passage or Inlet Orifice. :::

• Insure you have CORRECTLY --> "Sized" --and-- "Placed" Pilot AIR Jet. < !!
• FLUSH Pilot Air~Fuel Passage.
> JET
> JET passage -to- AIR Jet
(Use Bubble Syringe filled with a load of Carb Cleaner sprayed into a Container to collect Carb Cleaner for use in Syringe)
Block Mix Screw Hole and Intake Neck Micro-orifice.
• FLUSH AIR Jet -to- MIX SCREW Hole
Block FUEL Jet.

Test Passages.
Use Bubble Syringe.
Stuff mini fuel line in Pilot Fuel Jet Orifice. Other end in container of Carb Cleaner. Evacuate Bubble Syringe. Insert Syringe into AIR Jet. Block Mix Hole and Intake Neck Orifice. Draw cleaner from Hose into Bubble.

BUBBLE SYRINGE -->> a.k.a. "'Lil Baby Booger-sucker"
• • • • • • • •