[shinneh]

Alrighty, I have no idea what these things are called and it may be the reason that, with the carbs on, the bike can't start.

http://i264.photobucket.com/albums/ii178/shinjikun1091/carb.jpg

What are those little metal things called that I have circled. I know it's a bad picture, but if you know what they are then you prolly don't need a great pic. I know that when I squirt carb cleaner into either of the jets the cleaner comes out one of these holes, as well as the little holes that fuel ought to come out of.

 

[jbranson]

Not positive, but I think those are the air intakes for the idle air/fuel circuit.
JohnnyB

 

[Bateman147]

Those should be the air bleeds (and integral jets) that feed air to the emulsion tubes. The air is mixed with the fuel there and the fuel/air mix then comes out the needle jet around the needle. The ones to the side a bit are the air intakes for the pilot circuit as JB mentions. Both need to be open for the carbs to work right. Neither are generally a problem. It's almost always clogged pilot jets that are the worst offenders.

This is not your starting problem, but it is worth pulling the emulsion tubes and needle jets and making sure they're still round and not egg shaped. It's common for the needle to wear the needle jet bigger, making the bike run excessively rich and impossible to jet correctly.

I think those carbs might have the pilot jets buried under other jets unlike other more simple carbs - very easy to miss (if they're the carbs I'm thinking of). They're pretty darn small and usually always clogged shut. Easiest to buy new - but will clean up with extended running in an ultrasonic cleaner. Held up to the light you should be able to clearly see the hole in the jet - make sure it's clear and fully round with apparently sharp edges. It's best to have a new one to compare to if you don't have much experience looking through them. Badly clogged ones will not fully clean out with carb cleaner and air, might get clean enough to make the bike run, but not run well.

What are the carbs from?

Michael

 

[shinneh]

The carbs are from my 74 cb 550 that I believe has a 77' 550 motor/carbs in it. I have the original motor aswell and the 74 carbs have the same lil' air tube thingy. I was hoping not to have to take them apart just yet but I guess it's time.

 

[Bateman147]

The microfiche picture is terrible, but they only list slow and main jets so these carbs might be slightly more simple than I was thinking (ie they're regular carbs not the over complicated abominations I was thinking of). Just make sure when you take out the pilot jets that there aren't other smaller pilot jets buried under them.

When was the last time this bike ran?

Have you had the bowls off the carbs yet? If so what did they look like (and smell like) inside?

Removing and cleaning and/or replacing the pilot (slow) jets and the mixture screws and associated passages should be your first step regardless. Honda list price on the fiche I was looking at is $6.78 each.

You'll also want to remove the mains and emulsion tubes and inspect/clean. Blow carb cleaner and air through every passage. Carbs need to be spotlessly clean to work right. Check the tank - if there's even the slightest hint of crud or rust put the best filter you can fit on the fuel line without kinking it and cross your fingers. Always start with fresh gas - old gas has lost the aeromatic fraction that is critical to starting. Completely drain and refill the tank. It may take you more than one cleaning to get the float needles to seal correctly and not have the carbs leak. They're picky - bench test them for overflowing before installing back on the bike. Sometimes they'll still give you trouble even then.

Michael

 

[shinneh]

Thanks for the tips/info/advice. The last time the bike ran was 2 years ago. The bowls were pretty clean but I cleaned them up more with many many cans o' carb cleaner. Today I sprayed the crap through every hole I could find with cleaner and ran a tiny metal wire through the jet.

I'm-a gonna clean it a few more times because it was leaking pretty bad. The floats work great though i'm not sure if they are set correctly, I tried measuring with my micrometer at work but I uno, if my reading is right its at 26mm when the book says 22mm *shrug*

 

[HackAsaw]

seldom discussed but reality is that it is hard and expensive to obtain drills smaller than 0.135"

and some holes you need to make sure are clean are that size or smaller

so a handy thing to keep is the inners from fine wound junk cables

use the swedged end as a handle and unwind a single strand to wire thru those tiny holes

will save you some grief if this is something you don't know about already

 

[Bateman147]

There are 2 jets to clean - did you clean them both? The Main jet is easy to see and rarely clogged enough to be a problem. The pilot jet is often buried down in a hole and is commonly clogged by varnish or tiny crud. You need to remove it to clean it if you haven't already.

Michael

 

[HackAsaw]

I can't recall the last set I took apart, that actually needed cleaning

that didn't have the emulsion tube holes, and there are typically quite a few of them, stopped and most stopped solid

in my opinion

every single jet in a carb should be cleaned as well as every nook and cranny inside of it

that cable end makes a handy brush for chasing the crud out of the crannies too

 

[midge]

hey hack $3.12 at mc master carr will get you a .134 or any other size you need

 

[HackAsaw]

oooops! I meant to type 0.0135"

good catch

I have smaller but they do not look like normal twist drills

more like spades and are used for WW and Instrumentation type hole making, not too swift for putting in a pin vise and clearing holes since they tend to broach and ream when not rigidly and precisely located... and a half a thou or two enlarging of a pilot circuit makes a huge difference in smaller engines

and the point I so grandly failed to make in the process is that

many of the vital holes are smaller than the 0.0135"

especially the idle circuit jet holes in smaller carbs

just for a reference

the pilot jet size for a single or twin carb 650 triumph is 0.0135"

I'm not happy until it can be held up to a strong light and I see a very round hole thru it

and even when taking them out of a hot ultrasonic with the good cleaning juice, rinsing with hot water, and they drying with compressed air....

often they will still need poking thru to get completely clear

today's pump fuel is vicious and it has been for a long time

I'm sure many here never knew the joys of real pump gas that had lots of lead in it and very few other additives


man you could drag a bike or car out of the weeds after it had sit for a couple years

shoot it with some starting fluid and often they'd run like a champ and not need any attention the carb once you got some fresh gas flowing thru them

those were the days

 

[midge]

mc master carr item #2951a29

High-Speed Steel Micro-Size Twist Drill Bit .0134"/0.34mm Size, 3/4" L Overall, 5/32" L Flute
$3.12 Each

 

[HackAsaw]

great, you know how to find things at the Mc tool place

do you actually know what size hole the pilot jets in your 350 carbs have?

I'll give you a hint, smaller than that drill.

have any clue what size all those small holes in the emulsion tube/jet holder are?

 

[jbranson]

A while back I ordered a set of micro drill bit blanks at McMaster, not actuall drill bits, just the blanks. Down to sizes so small you can hardly see them. I mic'd them all, made a wooden case, labeled them, use them for sizing very small holes or cleaning out jets.
JohnnyB

 

[midge]

mcmaster carr has bits down to .0019

but just like johnny B i have a hole set of pins, from .025 to .002, so if and when i need to know I'll measure them, and if they need cleaning ill find an old piece of cable and give em a good poke,

 

[midge]

midge

 

[HackAsaw]

the only thing tougher than drilling holes that small is threading them

 

[HackAsaw]

so go ahead and drill them and send them my way if you need them threaded

 

[midge]

you know hack i have a weakness for nice little set of fine tools, now a days even good tools come in cheap plastic cases, seem to take away some of the charm

 

[HackAsaw]

yeah man, I love leather covered boxes or natural finished boxes showing all those perfect dovetails

not much at all comes that way these days