Tuning a rebuilt carb

[Rat]

They look ok except for the lower right .... it is not sealing around the top edge .... around 11 o’clock

Gord

[sphen]

Not much luck - I reset that diaphragm but it’s wanting to creep out. Did my best, and I think I made it worse. Just barely starts and a low rough idle - sounds like a Harley lol and vibrates about as much.

I’m in dark waters at this point. Might need to take it to somebody, or start completely over with the carbs, with new diaphragms.

Do y’all think I should just replace em? Saber cycle has them for 25/per. Not thrilled about dropping another hundred on the rack...sigh.

[Gowing]

I had torn diaphragms on my Yamaha 1100with mikunni carbs. I used harbor freight liquid rubber
to patch the rubber. To get by. The Yamaha diaphragms were 75.00apiece I think.
Just like any other part. Honda is best, aftermarket is ok usually. Used parts are inexpensive. Or make your own and screw everything up.

[sphen]

It’s not torn, just seems deformed and won’t quite sit in place.

And I’m not 100% sure that’s all my problems

[ericheath]

Try placing the slide and diaphragm into a pan of hot water, 140-150 degrees and then quickly install. It might expand enough to stay in place to get a good seal.

I don’t think your description fits the diaphragm as the culprit. It sounds like it isn’t gettin fuel.

Most of the time if it won’t idle and there’s no vacuum leaks, it’s the idle jet. 0.35 I think in yours. We’re you able to see a good hole when looking at a light? (I have to look at a light, to small to see through otherwise) Pretty easy to check if they’re clean or not. If you have poor closeup vision, use a magnifying glass.

Having floats set too low would also starve the idle jets. Good vids and how-to’s available to show you how to set them.

Save your money, try again.

[redglbx]

Sphen, Eric’s advice above is good, personally before I got to involved with getting the diaphragms properly seated I’d take a good hard look at the jetting, particularly the idle jets and their circuit. What you’re describing sounds like a plugged idle circuit. Personally I would pull the carbs, take the bowls off and remove the idle mixture screws, be careful not to lose the springs, the o’ring and the very tiny washer in the mixture screw bores. Make note of the order of how they came out.

Take them all out and then you should be able to spray carb cleaner through the idle jet and see it easily come out of the mixture screw hole, if it doesn’t you have a plugged idle circuit.

Now I also take the carb cleaner “straw” and taper the end on my belt sander/grinder/etc, so it better fits into the jet. I’m betting that this is your problem. While your in there make sure all the Jets are spotlessly clean and double check the float levels using the service manual method. Let us know.

[sphen]

I'll pull them again and see - i must have missed something.

Float heights were set, all parts cleaned and i could see through the hard parts, but apparently ive missed something on one or more.

I'll post back when i get it torn down again - particularly I'd like to show some pics for verification from you guys.

ON the float heights - I tilted the carb until the float arm just contacted the top of the float needle (the little spring loaded thingy on the top), and measure clearance that way. does that sound correct?

[ericheath]

If you do find idle jets plugged, and feel you had them clean before, check your fuel tank and fuel pump and fuel lines. Been there, done that too many times. I had one that the tank looked clean looking in through the fill hole, but using a mirror and flashlight I could see the top third of the tank was covered with flaky rust. It must have sat for a few years with a less than full tank. The part with no fuel was where all the rust was. Every thousand miles I was pulling the carbs and cleaning the idle jets.

[redglbx]

I’ll add that many years ago a very smart man by the name of Tim Ware (Tim’s Cbx) once told me when you clean you carbs and you’re sure that they are clean go back & clean them again because they’re not. Smart man !

Also he taught me that sometimes the little spring loaded pin on the Float needles goes soft and will not work properly to control the float. I was really struggling on my 80 cbx carbs and he was convinced it was the Float needle pins, so much so he sent a set to me free of charge with the caveat that if they worked I’d send him a check,,,,,, it was in the mail by the end of the week ! Truly great guy !

[sphen]

Thanks everyone.

New fuel pump, filter, tank was cleaned and relined. Hopefully that’s all good.

New float needles also.

[redglbx]

Sphen, one other thing I would check, since you had your tank cleaned and relined open the gas cap and take a look to see if the screens over the ends of the fuel pickups were removed prior to lining the tank or that the pickups had plugs put on them prior to lining, you may have plugged gas lines in the tank.

Remove the gas line coming off the fuel valve and try lightly blowing (air compressor) through the line, it should easily blow bubbles out of both lines in the tank when you switch the valve from the on to reserve positions. This of course is done with the gas cap removed and be careful not to blow fuel in your face or all over your bike.

[sphen]

tore the carbs down again and did another cleaning.

It looks like there's still room for improvement in the jets, particularly the slow jets.

i'm tempted to change out the jets. was looking in my stash, but what i have in stock was a replacement set for an earlier year 1200, so the jets are a hair small vs '86 sizes.

will see if i can get these cleaner and go from there.

[Track T 2411]

I typically soak the jets in carb cleaner or acetone for a few days. Neither will hurt the jets and will loosen up any crud inside. I then use a variety of softer materials, like toothpicks and the paper stems of q-tips to polish away any remaining gunk. Yes, it's tedious, and yes, I'm anal, but it works.

[redglbx]

Sphen, just replacing the jets alone probably isn’t the answer by itself. If you take the idle mixture screws out can you spray carb cleaner into the idle jets and have it come out of the idle mix screw hole ? If not that circuit is plugged and the bike will probably not idle. It’s gotta flow freely.

Also keep in mind when you pull the idle mixture screws out that there is a tiny spring, a really small washer & o’ring on the end, do not lose these, take them out and set them aside in something safe BEFORE you blow anything through the low speed jet circuit. Ya gotta have these parts for proper idle mixture.

[sphen]

[quote="redglbx"][/quote]

I discovered I had a missing oring on a idle
Mixture screw!! Womp womp

This evening I will shoot carb cleaner thru to see if and where it comes out. Last time around I shot some water thru (per the Howard guide) and recall all the passages being clear, but def will try again.

All the jets are now clear and have the same amount of light in the bores. Hopefully I’ve gotten all the crud out in the entire length internally. Hopefully better looking inside than out :

38673627-9328-40D8-8E58-A6B71F3F5AC6.jpeg