BlackSunshine stumbles at low RPM's......

[TomRodgers]

Hey guys...
First off....thanks for all the help so far!!!

New issue. Last night after busting a$$ to get done what SWMBO wanted, i was able to dive into the man-garage for a while.

The 3rd bike in the garage (the one im working on, picked it up 2 weeks ago)
was not running. The PO claimed he was a "shade tree" mechanic That alone brings the pucker factor to an 8.5 out of a possible 10.....

I first drained the oil (didnt look/smell bad), changed the filter. Pulled the plugs, not too bad of shape and gapped evenly. according to the manual correctly even. Pulled the tank off, drained the gas (weak smelling, old, but not syrup yet!!). Cleaned the petcock filters off carefully. . Vaccuum advance was not hooked to #2 carb. I fixed that...
Vaccum lines to the petcocks not hooked up. they were capped off with bolts. What a scab. the vac lines are kinda hard and brittle...but tried to use them. I replaced the carb holders. Sprayed the carbs off, but didnt dig in tooooo deep. bowls off, sprayed out, wiped out...(i am NOT a carb guy...i am sure you will be hearing from me this winter...or sooner... to rebuild them)

put new vac caps on 1 & 4 carbs....

opened petcocks....waited...right side moved really easy...to easy...but gas came pouring out #3 carb, so it was open.. . rapped on the bowls with a screwdriver handle and gas stopped pouring out...

sprayed all 4 with some hot sauce, pulled the choke, hit the starter, and VROOM. for 4 seconds. Repeated about 5 times. Repeated again, shut choke. cracked throttle a bit more...it ran. but only at 3k on the tach. if i let it come down from there, she would flutter out and die...

BlackSunshine has to the best of my knowledge not been running in about 2 years.

I will be replacing the vac and fuel lines 2nite or 2morrow. Any ideas as to the not wanting to run below 3000 rpm's?? Fubar carbs? i may swap them out with those off my 81 (that bike runs fine...just blows lamp fuses...) both bikes have same setup...4-1 pipe...pods.

[CatatonicBug]

3K rpm is where the main jets kick in. Sounds like a classic clogged primary jet issue. Time to open the carbs up and start cleaning.

[TomRodgers]

I was afraid of that !!!!! I have heard horror stories about this kind of thing!!!!!!

I guess the good news is that between 3 bikes, i have one set of carbs that work. one that needs work, and the other for parts if i need it.

Being a complete dumba$$ about carbs....and i mean COMPLETELY, i see rebuild kits all over the place for these things, but all the different sizes and numbers might as well be in some ancient language....WTF!!! even on this site i have seen different views on "size" of jets ect.

What im looking for is a good overall performance bike. it has a 4-1 (Kerker i think) and will have pods on it. looking to install a set of accel coils i picked up on ebay. i do not want to have to stop at every gas station to fill up to get to the next one....

as previously stated....ill be asking TONS of questions.... any photos would help. ill try and figure out how to post pics here, and take photos of the work in progress for all of your guidance!!!!

[Wildkat]

Try this:

Jettings

Your problem could be something as simple as just needing a more thorough cleaning...
The pilot circuit can sometimes require what many here call a triple clean (yep... clean them three times... can't hurt anyway)

General rule of thumb is: It's clean when you've been shot in the eye with carb cleaner through every hole...

and should you decide to do the modifications...
This is handy reference:

Mod jetting

[TomRodgers]

btw....withthe bowls off, i jammed the carb cleaner red tube up the center of the carb (large screw/with hole in the middle) and yes in deedy, i got shot in the eye with cleaner from all 4 carbs....

i know a real cleaning is in need...but im not looking forward to it....

[CatatonicBug]

(large screw/with hole in the middle)

That's the main jet. Unscrew it and clean the holes. There is another one that is a bit smaller that you need to concentrate on though. The pilot jet has holes in it's sides, and must be removed to clean those holes. Don't be intimidated by it. It's really not that complicated. Just be careful not to force anything and smear the soft brass screw slots in the top of the pilot jets.

Also, be sure to clean the hole in the bottom of the bown itself. That's the choke/enricher jet, and because it's at the bottom, it sucks all kinds of crud up through there.

[Incubus]

That's not where your problem is. You need to shoot carb spray up the small jet passage until it squirts you in the eye both from the air screw hole and from three little holes in the carb throat that you can't see until you rotate the butterfly. Getting squirted in the eye from those three holes is the real challenge. Not only getting them clear, but getting them clear enough for the carb spray to careen off the carb throat and carom into your eye. It's an art.

I was where you are. I am where you will be. Fear not your carbs. Follow the path.....

At least on those late model carbs you don't have the evil pointed air screws that break off in the holes when you even look at them.

Patrick

[TomRodgers]

you guys are great!!

i read the post on jetting sizes...

assuming (oh dear God..) that the stockers are 137.5 mains, and 42.5 pilots...

with the setup i have/want...pod filters, 4-1 pipe...i should use 147.5 mains and 45 pilots??? does this sound right?

[Crazcnuk]

Thes carbs are really pretty simple. Don't be intimidated by the voodoo image they have.

Just take them apart 1 at a time, at first, that way you have 3 examples of where everything goes! Later on you will take 3 apart, keeping one example, and the 3rd time you won't need any help. You'll know every part!

The above posters are right, you have to take out every screw, tube and jet. (except butterflys) blow cleaner through every hole, orifice and tube.

The pilot jets and needle jets (tubes) all have tiny little holes that need to be cleaned out. A sewing needle (welding tip cleaner) works well if they are clogged.

While in there check:

No deformation in any of those little holes (pilot jet, tubes)
No 'ovaling' of the hole where the needles ride in the tube.
Check needle/tube numbers and position (if adjustable should be in center normally)
Check pilot and main jet numbers against stock configuration
Check air jet number
Check diaphragms for holes.
Set floats at mimimum height from book to 2mm lower depending on symptoms. (Low speed stumble or load up, lower 2mm.)

[bikerphil]

i read the post on jetting sizes...

assuming (oh dear God..) that the stockers are 137.5 mains, and 42.5 pilots...

with the setup i have/want...pod filters, 4-1 pipe...i should use 147.5 mains and 45 pilots??? does this sound right?

The 78-79 early type carbs use the 137.5 stock main. The later 80 and up use a smaller main due to a design change. IIRC, 115 is the stock main size, but it should say in the chart in the back of the Clymers manual.

[Incubus]

My bike is a 79 Standard. I have a K&N filter (stock box) and a 4-1 pipe. I was advised by the mechanic at my local Yamaha dealer, an old-timer who has been working on these bikes since they first came out (and will talk about them for hours if you let him), to leave the stock size jets (137.5 main, 42.5 pilot) in my carbs until I find out if I have an issue. He said the only issue I possibly would encounter with my setup is sluggishness in the midrange. If I find that to be the case, he said, I should shim the needles, not change the jets. So that's what I did. I have not encountered any issues. I get clean burning plugs and rapid acceleration all through the power band.

What I am suggesting is if it was my bike I would clean up you carbs and leave the jetting alone unless and until I discovered whether I had a problem.

Once you've pulled your carbs a dozen times or so (you will, trust me) you will get to where you can go from fully assembled to carbs on the bench in about 15 minutes.


Patrick

[Wildkat]

The pilot jet will be the one in the lower left of this picture... I usually take a small piece of wire and run through each hole on the side to make certain it's clear...

(thank you to Dan Hodges who unwittingly let me borrow this pic)

That's not where your problem is. You need to shoot carb spray up the small jet passage until it squirts you in the eye both from the air screw hole and from three little holes in the carb throat that you can't see until you rotate the butterfly. Getting squirted in the eye from those three holes is the real challenge. Not only getting them clear, but getting them clear enough for the carb spray to careen off the carb throat and carom into your eye. It's an art.

The 3 holes that Succubus is referring to are in this pic underneath the butterfly and directly behind the hole in the middle that you can see:



You can barely see them... and truly... getting the carb cleaner to shoot you in the eye from this point is very difficult... but it's very necessary to make certain you are getting the fluid to flow through all three holes...

Somewhere around here is a diagram of the carbs and where each hole leads to... but my computer is running slower than mollasses uphill in January at the moment and I just don't have the patience to wait for the pages to load...

[Incubus]

Here in Austin, Kat, January is the only time molasses cools off enough to take liquid form.

[MrOzz]

...General rule of thumb is: It's clean when you've been shot in the eye with carb cleaner through every hole...

LOL yea, been there done that!!

Where eye protection. That stuff hurts!!!

Tom,

I would not worry to much. Cleaning the carbs are not too difficult. You should see the kleins I am cleaning off of a CB550 I just picked up. They will scare you.

I use pipe cleaners also to clean the jets. The work very well.

Good luck,
Ozz

[TomRodgers]

Anybody have photos of the teardown process? Like stated earlier...i am NOT a carb guy....but listening to you guys, relatively sure i can do it. i have torn down and rebuilt engines, transmissions, rearends and such on cars, rewired my whole house, learned how to lay brick in two days (to where an oldtimer for 40 years experience was impressed).... I just have an issue with tiny things...clumsy fingers i guess worst case....i have another set of carbs to work on !!!!