Next on the list

After spending weeks rewiring, I am on to the next 'to do' on my list. I never wired a motorcycle, created a electronics box and taken apart switches before so it was nice to get that under my belt.

Next are the carbs. The previous owner had straight throug long pipes wrapped from end to end. I cut them and installed HD Sportster mufflers. Much better look and sound for me.

First thing I noticed was kick back, sputtering and rough idle. I took the spark plugs out (see pic) and they are both black. So through some reading it seems it's rich. 5he spark plugs are 7s and not 8s so I can get that out of the way.

I plan on searching, downloading and reading a ton (like I did with the wiring) but first off questions
-how do I identify what carb I have and what year it is. The bike is an 81, would the carb be 81?
-do I try adjusting air/fuel mix before jumping in too deep?
-what's the difference between rebuild and rejet. If I have to take it out, I could essentially do it all, couldn't I?

Your carb is a Mikuni.
Hope that helps.
plugs SHOULD be NGK BP7ES
Yeah those plugs are real black, you need to do basic maintenance including verifying what jets are in the carbs. But black plugs can have MANY causes.
Carbs do look to be the correct 81 BS34
Tells are the side pull choke and the side drain screw on the float bowl.

Thanks gggGary. Do you suggest my next step is to take out the carb and inpect/the jets? Is there any type of maintenance I can do before trying to take it out

Verify strong blue spark at the plugs
Do NOT crank the motor unless both plugs are on the plug wires and grounded.
This is handy

Would be nice to see a couple pics of the bike.
What air filters do you have?
Reading
http://www.amckayltd.com/carbguide.pdf
This thread deals specifically with BS34s
http://www.xs650.com/threads/bs34-carbs-1980-xs650.50546/

http://www.xs650.com/threads/carburettors-from-the-grave.34737

Chachiboy said:

I plan on searching, downloading and reading a ton

Click to expand...

A very smart approach.

www.amckayltd.com/carbguide.pdf This is a good place to start with your carbs.
It has pics to help you determine what carbs you have.
Once you determine that there is a chart showing what the stock jetting for those carbs is.
There are step by step procedures for tear down, clean and inspection for the carbs. Once clean, the inspection will tell you what you need to replace.
If careful you won't need to buy much. Gaskets are robust and if not damaged cab be reused.
I don't know what your air filter situation is but your exhaust indicates some jetting changes may be needed.
The pic 3G posted, is that your carbs? if so they look like the ones on my 80.
The carb guide chart I mentioned earlier will tell you the differences between the 80 and later BS34's The side pull choke is one. Brass VS plastic floats is another.
Once you get things inspected and determine what needs replacing you can order the parts you need. I would order some jets, One up on the pilots, one and two up on the mains.
Reassemble the carbs per the guide. Making adjustments as you go. Things like float height, Bench sync. Just follow the guide.
Once assembled and back on the bike you can flow the steps in the 'Tuning for Mods" section of the guide to test the carbs, Use the results of the test to determine the corrective actions needed. Make ONE adjustment at a time test, make one change, test. Repeat as needed till the carbs are right.
Leo

Here are more pics. These are the air filters it came with. Not sure if these are stock (?) and not sure I will even keep them. Unless I twist tie them, the keep falling off

No those are not stock. with The CV type carbs you are running those pleated element pods are about the worst you can run. They cause an excess of turbulence to the air flow through the carbs. This causes a poor vacuum signal for the slide diaphrams. Thus causes slide lift issues and can be hard to tune out.
A long straight foam filter pods is a much better option.
Leo

Good thing I was thinking to change them out! Any recommendations on what filters I should think of getting? Model numbers or names?

Leo's right, those are junk.
Uni Brand
http://www.xs650.com/threads/is-there-a-uni-filter-for-the-bs34-carbs.2225/#post-24931
Even better in my mind is the stock airboxes.
http://www.xs650.com/threads/80s-airbox.56446/
Keep backing away and snapping pics.
You would not believe how many gotchas and oopsies the forum has found looking at guy's bike pics. Some of them may have been life saving!

Those cone filters have a flange in the mounting sleeve that blocks the air jets in the intake bell, causing a rich condition that won't tune out. Don't try jetting changes until you get better filters in place. As Gary says, with vacuum carbs you'll get the best performance from the stock still-air box.

grizld1 said:

Those cone filters have a flange in the mounting sleeve that blocks the air jets in the intake bell, causing a rich condition that won't tune out. Don't try jetting changes until you get better filters in place. As Gary says, with vacuum carbs you'll get the best performance from the stock still-air box.

Click to expand...

Thanks for the advice on the filters. I will look I to the Uni filter recommendation. Although the stock is best, I have deleted my battery box for a slimmed down electronics box

Are these ones any good? Or would the UNIs be the preferred choice? I notice that the suggested UNIs have foam. Better air flow? These ones have a similar filter to what I have now minus the rubber mounting.

No, those are no good either. You don't want any type of K&N style pleated filter. The pleats disrupt the air flow, make it turbulent, and these CV carbs rely on a smooth flow of air to lift the slides properly and smoothly. For your BS34 carbs, you'll want the UNI UP4229 or UP4229ST (dual layer).

grizld1 said:

Those cone filters have a flange in the mounting sleeve that blocks the air jets in the intake bell, causing a rich condition that won't tune out. Don't try jetting changes until you get better filters in place. As Gary says, with vacuum carbs you'll get the best performance from the stock still-air box.

Click to expand...

Grizld,
What about UNI or K&N on an extension/ velocity stack 50-100 mm long?
Surely, that would help with achieving a smooth/ non-turbulent air flow?

I started out using genuine K&N pods because, well, I had always used them in the past. But what I didn't realize or take into account was that I had never put them on CV carbs before, always just on normal slide carbs. I didn't know about the air flow issues they created. I did try them on extensions but it didn't help. Switching to UNIs fixed it.