TOPIC:

Greetings,

I'm hoping for some input on getting my BS34 carbs dialed in on my K2.  She's close,  just not there yet.

Background - bought the bike over a year ago with 4,900 original miles on it.   It had been sitting for a while.  The carbs were so messed up (wrong jets, wrong needles, bad diaphragms, missing pilot plugs, etc).  The bike barely ran.

I replaced the coils, wires, disassembled the carbs, put in carb kits, set the carb needles back to stock,  purchased new stock genuine Mikuni mains and new diaphragms. I synced the carbs to spec (within 2 -hg of each other), checked the valves and compression to try to rule out mechanical issues. I even bought a colortune to tweak the idle circuit and it seems good on idle, but not as good on the needle.

Everything seems to check out,  but she still runs very rich and fouls plugs.

Any suggestions?

Mods - 4-1 header
K&N air filter in stock air box

Did you put those plugs on top of the pilot jet/Circuitry? Without the plugs, they run way too rich.

Thought I mention it since you said it's BS carb.

Are you using the correct "heat range" plugs ?
Have you tried dropping the needles a notch ?

Good question. 
It took me a while to figure that one out ,  but yes I order 4 new ones.  The pic shows the larger mains that I replaced with the 122.5 later. 

You can't see from the picture,  but I'm running NGK B8ES plugs.

I went back to the stock needles that don't have any c clip notches.

What brand carburetor kits? Dynojet and Keyster are the only two I would trust. There are quite a few cheap kits out there that have really crappy jets and needles. With your mods, I bet the factory jets and needles will work just fine. A shim under each needle may be all that is needed to get the mixture spot on.

Could the plug fouling be oil? Maybe the valve stem seals have dried up and are allowing oil to enter the combustion chambers.

Are those homemade bowl gaskets?  Make sure they don't stick out too far and block the float from moving freely.

TexasKZ,

Thanks for the input.

I don't remember the brand of the kit, but I ended up doing exactly what you said.  I chucked the float needles and seats and replaced with genuine Mikunis from Dennis Kirk for that very reason (they were crap and didn't seal well at all).

And you were right,  originally the valve seals were dry and hard from storage, so I put in a whole new set.

The buildup is very dry, indicating carbon/incomplete combustion. 

Help me out with the needle shim.  If I place a shim under the needle, won't it pull the needle up by an increased amount, thus making the mixture richer?

Appreciate the feedback. 

I would check your choke plungers.

Yes, a shim will richen the mixture. These carbs were set up pretty lean from the factory, so with a low restriction air filter and lower restriction exhaust, a slight enrichment would be necessary. If all the jets and the needles are factory spec, then I would hold off on the shims until the problem is solved. As Cra-z1 notes, choke plungers are another likely culprit. If they are leaking, the mixtures will be rich.

TexasKZ,

That makes sense. 

The choke rod that goes horizontally through the carbs is not an area I have looked at for leaks.  Sounds like something worth looking at, since everything else is factory spec.

Not sure if I've seen any kits for that though,  have you? 

 

Refer to member Zed1015 for refurbed choke plungers, a lot of the guys on here are running them and are very happy