Topic: Noob Carb Questions... 82 CB650SC - VB44C Carbs

[jafierst]

I purchased a 81 CB650C a few months ago for $200.  It is running way to rich and fouling the plugs (this seems to be a common problem judging by the number of posts on the subject here.)  I bought a set of the VB44C carbs off of Ebay because I figured I'd rather spend the money rebuilding the VB44C carbs and end up with ones that work, instead of rebuilding the VB44A's and end up still running rich (from the previous 81 CB650C running rich posts).  When I received the new carbs they were filled with a white dusty residue (aluminum oxide?) and some gritty sandy stuff.  After removing all the jets and needles (with the help of a new easyout to remove a stuck jet and the dremel to cut a slot in a broken off idle screw) I soaked them in a 5 gallon bucket with hot water and a bottle of simple green.  I have ordered 4 Keyster KH-1078N kits (see image below from siriusconinc.com) and can't wait to install them.

Now for the questions:
1)  I think I read on here somewhere that I may need to grind off the ends of the screws that hold the throttle and choke butterflies on their respective shafts.  I see that the ends of the screws have been split and pinged over to keep them from comming loose.  I am afraid of messing up the treads in the butterflies if I just back them out.

2)  Should air be able to go through the Red circled port in the picture of the bottom of the carb?  I have tried filling it with carb cleaner overnight to see if it would leak out but it remains plugged or clogged.  Also, how do the holes in the top of the carb match with the holes in the bottom (I did figure out the Blue port goes to #1  )

3)  In the picture of the Keyster Kit... What is the item circled in red?  I don't remember removing anything like this...

4)  Would it be a bad thing to sandblast the bowls clean?  I can't imagine that it would make them worse off then they allready are.

Thanks in advance for any help!

[Ibsen]

As far as I can tell from the diagram in my Haynes manual, the jet you have marked with a round circle in the Keyster kit is the needle jet.

[jafierst]

Thanks Ibsen!  I definately didn't remove that yet, now I just need to get a small dowel rod and press them out.  Thanks again.

[Ibsen]

Canuck might be right about the needle jets since he has been there already. The workshop manuals I have for the 650 are very confusing about the parts diagrams for the different carbs used on these bikes and it is very difficult to decide which parts you will need to use or not.

But I'm a little confused by the fact that the parts diagram for the VB44 carbs on the parts diagram on the MrCycles website clearly shows that there is a needle jet there that is replaceable. It is part of a set that also includes the needle jet and it's spring and its retainer. My Haynes manual show the same jet needle in the parts diagram. And to make the confusion complete, it looks like the parts diagram in the Clymer manual have got the needle jet wrongly marked, although in the service chapter they show a picture of how to install a needle jet.
One thing you should keep in mind though is that after market needle jets don' t always have the accuracy needed. This has been a problem with the after market kits for the Honda GL carbs and the early Kawasaki KZ400 carbs (same type of vacuum carbs), so replacing them could make things worse, and not better. A good rule of thumb is that you should never throw away, or destroy a part during disassembly if you can avoid it. You never know when you will need it.
And why all this fussing about the needle jets? Because the jet needles and the needle jets are the two parts in the carbs that are bound to be worn over time. And in the range between off idle and up till approx 1/2 throttle where the vacuum slide (and needle jet) reaches it's most upper position,they are the heart and soul of the carbs. If you plan on riding this bike on full throttle all the time it doesn't matter that much if these parts are worn, but at lower speeds and at cruise speeds it will be very noticeable if they are worn or the wrong size. 

Another thing is that the difference in jetting is based on the model carbs you got, and what bike they were for.
The VB44-C carbs are listed as 650SC US carbs and have got smaller jets than the VB44-A carbs that was used on other US models. So 120 main jets and a 100 main air jets might be the correct jetting for the carbs. The VB44-C carbs are listed with 118 main and 80 main air jets. Both have got the same jet needle listed btw.

[jafierst]

Thanks for the replies guys.  I ended up separating them last night.  I now understand why Canuck suggested not to.  They came apart easy enough, but I can see that putting them back together is going to be loads of fun.  I wanted to see if I could find a decently priced alternative to those vent tees that everyone seems to have problems with.  I ended up ordering some barbed hose tees from McMaster Carr that should be able to be modified to fit, and for $2 each I figured it can't hurt to try.  I'm gonna head out to Lowes tonight and get a couple of small wire brushes for the dremel to clean up all the crap in the bowls.  I spent last night using a small pick trying to remove all the deposits, now I understand what it's like to be a dental hygienist.  Hopefully my kits will come in the mail this weekend and I can start the reassembly.

Next step will be to get the old carbs off the bike, I am not looking forward to that at all.  I've had them off 3 times since I've had the bike, but the airbox was never in when I took them off, so I had more room to work with.

[juntjoo]

Thanks for the replies guys.  I ended up separating them last night.  I now understand why Canuck suggested not to.  They came apart easy enough, but I can see that putting them back together is going to be loads of fun.  I wanted to see if I could find a decently priced alternative to those vent tees that everyone seems to have problems with.  I ended up ordering some barbed hose tees from McMaster Carr that should be able to be modified to fit, and for $2 each I figured it can't hurt to try.  I'm gonna head out to Lowes tonight and get a couple of small wire brushes for the dremel to clean up all the crap in the bowls.  I spent last night using a small pick trying to remove all the deposits, now I understand what it's like to be a dental hygienist.  Hopefully my kits will come in the mail this weekend and I can start the reassembly.

Next step will be to get the old carbs off the bike, I am not looking forward to that at all.  I've had them off 3 times since I've had the bike, but the airbox was never in when I took them off, so I had more room to work with.

Did that ever work out for you? If so what are the dimensions on that barbed t if you halogen to remember?