Topic: Rubber plug missing in the carburetors?

[Jimcg]

I took the carbs off my CB650Z to clean them, following an extraordinary good instruction I found here somewhere, l think it was recommended by member fizzlebottom. In that instruction, it shows a rubber plug supposed to sit under the slow jets. The carbs on my bike didn't have those plugs when I took them apart. I have bought a set  of those plugs. Do all VB carbs have those plugs and should I install them? How would gas get into the jet if there is a rubber plug?

My bike is a 1982 CB650Z and the carbs are marked VB54D.

I know the instruction isn't written exactly for my model of carbs but is still very useful.

Here is a picture of one of my carbs and the set of plugs.

url=https://flic.kr/p/2rnHBtR][/url]Rubber_plug_missing_or_not by Jim Gahnfelt, on Flickr


Rubber_plugs by Jim Gahnfelt, on Flickr

[seanbarney41]

Yeah, I have encountered this mystery before as well.  I was rebuilding a set of these carbs at the shop I was working at, I believe they were for an '81 or '82 cb650c.  Like yours, the rubber plug was not there.  Very similar carbs on other model bikes (such as the dohc 750) DO use that rubber plug and that jet is fed by a passage that comes into the side of the jet well from one of the other jet wells.  When I looked at the parts fiche for an '81 cb650c, the plug is depicted and numbered, but that number is nowhere on the parts list.  I took that to mean that those plugs are not meant to be in there for that model bike.  I left the plugs out and returned the carb rack to the customer.  That was about 3 weeks ago and I have heard nothing more from the customer.  No idea if he has installed the carbs or whether it runs good or not.

[MauiK3]

If there is no side entrance into the area under the jet then I guess one can infer that the plug cannot be there.

[seanbarney41]

Not sure about that...the side passage may be there whether the plug is used or not

[Jimcg]

Thanks for your answers. Then I'll just go ahead without the plugs. After all, the bike ran well. The reason I took them apart was because of a leak. I did check for a small hole on the side of the "tower" that the jet sits in but couldn't see any opening.

[Jerry Rxman Griffin aka MuthaF'er]

I have been cleaning my VB carbs on my 83 CB1100F. I'm waiting on some 12mm fuel line to the auto-petcock before I finish. They look identical to yours. Maybe VB 56? There were no plugs like you show in any of the 4. Where is it that you describe they might fit? The only thing I found UNDER the slow jets was at the threads was a metal backed seat o-ring for the spring that I accidentally found when I hit it with my compressor. Damn close call at 120psi! Not the same as you show and probably nowhere to be found separately.

[Jimcg]

I have been cleaning my VB carbs on my 83 CB1100F. I'm waiting on some 12mm fuel line to the auto-petcock before I finish. They look identical to yours. Maybe VB 56? There were no plugs like you show in any of the 4. Where is it that you describe they might fit? The only thing I found UNDER the slow jets was at the threads was a metal backed seat o-ring for the spring that I accidentally found when I hit it with my compressor. Damn close call at 120psi! Not the same as you show and probably nowhere to be found separately.

Look at the top of page 23 in this excellent rebuild guide
https://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revG.pdf

[Jerry Rxman Griffin aka MuthaF'er]

Excellent Jim!!!!!  and better pics than the manuals 

[Pbeattie89]

I believe there is a passage drilled in the side of the post that the jet threads into that supply's the slow jet.

Sent from my SM-G991W using Tapatalk

[fizzlebottom]

I can definitively say that there were no plugs for the VB44A or VB44C carbs used in '81 & '82 CB650s. But I have never seen anything about the VB54D carbs since that bike was built for export to a country other than the US or Canada.

Wish I knew more, but I think following the advice of others and checking for a hole in the jet post will get you the right answer. I suspect its the same as the VB44 carbs and you can omit the rubber plug.

[Mikey G.]

Another option is to check parts diagrams (CMSNL is my go-to), to see if the plugs show up there.  It's a great way in general to double check if you're missing things you don't even realize you're supposed to have.

[Jimcg]

Thanks for your answers. I did check for and couldn't find any holes, so I'll skip the plugs. Hopefully I will receive the accelerator pump parts soon and after that it's time to put the carbs back on the bike. Can't wait! The whole summer is almost over and I haven't been able to ride at all.

CMNSNL is a truly great source of information and parts. The problem I have is finding my specific model there. My 650 is standard model, not custom. The Honda model name for it is RC03 and it's from 1982.

[fizzlebottom]

Thanks for your answers. I did check for and couldn't find any holes, so I'll skip the plugs. Hopefully I will receive the accelerator pump parts soon and after that it's time to put the carbs back on the bike. Can't wait! The whole summer is almost over and I haven't been able to ride at all.

CMNSNL is a truly great source of information and parts. The problem I have is finding my specific model there. My 650 is standard model, not custom. The Honda model name for it is RC03 and it's from 1982.

I looked for the '82 CB650Z on CMSNL as well and couldn't find anything. I am finding a lot of conflicting info about which years the SOHC CB650z was produced, so I couldn't give an accurate idea. RC03 might refer to the '79-80 models, which probably originally came with PD carbs. I've seen RC05 and RC08 for later years. It wasn't uncommon for folks with PD carbs to swap CV carbs on simply for parts availability (or so I've heard). For the US model this would also require a cylinder head swap due to different intake spacing. And when taking the cylinder head off, there was an opportunity for some EU models to switch out the 50hp camshaft to the 63hp camshaft.

So you might have an '82 CB650Z with a swapped '79-80 motor but the original '82 cylinder head and carbs. I could be completely wrong about this though. You might have an fully original bike.

Honestly, none of this matters so long as you get the bike running right and enjoy the hell out of it.

[Jimcg]

Thanks for your answers. I did check for and couldn't find any holes, so I'll skip the plugs. Hopefully I will receive the accelerator pump parts soon and after that it's time to put the carbs back on the bike. Can't wait! The whole summer is almost over and I haven't been able to ride at all.

CMNSNL is a truly great source of information and parts. The problem I have is finding my specific model there. My 650 is standard model, not custom. The Honda model name for it is RC03 and it's from 1982.

I looked for the '82 CB650Z on CMSNL as well and couldn't find anything. I am finding a lot of conflicting info about which years the SOHC CB650z was produced, so I couldn't give an accurate idea. RC03 might refer to the '79-80 models, which probably originally came with PD carbs. I've seen RC05 and RC08 for later years. It wasn't uncommon for folks with PD carbs to swap CV carbs on simply for parts availability (or so I've heard). For the US model this would also require a cylinder head swap due to different intake spacing. And when taking the cylinder head off, there was an opportunity for some EU models to switch out the 50hp camshaft to the 63hp camshaft.

So you might have an '82 CB650Z with a swapped '79-80 motor but the original '82 cylinder head and carbs. I could be completely wrong about this though. You might have an fully bike.

Honestly, none of this matters so long as you get the bike running right and enjoy the hell out of it.

In my case it says CB650 RC03 in the registration document. The "Z" is something I thought was the name for the standard model, meaning non custom.

There are no signs of motor or carbs being replaced (which, of course, is no guarantee). The bike had been sitting for many years when I bought it a few years ago and had only been ridden a bit over 1370 miles (2200 km), which seems accurate when I compare to milage at the times it's been at road safety inspection.

But I agree, most important now is to get it running. Hopefully before winter comes. Still waiting for accelerator pump parts and problems with my order at cmsnl for the two lousy tee vents. Tried to make my own out of rubber hose and they look good but didn't find the proper type of hose. Tried with fuel hose first, thinking the hose might dissolve other types of rubber if fumes goes out there but that hose was to stubborn when I tried to join the carb pairs. Did another try with vacuum hose which seems to work but eventually chickened out. I asked myself how I would feel if it became a problem (either with the glue or the type of hose i used) after a while just because I tried to save 130 € and have to take the carbs off and apart again.

So now I'm stuck waiting for cmsnl while hoping for a long, warm and dry autumn in Sweden this year.