Topic: CB650SC Carbs... nerd time!

[smiffy1071]

Hello chaps! I have a 1982 CB650sc, which is a US market bike. Over the last 2 years or so, I've been changing the spec to make it more UK market.
This includes a different facing headlight, changing the switchgear, so I can turn off the headlight, changing where the daytime running lights are wired into, removing the 85mph stop peg on the speedometer, rebuilding the starter clutch (which was knackered) and Changing the standard VB44c carbs in favour of VB54 ones.

The reason I did this last change, is before, my bike would really struggle to do more than 80mph...
20 years ago, I had a genuine UK spec CB650sc-c which I clearly remember doing 120mph!

My question is, are US bikes really that slow, or do I have a dud one?

[CBJoe]

Welcome to the forums...

No....US market CB650's are not that slow.  Immediate questions that come to mind are;

*Have you checked for leaks in the carb manifolds or the airbox rubbers?? 
*Are you running with the stock airbox setup?
*have you replaced the 28 year old air filter?
*how do the plugs look (you've replaced them...right?)
*make sure that the Previous owner hasn't screwed with the front/rear sprockets.... what RPM are you running at when you hit 80mph?

You're lucky in that the VB44"C" carbs have the screw in slow jets that allow for easier removal and cleaning. 

Regards, Joe

[cb650]

try running with the air filter cover off.

[BK.RD.RNR]

Don't want to step on anybody's thread, If I should start my own then please say so...

I just had a question regarding the differences in carbs between an sc and non-sc model. I have an 82 650sc, and want to get a carb gasket/ rebuild kit. The problem is I have no intention of spending near $200 for 4 OEM kits. I was considering getting one of the ones on this site...

http://www.carbkitscapital.com/carb_kit_list_model.php?make=Honda&model=CB650

But there is no specific mention of them being for an SC model. I also notice the OEM part #'s are the same for the float needle between C, SC, and non-SC models.

Also has anyone purchased similar kits, and did they include the O-rings for the fuel rails? That is the only place where I have found and confirmed a leak.

Any input would be greatly appreciated.
Thanks,
BRR

[smiffy1071]

Welcome to the forums...

No....US market CB650's are not that slow.  Immediate questions that come to mind are;

*Have you checked for leaks in the carb manifolds or the airbox rubbers?? 

I didn't check, but I've now replaced all these for new ones

*Are you running with the stock airbox setup?

Yes

*have you replaced the 28 year old air filter?

It looked clean, but I just found a new old stock item...still in its box!

*how do the plugs look (you've replaced them...right?)

To be honest, the whole engine wasn't that great, the head gasket leaked, and it was losing oil faster than BP!
I've actually built up a good engine from parts of 3 others, and of course there are new plugs and HT coils & leads.

*make sure that the Previous owner hasn't screwed with the front/rear sprockets.... what RPM are you running at when you hit 80mph?

The sprokets were standard, it was pulling about 8000rpm

You're lucky in that the VB44"C" carbs have the screw in slow jets that allow for easier removal and cleaning. 

I can tell you when I took the carbs off, the vacuum take-off point (for synchronising) was full of black silicone, the vent "T" pipes between 1-2 carbs, and 3-4, were split, the accelerator pump diaphragm was split, and the main jets instead of being 120, was a 78!

Regards, Joe

[smiffy1071]

try running with the air filter cover off.

Much about how the bike WAS running has now been changed, for example it now has a different engine, and different carbs.  If it were still the same Id try this just to see if it was air starvation, but then it would leave the problem of what to do about it... after all, honda didn't design it to run like that!

[smiffy1071]

Don't want to step on anybody's thread, If I should start my own then please say so...

I just had a question regarding the differences in carbs between an sc and non-sc model. I have an 82 650sc, and want to get a carb gasket/ rebuild kit. The problem is I have no intention of spending near $200 for 4 OEM kits. I was considering getting one of the ones on this site...

http://www.carbkitscapital.com/carb_kit_list_model.php?make=Honda&model=CB650

But there is no specific mention of them being for an SC model. I also notice the OEM part #'s are the same for the float needle between C, SC, and non-SC models.



Yes there is, scroll down the advert to the bottom of the page you linked to, where it will say cb650 1981/2 cv carb rebuild kit.

These kits don't include the accelerator pump kit, which you will have to buy seperatly. Genuine honda price for that is over £80, which is outragious! Look for the aftermarket kit meant for CB900c models, K&L 18-2811. you will need to shorten the rod by about 4mm.

Also has anyone purchased similar kits, and did they include the O-rings for the fuel rails? That is the only place where I have found and confirmed a leak.

Very unlikely they will contain the o-rings you want. I've just done these myself, and it's a pain in the bum! Pay extremely close attention to how the throttles and chokes are linked together, before you separate the carbs from the frame, this will help you when you re-assemble them.
I took my carbs to work (I work for a large bus company in England, who might also run the yellow school buses in the USA) One quiet afternoon, I looked in the workshop, and searched through the collection of o-rings they had. I very soon found the 6 o-rings for the fuel rails, and the 6 smaller ones for the other rail.
In your case, I'd take one carb off the frame, and then remove the two solid pipes, and take them to your local car parts shop. They will have o-rings of all sizes, for just a few cents each.

Any input would be greatly appreciated.
Thanks,
BRR

[Hush]

The American market CB650 came with emmission control devices that stopped you enriching the mixture beyond a very small range, possibly that is the diff between the US and Anglo models.

[smiffy1071]

Yes, they did have large plastic caps which are glued onto the pilot air screws after they have been set up. Also, I notice when you compare the american and the english side by side, the airways are a little different, and of course the jetting is very different. The US is a size 120, where the UK is a size 98. the pilot jet is removable on the US one, but fixed on the UK.
I wonder how this affects the power output?

[cb650]

The cover thing does work.  Many have done it I have seen it work in person on a stock bike that wouldnt run right.  Even with a set of my good carbs.

[Soos]

Hello chaps! I have a 1982 CB650sc, which is a US market bike. Over the last 2 years or so, I've been changing the spec to make it more UK market.
This includes a different facing headlight, changing the switchgear, so I can turn off the headlight, changing where the daytime running lights are wired into, removing the 85mph stop peg on the speedometer, rebuilding the starter clutch (which was knackered) and Changing the standard VB44c carbs in favour of VB54 ones.

The reason I did this last change, is before, my bike would really struggle to do more than 80mph...
20 years ago, I had a genuine UK spec CB650sc-c which I clearly remember doing 120mph!

My question is, are US bikes really that slow, or do I have a dud one?

?
80??

Your carbs need professionally gone through?
Air leaks? cracked old O-rings?, lots of problems with cb650 carbs (IMO)
(I am secretly working on modifying a set to work W/O air cutoff valves, or a accel pump for the older '79/'80 cb650 carbs.)




I can hit 100 still, even though I have a 550 cam in my 650.
('79 cb650, 652cc(61mm pistons), 32mm CV carbs(not stock by any means), a 550 cam(yes a stock 550 cam), and a fairing)



However, with my 99% stock '79 cb650, I can hit 105.
(stock carbs, pistons, and no fairing on this one)


??



And YES, the rest of the world after '82 got BETTER CV carbs for the 650.
The slow jets SCREW IN instead of press in like the '79-'82 cb650 carb slow jets.

[Soos]

Yes, they did have large plastic caps which are glued onto the pilot air screws after they have been set up. Also, I notice when you compare the american and the english side by side, the airways are a little different, and of course the jetting is very different. The US is a size 120, where the UK is a size 98. the pilot jet is removable on the US one, but fixed on the UK.
I wonder how this affects the power output?

Depends on year and country of origion.


The '79's came out with 98's.(NON CV carbs)
The '81/82's I have seen had 105's(CV carbs)
The Canadian '84(?'83?) cb650 carbs I got (yes for the SOHC still) had 120's I believe.
l8r

[smiffy1071]

I did even toy with the idea of putting CB900F carbs on it, but wasn't sure how well it would work.
However, I've built the bike up now, and the engine seems to run quite sweetly. I just need to set up the timing properly, and then figure out why it won't charge. I think it's the rotor, as that is the only thing on the bike that has been changed since it last ran when it worked ok.
I'm going to swap the rotor for the one that was previously on it, and hope for the best....I'm really no good at all with electrics!

[BK.RD.RNR]

Don't want to step on anybody's thread, If I should start my own then please say so...

I just had a question regarding the differences in carbs between an sc and non-sc model. I have an 82 650sc, and want to get a carb gasket/ rebuild kit. The problem is I have no intention of spending near $200 for 4 OEM kits. I was considering getting one of the ones on this site...

http://www.carbkitscapital.com/carb_kit_list_model.php?make=Honda&model=CB650

But there is no specific mention of them being for an SC model. I also notice the OEM part #'s are the same for the float needle between C, SC, and non-SC models.



Yes there is, scroll down the advert to the bottom of the page you linked to, where it will say cb650 1981/2 cv carb rebuild kit.

These kits don't include the accelerator pump kit, which you will have to buy seperatly. Genuine honda price for that is over £80, which is outragious! Look for the aftermarket kit meant for CB900c models, K&L 18-2811. you will need to shorten the rod by about 4mm.

Also has anyone purchased similar kits, and did they include the O-rings for the fuel rails? That is the only place where I have found and confirmed a leak.

Very unlikely they will contain the o-rings you want. I've just done these myself, and it's a pain in the bum! Pay extremely close attention to how the throttles and chokes are linked together, before you separate the carbs from the frame, this will help you when you re-assemble them.
I took my carbs to work (I work for a large bus company in England, who might also run the yellow school buses in the USA) One quiet afternoon, I looked in the workshop, and searched through the collection of o-rings they had. I very soon found the 6 o-rings for the fuel rails, and the 6 smaller ones for the other rail.
In your case, I'd take one carb off the frame, and then remove the two solid pipes, and take them to your local car parts shop. They will have o-rings of all sizes, for just a few cents each.

Any input would be greatly appreciated.
Thanks,
BRR

Thank you very much, best of luck with your project

[smiffy1071]

Happy memories!

My last small bike the little Honda CD125T, and my first big bike after passing my test, the Honda CB650z, this was when I was 19, in 1989.



This is me and my bike back in 1992. It's a 1984 CB650SC-c, UK spec, and in a colour that you guys across the pond didn't get NH110M-U Magnum silver metallic.  I was 21!



And finally, my little collection of bikes in late 1992. Featured here, Yamaha RD200, Honda CB250G5, Restored CB650z, and CB650SC-c.



I worked for a large motorcycle shop at the time, and was able to find lots of very cheap parts!

[scunny]

nice collection.

[Soos]

I did even toy with the idea of putting CB900F carbs on it, but wasn't sure how well it would work.
However, I've built the bike up now, and the engine seems to run quite sweetly. I just need to set up the timing properly, and then figure out why it won't charge. I think it's the rotor, as that is the only thing on the bike that has been changed since it last ran when it worked ok.
I'm going to swap the rotor for the one that was previously on it, and hope for the best....I'm really no good at all with electrics!

Check out manjisan's fix, a good read is Kit's post on cb650 electrical charging problems.
Or you could troll through TwoTired's posts... to get electrically enlightened or confused.... (I got confuzled)


l8r

[Soos]

I want to get my hands on one of those cb650Z models.
 




l8r

[Pinhead]

For your regulator/rectifier check the link in my signature.

[smiffy1071]

I want to get my hands on one of those cb650Z models.
 




l8r

I was very proud of mine, I bought it when I was 19. It was black, with a 4 into 1 exhaust, no indicators, and an engine that was always weeping oil.
As I said, I worked at the time for a very large Honda distributor, and knew which dumpster to look in, to find parts which hadn't sold for a long time, and were thus considered dead stock.
So, I was able to get a brand new fuel tank and side covers in Candy Tanzanite blue, and both main exhaust pipes, and all 4 indicators for just £50....I just needed to order the 2 middle downpipes, and the blue tail piece.

After it was restored, I then sold it to my dad!