Carby Issues

[Ralf the RR]

Hi all,
My first post.

Just picked my Mighty Boy today.
It doesn't idle - just stalls.
Keeping it revving seems to work, but not practical.

Having a look at the carb, I think the previous owner has messed up the plumbing.
Currently (looking at the carb from the front) the top front hose is blanked.
The bottom hose goes to the secondary actuator.
The vac advance comes from the bottom LHS (RHS when looking at carb).

Anyone got a photo or can describe where all the hoses go would be very helpful. The manual doesn't really help me much.

Harry

[Flinny]

you need to get braydens attention, he'll sort ya out

[Trevor]

Check the idle solenoid. When you turn the ignition on you will hear it click, or turn the ignition on and unplug the wire that goes to the carb and just re plug in and out and you will here it click. no click no good. Other than that there will be blockage in the idle circuit.

[Brayden]

If you can supply a photo of what you currently have I can probably tell you whats in the wrong place.

Having hoses around the wrong way shouldn't affect the idle though. I would be taking Trev's advice and checking the idle solenoid. Apart from that I always rebuild the carby on any MB that I buy. Haven't bought one yet with a carby that was in 100% working order.

[Ralf the RR]

Thanks for the response.

Idle solenoid clicks.
Is there a way to actually verify that it works other than the click?

Here's a shot from the front.
I think the hoses are wrong.
http://good-times.webshots.com/photo/21 ... good-times


Here's where the vac advance goes (bottom of carb).
You can just make out the hose between the dizzy & eng mount.
http://good-times.webshots.com/photo/21 ... good-times

[ike849]

to answer your question....compared to the carbs i have;

- the front hose that is blocked off should go to the diaphram to open the secondary.
- the one that is going to the secondary should go to the dizzy.
- below your fuel hose on the front of the carb should be the pipe which connects to the hose that is currently connected to your dizzy. It should go around to the back and finish on the LHS of the idle mixture screw.
- on the RHS of the idle mixture screw at the back should be a short hose that connects to just above it.
- on the RHS of the carb should also be a short hose that connects to just above it. (yours currently goes to the dizzy)

i'm not sure if mine are the right way either as mine has a bit of jerckyness at at part throttle when throttling off (if that makes sense)....but other than that idles perfectly.


In saying all that brayden and trev are right, the hose positions don't have a great affect on idle, so probably won't be your problem.

1st check your idle screw, big hand adjustable screw to the right'ish of the accelerator and choke cables at the back. screw it in until you can see it is opening the throttle. Turn on car and adjust back to the correct idle.

2nd if that's not your problem, check the idle mixture screw (aka idle air metering screw). this is the screw i was referring to earlier with vacuum hoses to the left and right of it. (flat head screw that's brass looking).

VERY important count the number of turns it takes to screw it in fully (not too tight).
WRITE THIS DOWN ON PAPER!!!!

From memory mine was 2 1/2 turns. Now unscrew yours all the way out, being careful as there is a spring and tiny washer.

Spray some carby cleaner in there then compressed air. This will unblock the metering passage. Have a close look at the needle tip on the screw, if it is bent or has a big scratch on it you can pretty much throw it away as it will never 'meter' the correct amount of air again.

Re-assemble (remembering the spring & washer) screwing it all the way in and then the number of turns out you wrote on your piece of paper.

Start car and adjust the screw half a turn at a time to find the 'sweet' spot for idle. (can't remember if IN is leaner and OUT is richer or visa-versa)

Just for reference my other carb doesn't have the 2 hoses next to the mixture screw and it doesn't have the part at the front that the left hand one goes to. (all the holes have been blanked off by suzuki)

[Ralf the RR]

Thanks Ike,
Still a little confused though.

Swapped the secondary and vac advance hoses as you described.
Still confused about the others.

On the LHS of the idle mixture are 2 pipes, upper and lower.
One goes to the accel pump. The other I connected to the RHs of the carb.

The are no pipes on the RHS of the idle mixture.

It's now "sort of" idling. A bit high and inconsistent. Turning down the idle speed will stall it. Also the idle mixture doesn't do much.

[Al_Zhiemer]

When the car is idling, is there a strong fuel smell to the exhaust fumes??

If there is, at a rough guess i'm now thinking that the float needle is dirty or has a groove around it where it sits. this allows the fuel to basically keep flowing and causing the car to run rich...

On the rare occassion i have found that the float in the bowl may also need adjustment, if the bowl rises to high this allows to much fuel in as well. also causing it to run rich on idle...

Only way to see if either of these is the problem is to remove the top of the carby to check the needle and also the open and closed measurements of the bowl, be careful when doing this as most times it will destroy the gasket when you split them apart. Make sure you have a spare top carby gasket when you do this just in case you do destroy it...

Personally if your going to do this i would suggest buying a carby rebuild kit and doing the whole thing.

Cheers

[mini_kompressor]

Have you checked for an air leak? Any air leak will cause the simptom you are describing. Try spraying a little bit of carbyclean, or water, around the manifold gasket and around the carby whilst running and see if there's a change in engine behaviour.

[Brayden]

I'd just like to say that there are some great suggestions in this thread. I'm impressed we have a growing number of really knowledgeable members who are willing to share.

Top work guys.

Just as a note on this particular problem, Harry is your MB an automatic? I ask because you have an automatic carby - so there may be some differences between what you see and what people are describing in this thread.

[Ralf the RR]

I'd like to re-iterate Brayden's comments.

It's very helpful knowing that there are people with knowledge and willing to share.

Thank you all for your comments.
Still tracking down the problem.

To answer the question - it's a manual.

Also found out today - it's had an engine change.

Still not idling correct.
It's hunting. Can't say exactly, but probably from 1200 rpm for about 2 sec, then quickly up to maybe 1500/1800 rpm for about a second, then back down again.

Is it worth blocking off all the hoses and sticking with the basics.
Just need - Secondaries - Vac Advance - Accel pump.

[Jermaine]

could be inlet manifold leak.. spray airo start or somethin around it like suggested before.. and check the tension of the inlet manifold bolts

[Flinny]

can i just say, i've got 4 mb's and 5 carbys and they"re all different(set ups)
take it to someone who knows-money well spent.....good luck

[Brayden]

I'd like to re-iterate Brayden's comments.

It's very helpful knowing that there are people with knowledge and willing to share.

Thank you all for your comments.
Still tracking down the problem.

To answer the question - it's a manual.

Also found out today - it's had an engine change.

Still not idling correct.
It's hunting. Can't say exactly, but probably from 1200 rpm for about 2 sec, then quickly up to maybe 1500/1800 rpm for about a second, then back down again.

Is it worth blocking off all the hoses and sticking with the basics.
Just need - Secondaries - Vac Advance - Accel pump.

The plot thickens! What motor does it have now? F5A or F8B. I have a suspicion that it might have been upgraded to an F8B but still has an F5A (auto) carby fitted. That would explain a lot if it were true!

For the sake of $75 I would buy a carby kit and rebuild it though.

[Ralf the RR]

The plot thickens! What motor does it have now? F5A or F8B. I have a suspicion that it might have been upgraded to an F8B but still has an F5A (auto) carby fitted. That would explain a lot if it were true!

For the sake of $75 I would buy a carby kit and rebuild it though.

I've just had all the dramas of getting a blue slip.
The replacement engine is a F5A. Well that's what the guy put on the slip.
I didn't check it myself. (will later)

And you wouldn't believe it
It now idles.

And I haven't touched it since yesterday when it was hunting.
While driving it today, the idle was way high (maybe 2000/2500), but smooth.
Turned the idle speed down - and it's good.

So since yesterday - it cured itself.
Maybe I should call it Christine
However, my daughter already named him Max