Carb dirt issue...or not?

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Beryls_boss

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Hi all,
I have a 1600 twin port in my 71 early bay, running a 34 PICT 3.
It's a newish 'chinese quality' unit but it was easy to set up and seemed to be ok.
Only done 1000 miles in it as I don't do a lot of mileage.
I think the carb is ok.

We're based in London and on the way to the Latitude festival in Suffolk this year we broke down.
We were running fine and then we started bunny hopping.
I pulled over and the van stalled.
I got it restarted but it was coughing and spluttering with not much throttle response.
Then it cleared and we drove another 5 miles with it intermittently coughing and stalling, then restarting, clearing and driving fine.
My initial thoughts was dirt in the carb.
I called the AA anyway and they got us running by clamping the fuel supply, 'sucking the dirt through the carb' and then setting off- but with the choke full on (held by a cable tie). Got us to the campsite, 45 minutes and probably 30 miles away. That was Thursday.

On Saturday, i started the van , it ran fine for a few seconds, then spluttered and died.
I took the carb off, took the float chamber cover off, cleaned the chamber out (think there was black stuff in there), blew the jet in there through and put it all back together.
Started first time all fine.

On the Sunday at Midnight (going into Monday) it started fine and we drove home- 3 hours and a hundred and fifty ish miles in the dark. Didn't miss a beat, which I was thankful for!

Monday AM, I used the van to drop the kids locally to school- on second drop off, about a mile into the journey, ten minutes after start up, same issue, rough running, spluttering, died.
Took the carb off, couldn't see dirt, blew the jet through, put it all back on.....same issue! Spluttering, stalling.
Tried it a few times, eventually it worked and i drove home, no issues.

I bought an unknown condition second hand Bocar carb. Cleaned it, put new main gasket on it and put it on the van.
Same issue. Exactly.

I'm not sure where to start.
I'm not totally convinced it's dirt though- filter looks clean.
Can a fuel pump run intermittently?
Or the coil?
Points?
Any ideas on my next steps ?
Any help appreciated.
Thanks
Kevin
 
I’ll probably get the same - that’s why I’m asking where to start other than the carb. Don’t think it’s the carb itself.
 
First, I’d check your fuel supply to the carb. Take out the rotor button and pop the cap back on tightly. Pop the fuel pipe off from the carb and lay it into a large one or two litre water bottle about an inch or so and lay the bottle on its side. Instruct your glamorous assistant to crank it over while you hold the pipe in the bottle. On vinegar stroke, the spurt should be hitting the bottom of the bottle and bouncing about inside the bottle. If it is, then it’s after this bit and probably your carb, if it’s weak then it’s a blockage before this bit or a poor fuel pump slowing the supply. This way you can find fault or eliminate your fuel supply. It sounds to me though that there is air getting in there somewhere possibly in the manifold set up ? Or gasket issues.?


Ozziedog,,,,,,,keep us posted. :mrgreen:
 
First off without meaning to sound negative you’re in for an up hill battle using a repro carb, id highly recommend sourcing a good used carb or get a refurbed unit from Rage or cogbox.

But I digress, if your have issues with crap in the fuel you want to go through the whole fuel system. Drain and flush the tank, change the fuel filter and inspect the pipes and change if required as well as the fuel pump.
 
Thanks for the advice guys.
Carb wise, fair points about repro, I am considering a twin carb set up eventually.
Thanks Ozziedog- I was thinking fuel pump but it’s such a simple mechanical set up I wasn’t sure how it could work intermittently but I’ll give your fuel flow test a go as a starter.
Thanks again
 
Beryls_boss said:
Thanks for the advice guys.
Carb wise, fair points about repro, I am considering a twin carb set up eventually.
Thanks Ozziedog- I was thinking fuel pump but it’s such a simple mechanical set up I wasn’t sure how it could work intermittently but I’ll give your fuel flow test a go as a starter.
Thanks again


Just don’t set yourself on fire, and then you’ll have a starting point as to which way to go.

Ozziedog,,,,,,,,,go careful :mrgreen:
 
Great advice - van caught fire last year when the old carb , which had been smelling ‘ a bit petrolly’ for 4 years, finally let go. Luckily it burnt through the accelerator cable first so I got it early cos the van stopped moving . I am super paranoid around petrol now- no such thing as too careful.
 
K@rlos said:
First off without meaning to sound negative you’re in for an up hill battle using a repro carb, id highly recommend sourcing a good used carb or get a refurbed unit from Rage or cogbox.

But I digress, if your have issues with crap in the fuel you want to go through the whole fuel system. Drain and flush the tank, change the fuel filter and inspect the pipes and change if required as well as the fuel pump.

I've got a bocar and it works just fine, so my advice would be to check the other circuits around the carb - all of them. Get 2 quality rebuild kits and a can or carb cleaner and have a full dismantle. Reassemble, adjust & carry spare carb kit around with you. There's nothing like having a spare kit and a can of carb cleaner...... You only get problems when you don't have them with you.....
 
I know the thread is a few months old but I had similar to this but I had twin 34's . My bus went on a trip to Malvern (50 odd miles) for a vw show , it drove fine there with only a couple of slight engine power grumbles . Park up for the weekend. Then set off home after about 5 mins it kept spluttering and looseing power . Could pull over and it would tick over fine and even restart fine . Would rev fine but set off again 2 mins and it would die , this kept happening even though I changed a few things on the rd . After scratching my head and a mate pulling over to help we found out the fuel pump had become weak and it was basically supplying enough fuel to fill the carbs on tick over but as soon as it was underload the pump couldn't keep up with the demand and the carbs were emptying . I managed to get home by building up speed to the point where it would die dipping the clutch and coasting untill the carbs were full again . It took a while to get home but got me there . A new pump and was all good again . Just an idea and maybe give you something to think about [emoji106]

Sent from my FIG-LX1 using Tapatalk

 
bac2ba6 said:
I know the thread is a few months old but I had similar to this but I had twin 34's . My bus went on a trip to Malvern (50 odd miles) for a vw show , it drove fine there with only a couple of slight engine power grumbles . Park up for the weekend. Then set off home after about 5 mins it kept spluttering and looseing power . Could pull over and it would tick over fine and even restart fine . Would rev fine but set off again 2 mins and it would die , this kept happening even though I changed a few things on the rd . After scratching my head and a mate pulling over to help we found out the fuel pump had become weak and it was basically supplying enough fuel to fill the carbs on tick over but as soon as it was underload the pump couldn't keep up with the demand and the carbs were emptying . I managed to get home by building up speed to the point where it would die dipping the clutch and coasting untill the carbs were full again . It took a while to get home but got me there . A new pump and was all good again . Just an idea and maybe give you something to think about [

Sent from my FIG-LX1 using Tapatalk


That’s exactly why I wrote that above ^^^, fuel pumps don’t just stop working as a rule, they and their components get older and weaker with age (like me :? ) as they get older they pump less fuel because they’re worn out (like me) :roll: Diaphragm rubbers wear out, spindles wear out, push rods get worn etc etc. If you have an original pump then it’s possible to get a rebuild kit for it but even then, if it’s been made in the last couple of years it’s possible that the rubber components are no where near as good as the original ones. But with a lot of repro pumps, their life span is not measured in decades but in months and sometimes even weeks :shock: and part of this is to do with crap rubber and partly to do with the ethanol content of modern petrols. Another helpful thing if your pump is old, is a full tank will shove juice out and make it a little easier on a weak pump because of gravity.

Ozziedog,,,,,,,,, It’s a good place to start with the bottle test :mrgreen:
 

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