Technical Choke

[britbe]

Hello,

I’m struggling with the use of my manual choke in my 500R (1975). I’ve changed in my VW Bug the carburator with manual choke to an carburator with electric choke and I was wondering if this is also possible on my 500R? Someone has experience with this of can help me?

Thx!

Kr,
Bjorn

 

[bugsymike]

It's funny in the old days people with auto choke carbs ordered manual choke conversion kits for better control and economy. I fitted loads of manual conversion kits in the past. Maybe it just wants adjusting, I am sure there are people here who can advise on your model of carb.

 

[britbe]

Hello, thx for your reply! Indeed, maybe I should first try to adjust it. I was also trying to let my wife drive with the car, but the manual choke is not her best friend ;-)

 

[Toshi 975]

Hi Bjorn, I have never heard of anyone having problems with the choke on a standard carb. As you are probably aware the relevant part is not a conventional choke but actually a fuel enrichment device. Has your car got the original Weber 24IMB resticted carb fitted? If so you can help performance by switching to a 28IMB as fitted to the 126 version of the same engine.

Hello, thx for your reply! Indeed, maybe I should first try to adjust it. I was also trying to let my wife drive with the car, but the manual choke is not her best friend ;-)

 

[the hobbler]

Hi Bjorn, I have never heard of anyone having problems with the choke on a standard carb. As you are probably aware the relevant part is not a conventional choke but actually a fuel enrichment device. Has your car got the original Weber 24IMB resticted carb fitted? If so you can help performance by switching to a 28IMB as fitted to the 126 version of the same engine.

As David (Toshi) has pointed out, the "choke" is not really a choke---it is a 'fuel enrichment device'---there is no 'choke' butterfly in the carb's venturi. There is also not much that can be adjsuted--it is either fully 'ON' or progressively, as you push the lever down, OFF. Basically you pull it fully on (lever up) for a COLD start and slowly push the lever back down as the engine warms up. The 'choke' is not normally required for a 'HOT' start.

 

[fiat500]

Hello,

I’m struggling with the use of my manual choke in my 500R (1975). I’ve changed in my VW Bug the carburator with manual choke to an carburator with electric choke and I was wondering if this is also possible on my 500R? Someone has experience with this of can help me?

Thx!

Kr,
Bjorn

Bjorn, in what way are you struggling? Do you find the choke won't pull on properly or is is operating correctly but doesn't assist cold-starts?
It is possible to loose the clamp screw that secures the outer casing of the cable; the casing can also get damaged. Where the steel wire is clamped it uses a special bolt that, even when tightened, allows the cable to stay stay horizontal as the lever moves; this stops it from binding and gives a smooth action..
If anyone has previously used a braided cable rather than solid wire it could also cause peoblems.

 

[britbe]

Ok, I think I'm looking at the wrong piece then regarding my issue: it's very hard or sometimes impossible to start the car; also when I drive a few km's until the car is hot, if I then pull down the choke completely the car shut's off. Starting again is a hell.

Maybe the carburator is the issue then? I bought the car 2 years ago, I think it has already the 28 carb, looking at the picture?
But maybe it need a rebuild or I replace it.

 

[britbe]

Or should I invest in a 123 ignition?

 

[bugsymike]

What do the spark plugs look like, is the carb running weak?
An air leak could make the problem worse.

 

[Goldnrust]

As mentioned above, checking the spark plugs to see if you can learn anything about how the engine is running isn't a bad move.

There's no need at this stage to do anything as drastic as replacing there carb, but a strip down and clean up wouldn't do any harm, along with checking if the base of the car is flat (they can warp leading to air leaks) and running through the procedure to set the idle speed and mixture. I recently had an issue where my 500 wouldn't idle at all when it was off the choke, which turned out to be a plugged idle jet in the carb, 5 mins of cleaning and it was much better.

Do you have the hand throttle? Most more complicated carbs have a linkage that lifts the idle speed a touch when the choke/enrichment device is on to help the car idle when cold. The simple IMB carbs don't have this, but the hand throttle can help you just add a bit more idle speed to keep it from stalling till its warm.

 

[bugsymike]

If you suspect an air leak around carb base it may be possible to spray a little brake cleaner near it, if engine note changes you may have located it.
Don't get carried away with the spray due to fire risk.

 

[dangfiat]

I had that issue when I first got my 500F (with 650 motor). Was a hard start and would die off choke for the first 5-10minutess. Would die if I pushed the throttle until it reached operating temp. Terrible running.

It's fixed not, starts everytime right when I pull the lever (with choke on if cold). Still dies a bit when throttle until it warms a bit but it's much much better.

Here's what I did:
- Replaced & retimed points & condensor. Did it at 3000rpm/28 degrees (My generator won't power the timing light at idle)
- Replaced the carb mount & gaskets
- Rebuilt the 28IMB, used carb cleaner to clean everything out and put in new idle & main jet
- Replaced fuel filter (mine's at the tank just after the tube comes out)

The first 3 worked well, but the filter really helped (mine was old and yellow)

Still want to:
- replace fuel pump
- replace fuel tank outlet
- replace fuel lines
- check/fix valve clearances

Hopefully that'll clear everything up, but as it sits... the car really runs/starts very well from just the fixes I've done so foar

Ping if you have questions, we'll do our best to answer!

 

[britbe]

Thx for all the replies, really interesting info to test with!

I took a picture of my spark plugs, they are really black, I'm not that specialist but I guess that's not right isn't it?
I also need to mention that I always need to spray brake cleaner in the carb to start the car since I bought it. Does this help to locate the real issue?

 

[bugsymike]

Whow! those plugs are very sooty, I would be surprised if the car didn't misfire under load and run like a bag of ****.
At the least I would strip the carb, check correct jets etc. and ensure needle/float jet is working correctly, with correct float height etc.
Then road test with a new set of plugs.
Your first thread made me think it was running weak, those plugs are the total opposite.

 

[britbe]

Ok, I thought so... didn't look fine ;-)
I'm not a carb specialist, so I think it may be cheaper to just by a new carb then? Replacing the carb is no issue, I did that on other cars already. But testing & rebuilding them not.

Any suggestions for a good carb, or is the 28 I have the best?

 

[bugsymike]

Ok, I thought so... didn't look fine ;-)
I'm not a carb specialist, so I think it may be cheaper to just by a new carb then? Replacing the carb is no issue, I did that on other cars already. But testing & rebuilding them not.

Any suggestions for a good carb, or is the 28 I have the best?

I understand there are some cheap copies that are not much good, though there are others on Forum who can better advise than me on what to go for.
I come at it from a mechanics point of view so I would try a strip and rebuild first rather than throwing money at it, which may not cure the problem.
Often all you need is some good quality screwdrivers and a high pressure air line to blow out the jets etc. You can always take photos as you dismantle it and worse case scenario is fitting a new carb which you are considering anyway.
There are several Forum members here who could recommend the correct jet sizes and how to check the float height etc.

 

[britbe]

I understand there are some cheap copies that are not much good, though there are others on Forum who can better advise than me on what to go for.
I come at it from a mechanics point of view so I would try a strip and rebuild first rather than throwing money at it, which may not cure the problem.
Often all you need is some good quality screwdrivers and a high pressure air line to blow out the jets etc. You can always take photos as you dismantle it and worse case scenario is fitting a new carb which you are considering anyway.
There are several Forum members here who could recommend the correct jet sizes and how to check the float height etc.

Hi, in the meanwhile i’ve purchased a kit to renew my carburator. What do you mean with the float height? Where can i find more information on that and how do I measure this? Thx!

 

[britbe]

And if I renew the carb with which torque/nm do i fasten the bolts?

 

[bugsymike]

I assume the kit you bought is to "service" your old carb, if so it will maybe have new gaskets and a needle float jet etc. The float jet works basically the same as in a cistern or toilet, as in when the liquid reaches a certain height the float rises and shuts off any more to prevent overflowing. So the height is important for two reasons, if set too high the fuel will overflow/flood the engine etc. Whereas if too low a height the engine has a job "sucking" the fuel in resulting in poor running.
However looking at your spark plugs it is getting too much fuel at present.
Another point is to check your old float is not porous or fuel soaked, this results in a heavy float not being able to turn off the fuel flow.
Depending what type of float older brass ones usually have a tab sticking out that contacts the needle jet to cut off the fuel at the correct height, this type you gentle bend a little to get the correct height.
Fibre or solid type floats often can be adjusted by altering the needle jet height with washers where it is screwed in.
Regarding more detailed information on carb float height there is a section on the Forum dedicated to the early/classic 500s, whereas my knowledge is more general from many years in the motortrade.
Regarding nut torque on carb we would generally use a small hand spanner with light to moderate tightening sufficient to nip up the gasket but not to cause distortion of the carb base allowing air leaks etc.
A quick check that a carb needle jet was functioning was to blow (preferably with a clean plastic tube) at the fuel inlet and by turning the carb over in your hand at the same time you could feel when it shut or opened the fuel flow. This is not for float height merely the operation.

 

[britbe]

Many thanks all for your replies; an update from my side: in the meanwhile I've rebuild my carb (I'm a bit proud because I've never did this before ), I've changed the starter to an electric starter, put new spark plugs in it and renewed some pipes like air pipe, fuel pipe etc. And now it is starting like new! Me happy