Misc: Carburettors LEAKING CARBURETOR

[pmcmanners]

Hello everyone,

Can anyone help with a leaking carb?

Carbs has been stripped down, cleaned and put back together twice, but the front carb will not stop leaking when the petrol valve is open (continues to leak badly when shut). It seems to be coming from the small hole at the bottom of the carb (top of the threads (see picture). Bike runs/ticks over much smoother now.
The leak was there when the bike was delivered, but maybe not as much.

We made our own cork inserts for the fuel taps - these now don't leak or weep - RESULT.

We have tried adjusting the float to different positions. The float seems to stop the petrol coming into the float chamber when it rises.
As you can see from the picture, it is impossible to screw the bottom of the carb. all the way up to cover the hole as part of the hole is above the threads.

We did notice yesterday, that when we took the float chamber lid off, that the petrol was above the float which seemed strange as the float should be on top/ half submerged in the petrol.

Any ideas?

Thanks in advance.

 

[Simon Dinsdale]

That hole in question is there to act as a drain hole for the pilot system if the carb is over flooded by too much pressing of the float chamber tickler. Do not block that hole up because if you and then over flood the carb there is no way for the pilot system to drain down and so you will struggle to start the bike.

If fuel is dripping out of that hole in normal running conditions then the fuel level in the float is too high. Reasons for that could be the float has a hole in it and filled with petrol and so too heavy. Other reason could be the taper seat in the float bowl to float needle is not seating properly and so fuel is getting past it even when the float is trying to shut the fuel off.

Simon

 

[Albervin]

Another reason may be the carb is not correctly angled. These old carbs have a plaything that they can be enriched and leaned by rotating them on the manifold; basically raising or lowering the float level. First of all I would weigh the floats and check for leaks as Simon suggests. I have soldered up floats but you need to be "keen"...

 

[vibrac]

with the so called petrol nowadays perhaps this is the answer you will need a new float needle as well and £30! (Burlen)

 

[oexing]

When you look at the photos below I´d say that ominous hole is quite close to the correct fuel level in the carb - no ? And some jet blocks got that hole, some not so. So when you got a leak from that hole, why not just block it with a snippet of o-ring or some such ? And certainly nobody abuses the tickler for flooding the engine, nooo . Sure, typically the tickler often gets abused a bit and fuel will spill at the chamber cap then. But this is same with other carbs and not a big problem and no need for that hole. Just block it and maybe check fuel level . Three seconds pressing the tickler should do , no need to drown the carb for starting.

Vic

 

[chankly bore]

My bike is not standard, but when I had a type 29 on my original Comet I developed the wheeze of turning the fuel off again after opening the tap reasoning that the mixture would get weaker with each kick until the plot fired up- then on with the fuel tap. Saying that, it does seem your float is riding a little high.

 

[Speedtwin]

Simple fix,
your fuel level is too high, causing petrol to flow from the pilot overflow hole mentioned by Simon.
Set the carb position as best you can level wise with the float bowl attached.
Check your fuel height in the bowl, should be below the fuel mixture screw.
Make sure by testing with cap off if the fuel is being stopped when float level is achieved.
Measure your tickler!!!!!
Check your tickler is not holding down the float when the cap is screwed down, causing float flooding.

In order to get fuel height in my float bowls I chopped the ticklers down.
he fuel level in the float bowl is important since sorting mine my bike is flying.
Al

 

[nobby]

with the so called petrol nowadays perhaps this is the answer you will need a new float needle as well and £30! (Burlen)

I have also a problem with the 229 carb. Maybe can solve with a new float, but Burlen only has sets for top feed.
The bottom feed from the Spares Company with number PR6H has no picture and no mention of what type of carb it is for.
Anyone knows? I need the float and the needle...

 

[oexing]

For bottom feed I´d believe you could have any new float and do the groove for the needle clip on the old needle accordingly to match the top feed clip ?
As to fuel level: When you look at my photo above showing that ominous hole above the pin that locates the jet block to the body: Methinks this hole has to be sealed as the fuel level relative to the pilot mixture screw will be a bit higher than that hole. So how can it NOT leak from there ??

Vic

 

[oexing]

Your link deals with TT carbs. Question here is about 229 type, same goes for 274 Amals , I guess. Is there same brass plug with punch mark ? My thinking with these Amals was the fuel level has to be maybe max. 5 mm below air adjuster screw . So then that hole above the locating pin will be lower still - and drip.

Vic