weber carb help

[Telomerase]

Hi Everyone,

I picked up my first Westie yesterday and have taken today off work for some quality time, just getting to know each other.

After much blatting about she started to run rich with a lumpy idol. When I got back home the aft of the twin Weber 40s filter was soaking with petrol. I have put her to bed with the filters off to let everything cool down and dry out.

I don't have any experience with Webers, but I am thinking I need to lean the idle. Your advice pleas before I start tinkering.

Ta very much  

[Hammy]

Sounds more like a problem with the float/needle valve assembly, i.e. the needle valve is passing fuel when it shouldn't  - could be dirt if its been standing around.  Webers ought to run with a pressure regulator too - there should be one in the petrol feed pipe to the carbs  -roundish looking thing ! ( this stops too much pressure reaching the carbs and forcing fuel past the needle valves in the float chamber).

In your case the resulting increased float level would give a rich mixture.

Google "weber dcoe"  there are lots of diagrams and you can decide if its a job you want to do.

[Captain Colonial]

As Hammy said.  You can get a DCOE refurb kit for just a few quid and and tidy up the insides, not an awful job at all, very straightforward even for a numpty like me.

[Telomerase]

Thanks for the pointers, I will go on a crud hunt. The pressure reg is calibrated 0 - 6, I guess this is bar? Currently set to 1, I belive the Weber 45s should be fed at below 3.5 bar?

[Captain Colonial]

I believe the Weber 45s should be fed at below 3.5 bar?

Correct.

[Welly Jen]

Thanks for the pointers, I will go on a crud hunt. The pressure reg is calibrated 0 - 6, I guess this is bar? Currently set to 1, I belive the Weber 45s should be fed at below 3.5 bar?

It will be psi, not bar. Carbs are fed at a low pressure. Fuel injection uses higher pressures, 3 bar often (43.5psi).

Jenny

[Dave Eastwood (Gadgetman) - Club Chairman]

Yep, Jenny's beaten me to it; carb' regulators tend to be calibrated in PSI rather than Bar. 3.5 Bar would certainly fill the float chambers quickly, shortly followed by the rest of the engine bay    

3.5 to 4 PSI seem to be commonly used fuel pressures - 3.5 PSI is only 0.24 Bar!

HOWEVER, it's also not uncommon to see uncalibrated scales on these things, the 1 to 6 may just be a set of numbers and not an actual pressure. If you want to check the fuel pressure you'll need a proper gauge in the fuel line. Be aware though that the engine and carbs will most likely have been set up to work best at a certain pressure. If you change away from this pressure, you'll probably need another set up session on the rollers sooner rather than later.

[Telomerase]

Cool, I will stick to cleaning the needle valve and promise not fiddle with anything else.

How fussy are these cabs on octane? I had to fill up will 95 RON last time, there was no 98 at the pumps.

[Captain Colonial]

95 is fine.

[Welly Jen]

Yep, Jenny's beaten me to it; carb' regulators tend to be calibrated in PSI rather than Bar. 3.5 Bar would certainly fill the float chambers quickly, shortly followed by the rest of the engine bay    

3.5 to 4 PSI seem to be commonly used fuel pressures - 3.5 PSI is only 0.24 Bar!

HOWEVER, it's also not uncommon to see uncalibrated scales on these things, the 1 to 6 may just be a set of numbers and not an actual pressure. If you want to check the fuel pressure you'll need a proper gauge in the fuel line. Be aware though that the engine and carbs will most likely have been set up to work best at a certain pressure. If you change away from this pressure, you'll probably need another set up session on the rollers sooner rather than later.

Good point from Gadgetman. The 1 to 6 likely doesn't scale to psi either. Wonder if you can get a Spinal Tap style regulator that goes all the way to 11?    

Jenny

[flyingbanana]

^ You can get gauges that do...  

[Telomerase]

The fuel union on the aft carb came apart in my hands as I went to investigate the needle valve. I have epoxyed it up, now running sweet as a nut.

http://www.fastroadcars.co.uk/shop....tId=126

[Dave Eastwood (Gadgetman) - Club Chairman]

Excellent news.  

Probably worth replacing when you get the opportunity, just for peace of mind. (Epoxy can be affected by heat, though I'd hope the carbs weren't getting that hot )

[flyingbanana]

I would replace any fuel system plumbing as a high priority, unless you like BBQ-7s.

The fuel octane rating is of no great interest to the carbs but you might want to double-check ignition timing if you will be running mainly on 95 if it had been set up on 98.

As with most of these things, engines will be fairly tolerant in general usage, but if you want best performance, or like to use the full rev-range it would be sensible to check all the details.