Fuelling issue......??

Hello all, not posted in a while (although I've kept an eye on the forum occasionally).

The old girl has been stuck in the garage for a while, whilst other things in life took over. Took her out the other day for a proper run for the first time in about 12 months. Prior to, I'd given everything the once over and changed all the fluids, checked brakes etc.

Running great to start with, but after about 20 miles or so, she started to bog down under acceleration - eventually quite badly to the point where I had to pull over. She idles ok, and only way I could get back home was to have the choke all the way out.

Have had a rummage about yesterday & today and checked carb is getting fuel (supplied by electric pump), inlet filter to carb clean, also inline filter changed. Sprayed easy start around manifold to carb mounting, with no change whilst idling for possible air leak, with no joy. Pick up in tank checked and gauze filter on pipe not blocked. Tank drained and fresh fuel added. Jets in carb removed and cleaned - but no blockages or dirt found.

Any ideas that might point me in the right direction, as im convinced it's fuel related. Weber carb is relatively new - less than 1000 miles, so a little reluctant to strip it down at the moment.
Thanks in advance....
(Sorry for the long post)

When I had similar symptoms it was the coil getting hot, although I guess that has little to do with having to drive with the choke out.
Another time, different vehicle, it was the carb to manifold gasket.

Have you checked the breather in the petrol cap isn't blocked?

Anaconda said:

When I had similar symptoms it was the coil getting hot, although I guess that has little to do with having to drive with the choke out.
Another time, different vehicle, it was the carb to manifold gasket.

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Will investigate the coil regardless, just to dis-count it, although like you say, that wouldn't account for it running on the choke.

I was kind of hoping for a carb to manifold leak, but idle stays rock steady when giving it a good spray with easy start.....

kermit_rr said:

Have you checked the breather in the petrol cap isn't blocked?

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Yes, breather in the cap is good.
Thanks for suggestions - keep 'em coming....

A real Webber from a reputable source set up for a Series, pretty sure they are not all the same.
1000 miles might be 10 years old.

Anaconda said:

A real Webber from a reputable source set up for a Series, pretty sure they are not all the same.
1000 miles might be 10 k

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Yes, 32/34 DMTL bought from reputable weber source - and looked brand new in box etc. Jetted for 2286cc 11H engine, as previous owner had replacement engine fitted some time ago.
Carb was direct replacement for existing unit already fitted when I purchased, and jet sizes identical. Cross checked sizes with Haynes weber carburetor manual that I managed to get hold of.
Up to this point it's been running really well, so bit of a mystery!.......

Coil tested (with engine cold) - 2.5ohm & 8.5Kohm. Would it be worth testing when engine hot?

RP72 said:

Coil tested (with engine cold) - 2.5ohm & 8.5Kohm. Would it be worth testing when engine hot?

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Definitely

It could be old fuel, modern petrol goes stale very quickly these days, probably quite badly deteriorated after six months

There's a secret filter in the lid of the float bowl.

Well, hopefully, that's the problem sorted - fingers crossed.

Tried new coil, but no noticeable difference, so full strip down of the carb and bought a service kit.
Not particularly dirty at all - but everything was given a good soak and a clean in carb cleaner. All airways blown through with compressed air and rebuilt.

Seems to have eliminated the problem - runs well now. Must have been some sort of blockage somewhere.