lean running issue.

[timmo478]

Hi all, wonder if anyone can help. For some reason my engine has started to run lean. She packed up today on way home and only way I got her back was to give her very heavy throttle to keep the revs up. Had no time to use the foot brake or she would die. On restarting she would chuff out of the carb. Nothing obvious has changed. I'm thinking either fuel pump pressure or could the heat deflector between the manifolds leak back into the inlet and cause a lean run.
When clutching up to move off she had no power at all and had to feather the clutch with heavy throttle to get her moving.
Any help much appreciated.

[rhythmrider]

Lots of things can cause lean running.
Very common is dirt in the carb.
Are you running an inline fuel filter?

Incorrect float level or stuck bowl float.

Is it the same hot or cold?

[timmo478]

Hi rider, yes the problem was the same cold or hot. She just lost power on me coming home the other day. When trying from cold she didn't want to idle and needed a heavy throttle to keep her going. She also chuffed out of the carb every now and then. I checked fuel pump which is fine and I've also completely stripped the carb and checked all diaphragms for damage and jets for dirt. Also blasted out the carb fuel holes. Yes I am running a high quality high micron inline filter.
NOW FOR THE WEIRD BIT.
Upon refitting carb it made no difference. But after a couple of minutes she started to idle but still wouldn't rev without heavy throttle. I noticed the exhaust was emitting much higher compression and with carb cuffs I wondered was it timing. I advanced the dizzy about 6 to 7 degrees and she now runs sweet as a nut. Don't understand why the need to move the dizzy as it hadn't moved at all.
Any suggestions?
Worn dizzy drive?

[rhythmrider]

I can only speculate on the Distributor.
Depending on which distributor clamp you have installed, there are two places that could change the timing.

The one of two screws that hold the clamp have maybe 5-8 degrees of adjustment or the distributor itself if the clamp is lose on the distributor shaft.
If the clamp is tight, it could have been the screws that hold the clamp to the block.

I am not looking at it, but the Lucas distributors were a "stock" part and an adapter was fitted to the block where the distributor goes in.
Does not the distributor clamp bolt onto this adapter? Is there not one counter-sunk bolt that holds the adapter in place? If that were missing, the timing could change if the adapter was allowed to turn.

This all pure speculation off of "the top on my head"

[timmo478]

Thanks rider. All was checked and nothing had moved. My 25d4 dizzy was replaced for a complete electronic 1 not so long ago. I have a mounting tube which bolts to the block using 2 studs and nuts. Then the clamp bolts down to top of the tube where it's slotted for movement as you said. Then u have the pinch bolt to lock clamp to dizzy body. Gonna have to chalk this 1 up as a mystery I think. But I've done the spin on filter now and painted a few bits whilst I was there. I'll post a pic or 2.

[timmo478]

[url=http://s1280.photobucket.com/user/timmo ... 4.jpg.html][/url

[timmo478]

[rhythmrider]

Looking sharp! Nice pics. And I know you will find the spin-on filter to be a pleasure compared to the old canister type.