The dear old Series let me down big time last weekend on an event, so this weekend I am trying to sort it out but with no success.
2.25 Petrol. Carburettor - BM Parts (Bearmach?) Zenith pattern, replaced original carb about 6 months ago, has run fine up to now, idled at +/- 500 rpm like a sewing machine, although has always popped back a lot through the exhaust on long downhills. Slight blow at manifold/exhaust joint after fitting new exhaust. Carb has done about 2K miles, averaging 18-20 mpg.Symptoms - engine hot with lots of slow driving & idling (temp gauge below half as normal tho), suddenly refuses to idle and stalls. Only able to get it running by increasing idle speed to silly amount, and even then it was racing up and down and stalling without any intervention from me. I'm suspecting a big air or internal fuel leak, so yesterday I -
- dismantled carb and did the "Zenith fix" - flatted the top/body mating surfaces back to 100% flat and mirror finish (and boy did it need it - top and body were badly warped and the surfaces apparently machined with a chainsaw). Could get a 1mm feeler between top and straight edge at several points before I started
- attempted to seal the redundant passage in the body as noted on several "how-to" websites, only on this version of the carb there wasn't one
- set float height to 33mm as per book (this may need adjusting 1mm or so as I have removed metal from the top and body, but it should be the basis for a running engine I reckon)
- blew through all jets with airline
- checked fuel pump delivering - yes it was
- sealed air cleaner to carb flexible pipe with gaffer tape where it was deteriorating
- cleaned and remade all joints on assembly with smear of orange Hermetite (manifold/adaptor/carb) as well as correct gaskets
- broke and remade manifold/exhaust joint with Firegum - now no blowing at all.
It now runs better (in that it will at least run unattended) but only with a high idling speed, and the revs are still chasing up and down with a noisy patter from the exhaust. If I try to reduce the idle to something normal, it just waits a bit and then dies. It's still obviously VERY WRONG. Medium and high speed running is (and always was) fine.
I have now totally run out of ideas. Can anyone suggest anything else before I a) shell out 150 notes for a Weber, b) start looking for a diesel transplant, or c) let the dog have a go on the basis that he can't do any worse than I have?
All suggestions gratefully received. If you've read this far, thank you for staying with me :-)