Agreed, as my last post - at the start of this thread the knuckle-draggers had their finger pointed at the one thing - assuming correct install - it won't be; that Vapour separator NRC9772 . I only raised the issue in case there IS an install issue. Seems there isn't. This may be a fuel-starvation issue, this is NOT a vapour-lock problem.
The header reads vapour-lock, and then I saw why it isn't. Carb insulated, had I read the text, headline nullified, I'd look at coil/condenser. If tired, they get temparature dependent.
I'd shove a new coil / condenser on, because it won't hurt. Cheap, quick and easy to do. I'd be surprised if that's not it sorted.
You say you've rebuilt the carb? Then there's nothing left.Else...
£50 says your tank is rusty beyond help.
Thus, if you've covered everything else in logical order,coil /condenser breaking-down etc et, there's less to finger. More likely....
I run a 17H. It came with its Weber 32/34 DMTL. NOT to be confused with Weber 34ICH replacements famously bad on Series.... it's the best carb ever fitted to an LR and (along with better cam, head and manifold) responsible for the improvement in economy and low down grunt you get out of a 17H. It took decades, and a proper kicking from the Japanese, LR finally , finally sorted the issues with godawful Solex/ Zenith etc. You've all read those 'carb' threads arguing for Zenith or Solex that go on and on and on... and on.
And [stands back....] there's some in this thread telling you to put a Zenith / Solex on? If either was good there would be a clear winner and those threads could not exist.
Some 32/34 have a 12V feed to them, yours does... I see a spade going in - we're assuming this has 12V? It'll idle 'ruff' without. Pull it off at idle and hear the note change. No change? Check 12V and/or solenoid.
But... the Weber 32/34 DMTL is prone to being fussy about clean fuel, the 32/34 DMTL Weber needs kid-gloves, hence be filtered up to the gunnels. Else they WILL clog - ths
after a rebuild. Next to impossible to clean. Normally an upgrade to be rid of your more usual s&*t Zenith/Solex, in this case shoving an ACR SU HS6 on there, is actually no better, and might truly be worse. When it's right, the Weber 32/34 DMTL is very good. Unlike a Solex/Zenith, no good reason to replace with an SU. But if I'm right, SU it is.
An SU is easier to use, and less fussy. And I suspect (if clogged) you'll struggle to find properly jetted new examples of a 32/34 anyway? The 2.25 is jetted differently to the 2.5. Hence see pic above. An SU becomes the easy way out of the mess.
Ask me how I know...
Coil / condenser first.
17H in pic. Can I ask if 2.25 of this vintage got a starting-handle and starter-dog? I had to put a dog on my 17H. Metric thread, pricey and rare,