01-12-2023, 11:37 AM
That's interesting Ruairidh.
The plugs in the engine were NGKs and I can't remember when they were fitted, but within the last 30,000 miles. No 3 plug was fouling so I tried some KLGs that have been around for ages (KLG wentout of business in 1958 I believe) which were much the same. We invested in new Champion D21s. The cause was actually the sticking No3 exhaust valve.
The Champions do seem to work loose. I find that after a short run two usually are not as tight as I had left them. I might try the KLGs again. Seems unlikely as you say, but so does everything else.
I shall try changing the main jet back to 7.0 as it was, but leave the compensating jet at 7.5. I suspect that won't help.
The next step is to remove and check the manifolds and check the tappets which may have settled.
The really irritating thing is that when started from cold it runs very well indeed. Tickover with choke is perfect and performance excellent - until it starts to warm up.
The plugs in the engine were NGKs and I can't remember when they were fitted, but within the last 30,000 miles. No 3 plug was fouling so I tried some KLGs that have been around for ages (KLG wentout of business in 1958 I believe) which were much the same. We invested in new Champion D21s. The cause was actually the sticking No3 exhaust valve.
The Champions do seem to work loose. I find that after a short run two usually are not as tight as I had left them. I might try the KLGs again. Seems unlikely as you say, but so does everything else.
I shall try changing the main jet back to 7.0 as it was, but leave the compensating jet at 7.5. I suspect that won't help.
The next step is to remove and check the manifolds and check the tappets which may have settled.
The really irritating thing is that when started from cold it runs very well indeed. Tickover with choke is perfect and performance excellent - until it starts to warm up.
Jim