"sweet smell" kind of points to head leakage as that has a distinct smell nothing like burning or hot oil or hot metal.

Sean

ok... i used to get exactly the same thing happen with my prev 2 engines...

my original... it would run absolutely fine when driven hard, 75 was easy but when pushed for too long... a strange smell and lots of heat through the heatervents... if i carried on it would get jumpy and didnt like any accelerating atall... if i left it to cool down for a few mins it would be fine after...

D*lly engine... sorry timmy... but its not true about them engines... ours isnt brilliant.. anything 70+ for too long at it would get too hot and loose power... specially the first good run i had on the way back from trees back in may.. m1 on the way home... a very slight uphill and it was getting abit iffy at 65... then to the point where i had a lorry almost overtake which felt uuber embarresing...

i found a solution... the second it splutters, dip the clutch and off the throttle for a few seconds... let it cool down... and away you go as normal....

but... DYANE engine... i wouldnt say ive ragged the tits off it yet... but it runs extremely well.... havent had a single spluttery moment yet, and it seems to love being off the clock... and it has a huge difference between resting my foot on the accelerator and flat out... it really goes! i havent satnavved it yet, but recon this one will do 80!

so when they get all hot and spluttery and start kangarooing... thats a partial seizure?...

For anyone who regularly does long, fast motorway runs and/or revs the ar*e out of their cars, is it worth them fitting a larger oil filter cannister, which is reckoned to lower the oil temp (as I've read)?

A larger oil filter holds maybe 250ml more oil, out of the flow of cooling air - compared to 4 litres of oil in the aluminium sump, finned for cooling. I'd say that was negligible difference.

If you put an oil temp gauge on, with the sender in the sump plug, about the only times the temp'll start to rise are in heavy urban traffic.

I feel I am missing out on all this seizing and part seizing stuff. I guess I must try harder to make one of my engines seize or partially seize.

Over the years it has never been the first thing I have thought of when faced with a problem and low and behold I have never seized an engine. The fault has always been something less traumatic.

Try cutting back on preventative maintenance. An oil cooler that's barely visible's always helpful.

Oh !!!!

whats the best thing to clean the oil cooler with? any suitable solvent i can spay on it while i brush it?

Degreaser, carb cleaner, brake cleaner - anything like that. Or just brush petrol on.

Just don't use brush any stiffer than a toothbrush - you'll bend the fins - and DON'T SPRAY PETROL AT IT! (Especially not if you're smoking...)

Be gentle when cleaning it, if you damage it its a pile of fun to replace.

BTW have you checked your clutch. Whilst diagnosis by email is difficult, your comment about the smell would make me check that first.