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Hi everyone - I've been a lurker on this site for several years - and would not have been able to rebuild my CB500t/450 (72' 450 engine - in 500t standard chassis) without you - thank you to everyone - especially the experts among you - I've now done about 500 miles after reground valves (cams and followers skimmed by Phil Jolly engineering) rebore/new pistons, Pamco ignition, repaired clutch casing, unifoam on standard airboxes and lots of other stuff (including a broken speedo that howled just like an oil starved cam - nice moment...)

I did have one intermittent problem during running in - baulking at around 5000 in top gear under load (slight incline/headwind) other running was fine and I checked compression (cut down hose on to cheap gauge to see 170 + ) strobed timing, did valve clearances again, tank filler lid, stripped petcock, stripped and soaked carbs, set float heights, rerouted fuel line etc etc.

Sometimes though - if something quacks like fuel starvation and otherwise comes across as fuel starvation - IT IS BLOODY FUEL STARVATION.

The problem was with the new super duper black (insert correct fancy name) fuel hose the local BS bike shop sold me (that was its actual name, I should have been warned) it is very tough, about 9mm outer diameter, under 6mm inner. It fitted well, and I was sure the routing was fine especially after checking the pictures on this site - thanks again. I noticed the problem seemed worse in the recent bout of hot weather here in UK - it was around 25 degrees. The bike really just died going up a shallow hill - then quickly picked up again - but I could repeat and get the same results. Getting home I had a REALLY close look between the carbs with a torch, the left hand carb inlet is inbetween the carbs. Sure enough the pipe had collapsed/kinked just as it joined the carb inlet. Dropping off the float bowls confirmed only a very slight dribble coming out... basically - BINGO.

The pipe had been recut twice to get optimum length before - and I'd thought about the possibility of it being messed up. I think in colder weather this sort of pipe may be less likely to kink - only showing its true colours in warmer air (plus heat from engine during hot rides). Seems like it couldn't catch you out? Well me too - but it did and I've seen threads about an apparent fuel/baulking problem several times on the site. So have one more look - if you're getting any similar problems.

I replaced both hoses with the old style hose - clear with a reinforcing lattice pattern - outer dimension 12mm - inner around 6.5 to 6.8. It fits very loosely but with the supplied clips doesn't leak at all. And it definitely cannot kink. This stuff goes hard after a few years but I'm happy to replace it - plus you can see the fuel moving through it.

I obtained it from a British classic bike shop online - if you google BSA fuel line you should get it - also agricultural suppliers do it. Now thoroughly tested - the bike runs great.

I really hope this helps someone - I have a few other gems of very amateur info from the rebuild that I'll soon stick under the engine heading - that's it - Cheers.
 
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