Classic Triumph Bonneville

[KungFooBob]

Dazzler isn't worried about Ethanol, he's gonna run it on AVGAS.

[Mr. Dazzle]

Ethanol is currently a moot point cause it'll run on super unleaded. The 11:1 high comp pistons dictate that anyway and all the name brand super unleaded is ethanol free.

That said, I still fitted ethanol resistant seals and floats etc.

There's a way more fundamental reason I'll get it done professionally. Two actually. First off I really REALLY cannot be arsed with nasty chemicals and shitty sticky coatings, and secondly why TF would I spend thousands on all this repair/rebuild and then half arse the fuel system?

[Mr. Dazzle]

Dazzler isn't worried about Ethanol, he's gonna run it on AVGAS.

Back in his RAF days my FiL ran a Mini on AVPIN for about 5 mins.

https://en.wikipedia.org/wiki/Isopropyl ... prov=sfla1

[David]

Well.....is it fixed yet?

[Mr. Dazzle]

Well.....is it fixed yet?

No

Been getting my house fixed.

[Mr. Dazzle]

I had a good old look at the 'leak' in the fuel tank this weekend - I don't think it is a leak. Upon deeper reflection I also remembered I brimmed the tank (in an attempt to mitigate rusting) before I put it away and it didn't smell of petrol at any point.

So I've put a blob of epoxy over the scrape in the tank followed by a patch of tape and decided I'll probably get it repaired fully in the winter. I've also now got some fresh fuel hose and a couple of inline filters so it should just be a case of getting the tank back on and away we go. I can probably do that one day this week.

"Should".

[JackyJoll]

You’re not me, but I put the reasonably big inline petrol filter in the hose, then cut off the blockage-prone gauzes from the tap and the carb banjos.

[Mr. Dazzle]

It did feel a bit pointless fitting extra fuel filters when you consider the air filters are just bits of wire mesh which stop you sucking in anything too big.

[JackyJoll]

Fuel filters are to stop fuel starvation and/or flooding caused by dirt in the carburettors. Air filters are for reducing cylinder wear.

If you hsve the bellmouths with mesh over them, I may already have said this but they are worse than useless. They are restrictive, so they make the engine untuneable and they don’t filter dust out of the air.

[Cousin Jack]

If you have the bellmouths with mesh over them, I may already have said this but they are worse than useless. They are restrictive, so they make the engine untuneable and they don’t filter dust out of the air.

My old BSA had a bellmouth and no filter at all. You could poke your finger in all the way to the slide and beyond. Perhaps the piston/cylinder clearance was such that the odd bit of grit didn't matter.

[JackyJoll]

If you have the bellmouths with mesh over them, I may already have said this but they are worse than useless. They are restrictive, so they make the engine untuneable and they don’t filter dust out of the air.

My old BSA had a bellmouth and no filter at all. You could poke your finger in all the way to the slide and beyond. Perhaps the piston/cylinder clearance was such that the odd bit of grit didn't matter.

Britain isn’t a very dusty place, generally, and it was easier to tune the old bikes with no air filter. You can do 20-40,000 miles with no filter.

But a filter is a good idea: you can have better compression and less oil consumption for longer and an appropriate filter is not very restrictive.

Those tea strainers over the intakes are restrictive and they don’t filter the air.

[Mr. Dazzle]

Nah they just stop you sucking up stones and leaves, thats it. On this bike you can see the intake valves when you open the throttle.

You can tell they do bugger all cause pre-rebuild this bike had a thick layer of what looked like tarmac all over the combustion chamber. Combination of burned oil and dust.

In theory bellmouths should get more charge in at high revs if they're properly tuned. That's why racers (both car and bike) use them. Dubious benefit on the road though, other than looking funky.

[slowsider]

Thought the gauze was to prevent birds nesting...

[Count Steer]

Thought the gauze was to prevent birds nesting...

They're 'garage protectors' to keep mice out on bikes that are garaged for many months....

[JackyJoll]

I’ve seen it quoted from many reputable sources over the last 50 years, that the typical screw-on bellmouths give no power gain and are often worse than a bare carburettor.

Tuners claim they can sometimes get a performance gain from the narrower “velocity stack” type, like this:



or by fitting the carburettor on a longer stub.

Trouble is, if you manage to get benefit from a resonance effect at one rpm range, you’re probably losing out at some other rpm.

[Taipan]

A lot of air boxes have velocity stacks inside them. Also a plate opposite the stacks. Air boxes are tunable using these, normally for bottom end and midrange. Open carbs or bellmouths are only useful for wide open throttle.

There was a time when people were experimenting with ramps in intakes. The idea was that the ramp turned laminar flow into turbulent flow and a resulting better mixture of A/F.

You're absolutely right about mesh covers. If you add up the surface area they actually take, you'll soon see why they are known as restrictive!

[Mr. Dazzle]

Variable length velocity stacks are quite common in high performance engines, they're so effective they're banned in many motorsport series.

To me the mesh is just a practical thing to stop really big shit getting into the engine. As I said, at open throttle you can see all the way through to the back of the inlet valve, so you don't want bees/sticks/leaves/mice getting in there

[JackyJoll]

The authentic-looking air filters on late 1960s Triumph and BSA 650s are these and they are restrictive too, with a paper element.



They also develop cracks from vibration and fall to bits.

[Rockburner]

Nah they just stop you sucking up stones and leaves, thats it. On this bike you can see the intake valves when you open the throttle.

You can tell they do bugger all cause pre-rebuild this bike had a thick layer of what looked like tarmac all over the combustion chamber. Combination of burned oil and dust.

In theory bellmouths should get more charge in at high revs if they're properly tuned. That's why racers (both car and bike) use them. Dubious benefit on the road though, other than looking funky.

IIRC My Dad once showed me the internals of the engine on the HRD (IIRC) after it had been making some strange noises, that suddenly stopped..... by the indentations he figured out that a rather large nut (probably the one missing from the tank mount) had fallen into the bellmouth, through the valve inlet, and then somehow found it's way out of the exhaust valve and rattled its way out the end of the exhaust.

[JackyJoll]

Nah they just stop you sucking up stones and leaves, thats it. On this bike you can see the intake valves when you open the throttle.

You can tell they do bugger all cause pre-rebuild this bike had a thick layer of what looked like tarmac all over the combustion chamber. Combination of burned oil and dust.

In theory bellmouths should get more charge in at high revs if they're properly tuned. That's why racers (both car and bike) use them. Dubious benefit on the road though, other than looking funky.

IIRC My Dad once showed me the internals of the engine on the HRD (IIRC) after it had been making some strange noises, that suddenly stopped..... by the indentations he figured out that a rather large nut (probably the one missing from the tank mount) had fallen into the bellmouth, through the valve inlet, and then somehow found it's way out of the exhaust valve and rattled its way out the end of the exhaust.

The obvious advantage of a straight-through system!