DIY Inlet manifolds

[Guest]

My inlet manifolds on the 250 are buggered and getting parts for it here in Aus is useless, I dont want to wait any longer for parts from overseas so thought i would have a go at making my own inlet manifolds for the bike.

Cutting a flat piece of steel bar to the correct shape with the 2 small bolt holes and the large inlet hole, cutting a flat piece of rubber to the correct shape to seal them against the engine.

Getting a piece of round pipe cut down to about 2cm wide which will be welded to the flat bar and then a rubber hose slipped onto the round pipe with a hose clamp, and then the carby slipped into the other end, keeping it all within the same measurements of the factory rubber inlet manifolds.

The only problem i see is that the metal pipe itself will make the inlet passage smaller which could effect the way the bike runs as the intake area is restricted. Unless i make the inside diametre of the pipe the same size as the original rubber one and get a stepped down rubber / silicoln hose instead.

What do you think?...

[pete]

Mate you're keen! But it could be worth a shot...

Alternatively, Sudco seem to have replacement boots for some things, so potentially someone like Serco may have some suitable ones, although I can't imagine they'd be cheap...

[Woodsy]

The metal part would never need replacing, the only wear and tear part would be the rubber /silicon hose which can be had for only afew bucks at any autoparts store. What metal are the standard ones made from does anyone know?

[rustybronco]

I don't know what material the originals are made of. but, for what you need, mild steel will work just fine.

also, I wouldn't worry too much about the I.D. of those pipes. weld (or braze) away...

as for using a rubber gasket between the engine and pipe, I'd use gasket (hi-temp??) material.

***edit***
If it were me, I would find a piece of flat stock the proper thickness for the base plate and bore the hole in it using a combination wood/metal (bi-metal) hole saw chucked in a drill press.
remove the drill from the center of the hole saw, chuck it up in a drill press, keep it well lubricated so it stays cool and doesn't chatter, apply light pressure and go slowly. I've done it when I had to mate a Holly-Weber 2bbl to a CFI intake manifold. it works a treat.

[Woodsy]

Just need the metal and i'm set!