<-=- Club Bevel Heaven -=->

I’m in a right old dither on understanding the crankcase breather setup as I'm planning to junk the air boxes & put pods on the (40mm) carbs. The reason behind this isn’t just bling because I’m wanting plenty of space for a re-wire, new regulator & ignition.

From what I’ve read the factory solutions for such a setup came with bellows (750ss) or a catch tank (MHR) and both using an exit flapper valve.

I can understand the valve stopping the crankcase drawing in dirt etc but does it also have another, perhaps more important, effect on the crankcase pressure And I also understand the catch tank collects any oil but, again, does it's capacity have any effect on the crankcase pressure And when using the airbox I'm assuming there's a natural tendency for the crankcase pressure relief to be assisted by the induction. Again this will also be lost, thrice

I’m planning on doing the usual, keeping the tower and putting a vent filter on the end of the tube with perhaps a spring inside but will the lack of any pressure ‘control’ have an unwelcome effect on the crankcase pressure?

Andy B

Hi Andy: As you may have read already, I installed a Shendingen regulator (FH020AA), a Sachse ignition and better fuse box that uses new-style auto fuses plus a little K&N filter on the end of my original black plastic pipe. My 81 MHR never had the original black plastic breather box; the vent pipe fed forward over the vertical head to a little red metal tube that was mounted to the frame. No flapper valve but never had any oil mess either.

Here's a pic of my breather tube:


Take a look at the electrical section for my other pictures of the ignition and charging set-up.

Good luck,

Rick

plus a little K&N filter on the end of my original black plastic pipe. My 81 MHR never had the original black plastic breather box; the vent pipe fed forward over the vertical head to a little red metal tube that was mounted to the frame. No flapper valve but never had any oil mess either.

On mine, a Darmah, I also had no oil mess in the old airbox so it's reassuring to know that just an air filter doesn't seem to cause any issues. It's certainly the easiest & cheapest solution.

Take a look at the electrical section for my other pictures of the ignition and charging set-up.

Thanks, I had a quick look at the thread but I've got to get supper sorted first before I reply. Shepherds pie tonight, nom, nom, nom

Cheers,

Andy B

Just a small K&N filter does it on my '85 Mille MHR as well.

https://store.bevelheaven.com/Carb-Fuel ... vel-twins/
Yep, the little K&N works very well for this.