Another tale of a smoky Greeves twin

[John Wakefield]

Chaincase breather

Checked mine out this morning, gasket was ok ie not obstructing breather aperture, but the small hole through crankcase was a bit sludged up so poked it through with a piece of wire. This is worth checking out if you have a 2,3 or 4T

[Guest]

One last point. Drilling a hole in the filler cap will allow water to get into the chain case.

Make sure that any new vents are out of the way of any likely water ingress.

Keith

[Dogsbody]

Keith, better to drill and tap to take say an old cable adjuster, and put a length of battery breather tube on it and into a little bottle. Same with gearbox filler plug. Stops any pressurisation. Bottle really only necessary for racing as all breathers have to feed into a container. Colin

[John Wakefield]

Keith, better to drill and tap to take say an old cable adjuster, and put a length of battery breather tube on it and into a little bottle. Same with gearbox filler plug. Stops any pressurisation. Bottle really only necessary for racing as all breathers have to feed into a container. Colin

If the built in system is clear then it works fine so no need for additional drillings & breather pipes for normal road use.

[Guest]

Keith, better to drill and tap to take say an old cable adjuster, and put a length of battery breather tube on it and into a little bottle. Same with gearbox filler plug. Stops any pressurisation. Bottle really only necessary for racing as all breathers have to feed into a container. Colin

Interesting that. do all the comp guys use breathers like that?

Keith

[Dogsbody]

ACU regs state
"4.17 OIL CATCH TANKS& BREATHER SYSTEMS
Where an oil breather pipe is fitted the outlet must discharge into a catch tank located in an easily
accessible position and which must be emptied before the start of the race. The minimum size of a catch tank shall be 250cc for gearbox breather pipes and 500cc for engine breather pipes."

Mainly four strokes esp. classic tended to breathe to atmosphere, modern breathe into airbox because of emission regs. Not sure when it became mandatory to use catch tanks. Ducatis had a one inch crankcase breather pipe out to the rear back in the 60s! I always used breathers on oil tanks and gearboxes to release pressure as temps were higher than on road use especially in the Isle of Man and road circuits. Some road bikes had the breathers directed onto the rear chain pre Scott oiler days. Colin

[hawkie197]

Crankcase seals

Hi John, There are lots of examples (Villiers singles) running around with the seals just being retained by the interference fit.
If properly fitted they shouldn't give any trouble, here is copy from an old seal catalogue that gives you a guide as to what sort of interference fit is required, I know that it says press fit but I have never experienced any difficulty fitting them by hand.
Cheer Pete from the Antipodes

[John Wakefield]

Gearbox breather

Just to complete this thread here is a pic of the gearbox breather on the 2,3 & 4T gearbox. Its a groove in the mating face with crankcase.

[Dogsbody]

Looks like it was blocked with Red Hermetite - the bane of my life in the 60s. Thank God ( other Deities are available ) for ThreeBond. Colin

[John Wakefield]

Looks like it was blocked with Red HermetiteColin

Dont know about this gearbox I bought it as a spare a few years ago, looks nice & clean, just used it to illustrate the venting groove. No real need for gasket goo just a film of grease on gasket, or gaskets as these are used as most of you will know to increase distance between gearbox & engine to tension primary chain.