Hello everyone, I'm curious if anyone has experience with appropriate crank breathing on a TR7/T140? I'm currently looking at a Bunn breather kit but am hoping someone who has experience can opine on this topic. Is there another option I should look at? I've already shortened the primary breather tube by adding a joint with the K&N filter.

http://www.panther-publishing.com/defau ... ntentID=35

The stock setup is pretty effective, it just vents behind the rear fender.

The Triumph crowd don't use one-way breathers, it's not an issue in the same way a Norton is.

grandpaul wrote:The stock setup is pretty effective, it just vents behind the rear fender.

The Triumph crowd don't use one-way breathers, it's not an issue in the same way a Norton is.

Anyone know why?

swooshdave wrote:

grandpaul wrote:The stock setup is pretty effective, it just vents behind the rear fender.

The Triumph crowd don't use one-way breathers, it's not an issue in the same way a Norton is.

Anyone know why?

According to one of the TUC guys, the shared crank/primary breather set up allows the chaincase to act as a plenum for the expelled crank pressure. I believe, and judging by the common rocker leaks found on triumphs, they seem to have more issues with top end breathing.

acadian wrote:

swooshdave wrote:

grandpaul wrote:The stock setup is pretty effective, it just vents behind the rear fender.

The Triumph crowd don't use one-way breathers, it's not an issue in the same way a Norton is.

Anyone know why?

According to one of the TUC guys, the shared crank/primary breather set up allows the chaincase to act as a plenum for the expelled crank pressure. I believe, and judging by the common rocker leaks found on triumphs, they seem to have more issues with top end breathing.

Wonder what happens when you run a dry belt in a Triumph. I guess I should wait until I start on my Triumph project and find out for myself.

To run a dry belt in a later model (Meriden) Triumph, all you have to do is install a left main seal and epoxy in the level transfer holes drilled in the crankcase.

grandpaul wrote:To run a dry belt in a later model (Meriden) Triumph, all you have to do is install a left main seal and epoxy in the level transfer holes drilled in the crankcase.

And fit an alternative breather.

A few months ago as an experiment, I removed the plug from the timing tool hole (on the case behind the cylinders) while my 67 Bonneville was idling. Blipping the throttle off idle, it was obvious how much freer the engine wanted to rev when it was able to breathe and relieve the crankcase pressure (and this bike still has the stock timed disc on the camshaft). Try it sometime. When I get around to having an adapter made allowing me to attach a breather hose to this hole, I plan to attach an XS 650 valve and then vent out the back.
This might be worth considering for your street-tracker Dave. After you eliminate the venting into the primary case in order to run a belt, you'll need to vent the crankcase pressure somewhere.

sidreilley wrote:A few months ago as an experiment, I removed the plug from the timing tool hole (on the case behind the cylinders) while my 67 Bonneville was idling. Blipping the throttle off idle, it was obvious how much freer the engine wanted to rev when it was able to breathe and relieve the crankcase pressure (and this bike still has the stock timed disc on the camshaft). Try it sometime. When I get around to having an adapter made allowing me to attach a breather hose to this hole, I plan to attach an XS 650 valve and then vent out the back.
This might be worth considering for your street-tracker Dave. After you eliminate the venting into the primary case in order to run a belt, you'll need to vent the crankcase pressure somewhere.

They say a lot of oil comes out of a breather in the TDC plug hole.

I did find that after returning from from a trial spin of several miles without a plug in the tdc hole, there was an oil film on the top of the transmission and on the frame behind it. How significant an amount it would be I don't know. The oil seems to be atomized enough that it's not apparent coming out of the hole while watching it run though. My thought is that the valve will keep the oil from being pumped out and assuming the valve and hose are mounted above the tdc hole, gravity will drain the oil back to the engine sump.
I'm anxious to give this a try, I figure the worst that can happen is that a little extra oil will drip out the vent hose under the rear fender.