Oil seepage around tach cable 850t

[Joshtjeerdsma]

I have put on a new tach cable, kept oil level below halfway between 2 dip stick marks, and replaced all breather hoses. I still have substantial seepage coming out of the tach drive and making a mess of the bike. Any ideas? Thanks

[guzzisteve]

A new breather box.

[Joshtjeerdsma]

I blew through all the pipes on the breather box when I had it out and none were clogged. I did not know how to test it, so that was what I did. Also, I keep reading about vents off the breather box to the atmosphere. My box has 2 lines to the engine, 2 lines to the valve covers,and 1 line to the gearbox. No line to vent to air.

[guzzisteve]

No line to the gearbox, on the bottom a big to crank vent, a small to drain back to crankcase. On top 1 into 2 to valve covers and bottom corner to atmosphere down behind starter.
Gearbox vent on back cover should go up w/hose in and along side of upper frame rail next to top of side cover so if any comes out it runs back into the trans.

Found your problem IF the disc in breather box is working on the spring.

[Joshtjeerdsma]

Ill give that a try. It makes perfect sense as my gearbox was also leaking out of odd spots. Thanks

[LeRoy]

No bike should leak out the tach drive unless it's a Norton Commando.

[Joshtjeerdsma]

Thats funny. My commando had a nagging tach drive leak untill i upgraded the breather. I didnt realize the similarities till now. Part of the reason that I acquired the Guzzi was to have a bike that didnt leak as bad as the old English bikes Ive had.

[nc43bsa]

There is an aftermarket fix for the Commando tach drive that replaces the silly o-ring with a proper lipped seal.

[Groover]

I think this is what guzzisteve may be talking about? Anyway, I think this may be the problem.. maybe it's stuck shut.

http://www.mgcycle.com/index.php?main_page=product_info&cPath=71&products_id=1007

[guzzisteve]

No, he has one of these--http://www.mgcycle.com/index.php?main_page=product_info&cPath=71&products_id=490

And the angled spigot on bottom which is the outlet to vent to atmosphere was hooked to the gearbox vent.
The crankcase pressure in the box forces a closing disc to move on a pin & spring arrangement that gets rusty.
The checkball started being used on the T3 w/the started making an airbox & paper filter

[Groover]

No, he has one of these--http://www.mgcycle.com/index.php?main_page=product_info&cPath=71&products_id=490

And the angled spigot on bottom which is the outlet to vent to atmosphere was hooked to the gearbox vent.
The crankcase pressure in the box forces a closing disc to move on a pin & spring arrangement that gets rusty.
The checkball started being used on the T3 w/the started making an airbox & paper filter

Ah, OK. I did not know that. Good clarification, thanks!

[nsmith]

my 1975 850t has the ball check in the large crankcase port. always had trouble with the breather leaking in different places. About 8 years ago I made my own breather system out of some 3/4" of copper hasn't made a leak since. but nowadays I don't drive the old girl that much I guess she's enjoying her retirement.

[John A]

I think this is what guzzisteve may be talking about? Anyway, I think this may be the problem.. maybe it's stuck shut.

http://www.mgcycle.com/index.php?main_page=product_info&cPath=71&products_id=1007

I thought the new style check ball assy had a square out let so the ball could not close off and pressurize the crankcase? When that check ball closes off it will dump about a quart of oil out the breather very quickly at road speed. What happens is the case gets pressurized and the oil is pushed back up the internal drain down to the level of that drain so the factory made the check valve so it couldn't completely close off. It was a head scratcher figuring that one out when it happened to me , coming back from an Oklahoma rally in '83.It would dump a quart out the breather drain in 10 seconds. I think Dave Richardson covers it in Guzziology

[jacksonracingcomau]

I thought the new style check ball assy had a square out let so the ball could not close off and pressurize the crankcase? When that check ball closes off it will dump about a quart of oil out the breather very quickly at road speed. What happens is the case gets pressurized and the oil is pushed back up the internal drain down to the level of that drain so the factory made the check valve so it couldn't completely close off. It was a head scratcher figuring that one out when it happened to me , coming back from an Oklahoma rally in '83.It would dump a quart out the breather drain in 10 seconds. I think Dave Richardson covers it in Guzziology

Early PCV's were crimped, these can and do stick as you describe,
Later (early-mid 80's)  have circlip holding ball in, these don't stick but none of them like being covered in mayo , biggest reason for failure in both types
Never seen one that doesn't shut off, that would negate it's purpose, to relieve crankcase pressure by allowing blow but not not suck
Positive Crankcase Ventilation or somesuch

Steve nailed OP's question well, breathing into gearbox was never going to end well

[Groover]

Do the newer ones (81) that use the PCV check valve also have the spring-plate inside the breather box?

[guzzisteve]

No, it's just a separating box w/wall inside.

[jacksonracingcomau]

Do the newer ones (81) that use the PCV check valve also have the spring-plate inside the breather box?

As far as I remember, circlip PCV came with frame breather models only
But crimped ones did use spring plate in breather box on 850T and LM 1 & 2 maybe last GT850's too

I've used circlip PCV in all types, don't think you can buy early crimped ones now

[pete roper]

If fitting a later type ball valve its best to disable the flapper in the breather box as at certain points the harmonics in the system can make them work against each other.

If as tou stated earlier you have no vent to atmosphere and have plugged the gearbox vent onto the collector box you have then created a sealed system and the entire engine and gearbox is going to try and inflate itself! You're lucky it hasn't blown the rear main seal.

Pete

[jacksonracingcomau]

If fitting a later type ball valve its best to disable the flapper in the breather box as at certain points the harmonics in the system can make them work against each other.
Pete

Eloquent as ever, true musician, harmonics
FWIW
My 78 LM came with crimped PCV and flapper in box, OE from factory
I did put late circlip one in only cos saw crimped stuck on others
But never have harmonics confused it

But the flapper did stick,early V700 esp, not sure if any LM boxes did it, anyway your advise sound as a pound, no need for 2 PCV's

[Joshtjeerdsma]

No serious leaks anymore. I only put maybe 50 miles on with that breather arrangment, so hopefully the rear main is good. The bike had been sitting awhile when I got it, so hopefully the previous owner didnt put too many miles on with the breaher like that. This is a great forum! Thanks all.