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Timing cover engine breather

5K views 19 replies 11 participants last post by  439433 
#1 ·
Have any of you gone fron a timing hole breather to a timing cover breather system ?.
Has it helped with the oil blowing out the breather tube ?.
What's your opinion on a better way to go.
Thank you as always.
Bill
 
#3 ·
Exactly, when I got the belt drive dry clutch set up, it came with a breather system that goes through the timing plug hole.
My engine spits a lot of oil directly off the crankshaft, it coats the back of my bike so I don't have to worry about rust, that's why I was asking about anyone with experience with the breather going through the timing cover.
I'd like to keep the majority of the oil in the tank.
 
#4 ·
Hi Bob
You have to be careful in the timing cover also,
The pressure relief valve has two oil dump ports, on into the crankcase the other into the timing chest, this oil is picked up by the timing gears and flung about in the timing chest, it is full of oil mist just ready to be drawn out of the engine by the breather draught. I have tried a breather in the timing cover but it was a struggle to keep oil out of the breather tube.
There is an internal chamber neat the front engine mounting, people have a lot of success with modifying the crankcases and fitting the breather here. The downside is that you to completely strip the engine to make the modification.
Regards
Peg.
 
#5 ·
My dual engine land speed racer breathers...Zero oil blows out even at 7000 plus rpm...I did the same on a unit 650 engine with a 750 kit asxthe 9nly breather...after about 100 miles a few oil dropswould form at the breather tube exit...

746777
 
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#7 · (Edited)
that front cavity where the motor mount bolt runs through is where i put the breather on my last two 1970 LSR motors. i had put a dry belt on this machine and needed to isolate th eprimary from engine oil, so i installed a crankcase seal and had to re-locate a breather

to put a breather up front, you can drill and tap the cavity for a spigot. i put them on the top, but they work on the sides as well:



drill some 1/4-inch equalizer/drain holes into the crankcase:



put in some stainless mesh to keep oil splash out of the tubing:



screw in a hose barb spigot



run some hoses to the rear:



if you want, you can also vent the crankcase from the rocker boxes. the pressure balancing from these is not negligible:





i use a catch bottle back there, as this is a race bike. but just an open breather works as well, so long as you run it all the way to the end of the fender so it doesn't drip on the rear wheel.



mine blows much more than a few drops without a catch bottle, and alarmed my neighbor in th epits who runs an immaculate ZX14. i told him the back of my bike always looked that way and he calmed down.
 
#9 ·
how have you run the breather pipe from the timing hole ? - have you tried running it straight up as high as possible to the underside of the fuel tank before turning it to the rear of the bike - might give any oil time to drain back - just a thought !
-- and what diameter hose - bigger is better i would think
 
#10 ·
I have seen some breather pipes that are 1 inch diameter which would slow the air speed and therefore less oil would be taking air pressure carrying it up and out. I would agree with WOL on larger pipe.
Interesting, that my primary case vented normal engine, emits no oil and virtually no air can be felt coming from the end of the pipe.
 
#11 ·
The hoses I use are 7/8 ID....Not seen on my double are the rocker box 1/4 inch breather hoses.No catch cans becuase the don't drip oil...
My single engine racer has a front breather hose like Speedrattle plus a 5/16 hose from the timing cover.
 

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#13 ·
Hi Bob, How are you breathing the frame? I've found during hard breaking down hill oil will run up top tube & drain down the vent hose back to primary.

The later bikes have frame vent to top of exhaust rocker boxes. The thought of breather from top end is interesting. I've ran my motor with valve covers off to observe oil flow. Very minimal splash up there. The 2 oil drain holes in tappet block are similar size as 2 breather holes on cam end disc, if you vented both boxes. Then use check valve like off Yamaha 650 or Norton breather kits. With good rings the cam disc breather works well & can even create negative pressure in breather hose.

An interesting puzzle. I'd think the TDC plug hole vent would put out more oil than could drain back??

Here's breather on '69 Bonnie for reference. The Triangles only line up fully for a moment as pistons fall. They are covered as pistons rise. I don't know this, but breather hole (1/4") in hollow cam might act as centrifugal oil separator??
Don
 

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#14 ·
Hi all.
Well, I did tap into the top of the timing cover, it's not all kinds of pretty, but works well.
I had to have my bike flatbedded home at the end of riding season last year, I'd kick and kick and kick, with no luck at all, even with coasting and popping the clutch - which would normally work, didn't, that's the reason for the flatbed.
I had read that it might be the tapped gap, or the carb adjustment, so today I checked the gaps, that wasn't the problem, I've always kept up with that so it didn't make any sense that they would be out.
Took the Mikuni's of for a cleaning and found a bunch of dirty engine oil at the very front lower intake of both carbs clogging the vents, gave them both a good spray of gumout, got the bike back together, and two kicks - it fires right up.
Now, back to the breather.
Venting through the timing hole was coating the back of the bike right up to the front of the back fender, AND - the carbs.
After starting the engine and watching the breather tube, I got no splash of oil like I got out the timing hole.
Problem solved.
Now, like I said, it ain't pretty, but it works just fine.
 
#16 ·
I'm curious - does this kind of oil blowby affect the a/c "new bonnevilles" to the same extent too? Since I don't have an airbox in my frame anymore, I was wondering what I'll need to do. Clearly a small stubby breather filter on top of the crankcase might create an oily mess.and I might be forced to run a long tube up and under the tank.
 
#19 ·
Hi,
this kind of oil blowby affect the a/c "new bonnevilles" to the same extent too? Since I don't have an airbox in my frame anymore,
Mmmm ... it depends ... a "how long is a piece of string?" question:-

. The pistons on these old heaps move up and down together so, even without combustion pressure getting past rings and pressurising the crankcase, the crankcase volume under the pistons changes substantially during every crank revolution.

. Then these old heaps had much looser tolerances between components even when new than modern engines, especially if your bike's engine is water-cooled.

. In theory at least, your bike's engine should have less "blowby" pressuring the crankcase and then being vented with oil mist. However, it will be increased by ring-bore wear, same as on these old heaps and, if you haven't replaced the airbox with some other inlet air filtration, ring-bore wear will be faster.

Clearly a small stubby breather filter on top of the crankcase might create an oily mess.
Ime, it will do - my triples (120 degree crank throws) have very little crankcase volume change during crank rotation but some escaping oil mist does still "create an oily mess" around the K&N filter. :(

might be forced to run a long tube up and under the tank.
Risking stating the obvious, you shouldn't be fussed so much about length as increasing the diameter - that'll not only slow down the vented air but also allow any oil then condensed to drain back into the crankcase. Also, a large-diameter hose gives the option of fitting a 'baffle' like the stainless pan scourer pictured in post #7.

The troubles with the timing-hole breather suggested to the OP by the belt primary-drive maker were: that hole has the spinning crank flywheel just below it, that throws actual oil into the breather; the hole is small-diameter so, even if the OP could work out a way of attaching a large-diameter hose, once any oil was in the hose, it didn't have any way of draining back into the crankcase 'til the engine stopped. Length is only necessary to carry the vented air away from the rear of the bike.

Hth.

Regards,
 
#18 ·
If oil is coming out of the silly long fender oil tube it's because of the stupid design or a engine with excessive blow by....Even with a good engine the long tube is a trap for moisture and crankcase oil vapor...On my T140D the primary breather has a short hose capped with small pod filter. It doesn't make an oil mess and no hideous fender oil tube...The filter is easy to conceal..
 
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