Oh my, this happened

[Schwany]

I was running the timed breather and a breather off the back of the timing case on my altered P11 engine. Tried to hit 100MPH on a previous ride which shouldn't be an issue and ran into a wall at 93MPH. Engine went limp like the cam went flat at 93MPH. That is not what happened, so don't dwell on it. I removed the plumbing and plugged the time breather port, and now the JS2 cam and engine comes to life like it used to. Unfortunately, on my test run I forgot that Hwy 5 was closed Northbound into Seattle. I hit 70 in 3rd (5 speed TTi box) the engine exhaust note started singing and farts wouldn't you know it I came up on a long assed line of stop and go traffic 4 lanes wide Northbound. Was trapped in it for half an hour. Will try again Wednesday but in the other direction. lol

There is a point in there and it is running both a standard timed breather and a reed valve breather on the back of the timing case does not work well at high RPM on "my" engine. I know who is going to say but I never have a problem with that set up. If that is true, have you done 100 MPH and beyond with both breathers attached? My goal is 120MPH by the way. Should be exciting to see if it stays stable. Yeehaw.

 

[MichaelB]

I have no experience running both, but have a question.
Are they plumb together to the same recepticle?

 

[o0norton0o]

I'm not sure if you mean me, but I also run the double breather, except I drilled out the timed breather and mounted Jim Schmidt's camshaft port reed breather in that port so my set up is double reed breathers which is a little different than yours.

I have hit the top speed wall myself some years ago. I could only go 83mph. If I twisted the throttle more it didn't go any faster. Somewhere I read that if you hit the wall then close the throttle a bit and it speeds up for second before it begins to decellerate that it means you are running too rich. The idea being that closing the throttle leans it out for a second and the surge is a momentary better A/F ratio. I was running 240 mains so I changed to 220 and had 260's and jet key in my pocket because I wasn't sure if I was rich or lean. I zoomed right past 83mph so the 220's was the correct choice in my case.

In your case, I would encourage you to do the same test. Throttle it until it stops accelerating then back off the throttle and see if you get that little momentary surge. The whole range your issue is happening in is dominated by the choice of main jets, so I wouldn't be surprised if your issue was your choice of main jets.....

 

[Schwany]

I have no experience running both, but have a question.
Are they plumb together to the same recepticle?

Short answer is No they are not plumbed together. Only thing they have in common is both devices vent the crank case.

The cNw reed valve plumbing goes to the oil tank froth tower. The oil tank is vented to a catch can like device that vents to a small conical air filter.

The timed breather plumbing vents to atmosphere through a PCV valve and the oil mist blown through dribbles onto the chain.

Tying them together with a T or Y fitting messes with the reed valve and is slightly worse.

I'm not looking for help tuning. I'm passing along an experience that may only exist with my engine configuration. I thought it was working until I tried to do the ton.

 

[o0norton0o]

Interesting, because before I added the camshaft port reed breather, I did have the reed breather on the timing chest modification and the stock camshaft rotating discs breather both on the same hose connection plumbed into the oil tank breather port and I had no trouble hitting 100mph.

I bet its those weird carbs that you run... Aren't they made in some communist country??

 

[Schwany]

I'm not sure if you mean me, but I also run the double breather, except I drilled out the timed breather and mounted Jim Schmidt's camshaft port reed breather in that port so my set up is double reed breathers which is a little different than yours.

I have hit the top speed wall myself some years ago. I could only go 83mph. If I twisted the throttle more it didn't go any faster. Somewhere I read that if you hit the wall then close the throttle a bit and it speeds up for second before it begins to decellerate that it means you are running too rich. The idea being that closing the throttle leans it out for a second and the surge is a momentary better A/F ratio. I was running 240 mains so I changed to 220 and had 260's and jet key in my pocket because I wasn't sure if I was rich or lean. I zoomed right past 83mph so the 220's was the correct choice in my case.

In your case, I would encourage you to do the same test. Throttle it until it stops accelerating then back off the throttle and see if you get that little momentary surge. The whole range your issue is happening in is dominated by the choice of main jets, so I wouldn't be surprised if your issue was your choice of main jets.....

I was thinking about your setup. So essentially the timed breather is just a hole into the crank case with a reed valve in your scenario. That probably would work better, but I like the plumbing not being there anymore. I've had it hooked up and removed several times. It's nicer without it. The cNw breather does the job.

Nope on the tuning advice. Removing the timed breather plumbing and raising the needle making it richer livened things up a lot. I have no issue, sorry for the confusion. I am actually a very good tuner. Like I said the wall wasn't there until I went for 3 digits on the speedo. I'll get there next time out. Thanks anyway.

By the way, in the 90's my little old P11 would do 108 MPH before the front started to wiggle a little. I didn't have a steering damper or the suspension I have today, so I should be able to hit 120 MPH. Will know soon.

 

[Schwany]

Interesting, because before I added the camshaft port reed breather, I did have the reed breather on the timing chest modification and the stock camshaft rotating discs breather both on the same hose connection plumbed into the oil tank breather port and I had no trouble hitting 100mph.

I bet its those weird carbs that you run... Aren't they made in some communist country??

I'll bet it was the fastest Norton ever.

Why did you add the reed valve to the timed breather? Reduce oil leaks?

Keihin carburetors are made in Japan, US, Mexico, and Brazil.

By the way, I added the timed breather back into the mix because you said it worked with a reed valve on the timing side. It doesn't on my engine. Your engine is sort of vanilla though, so very different flow characteristics.

 

[o0norton0o]

I thought the disc breather was actually so much less efficient than a reed valve that it reduced the vacuum on the up stroke. Adding the reed valve took away that last oil leak at the tachometer drive port. After I added the camshaft reed valve, my bike really doesn't leak (much)

You should come out my way for your speed run. I have a spot that is like a drag strip with almost no traffic on it.

 

[baz]

I run the timed camshaft breather plus a reed valve off the timing cover teed together
No extra holes in the inner timing cover I have no trouble getting past 100mph and no oil leaks
I've run past 7500 rpm in the lower gears but don't make a habit of it or I'll end up with 54year old con rods poking their heads out the cases for a look around

 

[kommando]

The Disc breather is fixed in when it operates, like the timing of camshafts pre variable cam timing. So it works optimally at certain revs and at other revs will not function as well if at all. The reed valve operates based on the revs it sees and is responsive enough to cope with all revs you would see in an old Norton /twin. They were after all first used in 2 strokes to allow higher revs for this very reason. So its perfectly possible for the fixed Disc breather at high revs to create conditions that stop the reed valve from working as well as its stops seeing the signal for it to work. As the reed valve is designed for high revs then disable the disc breather, also try to get that reed valve closer to the sump where it receives a stronger signal.

 

[Schwany]

I stated that I had already solved the hitting the wall performance problem in my original post for those that missed it. I knew what the problem was the second it happened. The timed breather and reed valve don't get along at high RPM WOT. I'd run into it before, but had other issues then that could have also contributed. I removed the timed breather plumbing then. I solved those other issues ignition mostly and thought I'd give it another try since others here said it works. It does not for me. If having a timed breather and reed valve tied together or not is working for others, the key might be a milder engine configuration with dual exhaust. Whatever the case, I won't hook up the timed breather again.

I expect the guys with 750 engines built like mine will start posting that they run a timed cam breather and a reed breather tied together and do 140 MPH on the track every weekend.

 

[Schwany]

I thought the disc breather was actually so much less efficient than a reed valve that it reduced the vacuum on the up stroke. Adding the reed valve took away that last oil leak at the tachometer drive port. After I added the camshaft reed valve, my bike really doesn't leak (much)

You should come out my way for your speed run. I have a spot that is like a drag strip with almost no traffic on it.

Only thing I noticed with the cam breather and reed valve both hooked up was my catch can didn't get much in it, and my top end was dead.

Maybe after Hwy 5 is open again Southbound and I make sure I can do it.

 

[Schwany]

Crap, looks like the quest for finding a typical top end speed with my current engine is over for a while.

Here's what my oil looks like. It's fine brass or bronze. Engine still runs good, but it's noisy. The little bubbles are bubbles not metal. Definitely have an air in the oil issue. Oil pump could be sucking air due to a cut rubber seal when I put the timing cover back on after installing a rubberized cam chain adjuster shoe and the offset cam key.

I'm fairly certain I know where the bronze would be coming from. If it is brass my mains are coming apart. Whatever the case it looks like I have some changes to make soon. Time to clear some bench space for engine parts.

 

[Triton Thrasher]

Somewhere I read that if you hit the wall then close the throttle a bit and it speeds up for second before it begins to decellerate that it means you are running too rich. The idea being that closing the throttle leans it out for a second and the surge is a momentary better A/F ratio. I was running 240 mains so I changed to 220 and had 260's and jet key in my pocket because I wasn't sure if I was rich or lean. I zoomed right past 83mph so the 220's was the correct choice in my case.

May be just a different way of seeing/describing things, but the classic test for Amal main jet size is have it pulling hard at full throttle and quickly close the throttle to 7/8 open. That briefly enriches the mixture.

If power feels stronger when you do that, the main jet is too small.

If power drops off, then slightly recovers, the main jet is too big.

 

[o0norton0o]

May be just a different way of seeing/describing things, but the classic test for Amal main jet size is have it pulling hard at full throttle and quickly close the throttle to 7/8 open. That briefly enriches the mixture.

If power feels stronger when you do that, the main jet is too small.

If power drops off, then slightly recovers, the main jet is too big.

That sounds exactly opposite of my experience. Slightly closing the throttle when I hit the 83mph wall, made the bike surge momentarily, and the main jet turned out to be too big, so that means that closing the throttle actually momentarily leaned out a main jet that was too big. The correction that worked was a smaller main jet. 220's

 

[Schwany]

I still might take it for one more long pull. The rods are not likely to come off the crank and I can probably make it home with it beating on itself. It's been noisy for several hundred miles and made it home every time. Sure wish it was still as quiet as it was when I first put it together. It was sewing machine quiet. The quiet didn't last long though.

Amal carburetors are of no interest to me whatsoever. Only time they worked well for me for a little while until the slides stuck or the manifold o-rings leaked is when the engine was stock and had dual exhaust. When I put a 2 into 1 exhaust on the tune went out the window. I fixed it with dual Mikuni carburetors on Commando Mikuni after market kit manifolds I modified for the P11.

Yeah I know nobody but me has ever had an issue with Amal carburetors on a modified Norton engine. Everybody else can go 140 MPH all day long.

Carburetion had nothing to do with my issue. It was the timed breather. The mains are fine as is every other part in the 35mm Keihin carburetors I'm using. Sudco got it right for my engine and exhaust configuration.

 

[kommando]

Oil cavitation can occur in the pump when certain oils are used, change to a different oil and the cavitation disappears. When cavitation happens the oil with all those tiny air bubbles cannot create enough oil film thickness and the journal will touch the big ends instead of riding on the oil film.

 

[o0norton0o]

Sorry, I didn't meant to hijack your thread. My original comment was just about hitting the wall and the bike wouldn't accellerate past a certain speed. Your issue seemed similar, so I mentioned my experience in an attempt to add another possibility contributing to your issue.

Getting back to your issue... I guess the combination of some metallic tint to your oil and you now think your engine sounds like it's getting noisy is a bad combination and worthy of some further investigation. I'd mention my own recent experience with tearing down my engine this winter because of a noise I didn't like, but that would be another story about me..... so good luck

 

[Schwany]

Sorry, I didn't meant to hijack your thread. My original comment was just about hitting the wall and the bike wouldn't accellerate past a certain speed. Your issue seemed similar, so I mentioned my experience in an attempt to add another possibility contributing to your issue.

Getting back to your issue... I guess the combination of some metallic tint to your oil and you now think your engine sounds like it's getting noisy is a bad combination and worthy of some further investigation. I'd mention my own recent experience with tearing down my engine this winter because of a noise I didn't like, but that would be another story about me..... so good luck

No big deal I expected some side tracking. I already know your story about the timing side, camera and so on.

My stories are always about me unless I'm helping someone in PMs.

 

[Schwany]

Oil cavitation can occur in the pump when certain oils are used, change to a different oil and the cavitation disappears. When cavitation happens the oil with all those tiny air bubbles cannot create enough oil film thickness and the journal will touch the big ends instead of riding on the oil film.

Lucas needs a lesson on how to manufacture oil apparently.

I thought rod big end shells had a copper layer under the top layer and not a bronze layer. The color in the oil is bronze. That said I'm using whatever shells MAP sent along with their long rods and light weight pistons. I didn't section the shells to see what they were made of. I just installed them along with a new standard sized journal crank.

The bubbles showed up in mass toward the end of draining the oil tank. I doubt it's the oil used. Probably more to do with beating the engine too often in lower gears and having the oil line for a oil pressure gauge blow off doing 70 MPH cruising on the Hwy and not noticing it until my left leg got really warm. That and a cut oil pump seal. Oil pressure is good at the rockers, but the crank might not be good anymore.

If the color is coming from wear on what I think it is all I'll be able to say about it is I thought so. Another one of those I'm the only one it has ever happened to situations.