crankcase reed breather

comnoz · Mar 19, 2012

comnoz said:
Dances with Shrapnel said:

comnoz said:

The reeds I am using can not keep up with the pistons at rpms over 7500 rpm and that is why the pressure starts rising. Jim

Click to expand...

Good stuff there Jim and a big thanks to Hannah. Looks like some solid product development and proof of concept; that's what I like to see.

So for those who race at and above 7,500 rpm is there hope for a suitable reed valve that will continue to scavenge?

Click to expand...

The standard reed will continue to maintain a vacuum to around 8000 if you are using the thin piston rings so they don't flutter. I have seen a little more depression at very high speed by installing two reeds stacked one on top of the other to make them stiffer which raises the resonant frequency. The trade off is more pressure down low.

The testing done on my old motor is about worst case. It has been thrashed on the dyno and the road for over 50,000 miles now. The leakdown is getting high and it is getting pretty noisy. It still only uses about a cup of oil in 2000 miles. I credit the crankcase vacuum for that.

After thinking about it the the neutral pressure at 7500 rpm is not really too bad. I put the fitting on my stock MK3 with just an open breather and the first time I revved it it blew the water out of my manometer. :cry:

motorson · Mar 19, 2012

put the fitting on my stock MK3 with just an open breather and the first time I revved it it blew the water out of my manometer

.

When I was working on Hondas in '84 I had a 750 four hooked up on mercury gauges to balance the carbs. I ran it up to make sure it was all balanced out and when I let off the gas it sucked all the mercury in all four columns into the engine. I wish I had a video of the horror on my face!
Dan.

comnoz · Mar 19, 2012

You don't want to do that nowdays. Mercury is tough to get and expensive when you find it. And you would have to declare a national emergency for a hazardous materials cleanup. :shock:

bwolfie · Mar 19, 2012

I have 8 pounds of mercury for sale if somone needs it. My grandfather would collect mercury switches for scrap hence the 8 pound jar.

comnoz · Mar 19, 2012

bwolfie said:
I have 8 pounds of mercury for sale if somone needs it. My grandfather would collect mercury switches for scrap hence the 8 pound jar.

Sold, I think. What would you need? Jim

swooshdave · Mar 19, 2012

motorson said:
put the fitting on my stock MK3 with just an open breather and the first time I revved it it blew the water out of my manometer

Click to expand...

.

When I was working on Hondas in '84 I had a 750 four hooked up on mercury gauges to balance the carbs. I ran it up to make sure it was all balanced out and when I let off the gas it sucked all the mercury in all four columns into the engine. I wish I had a video of the horror on my face!
Dan.

This is one of those instances that imaging in the look on your face is more valuable than video.

Didn't it just spit the mercury back out the exhaust?

Hobot · Mar 19, 2012

Hg is a LOT heavier than water or anti-freeze of ATF, so not near as sensitive to pulses or pressure changes. Hg would be good in a ring around the flywheel fro dynamic balance and shock absorption. Sucked into hot runing engine and not enough to 'hydrolock' it should be mostly vaporized and spit out as very toxic fumes. Sucked into a shutting down engine should still mostly spit it out but might recact with metal parts, but I'm not that up on Hg on hot Al but steel, pretty well ignores it. Like octane, once you have enough then more is not noticed to help any.

Do these more effective reeds work so well crank case seals become an issue?

comnoz · Mar 19, 2012

hobot said:
Do these more effective reeds work so well crank case seals become an issue?

I have not seen any bad effects. Jim

Hobot · Mar 19, 2012

Ok, thanks, I'd heard tales of such effective evacuators in British Iron type twins they had to flip seals or lose the vacuum. Don't remember how they did that though. I've also pondered scupper valve end of breath hose, worked a treat in my hydroplanes that took on water from cutting through waves or the rooster tails of others dumping it in cockpit.

Aka Duck Billed Valve

comnoz · Mar 19, 2012

On my racebike with the belt driven vacuum pump I would install the main and points seal upside down so they didn't allow air in. But I was drawing 15 inches HG with that. The reed breathers don't create anywhere near that much vacuum. Jim

Hobot · Mar 19, 2012

Oh ok then you are at least one extremist that sucked their seals inward. For normal life bikes its better just to not leak w/o having seals to deal with too. The reed valves in 2 strokes that rev over 10K all seem to depend on air pulses to close them, so I assume at around 7500 rpm in Nortons they just flutter into a blur with a slight gap left open. Thanks for the mechanical treats this post covered.

olympus · Dec 28, 2021

comnoz said:
So Hannah [one of my teenagers] said if I am going to post a movie it needs to be better. So here is take two of the crankcase vacuum test. Click on it to view.

View attachment 42974

I'd be interested to see the video clip ....but cant open it. any ideas, has it been pulled??

L.A.B. · Dec 28, 2021

olympus said:
I'd be interested to see the video clip ....but cant open it. any ideas, has it been pulled??

It's an image, not a video.

Time Warp · Dec 28, 2021

olympus said:
I'd be interested to see the video clip ....but cant open it. any ideas, has it been pulled??

There is nothing related in the full video list either.

https://www.youtube.com/channel/UCSn9JCMr-y7D1vVJFT4IJ8g/videos

crankcase reed breather

comnoz

motorson

comnoz

bwolfie

comnoz

swooshdave

Hobot

comnoz

Hobot

comnoz

Hobot

olympus

L.A.B.

Moderator

Time Warp

.......back to the 70's.

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