Motormite brake 80190 booster vlave

E

Eggsy

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Apr 28, 2025
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Can anyone send me a video link or instructions on how to install this check valve on my 1973 750 commando?
Thanks
 
Eggsy said:
Can anyone send me a video link or instructions on how to install this check valve on my 1973 750 commando?
Thanks
Click to expand...
To be honest, you are better off using a proper (metal) reed valve. I believe the Motormite is just a rubber flap, which will eventually stop working.

The MikesXS valve is very popular..

www.mikesxs.net

PCV Reed Valve - Crankcase Breather

Color/Finish: Silver Material: Metal Dimensions: Overall Length: 86.50mm Width (at widest point): 28.85mm Engine Inlet OD: 14.15mm Engine Inlet 11.85mm Filter (Air) Outlet OD: 12.00mm Filter (Air) Outlet ID: 9.45mm Fits: Universal Note: Easy Installation (Linked Below)
www.mikesxs.net www.mikesxs.net

Or search EBay for “EGR valve”
 
Eggsy said:
Can anyone send me a video link or instructions on how to install this check valve on my 1973 750 commando?
Thanks
Click to expand...
I assume you are interested in crankcase ventilation...

IMHO, a PCV valve at best does a part of the job. A crankcase mounted reed valve does more. They fully seal on the piston upstroke and open on the piston down stroke. Since they are low on the crankcase, they extract excess crankcase oil very quickly - MUCH faster than the oil pump.

My choice is the cNw offering. For 72/73 750's they bolt on. For others, the cases require machining, so I only use them when rebuilding an engine.

The JS Motorsport has options. 1) requires crankcases with the large sump filter on the bottom of the case. 2) works with 72/73 750 cases. 3) inline like a PCV valve but with a real reed valve (personally, I would not use this option since the other two are available.)

The NYC Norton requires crankcases with the large sump filter on the bottom of the case and if I'm not mistaken, they won't work on the older frames where the center stand mounts to the frame (I may be wrong about this).

All these options cost much more than a PCV valve, but then the likelihood of blowing out the crank seal or hydro locking the engine is quite a bit less.
 
Last edited:
cliffa said:
To be honest, you are better off using a proper (metal) reed valve. I believe the Motormite is just a rubber flap, which will eventually stop working.

The MikesXS valve is very popular..

www.mikesxs.net

PCV Reed Valve - Crankcase Breather

Color/Finish: Silver Material: Metal Dimensions: Overall Length: 86.50mm Width (at widest point): 28.85mm Engine Inlet OD: 14.15mm Engine Inlet 11.85mm Filter (Air) Outlet OD: 12.00mm Filter (Air) Outlet ID: 9.45mm Fits: Universal Note: Easy Installation (Linked Below)
www.mikesxs.net www.mikesxs.net

Or search EBay for “EGR valve”
Click to expand...
I been using this type of reed valve for years a Yammy 650 reed valve (Mikes XS valve), only cost me $24 at the time and sits in between my engine plates, no machining at all just hang with the breather hose coming out the back of the timing crank case where the original breather comes out, my breather hose goes into a catch bottle behind the GB and engine plates, you can just see the top of the catch bottle, been with this set up for over 35 years, it gets very little oil in the bottom of the catch bottle, but you got to have a big air hole at the top for the pressure to escape.
Motormite brake 80190 booster vlave
 
I use the same valve. It doesn't return sumped oil, but I believe, does a good job allowing the crankcase to breath. A very noticeable difference from before to after.
 
Anyone able to compared the carbon fibre Peewee reed referred to above to the usual steel reed in the PCV’s? Would be possible to swap over?
 
Hm, Eggsy, no one answered your question. The Motormite valve is the KISS principle in action (keep it simple, stupid). I have used a Motormite on my '73 850 for about 5 years; I plumbed it for the vent hose to come out of the case and across to the left side behind the engine with the larger sized tubing that fits both the fitting at the case and the Motormite intake, then a smaller diameter tube up to the oil tank. If I remember correctly it was the same sized tubing as originally came stock on my '73. Sorry I didn't go out and measure but I am thinking maybe the bigger tube is 5/8, 11/16 or 3/4 i.d. out of the case, and maybe 1/2 or 3/8 out of the valve up to the breather fitting on the oil tank. After you measure you can get the right tubing at any auto parts store, along with hose clamps. Easy Peasy.

Mine works fine, vents fine, no obvious oil past it in the line, and it improved oil consumption in the engine and lessened oil leaks. After using it a while, I didn't see any reason not to continue to use it, and it is remarkably inexpensive. It is cheap enough (costs about the same as a 16 oz latte) that you can replace it whenever you need to, although mine is still good. In fact, after 5 years, it still works well enough that to drain the oil in the crankcase, I have to take the breather line off, because it still holds a vacuum well enough not to let the oil out the crankcase bottom drain unless you provide it a way to get air into the crankcase to replace the oil. In other words, it's still doing its job. I'm sure the various reed valves and breathers mentioned above work at least a little better, and on a '72 Combat definitely one designed for that engine would work a lot better, but it's hard to beat the $5 solution on a pre- or post-72 Commando.

And to be fair, if I were racing this bike, I probably would go for a reed valve, but this is a street bike that gets ridden mildly, and rarely sees 6000 rpm
 
I had the Motormite booster on my 850's breather line near where it attvhed to the tank. After a few months it seemed to no longer work as well...you could feel the air pulses at the breather pipe output just inside the tank filler neck..with a finger over the pipe opening (just after startup, cold oil!). Thse pulses were much weaker after some months. Switched to the XS350 metal reed valve and that still gives great pulsing after many years of use.
 
linker48x said:
Hm, Eggsy, no one answered your question. The Motormite valve is the KISS principle in action (keep it simple, stupid). I have used a Motormite on my '73 850 for about 5 years; I plumbed it for the vent hose to come out of the case and across to the left side behind the engine with the larger sized tubing that fits both the fitting at the case and the Motormite intake, then a smaller diameter tube up to the oil tank. If I remember correctly it was the same sized tubing as originally came stock on my '73. Sorry I didn't go out and measure but I am thinking maybe the bigger tube is 5/8, 11/16 or 3/4 i.d. out of the case, and maybe 1/2 or 3/8 out of the valve up to the breather fitting on the oil tank. After you measure you can get the right tubing at any auto parts store, along with hose clamps. Easy Peasy.

Mine works fine, vents fine, no obvious oil past it in the line, and it improved oil consumption in the engine and lessened oil leaks. After using it a while, I didn't see any reason not to continue to use it, and it is remarkably inexpensive. It is cheap enough (costs about the same as a 16 oz latte) that you can replace it whenever you need to, although mine is still good. In fact, after 5 years, it still works well enough that to drain the oil in the crankcase, I have to take the breather line off, because it still holds a vacuum well enough not to let the oil out the crankcase bottom drain unless you provide it a way to get air into the crankcase to replace the oil. In other words, it's still doing its job. I'm sure the various reed valves and breathers mentioned above work at least a little better, and on a '72 Combat definitely one designed for that engine would work a lot better, but it's hard to beat the $5 solution on a pre- or post-72 Commando.

And to be fair, if I were racing this bike, I probably would go for a reed valve, but this is a street bike that gets ridden mildly, and rarely sees 6000 rpm
Click to expand...
Thanks for the reply
 
linker48x said:
Hm, Eggsy, no one answered your question. The Motormite valve is the KISS principle in action (keep it simple, stupid). I have used a Motormite on my '73 850 for about 5 years; I plumbed it for the vent hose to come out of the case and across to the left side behind the engine with the larger sized tubing that fits both the fitting at the case and the Motormite intake, then a smaller diameter tube up to the oil tank. If I remember correctly it was the same sized tubing as originally came stock on my '73. Sorry I didn't go out and measure but I am thinking maybe the bigger tube is 5/8, 11/16 or 3/4 i.d. out of the case, and maybe 1/2 or 3/8 out of the valve up to the breather fitting on the oil tank. After you measure you can get the right tubing at any auto parts store, along with hose clamps. Easy Peasy.

Mine works fine, vents fine, no obvious oil past it in the line, and it improved oil consumption in the engine and lessened oil leaks. After using it a while, I didn't see any reason not to continue to use it, and it is remarkably inexpensive. It is cheap enough (costs about the same as a 16 oz latte) that you can replace it whenever you need to, although mine is still good. In fact, after 5 years, it still works well enough that to drain the oil in the crankcase, I have to take the breather line off, because it still holds a vacuum well enough not to let the oil out the crankcase bottom drain unless you provide it a way to get air into the crankcase to replace the oil. In other words, it's still doing its job. I'm sure the various reed valves and breathers mentioned above work at least a little better, and on a '72 Combat definitely one designed for that engine would work a lot better, but it's hard to beat the $5 solution on a pre- or post-72 Commando.

And to be fair, if I were racing this bike, I probably would go for a reed valve, but this is a street bike that gets ridden mildly, and rarely sees 6000 rpm
Click to expand...
Thanks
 

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