Author Topic: RE: Can I convert a CB750 engine to an Air Compressor? (Read 4467 times)

Retro Rocket · « **Reply #25 on:** October 20, 2012, 03:45:42 PM »

You would need to close off the exhaust valve to stop air being forced out the exhaust port, that would mean altering the camshaft or doing something with the valve springs and timing. I also think it would run at a lot less than half the horsepower being suggested in the other thread because the 2 lazy cylinders would rob more power as they are being dragged around. The compressed air from the engine will be hot and may contain engine oil. This could be a problem for some applications like blasting or painting. You would need a separator to remove oil from the air and a pressure relief valve as well. It can and has been done but i don't think it will be very efficient and may cost more than its worth, primary chains will rattle their butts off...

chewbacca5000 · « **Reply #26 on:** October 20, 2012, 05:42:24 PM »

Girls in binkis riding snowmobiles and CB750s that can time travel I love this thread! Maybe I can go back to 1969 and bring back a sandcast!

As for running on 2 I think we determined that it won't work, but firing on three cylinders might work ok. As for the exhaust just remove the tappet screw so the valve does not open. No need to grind the cam. Air goes in threw the intake and out the spark plug hole. An oil / water separator is a given.

I already have the engine. Just need a 12 mm fitting, a check valve, and a plug for the number 4 carb.

phil71 · « **Reply #27 on:** October 20, 2012, 06:22:35 PM »

One other thing.. these engines were designed to run on leaded fuel.. which means a certain degree of top cylinder lubrication.. in this setup, you can bet that the rapid condensation compressed air causes will rust that chamber pretty fast. ever notice how much rust comes out of any compressor's tank, and how often?
One cylinder is not a lot of volume. It would be good for filling up a tire or basic utility , but definitely not on par with say a 60 gal cobalt from Lowes (real reasonable btw). Trying to fill a 30-50 gal tank and maintain 120 psi would probably blow thru a head gasket or rings pretty fast. It's doable, but if you look at harbor freight, you'll find a massive twin cyl compressor and 6hp electric motor for under $300 combined.. but then you'd better have a serious tank with welds that can handle it, or .. well, you know what can happen.

750resurrection · « **Reply #28 on:** October 20, 2012, 06:47:05 PM »

Quote from: phil71 on October 20, 2012, 06:22:35 PM

One other thing.. these engines were designed to run on leaded fuel.. which means a certain degree of top cylinder lubrication.. in this setup, you can bet that the rapid condensation compressed air causes will rust that chamber pretty fast. ever notice how much rust comes out of any compressor's tank, and how often?
One cylinder is not a lot of volume. It would be good for filling up a tire or basic utility , but definitely not on par with say a 60 gal cobalt from Lowes (real reasonable btw). Trying to fill a 30-50 gal tank and maintain 120 psi would probably blow thru a head gasket or rings pretty fast. It's doable, but if you look at harbor freight, you'll find a massive twin cyl compressor and 6hp electric motor for under $300 combined.. but then you'd better have a serious tank with welds that can handle it, or .. well, you know what can happen.

A tank rusts because pressure is left in it. If you relieve the pressure after use, it doesn't rust.

750resurrection · « **Reply #29 on:** October 20, 2012, 06:50:09 PM »

Quote from: rb550four on October 20, 2012, 03:38:53 PM

The 750 is powerful but, it just can't supply enough giggahertz to propel an average human back in time, but if it could propel an average human to the future, that human could bring back the necessary information that we'll need to be ready for the future before the future is the future. Right?And if this is true, does that mean we have no future and only a past,or a past with a predictable future?
All This because some poor guy wants an air compressor.

OMG ! Build thread

Retro Rocket · « **Reply #30 on:** October 20, 2012, 08:24:36 PM »

Quote from: 750resurrection on October 20, 2012, 06:47:05 PM

Quote from: phil71 on October 20, 2012, 06:22:35 PM
One other thing.. these engines were designed to run on leaded fuel.. which means a certain degree of top cylinder lubrication.. in this setup, you can bet that the rapid condensation compressed air causes will rust that chamber pretty fast. ever notice how much rust comes out of any compressor's tank, and how often?
One cylinder is not a lot of volume. It would be good for filling up a tire or basic utility , but definitely not on par with say a 60 gal cobalt from Lowes (real reasonable btw). Trying to fill a 30-50 gal tank and maintain 120 psi would probably blow thru a head gasket or rings pretty fast. It's doable, but if you look at harbor freight, you'll find a massive twin cyl compressor and 6hp electric motor for under $300 combined.. but then you'd better have a serious tank with welds that can handle it, or .. well, you know what can happen.

A tank rusts because pressure is left in it. If you relieve the pressure after use, it doesn't rust.

Tanks also rust because of the moisture inside that comes from compressing the air, i thought that would be obvious....

750resurrection · « **Reply #31 on:** October 21, 2012, 05:22:29 AM »

When you release the pressure from the tank, the moisture is expelled, so unless you're an idiot, your tank doesn't rust, that should be obvious.

750resurrection · « **Reply #32 on:** October 21, 2012, 05:27:39 AM »

Quote from: chewbacca5000 on October 13, 2012, 06:22:35 AM

I would like to convert a CB750 engine into an air compressor and use 2 cylinders as an air compression can this be done?

The other option would be to use the engine to power an air pump.

Are either of these workable?

Thanks!

Since phil and retro cannot stand the idea that you'd "misuse" a cb750, they will tell you every horrible tale their mind can dream up, in order that you not misuse their precious engine that you own.

Just be aware of that. If there are others who have the same mental bent, they will no doubt discourage you every chance they get as well.

That's why they are here, to tell you "No!"

FrankenFrankenstuff · « **Reply #33 on:** October 21, 2012, 06:47:06 AM »

[img width= height=]http://4.bp.blogspot.com/_tdumTrUEi5A/Rnfp1saAdUI/AAAAAAAAALQ/v_qZki8rZQg/s400/just_do_it.jpg[/img]

Too much bla bla bla...make some air. make a vid.

phil71 · « **Reply #34 on:** October 21, 2012, 10:05:04 AM »

Ok 750, why don't you do it then?

Stev-o · « **Reply #35 on:** October 21, 2012, 10:24:14 AM »

This might help but not sure of thread size.

http://www.ebay.com/itm/Super-Air-Engine-Spark-Plug-Air-Compressor-Car-Truck-Tractor-/140863977793?pt=LH_DefaultDomain_0&hash=item20cc25b941

Retro Rocket · « **Reply #36 on:** October 21, 2012, 02:54:58 PM »

Quote from: 750resurrection on October 21, 2012, 05:22:29 AM

When you release the pressure from the tank, the moisture is expelled, so unless you're an idiot, your tank doesn't rust, that should be obvious.

Not many sensible posts from you mate, in my experiences {i'm a painter of all substances by trade} ALL compressors have moisture relief valves [underneath the tank, which are NOT pressure relief valves}, regardless of what you do to the pressure the tanks hold moisture, it should be blatantly obvious to anyone thats ever sprayed anything because, if water wasn't a problem then why do you use "moisture traps".... Got it yet...

As far as this rubbish goes,

"

Quote

Since phil and retro cannot stand the idea that you'd "misuse" a cb750, they will tell you every horrible tale their mind can dream up, in order that you not misuse their precious engine that you own.

Just be aware of that. If there are others who have the same mental bent, they will no doubt discourage you every chance they get as well.

That's why they are here, to tell you "No!"

"

Its glaringly obvious that you know nothing about most members here

your words AGAIN, you just love twisting anything to suit your agenda, i would like to see it done, as i've already said, just some of the earlier claims were incorrect, taking away 2 cylinders doesn't give you half the horse power, simply because the engine {2 cylinders} will be driving the unpowered cylinders, which would be similar to HP losses between the crank and rear wheel on a normal running bike.... You are obviously unable to comprehend anything without being a fool and your stupid argumentative replies are getting boring...... Try again....

rb550four · « **Reply #37 on:** October 21, 2012, 03:07:59 PM »

So, this horse walks up to the bar,
and the bartender says "Why the long face?"

chewbacca5000 · « **Reply #38 on:** October 21, 2012, 03:31:44 PM »

Quote from: rb550four on October 21, 2012, 03:07:59 PM

So, this horse walks up to the bar,
and the bartender says "Why the long face?"

This is one of my favorite jokes.

Retro Rocket · « **Reply #39 on:** October 21, 2012, 03:34:05 PM »

Chewy, hurry up and build the compressor mate.....

chewbacca5000 · « **Reply #40 on:** October 21, 2012, 04:27:49 PM »

I got to build real engine for a real cb750 before I do that. I am not super excited to lug the 180 beast out of its tomb in my basement anytime soon.

I'd be more inclined to hook up a air house to number 4 on a running bike and see how quick it can pump up a 30 gallon tank.

Retro Rocket · « **Reply #41 on:** October 21, 2012, 04:39:56 PM »

Quote from: chewbacca5000 on October 21, 2012, 04:27:49 PM

I got to build real engine for a real cb750 before I do that. I am not super excited to lug the 180 beast out of its tomb in my basement anytime soon.

I'd be more inclined to hook up a air house to number 4 on a running bike and see how quick it can pump up a 30 gallon tank.

You can buy those cylinder pump hoses here, they also come in 4WD kits as part of the tire repair kit...Handy but i always thought that using exhaust gas to pump up a tire should be a temporary thing, not sure what the gas would do to a tire long term...

FrankenFrankenstuff · « **Reply #42 on:** October 21, 2012, 06:17:08 PM »

Quote from: chewbacca5000 on October 21, 2012, 03:31:44 PM

Quote from: rb550four on October 21, 2012, 03:07:59 PM
So, this horse walks up to the bar,
and the bartender says "Why the long face?"

This is one of my favorite jokes.

I thought the joke was "Celine Dion walks into a bar..."

Retro Rocket · « **Reply #43 on:** October 21, 2012, 06:39:11 PM »

Quote from: The Honorable Mr. FrankenFrankenstuff on October 21, 2012, 06:17:08 PM

Quote from: chewbacca5000 on October 21, 2012, 03:31:44 PM
Quote from: rb550four on October 21, 2012, 03:07:59 PM
So, this horse walks up to the bar,
and the bartender says "Why the long face?"

This is one of my favorite jokes.

I thought the joke was "Celine Dion walks into a bar..."

Wouldn't the punch line be, "why the bad head".....

dave500 · « **Reply #44 on:** October 22, 2012, 02:34:15 AM »

why not use all four cylinders driven by a belt?you gut all the transmission out of it leaving whats required for the oil pump and couple an electric motor via pulleys?dump the cam and fit reed valves on the inlet,,the exhaust stays closed all the time and pressure is tapped from the plug holes?a bit like this.

phil71 · « **Reply #45 on:** October 22, 2012, 08:26:43 AM »

that seems like the best possible way to do it!

chewbacca5000 · « **Reply #46 on:** October 22, 2012, 05:18:41 PM »

Quote from: The Honorable Mr. FrankenFrankenstuff on October 21, 2012, 06:17:08 PM

Quote from: chewbacca5000 on October 21, 2012, 03:31:44 PM
Quote from: rb550four on October 21, 2012, 03:07:59 PM
So, this horse walks up to the bar,
and the bartender says "Why the long face?"

This is one of my favorite jokes.

I thought the joke was "Celine Dion walks into a bar..."

I thought it was guy walks into a bar and ask the bartender, "what's with that big jar of money on the bar".

Bartender replies, "It's my horse, he is depressed put 10 dollars into the jar and if you cheer him up you can keep the whole jar".

Guy whispers to into the horses ear the horse starts laughing. A couple weeks latter the guy walks back into the bar and sees another jar of money, and the ask the bar tender, "What's with the jar of money I got your horse to laugh.

The bar tender replies, "That's the problem he won't stop laughing". So the guy whispers into the horses hear and he stops laughing. Bar tender replies, "That is amazing what did you say to him".

Guys says, "To get him to laugh I told him that I was bigger than him, and to get him to stop I showed him".

chewbacca5000 · « **Reply #47 on:** October 22, 2012, 05:23:49 PM »

Quote from: dave500 on October 22, 2012, 02:34:15 AM

why not use all four cylinders driven by a belt?you gut all the transmission out of it leaving whats required for the oil pump and couple an electric motor via pulleys?dump the cam and fit reed valves on the inlet,,the exhaust stays closed all the time and pressure is tapped from the plug holes?a bit like this.

Dave,

You just about summed up my problem the huge electric motor. Where I am there is not 3 phase power for such a beast. Most I could must is 7.5 HP single phase.

Do you have 3 phase 220 where you live? If so you could run 15 or 20 HP electric motors.

I really like your drawing BTW!

dave500 · « **Reply #48 on:** October 22, 2012, 11:34:08 PM »

in australia our house hold supply is 240v,,our three phase is 415v,,how does that grab ya?you could probably spin a 750 over ok on your normal supply,a decent cement mixer motor should have the torque,just work out your drive ratio,,youll have two pistons at a time compressing like 370cc per pump stroke,i think its doable this way easier than running two on gasoline?the starter motor might spin the thing at a thousand rpm,,have a look at the starter gear ratio as a ball park and work it out from there?whos keen to crank their 750 with the kill switch off and note the tacho rpm?i dont mean for you to power it with a starter motor!

speedy gonzalais · « **Reply #49 on:** October 28, 2012, 02:27:42 PM »

you would need a big old motor to run the engine with cam aswel, wouldnt be very energy efficient. most compressors run on the same principle as 2 stroke engines with no mechanical valves, you could grind off the exhaust lobes on the camshaft ,then as mentioned above extract the air through the plug holes with a good non return valve.

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Author Topic: RE: Can I convert a CB750 engine to an Air Compressor? (Read 4467 times)