Author Topic: RE: Can I convert a CB750 engine to an Air Compressor?  (Read 4462 times)

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Offline chewbacca5000

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RE: Can I convert a CB750 engine to an Air Compressor?
« 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!


Offline 70CB750

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #1 on: October 13, 2012, 06:28:00 AM »
Workable - yes. Efficient - not so sure. Basically you will change nearly perfect technical solution to make one that's more hack than anything else.

You would have to figure out cooling too for longer runs  - not worth the trouble imho.
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Offline FrankenFrankenstuff

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #2 on: October 13, 2012, 09:10:46 AM »
should be about 140 psi per cylinder. I have seen guys that converted COX model plane engines into fuel pumps with success.

Offline Stev-o

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #3 on: October 13, 2012, 09:35:32 AM »
Chewy - you gettin cabin fever already?!   Put that motor into a frame and convert it into a snow machine! 
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline chewbacca5000

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #4 on: October 13, 2012, 10:39:26 AM »
Chewy - you gettin cabin fever already?!   Put that motor into a frame and convert it into a snow machine!

Yeah, I think that is what is happening cabin fever.

70CB750 is right is might be more of a hack than anything else, but at 140 PSI it might pump some good air 736 /4 = 184 per cylinder * 2 cylinders is 368.  With that displacement it should equal 5 to 7.5 HP or 18 to 26 CFM.  Not sure of my math just comparing it to the displacement of small engines and air pumps.

As for cooling add a 12 v Radiator fan.



Offline seanbarney41

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #5 on: October 13, 2012, 11:45:12 AM »
back in the 1990's  I used to read Hemmings Motor News a lot...I remember some guy had a running ad for a kit to convert a chevy small block v8 into an air compressor using the same idea, half the cylinders ran on gas as normal while the other half compressed the air, never heard any claims as to how well it worked...with the price of gas what it is today, I don't see any practicality to this unless you need a compressor somewhere where there is no electricity
If it works good, it looks good...

Offline chewbacca5000

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #6 on: October 13, 2012, 03:20:17 PM »
Schramm made something very similar 1/2 tractor 1/2 air compressor it was called the Pneumatractor and it ran off the front 3 cylinders and used the back three to pump air.  See first pic.

After applying fixes to my Harbor Freight sandblaster found here Sandcarving Pressure Pot-102 my sandblaster really kicks some butt.  This is with a compressor rated at 9 CFM at 90 PSI.  It will blast the heck out of anything including catalyzed paint for a few minutes.  No clogging with stand pipe and  larger valve.

I think if I can get up to 25 CFM or so I will be good to go.

As for cost I am weighing cost of electrical work and performance vs gas cost.  CFM is the major issue.  The cut off for electric without 3 phase is 7.5 HP.  A setup like this with good parts runs around 2 K.

All you would have to do is remove the slides from 2 carbs, plug up the seat to prevent gas flow, and make and adapter on the exhaust to pump air.


Offline rb550four

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #7 on: October 13, 2012, 07:08:02 PM »
Can you make a 750 snow machine please.
A few Honda 500's, a few Honda 550's, a few Honda 650's, '72 cb 450, a couple 500/550/650 hybrids, and 2001 750. 
  550 Snowbike -Somebody had to do it.
  http://forums.sohc4.net/index.php/topic,101678.0.html             
http://forums.sohc4.net/index.php/topic,137317.msg1550907.html#msg1550907

Offline Stev-o

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Offline chewbacca5000

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #9 on: October 13, 2012, 08:15:36 PM »
Can you make a 750 snow machine please.

Like this...

How about I build it and you ride it!  Reminds me too much of snowboarding.  Needless to say that did no go well.  Cool video though!


http://www.motorcycle-usa.com/20/2289/Motorcycle-Article/EXPLORER-Snow-Bike-Conversion-Kit.aspx

Offline Stev-o

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #10 on: October 13, 2012, 08:33:45 PM »
I snowboard and would ride that as well!  Would have to be in deep powder not icy NY hills! Falls are much softer on powder.
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline MrGardman

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #11 on: October 14, 2012, 04:11:49 AM »
You know it's funny that you are talking about a snow machine. I went to the Honda convention in Washington DC in the very early 70s. Amongst all the bikes and hoopla  Honda showed a video of their prototype snowmobile using a CB750 engine. The thing never made it to market but Honda was at least looking at it.

Offline chewbacca5000

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #12 on: October 14, 2012, 06:07:30 AM »
Steve, are you some kinda wuss what's a little ice.

MrGardman,

Here is a thread on the sled you speak of. http://vintagesleds.com/bs/index.php/topic,63145.msg710827.html#msg710827

Apparently is has a sand cast engine inside.

Offline rb550four

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #13 on: October 14, 2012, 07:14:35 AM »
I toyed with the idea of that snow/bike/conversion kit  type idea, great for lightweight dirt bikes. The sohc 4's are too heavy for that chimpy little set up, not enough track to move the weight, and certainly not enough ski to steer ,now we're talking about 500 lbs with a high center of gravity balanced on ice on two points and one of them is gonna spin, ya get dead quick on that, that's why snowmobiles have  multiple points and two of them are for steering.
For those southern members if you havent seen the way  a snowmobile is put together, it's amazing, it's a cookie sheet with a motor.
  I was looking into a removeable track type set up for a Rhino, but it would set ya back $3000+.
Those 3 wheeled Can Am spiders would be the machine to covert, I wrote that to the factory years ago,an all  season machine, they haven't done it! It's made by Bombadiar, the very same people who make the track and everything else for skibdoo and other snow mobiles,Wtf ? for $15000 you can be a dweeb on wheels all summer and  King of the hill in the winter on the same machine.
  Interested in making a snow machine yet? 
A few Honda 500's, a few Honda 550's, a few Honda 650's, '72 cb 450, a couple 500/550/650 hybrids, and 2001 750. 
  550 Snowbike -Somebody had to do it.
  http://forums.sohc4.net/index.php/topic,101678.0.html             
http://forums.sohc4.net/index.php/topic,137317.msg1550907.html#msg1550907

Offline Stev-o

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #14 on: October 14, 2012, 10:07:41 AM »
A little ice is prolly why your snowboard day did not go well!
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline FrankenFrankenstuff

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #15 on: October 14, 2012, 10:09:16 AM »
What did I miss? How did this go from compressor to sled? Either way sounds great. I know a guy that rides an old CB450, in his saddlebag he brags about having everything he would ever need to fix the bike in case of breakdown. Aside from the tools and inner tubes he also has a pump hose that mounts into the spark plug hole...start the bike to fill the tire, then just pop your plug back in and away you go.

Offline chewbacca5000

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #16 on: October 14, 2012, 03:40:23 PM »
Thanks FB if I get bored enough and am looking or a new project I may give this a try.  You could probably get useable air on the exhaust stroke too.

To Steve yes it was icy, and I was trying to impress a girl.  I don't think she was too impressed by my repeated falls.  I even get some killer arthritis from time to time.

Offline FrankenFrankenstuff

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Offline Stev-o

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #18 on: October 14, 2012, 06:48:03 PM »
That was awesome, and I like this too!

HOT BIKINI SNOWMOBILE RACES
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline chewbacca5000

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #19 on: October 20, 2012, 10:58:13 AM »
So I did a comparison of my Harbor freight 5 CFM at 90 PSI air compressor to Cylinder Number 4 on my Honda CB750 185 to 190 PSI to see which put out more air and the results surprised me.  My regular air compressor put out a gentle stream of air while Cylinder 4 on my Honda CB750 put would move my hand with the air pressure.


The compression of my CB750 is probably in the high 9s while the air compressor is probably around 8 something.  If I get enough ambition I might get an adapter like FB is talking about and see which fills the 30 gallon tank faster. 

If I get a fill rate of 3 to 4 times on that one cylinder I will take this 1/2 engine 1/2 compressor idea seriously.


Offline 750resurrection

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #20 on: October 20, 2012, 01:53:09 PM »
Hey Chewy , according to your pop sci article in the other thread, they just took off the adjuster screw and locknut on #4 valve tappet.
 I didn't catch how they moved the air but I'd assume the plug hole.

 That way #4 intake is a pumping in the air - plug hole takes the pressure out.  ;D

 My 750 was running on 2 for some time last week... lol - so heck ...

 They got 20 cu ft / min at 400 rpm  :o, said no special needs on the engine, made like 3 more, sold 2, and used it for some time.
 
 I've checked the pistons a few air compressors they are really dinky compared to the 750s.

Offline rb550four

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #21 on: October 20, 2012, 03:19:48 PM »
Why just stop at an air compressor? Extend the swing arm 5 feet or so and use the 750 as the drive engine for a 2 stage compressor and right next to that a generator AC and DC.
  You could run the entire shop on that engine. The lights,  the air, you could do all kinds of innovative stuff, this looks like the makins  for somethin genius. Are ya game?
A few Honda 500's, a few Honda 550's, a few Honda 650's, '72 cb 450, a couple 500/550/650 hybrids, and 2001 750. 
  550 Snowbike -Somebody had to do it.
  http://forums.sohc4.net/index.php/topic,101678.0.html             
http://forums.sohc4.net/index.php/topic,137317.msg1550907.html#msg1550907

Offline phil71

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #22 on: October 20, 2012, 03:22:03 PM »
with a flux capacitor, it could also serve as a platform for a time machine, which will come in handy to go back and talk yourself out of making the compressor, and nitrous injected CB 550 before one or the other explodes and hurts somebody .

Offline dave500

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #23 on: October 20, 2012, 03:32:16 PM »
what ever happened to the old model t fords up on bricks with a drive belt hooked to the hub?

Offline rb550four

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Re: RE: Can I convert a CB750 engine to an Air Compressor?
« Reply #24 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.
A few Honda 500's, a few Honda 550's, a few Honda 650's, '72 cb 450, a couple 500/550/650 hybrids, and 2001 750. 
  550 Snowbike -Somebody had to do it.
  http://forums.sohc4.net/index.php/topic,101678.0.html             
http://forums.sohc4.net/index.php/topic,137317.msg1550907.html#msg1550907