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Onan 705cw 19??


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  #1  
Old 10-17-2017, 12:01:55 PM
woobs420 woobs420 is offline
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Default Onan 705cw 19??

Hello all I helped a buddy pick up a 705cw in good shape with the housing and a bunch of 8/3 SO cord for $450. I have tried some searching here but cant seem to find a good serial# listing. Hopefully someone around here may be able to tell us just how old this thing is? There is a bronze plate on it that is stamped 1972 but I feel that it should be much older.

Specs are as follows
Model 705CW-3R/663L
Serial 102C700516
Gen Data 705CW3C1C

It's main use will be to backup an off-grid solar home and power some shop equipment. It had been sitting for a few years inside and I plan to give it a quick go through are there any problem areas that should be looked at? Not sure if the genny head bearings might need lube or other maintenance. And yes I know oil is a personal thing but so far we are going with mobil1 euro spec 0-40 due to the high zinc.

Anyways any tips or things to go over on this would be greatly appreciated.

Thanks!

Felt like I looked for hours but of course I just found the serial number thread. Looks like Oct. of 1962.
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  #2  
Old 10-17-2017, 05:02:30 PM
MBB MBB is offline
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Default Re: Onan 705cw 19??

Are you sure this model number is correct?
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Old 10-17-2017, 05:16:01 PM
yellowlister yellowlister is offline
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Default Re: Onan 705cw 19??

Made 10 of 62.. model looks ok, may be 7.5 cw but I never payed much attention to how many numbers should be at the end

I would go with 15w40 being it's cold up there.. make sure your mechanical fuel pump diaphragm is not leaking fuel into the engine.. and check the magneto out.. and see if it will fire.. not much to them..

They use ALOT of fuel..

Last edited by yellowlister; 10-17-2017 at 06:09:16 PM.
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Old 10-17-2017, 06:15:27 PM
Scarman Scarman is offline
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Default Re: Onan 705cw 19??

Hi There I donít have much experience with Onan Engines. I happened to pick this one up recently. Itís got a Fairbanks tag on it Can anyone tell me anything about it?
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Old 10-17-2017, 06:40:53 PM
yellowlister yellowlister is offline
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Default Re: Onan 705cw 19??

Quote:
Originally Posted by Scarman View Post
Hi There I donít have much experience with Onan Engines. I happened to pick this one up recently. Itís got a Fairbanks tag on it Can anyone tell me anything about it?

It's all onan.. aside from the mag and carb.. pretty much a cck.. it's twice the cubic inch of a cck. Would be good to pull the heads off and clean up any carbon and clean the valves and seats and see if you can still see the cross hatchings in the cylinder bore
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  #6  
Old 10-17-2017, 06:48:44 PM
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Default Re: Onan 705cw 19??

Yellow I ask because im looking the build sheet up and I find no similar model number. In most cases its because the tag was un-readable and I can almost always find it. Not every time though.
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  #7  
Old 10-17-2017, 07:44:32 PM
woobs420 woobs420 is offline
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Default Re: Onan 705cw 19??

Yup all numbers correct plate is clean that's all of them.

---------- Post added at 07:25:47 PM ---------- Previous post was at 07:17:59 PM ----------

Quote:
Originally Posted by yellowlister View Post
Made 10 of 62.. model looks ok, may be 7.5 cw but I never payed much attention to how many numbers should be at the end

I would go with 15w40 being it's cold up there.. make sure your mechanical fuel pump diaphragm is not leaking fuel into the engine.. and check the magneto out.. and see if it will fire.. not much to them..

They use ALOT of fuel..
Hmmm just how much fuel? Guess ill find out soon. I am assuming the diaphragm is in good shape we did run it for a few mins it purred like a kitten with no fuel smell in the oil. Honestly I have never dealt with a magneto before but I get the general idea. Anything specific to look for on the magneto area other than the obvious like pitted points etc.?

Quote:
Originally Posted by yellowlister View Post
It's all onan.. aside from the mag and carb.. pretty much a cck.. it's twice the cubic inch of a cck. Would be good to pull the heads off and clean up any carbon and clean the valves and seats and see if you can still see the cross hatchings in the cylinder bore
2x the ci of a ccw? Wow what are the hp ratings for the ccw? Even with the high fuel usage (gasoline model here) I gotta say I am in love with this thing all 700 or 800lbs of the beast. I have a cheap china diesel 5000w jobber and I think the gen head of the onan is almost the size of the gen and motor of the diesel combined. Forged crank and rods sounds like an older v-twin in a way. I fully get why some on here talk of "Onanititus". Did I spell that right?

There is also a underhood light. To me it looks aftermarket has anyone else seen this set up from factory?
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Old 10-17-2017, 08:37:09 PM
yellowlister yellowlister is offline
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Default Re: Onan 705cw 19??

The 10 cw is 88 ci.. not sure what the difference is from the 7.5.. probably just generator end output

Yep there big and heavy.. half the rpm of that China job.. and will easily pull 7500 watts all day long...try that with your diesel and see how long it takes to blow up.

My 10cw uses about 2 1/2 gallons at half load am hour lol..

You can put a dap of grease on the rotor that rides the breaker for the points.. just a general inspection is good to.

The light could be factory onan would do special things like that on request...does yours have a factory enclosure?
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Old 10-17-2017, 08:51:47 PM
Vanman Vanman is offline
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Default Re: Onan 705cw 19??

Seems like these are another engine that would do well, regarding fuel consumption, with higher compression.
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Old 10-18-2017, 04:37:54 AM
woobs420 woobs420 is offline
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Default Re: Onan 705cw 19??

Quote:
Originally Posted by yellowlister View Post
The 10 cw is 88 ci.. not sure what the difference is from the 7.5.. probably just generator end output

Yep there big and heavy.. half the rpm of that China job.. and will easily pull 7500 watts all day long...try that with your diesel and see how long it takes to blow up.

My 10cw uses about 2 1/2 gallons at half load am hour lol..

You can put a dap of grease on the rotor that rides the breaker for the points.. just a general inspection is good to.

The light could be factory onan would do special things like that on request...does yours have a factory enclosure?
2 1/2gph holy smokes! Don't even think my Jeep uses that much. Well thankfully it will mostly be a backup battery charger when there is no sun for days.

As to blowing up that diesel you wont believe it but I have over 2500 hours on it mostly running close to capacity charging a very large battery bank. Figured I would be happy with a year or two for the $950 new I paid for it but here we are a good 6 years later and it is still running fine. Only thing I have ever done to it is frequent oil changes with Mobil1 Turbo Diesel oil.

Yes it has an enclosure with a flip top. Even the enclosure is pretty heavy duty. I will post some pics after the weekend when I have her hooked up. The only mech issue I have found so far is that the elec. choke has been bypassed I will eventually need it as it would be nice to have the inverter auto start it as needed.

Thanks for the advice.
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