Onan without a birth certificate

[Chat6155 3]

Hello all.   Hoping for some knowledge from Onan folks.

 

 

I'm attempting to 'backwards build' a model number for a recently picked up, well used [read: semi-trashed] Onan generator as a possible winter project.   As these things go, the righthand cooling tin that was appearently home to any and all I.D. is gone.   It's a cast iron horizontal twin, 3.250 bore x 3.00 stroke.   Equipped with a Marvel-Schebler carb.   Each cylinder has one 5/16" [3/8"?] stud that attaches both the intake manifold and muffler mounting flanges.   The air filter is a rectangular box mounted behind the righthand cylinder.   The only number I've found is 560553 stamped into the block behind the left cylinder.   I believe it's in the CCK family of engines.

 

 

Turning it over by hand indicated that it has good compression and no abnormal noises coming from deep down inside.   I'd like to be able to order parts for it and hopefully get the engine running again [the gen is trashed beyond any hope of repair], but without any i.d., parts guys don't seem too interested.

 

 

Any help would be appreciated.  Thanks.

[Martin 2,130]

pics would help on this as well.

ive had a few different onans and the guys over at smok stak forums were a great help for id and manuals etc.....  join up and ask in the generator section. they would probably appreciate pics as well.

 

http://www.smokstak.com

 

are you going to use it for a generator again or something else? the reason i ask is most onan generator motors have weird crank ends and make them very hard to use for other jobs.....

and they can make you poor buying parts for them........

[Chat6155 3]

Would like to use the engine on another project as the gen is trashed.   I'm sure when I seperate it, the crank will have the short tapered shaft.   Not a problem there, found a place online that sells pulleys with tapered bore.   Here are some pics as I began to disassemble it down to basically a long block [pulled the right cyl head just to measure bore & stroke]...

[Chat6155 3]

Martin,

 

Thanks for the link to smokstak.   Looking through their manuals, I did determine it's either a CCK or CCKA [carb] and would be at least a Spec J [ball joints on gov linkage].   Just need to fill in some more of the blanks.   Hopefully, others here and smokstak will be able to come up with something.

[Chat6155 3]

After a bit more researching, and talking with those at Smokstak, I've been sucessful in 'backwards building' the model and serial number for my genset.   Thanks again, Martin.   Suprizingly, they said it was built around Feb, 1957.

 

Anyway, went out today and muscled off the generator.   Then decided to further the Jenny Craig weight reduction game by removing the flywheel.   Removed 4 bolts in the center and, much to my suprize, the 'flywheel' was simply a thin aluminum housing with cooling fins.   This hid what appears to be either another generator or the 12vdc starter.   As the pictures show, it has one large guage [battery cable / solenoid type] cable and 3 smaller guage cables coming out of it.   I've never seen anything like this in looking through the Onan manuals and was wondering / hoping some here could shead some light?   If it's what I think, I'm assuming the larger cable is the Bat + to feed the starter and the 3 smaller wires are from the intrigal alternator used to charge the battery?

 

Also, in the last picture, there are slots in the mounting legs for the brush holder.   Is there a reason?   Alignment?   If so, any advise as to 'how to'?

 

Thanks again.

[shorts 182]

It looks like you have removed the control part of the generator but the alternator/generator are still attached the fan/flywheel in the picture is for cooling the generator, the coils in the can are the field coils and the armature is still attached to the crankshaft, remove the brush assembly from the back of the gen. then remove the nut on the end of the armature and remove it then unbolt the fields from the back of the engine.

[Chat6155 3]

Shorts,

 

If your speaking of the 120/240vac gen, I removed that heavy s.o.b. from the opposite side of the engine.   It indeed reveal the short stubed tapered crank end.   These pictures are from the flywheel side [the cam gear cover is behind the rotor/stator in the pics, and the standard setup govenor linkage just bearly visible at the top of the pics].   The only things I removed from this side was the standard shaped Onan blower housing and the round 'drum' with the cooling fins [and balance holes around the inside of the circumference, as pictured].   There was no 'control part' on this side.   The four wires [one large guage and 3 smaller guages] shown were attached to individual insulated studs mounted on the top right of the blower housing.

 

Actually, I'm biting at the bit somewhat to put a healthy battery to it to see if it does spin the engine over, but don't want to burn/cook/destroy it in the process.

[WH nut 553]

Im thinking that might be your starter generator

[Chat6155 3]

WH,

 

Yes, I'm sure now also.   Decided to throw caution to the wind, based on Onan's 'basic, no frills' design theory, and decided there was no other reason for the heavy guage cable except to hook to a starter solenoid.   So, fired up the 312H, and while she was sitting at a fast idle, put the jumper cables in use.   It indeed cranked over.   It didn't crank fast to try to start it [if secondary ignition and carb were in place], but fast enough to remind me that I hadn't plugged the hole for the oil pressure guage!   Was worth the minimal cleanup to know that at least if I get it further along to being a stand-alone, I have a way to start it.   The owners manual for the complete genset states "...battery size is SAE group 1H [2 in series] @ 105 amp-hour...".   I can now see why, while it was cranking, when I placed my thumb over one of the spark plug holes, she momentarly stopped.

 

Now, need to find a base / oil sump that has the 4 mounting feet!

 

Are you still active Air Force?

[WH nut 553]

^{No Chat, I retired guard last January, been almost a year now. I had 32 years in}

[Chat6155 3]

I retired in 99 after 24 years.

[WH nut 553]

I retired in 99 after 24 years.

Well thank you, what did you do? I was a 2T3 for 27 years them cross trained to 2T2 for the last 5 or 6

 

 

[Chat6155 3]

Thank you, also.   Jet engine tech.   426 [i think...they changed the afsc's, ummmm, mid-late 80's, early 90's [?].   I knew where I was and what I had to do, so I stored the numeric classification infomation in the lost brain cells of the 60's.   B52D's, KC135A's [Viet Nam returns] & A10's.