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Onan DJA decompression pin removal


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  #1  
Old 09-21-2015, 09:22:57 PM
Schick Schick is offline
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Default Onan DJA decompression pin removal

Hello,
I have a DJA with no tag - air cooled. My problem is that the snap ring on the decompression release pin will not stay on. When I got this the snap ring was wired on but it broke. The top of the pin looks worn and I suspect the previous owner had been fighting with this for awhile. I am considering trying to find a pin and replace it but cannot really tell from the parts manual how it attaches. It looks like it might be threaded and screw in. Does that seem right? I also see two different part numbers (110A1351 and 110-1444) in two different manuals (manuals 967-0224 and 967-0311) and this is confusing me a little, as all the other decompression parts appear to use the same numbers in both manuals. Also, I do not have an original snap ring, but rather a 7/16 ring from a generic kit. Is it possible it is some other size snap ring? If you know how the pin is removed that would be wonderful as I certainly do not want to do any damage as this is a fantastic generator!
Thanks,
Rob
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  #2  
Old 09-22-2015, 06:49:58 AM
sdowney717 sdowney717 is offline
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Default Re: Onan DJA decompression pin removal

Post some good pictures of the problem.
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Old 09-27-2015, 12:10:19 AM
Schick Schick is offline
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Default Re: Onan DJA decompression pin removal

Sorry about the delay responding. The generator is 40 Km away so I only get to it every week or two. I found the SN stamped on the block and am hoping that someone can help me to determine exactly what I have. It is; 815162. I got a few pictures of the decompression release pin, as well, and tried to move it today with no luck. I really need to determine how it removes as it appears that the groove for the snap ring is damaged.
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Old 09-27-2015, 08:24:39 AM
sdowney717 sdowney717 is offline
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Default Re: Onan DJA decompression pin removal

By snap ring, you mean a one of these round hardened rings with 2 holes?
external retaining rings also come in metric sizes, so cutting a deeper grove might fit better,
Snap rings also come in different widths. Maybe cut a wider groove for a thicker stronger ring.
If the groove is damaged, how about simply use a fine blade thin file or hacksaw and cut a deeper ring groove into the pin.
Then a new snap ring would likely hold into the groove. You need a flat perpendicular groove or the ring can wedge up and pop off. so cut carefully.

The pin is either pressed into the head, or screwed in with threads. Rocker studs on GM engines like my Roadmaster 350 uses pressed in studs into the heads and they hold the valve rockers.
My guess is it is pressed in.

Other idea is drill a hole a little further down this stud and reassemble the valve relief then insert a roll pin. if their is room for the mechanism to function.

Other idea is drill a center hole and tap for a bolt, then use a grade 8 bolt and washer to hold on the relief mechanism.

Last edited by sdowney717; 09-27-2015 at 09:07:18 AM.
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Old 09-27-2015, 08:59:13 AM
Kevin K Kevin K is online now
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Default Re: Onan DJA decompression pin removal

I had the same problem with my DJA when I got it home. The snap ring popped off and the engine would not stop. I put the snap ring back on and again it popped off. I replaced it with a new ring, which had considerably more tension than the old ring, and it's been fine ever since. The groove on my decompression pin was OK.

Originally, I thought this is a pretty poor design. There is quite a bit of upward force on the decompression arm when it moves into position to hold the valve open. The instructions for adjusting the decompression set screw read: "If the screw is tightened more than one turn, the exhaust valve could hit the piston". It's possible the snap ring is designed to pop off if the screw is set too tight, preventing damage to the valve or piston.

You might want to check the decompression set screw adjustment to make sure it is adjusted correctly.
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Old 09-27-2015, 09:02:55 AM
sdowney717 sdowney717 is offline
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Default Re: Onan DJA decompression pin removal

Yes, hard to tell from the picture if the groove is damaged.
Maybe his snap ring is not the right size.
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Old 09-29-2015, 12:25:34 PM
Schick Schick is offline
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Default Re: Onan DJA decompression pin removal

Thanks, I set the valves and adjusted the set screw to specs as per the manual, this last time so I think I will try to find some better sized retainer rings and try that, then if still a problem, maybe try a roll pin or cotter pin.
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