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Discussion Starter #1
I’m assessing a damaged engine given me for my first rebuild. It was supposed to have been running but smoking when replaced but I had no idea I’d encounter a shattered rod. I know parts are going to be hard to come by, so it may not be worth the trouble even if it is rebuildable.

Right now, I can’t seem to get the valves out. Looked at videos I could find and service manuals but I’m missing something. I’m usuing a B&S valve compressor I bought but I’m thinking it’s not the right tool for the job. I can compress the spring, but there don’t seem to be keepers that just slide out. It is probably a big duh for you guys but do I compress the keeper and spring or just spring? Do I have to buy this special tool or is there a home shop hack?
 

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There is a "disc" (prts 30 and 47 in the drawing) into which the keepers (prts 28) slide. This disc needs to be compressed along with the spring to release the keepers. The keepers are wedge shaped and fit into grooves on the valve stem and a tapered recess in the disc.

Drawing here so we're talking about the same parts; Onan T260G-GA024/3851A lawn & garden engine parts | Sears PartsDirect

This is the type of spring compressor I use.. Lisle 23300 Small Engine Valve Spring Compressor, Automotive - Amazon Canada

Be careful taking it apart, would suggest bagging and labeling any small parts as well as taking pictures. If it ate a rod, there will likely be aluminum on the rod journal..do NOT try to remove it by scraping. An over night soak in a lye/water bath will eat the aluminum off, then polish lightly with crocus cloth or similar before taking measurements.

Measure everything up before making a call on whether to rebuild or not. Boomer @ Boomers used Onan engine parts may have the parts you need...I'd even go so far as to say it's likely. He is also a literal fountain of knowledge on Onans.


Good luck with it. :)

Al
 

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Discussion Starter #3
There is a "disc" (prts 30 and 47 in the drawing) into which the keepers (prts 28) slide. This disc needs to be compressed along with the spring to release the keepers. The keepers are wedge shaped and fit into grooves on the valve stem and a tapered recess in the disc.

Drawing here so we're talking about the same parts; Onan T260G-GA024/3851A lawn & garden engine parts | Sears PartsDirect

This is the type of spring compressor I use.. Lisle 23300 Small Engine Valve Spring Compressor, Automotive - Amazon Canada

Be careful taking it apart, would suggest bagging and labeling any small parts as well as taking pictures. If it ate a rod, there will likely be aluminum on the rod journal..do NOT try to remove it by scraping. An over night soak in a lye/water bath will eat the aluminum off, then polish lightly with crocus cloth or similar before taking measurements.

Measure everything up before making a call on whether to rebuild or not. Boomer @ Boomers used Onan engine parts may have the parts you need...I'd even go so far as to say it's likely. He is also a literal fountain of knowledge on Onans.


Good luck with it. :)

Al
 

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Thank you for the detailed description. The diagram was a bit fuzzy, and another one I have is clearer but still lacks identifying detail. I ordered the part you recommended. Thanks for Boomer’s link too and advice about cleaning the insides of particles. The mess inside included a fine, gritty dust. Some of it picked up with a magnet and the rest must be aluminum. The lye bath... I have some granulated lye or Purple Power degreaserI think is caustic. I don’t want to damage the block, which looks is aluminum. I suppose your saying it will eat fine particles but not anything else? I’ll take some pics of the keepers. Thank you thank you!
 

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Discussion Starter #5
Just another clarifying question... the disc you refer too looks like one small cup set within another. There is a recessed groove at the stem with what looks like a ring clip (for lack of better). Do both disc in disc get compressed with the spring?
 

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To clarify...you have to remove the crank from the block to put it in a lye bath...the crank and only the crank can by cleaned with the lye bath...the lye will eat anything made from aluminum.

Once the aluminum has been eaten off the rod journal by the lye, rinse the crank very well with clean water, then dry and spray it down with WD40 to prevent corrosion.

Wash the block out with solvent, dry and inspect for damage

It's the larger, outer disc that needs to be compressed with the spring.

Al
 

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Discussion Starter #8
Well, got my Lisle tool in... couldn’t wait to try it out. Got first valve out lickety split! Second a bit harder and broke the tang off the fork. Dang just bought it. Swapped over to the smaller fork got third valve out. Fourth wouldn’t work with smaller tang, swapped to the other fork and... well... duct tape holding position got it out too. Next up crank gear!
 

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You need a special tool to pull the crank gear, take the time to obtain it before trying to pull the gear.

It's REALLY on there, and can be stubborn. Trying to "cheat" by not getting the correct tool can result in a broken crank case and/or a destroyed gear that will either render the entire project a "no go", or raise the total cost of the project.

A quick google for Onan crank gear puller will turn up some images of tools that work.

Al
 

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I encourage you to have a closer look at some of the tools folks have used, and read through a few of the threads that the google search turns up. Some things work...some things don't.

There's also a thread here on rebuilding an Onan that's worth reading through, and a series of videos on youtube worth watching.


Prt 1...all are worth a watch;


Al
 

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Discussion Starter #13
I encourage you to have a closer look at some of the tools folks have used, and read through a few of the threads that the google search turns up. Some things work...some things don't.

There's also a thread here on rebuilding an Onan that's worth reading through, and a series of videos on youtube worth watching.


Prt 1...all are worth a watch;


Al
Great video series, very helpful.
 

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Discussion Starter #14
Have to learn to bookmark when I find something useful... what about this setup? I couldn’t copy the pic and/or quote like I wanted.

 

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That should work fine.

Suggest you use socket head cap screws going into the gear (black with internal hex drive, sometimes called "Allan head screws"). Stay away from stainless versions as they have lower tensile strength...black oxide finished are the ones you want. Brighton Best, Un-Brako, and Holo-crome are quality fasteners, don't use the leftovers from Ikea. ;)

If you cannot find those, use at least grade 8...normal zinc plated (grade 2) hardware store screws will strip out or break and cause more grief.

Don't know how much of this sort of thing you've done, but thread the flywheel bolt back into the crank shaft...just bottom it out finger tight...this will protect the end of the crank from being damaged by the puller.

Al
 

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Discussion Starter #16
This is the first time I’ve gotten into an engine like this. I tore down a Ford 350 M once, but ended up abandoning the project. I wanted to do this a long time and I very much hope I can complete it. I put the flywheel bolt and washer in and noticed the dimple in the bolt head. Smart engineering, looking ahead like that. Thanks for the tips, I need them. Took a bunch of my time fabbing up a plate. I didn’t have any flat stock so I cut some 3 1/2 inch angle. Drilled a hole as big as I could then used small bits on outer edge to make it big enough to go over the shaft and cover the gear. Dremmeled it round as I could. Crude but should work. Should have cut the hole with my new plasma cutter.
 

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You can do this, just don't work ahead of the point where you've thought it through. Slow and methodical wins... and gets you a running engine. :)

Might be a little late, but I'll mention it anyways...as much as is possible, stick with the dis assembly procedures laid out in the link/video...mark parts so that they can be put back together in their original places...pictures are good too. If possible, keep each valve with it's original spring, retainer, keepers and rotator cups...and marked as to which cylinder they came from.

Have you pulled the remaining rod yet? Same goes for connecting rods and their caps...leave the piston on the surviving rod for now, but mark rod and cap so they cannot be accidently mixed up or turned around. When pulling the piston, remember to put something on the rod bolts to prevent gouging the rod journal.

If you've removed the rear bearing plate, slip it back on and bolt it finger tight...to support the crank properly until you've the gear removed and are ready to pull the crank.

Post up some pics of where you're at with it...people like pics. ;)

Al
 

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Discussion Starter #18
Always good advice from you Al!

Here’s some pictures. Maybe along with those posted by others and the mentoring folks like you give, it’ll help somebody. Not showcase work here, but functional.

Started with 1/4 in x 3 1/2 in angle. Used metal disc on grinder to cut it, then used step bits to cut as big a hole as I could. Used the large shaft washer and marked with sharpie for hole size. Then small drill holes cut out between using rotary tool to get to final size of shaft. Rounded out by coarse rotary sanding.

Installed the flywheel bolt and washer finger tight as you said. Used 3-jaw puller gripped under attached plate. Hammer used to tap a slipping jaw back under the plate.

It worked, I’m relieved to say! First time ever using the 3 jaw pullers I’ve had for years.
 

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Good stuff!:cool:

Should be at the point where you can remove the remaining rod/piston assembly if it's not already out and then take the crank out. Post a pic of your crank showing the rod journal...

You'll be doing some cleaning of parts for a while. Use a spray of wd40 or something similar on bores and steel parts afterward to stave off corrosion. Are you able to measure bores and journals? About the minimum is telescoping bore gauges and micrometers. Vernier calipers are often referred to as "very nears"...and do not have the accuracy you need here.

Might be able to borrow those if you're lucky enough to know someone that has them.

Also time to find service information on this engine...need to know what the wear limits are, as well as allowable taper for the bores and out of round limits.

I was able to find this, but it does not give wear limits, only min and max. But there is other useful information there...


Al
 

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Discussion Starter #20
The gear came out with this set up. I used 1/4 inch steel plate bolted to the gear using 10-32 x 1/2 in. black oxide Allen head screws recommended. Even so the pull still bent the plate. I thought of using an impact tool but opted out so I could watch the progress better.
 

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