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Thread: Cat 12 8T grader starter for pony griniding

  1. #1
    Join Date
    Mar 2020
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    Mancos, CO
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    Default 1955 Cat 12 8T grader, rebuilding to use!!

    Greetings, I've been surfing the forum here at ACMOC for a while as I contemplate the purchase of an Cat 12 motor grader. It is 1955 vintage, made a couple hundred units before they changed to a wet clutch.

    Yesterday a friend and I went over and got it running, as it had been sitting for the better part of a decade according to the seller. Both the pony and the main engine run fine and sound pretty good. One issue we noticed was that occasionally the electric start on the pony would just grind, rather than spinning the belt and pony engine over. It was trying to turn the belt a bit as it was grinding...

    I've searched, but all I get are threads looking to replace the pony with electric start, or saying that the lever engaged pinion is grinding. Neither of those are what I want...

    I didn't see a "bendix" on the starter, only a ford-type starter solenoid. Is there a one way clutch in there, or some sort of centrifugal engagement that's likely just gummed up? It did not sound good when it wasn't catching... Just looking for some quick feedback on this issue before I buy this grader and find out it's something major.

    Once we seal the deal, I'll immediately pick up the operators manual and service manual for it, and that will probably answer my question, but buying manuals for a grader I don't yet own seems a bit foolish.

    Thanks for feedback!!
    Looking forward to getting this old girl out and grading again soon!
    New member Chris
    Last edited by 1stDeuce; 05-03-2020 at 02:38 PM.

  2. #2
    Join Date
    Nov 2007
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    NW Ohio
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    You have to loosen a 5/8" lock bolt on top of the starter holding housing then slide the starter out, most likely the bendix is dry, don't grind it too much or you'll be trying to find another drive gear if it isn't to late already.

  3. #3
    Join Date
    Nov 2006
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    Faunsdale, AL USA
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    Itís an old fashioned bendix design with a spring torsional shock absorber built in. If the spring was broken I donít think you would even get a grinding sound.

    I expect taking the starter out of the mount and or just unbolting the belt pulley/driven gear assembly will expose the problem in the gear teeth not meshing up.

    Should be some dead starters around with those parts if yours donít respond to a clean up.

    The starter can be hard to get out of its mount even after removing the lock bolt. Easy does it, lots of penetrating oil soaking, heating the mounting ring to expand it, tapping on the starter nose etc. Itís possible to break the mount.
    D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time

  4. #4
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    Mar 2020
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    Mancos, CO
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    Thanks fellas!! I did see the jam nut that holds the starter in, and this particular one is actually a tiny bit loose, as I could see the starter motor wiggle a bit when my friend hit the button. I'll yank it out and clean up the works and poke it back in. It's possible it's just slipped out some I suppose... Is it supposed to go all the way in, then tighten the set screw? I'll let y'all know what I see...

  5. #5
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    Nov 2007
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    NW Ohio
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    Yes all the way in, there is a small hole in the starter housing where the set screw/bolt fits into.

  6. #6
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    Jul 2016
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    Lancaster CA
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    If the helix twist on the shaft is dry or sticky the bendix drive will not go in and engage the driven gear before the starter is spinning full speed. This is what causes the grind noise. Dress up the drive gear and lube the helix. The torque of the initial turn of the starter is supposed to put the drive into the driven gear instantly.
    Cat 12 grader, 8T6995 running and restoring, Cat 12 grader 9K3585. parts machine, Adams leaning wheel Pull grader Mod # 22, ser#438

  7. #7
    Join Date
    Mar 2020
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    Mancos, CO
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    Quote Originally Posted by oldbeek View Post
    If the helix twist on the shaft is dry or sticky the bendix drive will not go in and engage the driven gear before the starter is spinning full speed. This is what causes the grind noise. Dress up the drive gear and lube the helix. The torque of the initial turn of the starter is supposed to put the drive into the driven gear instantly.
    Thanks Oldbeek!!

    We got it moved to the ranch yesterday. The starter ground again a few times, but the pony now fires right off when I mess with the choke. Seems to run best with the choke lever just a little out. All the way in seems to run worse. I am assuming all the way in is choke off, but don't have my OM yet...)

    I'll pull the starter out and get it working better before we try to start it again.

    I did notice this time that as the pony rolls over there's a definite "clunk" that seems to be once per crankshaft rev. I saw that the flywheel can come loose and make a clunk, but it seems like that should be twice per rev.... Hopefully its not a rod bearing... It does run well once it's running, with no audible knocking over the tiny-mufflered exhaust "roar".

    I drove it about 3 miles to the property where it'll get worked on for the next few months and found out that it also jumps out of gear when you go downhill. Luckily I was able to mash the throttle and stick it right back in gear, then drive the next half a mile holding the gear shift forward. With a marginal parking brake and no main brakes, I did not want to have to drop the land anchor on a freshly graded road... The main trans shift lever is REALLY loose. If you know where the gears are, you can shift, but there's no discernible H pattern left...

    "To do" list is pretty long...
    Put a battery in it
    Fix the starter
    Change both engine oils
    Add brake fluid, bleed the brakes, see how fast the fluid runs out the wheel cyls
    Swap around some control links/caps between the blade lift and scarifier lift -- No shims left in blade lift rods and lots of slop but lots of shims and little slop in the scarifier lift rods...
    Make a new seat cushion so it stops poking me in me soft bits
    Figure out what bushes can be replaced to reduce the current 1 full turn of steering slop
    Put a dang muffler on it!!
    Check clutch adjustment
    Hook up a fuel shutoff valve of some kind for the pony. (cab mounted valve has been bypassed with a loop of rubber hose)
    And finally: Go grade and see what else comes up!

    We'll probably buy it two new tires a year, and get it back on 13.00-24's in a couple of years. It's currently on ancient 14.00's, and I don't see the need for bigger tires on a nice little grader.

  8. #8
    Join Date
    Nov 2006
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    Pittsford NY
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    Choke out to run problem is easily solved. Take the carb off, drill out the lead puck in the passage that runs along the bottom of the fuel bowl, then using your fingers, run a twist drill in there to clean the gunk out. If you decide to take the bowl off the throttle body (no need to), loosen the bolts and carefully pry the bowl back along the bolts. Once it's loose, then take the bolts out and slide the bowl off in the same direction avoiding damaging the tube jet.
    You'll need a gasket for the carb base and that's about it. Don't know about the grader but control is in choke off on the D2, and control out for closed throttle.
    Last edited by Neil; 04-17-2020 at 07:24 AM.
    Cheers,
    Neil.

  9. #9
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    Quote Originally Posted by Neil View Post
    Choke out to run problem is easily solved. Take the carb off, drill out the lead puck in the passage that runs along the bottom of the fuel bowl, then using your fingers, run a twist drill in there to clean the gunk out. If you decide to take the bowl off the throttle body (no need to), loosen the bolts and carefully pry the bowl back along the bolts. Once it's loose, then take the bolts out and slide the bowl off in the same direction avoiding damaging the tube jet.
    You'll need a gasket for the carb base and that's about it. Don't know about the grader but control is is choke off on the D2, and control out for closed throttle.

    After you clean the idle passage in the bottom of the carb a .177 air rifle pellet works perfect to tap in to seal it again. Some get fancy and tap it to a small screw for future cleaning.
    1937 Cat #11 tandem auto patrol,diesel, w/plow and wing, 6K506SP, 1937 RD 4 Ag Crawler RD5356, 1939 Cat 22 2F5429, 1952 Model 212 Grader 9T03427, 1953 2U D8 Dozer 2U20751, 1961 922A Rubber Tired Loader, 59A812, LeTouneau LS Cable Scraper, Cat/Lincoln 600 AMP Dual Welder, DW-21 Cat Scraper, DW-10 dump wagon/water wagon

  10. #10
    Join Date
    Aug 2019
    Location
    Washington
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    165

    Default

    Sometimes a grinding starter is a result of a low battery.
    Cat D6 5R

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