AMC Eagle Den Forum
The Mighty 258 => Engine Electrical Systems. => Topic started by: Canoe on July 02, 2020, 05:46:50 PM
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My starter is not playing nice with the new flex plate. I had to replace the flex plate after what I thought was kickback from a loose distributor ripping some teeth off of the flex plate. https://forums.amceaglesden.com/index.php?topic=42076.msg326956#msg326956
The new flexplate was set against the old and confirmed to be the same tooth count, size, etc..
The engine and bell housing were aligned with the pins and closed together, before securing with the bell housing bolts. (Bolts went in without too much fuss, except the 12 o'clock, which I could get started while holding it in the tips of my fingers, and then it took a number of socket extensions, including wobble extensions, and twelve hours of the socket slipping off and resetting, to secure and torque that one bolt...)
The starter is making a horrible noise but turning the engine over. Sometimes it would sound like the starter motor was binding and it would pause, then continue turning over and the engine starts. The starter appears to have lots of turn-over power.
- I did a lot of searching and there's talk about Ford vs. AMC bendix having different tooth counts, or extention, but nothing seems to be definitive.
- The bolts appear to be original Grade 5, but are not shoulder bolts, which some say are necessary to prevent any play.
- To ensure correct mating, I removed the starter. The flexplate teeth on the starter side are very sharp; but not on the other side of the teeth. The tips of the teeth appear and feel fine.
- I thoroughly cleaned the plate the starter installs against (grease and some bits of paint in places) and ensured the bolts were properly torqued when re-installed.
- This has eliminated the binding, but not the horrible noise as the starter turns the flexplate.
I'm going to get shoulder bolts to see if this helps.
I also found the following on shims to limit the engagement. This is different from shimming the GM style starters were you can shim for the distance of the flexplate centre to the bendix drive centre.
Ford/AMC Motorcraft Starters
Subtle changes to these starters over the years do not affect interchangeability
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In the case of AMC and Jeep, all Motorcraft original starters will have a two-bolt nose. They could have either a two-rib or a five-rib casting; however, you will discover that all replacement starters will be two-bolt, five-ribbed nose units. All of these AMC starters will interchange if you are using the two-bolt, five-rib nose with a 4½-inch case:
Any time you are substituting starters, you need to pay special attention to the flywheel or flexplate clearance. Spacing can be corrected with the use of one or more shims. The Ford part number for the two-hole shim is D7TZ-11N004. These are also available through your local auto parts store; the NAPA part number is 655-1188. These shims are about .10 inches thick. ...
The starter weights a fair amount and its torqued tight when installed. Can I make my own gasket out of the usual fibre material or layers of same, or should this gasket be metal?
Does anyone have any info or insight into this starter issue?
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Sounds like the bendix drive is going in too far causing the grind. The shim may work. Maybe the flex plate was installed backwards..?
The Ford starter differs in the nose length. (Maybe bendix tooth count, too.) Pretty sure the Ford starter will jam on an AMC because of the difference, Ford being longer.
Hopefully someone more knowledgeable will chime in...
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Sounds like the bendix drive is going in too far causing the grind. The shim may work. Maybe the flex plate was installed backwards..? ...
My gut reaction is that the Bendix is going too far, but I don't know. I can't see a way to measure clearance or alignment with the starter installed.
I may have installed the flexplate backwards, but there was something about it that made me think that would be hard to do. But that was a few years ago so it's kinda fuzzy.
Eaglepedia shows it the way I remember.
Easy enough to check by pulling the starter.
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There is some kind of dye or paint that's used to see how well differential gears mesh for shimming purposes, (if I remember correctly). I wonder if it would help see how the bendix gear meshes with the flex plate?
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Cheap water-based craft paint will work painted on the Bendix teeth, but I don't trust that I could interpret it correctly. It may also work on the shaft to see how far the Bendix extends, but I've not seen that use. That step may be necessary.
With the clean mating surfaces, I'm certain that the mounting is square to the flexplate, but I could be surprised and they're not.
Using shoulder bolts is easy.
Making a metal shim is easy enough. Quickly tell if there's an improvement.
I think I just realized that I've got the mating surface as reference, so I should be able to use my calipers to compare the Bendix travel to the distance to the flexplate gears. If that checks out o.k., then the paint would tell the alignment story. I think.
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Took the starter off.
After being used for a few days mounted well torqued against the cleaned flush/smooth plate, the noise is somewhat quieter and the flexplate teeth are not near as sharp as they were before that.
The flexplate is mounted flipped the correct direction.
From the smoothing wear on the Bendix teeth, it looks like it has plenty of engagement, and doesn't bottom out.
From the mounting plate to the teeth is 21.6 mm.
Moving the Bendix by hand, it seems that it extends too far and has intermittent contact with the nose housing.
I got two standard Grade 5 bolt with some un-threaded shank. That makes it a little bit quieter too.
With those bolts in the removed starter, there's still a lot of play. With some wear in the mounting plate, I can see how the weight of the starter taking it a little lower would put the Bendix closer to the centre of the flexplate. The extra width in the mounting holes lets the plate provide the registration. If that plate has wear, I can see how shoulder bolts would provide a more original registration IF the holes are accurate.
Even though the wear marks on the Bendix were in a good position, as a test, I put 1 mm washers in place, with three more along the outside edge. It was noticeably quieter, but still makes more noise than it should.
I'll have to do a full starter bench test to see what the Bendix extension and housing clearance is when powered.
I think I'll have to try either shoulder bolts or something to lift the starter so the wiggle room in the bolt holes let it be farthest from the flexplate centre.
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Thought. It should only take one Shoulder Bolt - in the lower position - to provide the lift/registration correction if that opening has enlarged and is not providing correction registration anymore. One way to find out.
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No luck finding a shoulder bolt that fits. Not even close. The standard 3/8" thread is for a 1/2" shoulder, with a too long shoulder and too short threads. No point in getting the 1/2" turned down to fit the starter's flange hole.
For the lower bolt, the depth of the flange on this starter is 3/8".
Somewhat wider than the 3/8" bolt (bolt at 9.2 mm wide), the width of the hole is 10.7 mm (slightly under 3/8").
I'm considering wraping the bolt with some wire to form a "shoulder", with a coating of JB-Weld High-Temperature putty to help hold it in place. That or make a sleeve, but I haven't the proper tools for that.
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Frig!
Going with replacing the bolt with a stud.
Will trim down a T-bolt or threaded-insert to match the starter's bolt hole size.
That should match a shoulder bolt function well enough for this use.
No lucking getting a bolt long enough that's threaded the whole length.
Will make a stud from a carriage-bolt that I'll have to grind the sides of the head off of.
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definitely keep updating your results. long story here but when I last drove my eagle it was eating starters. throw in a move buying a foreclosed house. than trying to make it a happy home. well I had no time to see my issue. it just sits in my garage. soon I hope to dig into it, meaning someday.
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Starter continues to be quieter than usual with the 1 mm washers. I note there is some pitting on the bearing surface of the starter flange that was blasted clean sometime during the refurb/reman process, so perhaps the starter is sitting closer than it should, but where the wear marks are on the Bendix teeth (seems fine) suggest that's not it.
- For a stud to replace the lower bolt (this should make it easier to install the starter anyway), I got a 3/8" stainless carriage bolt and ground the "overhang" of the head off so it leaves the square portion of the head.
- I plan to install this from the back side where the bolt threads would stick out if the bolt was long. Leaving this square head will allow me to easily back this "stud" out if I ever need to.
- Grinding: with the bolt held in a vice face with hard-rubber inserts to not damage the threads, and with the bolt aimed down and out from the jaw ends at a 45 degree angle, I'd grind a little, then lift a container of water up to submerge the bolt, so the heat couldn't build up and damage the bolt's strength. - On first install of this stud I plan:
- To not set the remaining square-cb-head tight to the housing, but leave it a thread or two shy. This will let the threads take the load as it would if a bolt was used, as it does when stock.
- I'll put a drop of semi-permanent thread-locker on the last three threads that will go into the housing, finishing turning it in to where I want it, then torque the nut over lock-washer to hold the starter torqued to spec while the thread-locker sets. - To allow this stud to mimic a shoulder-bolt so it provides some of the position registration for the starter (instead of a worn plate opening allowing the install location to sag the wiggle room of the bolt-to-flange-hole), I'm making an internally threaded-cylinder to thread onto the stud.
- I used a cheap 3/8" bolt to hold a 3/8" T-nut so I could grind the T-nut flange off.
- I was aiming for a 3/8" cylinder height left, but got sloppy when I started squaring it off and ended up with an uneven height after I cleaned it up, varying between 4.5/16" and 5/16". It will fit within the flange of my starter and should be good enough for a test of concept. - I started thinning the internally threaded cylinder that was left of the T-bolt from the prior step.
- I first used a flat file to get the cylinder's outside parallel to the bolt, and then an even thickness from the bolt.
- Then I put the bolt in a drill and used a large flat file to start thinning the resulting cylinder down to the target outer thickness. Not exactly a milling machine, but it's what I've got. I expected this to be faster than doing it by hand, but the even roundness also improved significantly.
(That process was set aside after some fries in a stove-top pan got majorly burnt at my Dad's and distributed some light to medium density smoke throughout the first floor. No heat/flame damage. Box fan in a window cleared out the smoke out, and after an hour nearly all of the smell, with a HEPA air filter unit left sitting in front of the cold-air return for any fine particles left floating around. Tomorrow we'll test to see if any grease on the walls, to see if we have to address that.)
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Aaaand, I realized that with the lower bolt as a stud with sleeve for a tight fit to the starter flange, dropping the weight of the starter when installing could lead to finding out which was weaker: the stud, the starter flange or the housing. I really don't want to find out.
So the upper will be that "stud" I made (with no sleeve), for ease in getting the starter in place and securing it only finger tight so it can move within that stud to flange hole play. Then a bolt with the "shoulder" sleeve can be secured in the lower bolt position, providing the registration. Rotate the starter within the upper play so the starter is furthest from the flexplate. Tighten and torque.
That's the theory.
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I went back to see what I wrote
I thoroughly cleaned the plate the starter installs against (grease and some bits of paint in places) and ensured the bolts were properly torqued when re-installed.
and I didn't mention the raised metal along the lower edge of the hole the starter mounts into, that I filed off level to the plate as part of cleaning the plate. I'm now thinking that at some time the bolts were not tightened adequately and a starter sagged down hammering the plate locator opening over time.
I've marked a housing plate photo I found on the www with the location where the raised edge was.
So, shoulder bolts or equivilent functionality should locate the starter to its correct location. I'd expect pushing the starter upwards in the plate hole and managing to secure the bolts with the starter in that position would work, but I have no guarantee the upper part of the hole wasn't also affected by a sagging starter.
Current plan is to go with upper hole with a stud and threaded-sleeve to act as a shoulder bolt, and let the starter pivot off that down & outwards within the lower bolt play to get the lower bolt in place.
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I had an experiance like this on a Ford Van. I found the plate to be the culprit the hole in the plate is supposed to align the starter. At some time the starter had came loose and caused the plate hole to enlarge just enough that even after tightening the bolts the starter never set right again. Ended up replacing the plate and problem solved
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... the culprit the hole in the plate is supposed to align the starter. ...
This is exactly what the issue is supposed to be.
There's the seemingly mythological "stock" shoulder bolts for mounting the starter, but the parts catalogue and all of the stock setups people have found use fully threaded bolts. I couldn't find a shoulder bolt that would fit.
Stud for upper: no go. I forgot the bolt starts from opposite sides for mounting the starter.
Stud for lower: carriage bolt with the found head ground off but leaving the square portion is a no go - square portion won't clear the bell housing when put in from the housing side. Had to grind the corners off the square head to take it back to the thread thickness.
Success!!!
Just a tiny bit of the former noise. Doesn't sound like anything is getting trashed. Starts sooner/faster. People no longer look when I start it.
Lower bolt replaced by stud, with threaded-sleeve to function like a shoulder bolt:
- carriage bolt, head ground down until it's as narrow as the threads, then cut a slot for a screwdriver in what is left of the head
- screw into the bell housing lower bolt hole from the housing side, with a drop of reversible thread-locker on the last few threads
- 3/8" fender washer 1.5 mm thick as a shim goes on the stud
- DIY threaded-sleeve:
- the hole in my starter flange for the lower bolt is ~1.7 mm wide, 3/8"+ deep
- 3/8" T-bolt, flange ground off, height left is 9/32 to 5/16 (sloppy grinding, but it's less than the depth)
- narrowed the resulting threaded-sleeve down to 1.5 mm (using a drill with bolt & sleeve and a flat file) - the "good" end (unground) of the threaded-sleeve goes on the stud first, threaded down so it secures the shim/washer finger tight
Starter Install:
- Starter easily fits in place, with the lower bolt hole over and on the stud & threaded-sleeve with the starter flange up against the shim/washer
- support the starter and get the lock washer and nut on the lower stud finger tight, then ensuring the starter flange is against the plate/shim/washer, tighten until the lock washer is slightly compressed
- starter can move slightly with the play between the stud, sleeve and flange hole
- if the locator/plate hole is worn oversized, the starter can pivot on the lower stud within that hole - place the upper bolt through its hole, placing the 1.5 mm thick fender washer as shim/washer on the bolt
- hold the starter tight in place and start the upper bolt
- when the upper bolt is finger tight, the starter is sitting with its weight taking up any play between holes and upper bolt or lower stud&sleeve
- tighten upper to firm
- tighten lower beyond firm to snug
- torque upper, then torque lower
NOTE: I don't believe the fender washer as a shim is an essential element of this working; but I might be wrong. I had some improvement using a 1.1 mm regular sized washer, so I wanted to try this with a larger washer for more stability. 1.5 mm was what I had in the bin. As per the MSR, you have to check the extension of your starter's Bendix vs. the distance from the locator plate to the flexplate teeth. A shim could come into play to allow you to adjust the extenion to fall within the range specified.
There may be some optimizing possible by moving the starter within the play available with this setup. If one's results weren't as good as mine with the above stetup, one could try adding a threaded-sleeve to the upper bolt.
I am amazed that given the play in the bolts to holes, such a little difference has so much influence.
The way I did it, the location is determined by the lower stud with threaded-sleeve with its play having the starter "down" and the upper play places the starter down and out from the flex plate as its play "pivots" the starter outwards on the lower stud's sleeve. I think.
The mounting/locator plate surface to flexplate teeth is 21.10 mm. That's the upper limit in the TSM & MSR (19.6 to 21.1 mm). I'm using a washer as shim of 1.5 mm, and there's no longer paint on the plate. I'll have to revisit that shim thickness after some days or weeks, to check the starter Bendix for wear marks. I'll adjust, or make a full size shim or remove the shim/washers.
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Just to document for posterity, I cross-referenced the 2 starter bolt part numbers to the AMC Standard Parts Catalog. Here's the poop:
J4001884: BOLT, Hex Head, with Conical Spring Washer, 3/8x16, 1.190" long, Grade 5, plain finish
J4006684: BOLT, Hex Head, with Conical Spring Washer, 3/8x16, 1.375" long, Grade 5, plain finish
These are not shoulder bolts. I recently had my original starter off my '85; and there was no play between the bolt holes and the bolts. No "adjustment" at all. I still wonder if your starter nose is off of something else (Ford application?). Did you see any part number stamped on the nose anywhere?
Probably doesn't help; but there it is.
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Which year(s) are those part numbers from? I know the (some?) '88 uses a different starter.
I have a vague recollection of conical spring washers on my '81 wagon's starter.
The length of threads in the housing for the lower bolt is longer than that of the threads in the upper.
For this starter, its nose is a longer nose and longer Bendix than the standard Ford ones, but I've no assurance it's the AMC setup. There is significant play between the holes and the 3/8-16 bolts, thereby relying solely upon the locator plate for registration of the starter to the centre of the flexplate, with the starter being able to move, hence exert force, hence wear, on that opening in the locator plate.
Update on noise.
- 1/15 starts, starts with noticeable noise
- 1/15 starts, starts with a pause, then resumes turning over and starts (going to check electrical cables to eliminate that)
- the rest of the starts are quick and low/no noise - wonderful
The "shim" is provided by two fender bolts, not a proper full shim gasket. That may be a factor, but at the proper torque of 18 ft.lbs., it shouldn't be?
It sat for six or seven years with a full tank of gas. Finally ran that down to 1/4 and filled it up again. Running smoother now with a little more power, so I redid the vac gauge dizzy setting. Doesn't seem any different. We'll see how it drives tomorrow.
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Not sure if this well help but...
https://www.hemmings.com/stories/article/ford-amc-motorcraft-starters
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Those 2 bolts I mentioned are indeed only from 1979 thru 1987. Parts book says '79 thru '83 take 2 of the J4001884 bolts. Is your car an '88?? I'd be happy to look up the '88 bolt info just for grins.
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No, mine's an '86 and I'd already looked up the parts when I found the discussions about the mythical shoulder bolts.
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Not sure if this well help but...
https://www.hemmings.com/stories/article/ford-amc-motorcraft-starters
A little. That's what I quoted from in my first post.
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What noise was left was decreasing.
Until today. The noise is back and with a vengeance. Worse. So bad I drove home without stopping anywhere so I wouldn't have to start it again. Starter is firm in place. Will have to investigate.
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... Will have to investigate.
Startup, it did not want to rotate after engaging. Third try it did. Drove to my garage. Top shield of the cat fell off and got crunched along the way.
Pulled starter:
- 2/3 of the Bendix teeth are ripped off, exposing the shaft all the way back to where the teeth start.
- One of the washers that is on the shaft at the nose fell out, ripped open and mangled.
- I'll have to pull the plugs and rotate the engine to inspect the flexplate in situ.
- Will need to get all the pieces out. Really hoping a magnet helps enough with that.
Not a happy camper.
Torn between a new/reman starter vs. getting a Bendix and rebuilding this one.
I'm thinking the stress it was put under ripping those gear teeth off means putting a new Bendix in would be a suspect fix?
Still don't know the original problem; only that going to lower stud & 'shoulder' eliminated most of the noise most of the time. Also, the flexplate may have had a fault.
p.s.
Got a air cleaner assembly in 5 1/8" to put on top of the 2150. There were only two in the scrap yard to choose from. Neither were offset, so I'll have to do a little fab work. If I had nothing else to do, that would be fun.
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photo of destroyed starter Bendix gear
the gouges in the opening aren't encouraging - probably some teeth damaged by the Bendix gear bits flying around... :(
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Fishing for Bendix gear bits at the bottom of the bell housing using a magnet. The idea is to drag them to the starter hole opening to get them out of there. I don't want anything left in there to bounce around and interfere with the flexplate and new starter. And if there's a flexplate tooth found, I'll need a flexplate for sure.
Two 3/8" rare earth magnets didn't work. I can feel them grab steel bits, but they loose their hold on the bits when I try and drag them upwards towards the hole. The Al housing is too thick, like an air gap, to maintain a hold on the bits. I'll try a pair of 1".
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Two stacked 1" disc rare earth magnets with a steel backing disk were able to attract and drag the broken Bendix gear teeth to the starter opening. Lots of little steel spinters. Magnets were very effective at pulling those out of my fingers. I retreived the four missing gear teeth. All nine accounted for: five still on the starter and four pulled out.
Pulled the plugs and had my nephew rotate the crank while I inspected the teeth on the flexplate. All its teeth are there. No obvious defects. This was not a high-quality inspection; I need to do better, but can't see how I can do that without pulling the flexplate out. I also need to check the locator plate to tooth distance for all teeth, to check for warping that wasn't obvious to the eye.
Checked that the locator plate is flat by using a steel rule.
- Possibility that the starter was turning before the Bendix was adequately extended and engaged.
- Possibility that the DIY threaded sleeve added to the lower stud (replaced bolt) was not adequate - may need the same on the upper bolt.
- Possibility that the two fender washers as shims are inadequate to hold the torqued starter from bending away from the flexplate teeth. Will remeasure the locator plate surface to flexplate teeth distance, and bench test the new starter for extension-before-turn and measure its extension, to ensure those are in spec.
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Have starter in hand.
Have the small plate off and will do a close inspection of the flexplate.
Will try and get some paper in place to test for space inside the starter mounting hole, to see if I can get a piece of steel in there with a 4.5" 3.25" hole cut in it to provide the correct hole size and location (the hole in mine is worn elongated lower). I don't know if there's enough original hole to allow for correction location. If there is, I figure I can JB-Weld and pin it in place and easily clear the flexplate. P.S. then fill the original plate up to match the inserted plate with the correct hole size.
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Finally have time to get back to this.
I'm not liking using the partially chewed flexplate. Seems my choices for a replacement for the J3232138 are:
- ATP Z-101
- Pioneer FRA-108
Anyone have any advice on the quality of the ATP vs. the Pioneer?
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Finally got back to this today.
Barely any room for my intended 1/8" 'gasket' mounted to the inside of the location plate, with a correct sized starter hole to fixed the enlarged hole. But it can be done, and extended towards the flexplate centre outside of the starter flange so it can have two bolts securing it in place in precise registration while the JB-Weld dries and staying captive.
My starter lower bolt to stud with threaded-on 'shoulder' mod won't work with the new starter.
- The old starter's lower bolt hole in the starter flange is 11.0 mm. Mod would mount this starter closer to where it should be, in spite of the enlarged hole in the location plate. Don't know if this was/wasn't good enough, or if the starter blew its bendix gears due to binding from damage already done to them or to the flexplate teeth.
- That hole on the new starter is 9.6 mm. Mounting bolt fits in with minimal play, and even less once the bolt is in far enough that the unthreaded shank (like a shoulder) is in the flange. I'd expect this means the new starter will bolt in much closer to the correct location re. the flexplate. It also means I get to remove the stud I made and installed in the lower hole in the bell housing...
I think it's time to measure the upper hole in the bell housing... If it's tight enough to the bolt shank, there's no point in the fixing 'gasket', as the difference in mounting position would be under 1 mm, possibly under 0.5 mm.
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Seems the whole starter issue may have been self-inflicted. The Bendix gear rested below the flexplate and it would manually extend to fully engage the flexplate teeth. But I never bench tested the extension using power.
Now I see that the old starter's Bendix rest position is well below that of the replacement starter. Measuring the new starter, its below the flexplate teeth, but just. I may need a gasket to ensure it clears. It will easily have full engagement.
It's plausible that the old starter simply didn't extend far enough for a full engagement under voltage. But in its damaged state, I don't think it's valid to measure that now...
On the mounting of the new starter,
I got two stainless 3/8" 1 1/2" bolts, which have an un-threaded shank next to the head. The shank is under 3/8" and tapers somewhat narrower towards the start of the threads. With just a little play, they would act fairly well like a shoulder bolt for the flange hole & bell-housing hole sizes. I considered wrapping the shank with some thin wire for a tighter fit.
Encouraged as a shoulder bolt substitute to provide starter registration relative to the bell-housing, to see if there was better, I went to a different store. I got two more of the same stainless bolts: same size, even same manufacturer and same stamps on the head, but they have a slightly different colour tone. These shanks start barely under 3/8" (so close I can't measure the difference with the plastic calipers) and tapers but less slope and to less narrow than the first pair - nearly square to the axis and off by less than can be measured with these plastic calipers (although they allow the taper to be detected). These second two have distinctly less play in their respective holes than the first pair. These will very closely register the new starter to the bell-housing.
Now for the detailed inspection of the flexplate...
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Found burs at each end of each tooth on the flexplate from when they were cut. Seem small, but as what all contributes to starter issues is unknown, I decided to address them.
I used a Dremel with a small stone head to "whisk" each tooth end until the burs were gone. And a light skim across the top of the tooth to smooth any roughness. And a touch up the height of each forward tooth end to smooth minor nicks. A few of the teeth seemed to have taken some small intent damage from the starter gears blowing apart, so I smoothed those too. Then brushed with a brass spinning brush driven by a drill. All done through the starter locator hole... So a lot of small hand-turns of the engine.
Runout of the flexplate looks good.
Next is bench test the start to ensure its Bendix gears extends fully. Then test fit the new starter and hand-turn the engine to check for clearance with the flexplate teeth.
No more trusting that the parts I receive are proper.
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Success - partial.
With the:
- 3/8" shank on the bolts,
- the matching 3/8" lower bolt hole in the flange on the starter, and
- the ~3/8" hole in the bell housing,
the starter bolts up in the only possible position - in spite of the enlarged hole for the starter in the locator plate. With a the minor difference in the axis of the threaded holes for the two bolts, there is no play when the bolts have the starter against the plate against the bell housing; both when just finger tight and of course when torqued tight. There is no other possible position.
Turns over very nicely.
Doesn't start... (but was running and shutdown to pull the broken starter).
So I don't yet have confirmation of my measurements that the flexplate teeth clear the resting starter's teeth, although I did turn the engine through 360 degrees by hand without any noise.
p.s.
To get the widest part of the slightly tapered shank in play, I didn't use a lockwasher, but liquid threadlocker.
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Turns over fine.
Nearly all of the time.
Occasionally, turnover stalls, then resumes. I suspect there's one part of the flexplate where the teeth are not cut quite right, resulting in a 'valley' that is not quite deep enough and the starter-to-flexplate binds. This turnover stalling seems to match what I recall just before the old starter's Bendix gears exploded.
I assume my easiest way to find this is to get setup to pull the starter, then keep starting it until I get the beginning of the stall/bind and quickly turn the key off. Hopefully that will leave the part of the flexplate with the issue at the starter locator hole in the plate.
I guess I need to make a template of what the valley cut should be, so I can place it tooth by tooth to find which has the issue(s).
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Here's the photo of the old & new starter, showing the difference in the lower bolt hole, which is significally smaller in the new starter, meaningfully closer to the 3/8" bolt size. There are differences in the dome too, but they both show the five ribs. Both are refurbs from Champion, and both (and the prior that got its dome destroyed by engine kickback) had astoundingly more power/speed turning over the engine than I've ever had in an Eagle. And this is on a rebuilt engine, 4.0 head and new/tight cylinder rings.
Also, the photo of the two pairs of 3/8" 1.5" stainless bolts, which have shanks. Both have hugely less play in the lower bolt hole than bolts that are threaded without shanks.
- The pair on the left have narrower and more tapered shanks, and have double or greater play in the bolt hole than the right pair.
- The pair on the right have shanks that start at the head at so very close to 3/8", and have less taper - meaningfully closer to a shoulder bolt, and have significantly less play in the bolt hole. These 'tighter' bolts are the ones I used to install the new starter.
I attribute the success in spite of having an enlarged hole for the starter in the locator plate, to:
- the 3/8" size lower bolt hole in the new starter,
- the shank on the bolts so they act much like a shoulder bolt, and
- using thread-locker instead of a lockwasher, so more of the shank and the widest part of the shank is within the bolt holes,
so the registration of the starter to the flexplate is determined by the bell housing, not the hole in the locator plate.
I would expect for those starters with an oversized lower bolt hole in its flange, that an insert of solid rod of that hole's diameter could be cut to fit the flange hole, then drilled out dead-centre at 3/8", would provide the same or similar registration benefit that I got in the new starter with the smaller hole. This is similar to what I tried earlier with the stud I made with the threaded 'shank' on it, but would be meaningfully more precise.
I expect that the 'gasket' I was planning to correct the enlarged locator plate starter hole is NOT a good way to address this problem: it's a lot more work, and is dependant on an error-prone judgment to locate the correct size hole to provide starter location registration. Using bolts with shanks closest as possible to 3/8" to closely function like shoulder bolts is clearly a superior way to go.